New paper in GRL confirms link between sun and clouds on global scale

[Saul]

No it isn't. 20,000 years ago was the coldest part of the last glacial period and insolation at 65N was ~20Wm² less than it is today.

Insolation was not 20 W/m^2 less at 65N 20,000 years in the summer. (Note the summer insolation at 65N is supposedly important in Milankovitch's theory.) 20,000 years ago was the start of the current interglacial. 20,000 years ago perihelion (earth's closest approach to the sun) occurred in June. Therefore summers at 65N 20,000 years ago were significantly warmer (due to insolation) than they are today. (Planet was still cold 20,000 years ago as the massive ice sheets were starting to melt. Have you heard about the glacial/interglacial cycle?)

Currently the Earth is farthest from the sun in June and closest to the sun in January. Therefore summers at 65N are colder due to insolation than they were 20,000 years ago. The insolation during summers at 65N is the same today as it was during the coldest part of the last glacial period.

Now the question all curious scientific minds want to ask is why does the planet get colder and colder, then at the coldest point in the glacial cycle the ice sheets melt for a short interglacial period and then suddenly there is abrupt cooling. What is the 100 kyr problem? (See link at end of this comment.)

Do you know anything about Milankovitch's flawed theory? Do please explain the mechanism. I am curious about your thoughts and knowledge of obvious flaws in Milankovitch's theory. Great theory if one ignores the paradoxes.

http://ocean.mit.edu/~cwunsch/papersonline/milankovitchqsr2004.pdf

“Quantitative estimate of the Milankovitch-forced contribution to observed Quaternary climate change” by Carl Wunsch

“A number of records commonly described as showing control of climate change by Milankovitch insolation forcing are re-examined. The fraction of the record variance attributable to orbital changes never exceeds 20%. In no case, including a tuned core, do these forcing bands explain the overall behavior of the records. At zero order, all records are consistent with stochastic models of varying complexity with a small superimposed Milankovitch response, mainly in the obliquity band. Evidence cited to support the hypothesis that the 100 Ka glacial/interglacial cycles are controlled by the quasi-periodic insolation forcing is likely indistinguishable from chance, given the small sample size and near-integer ratios of 100 Ka to the precessional periods. At the least, the stochastic background‘‘noise’’ is likely to be of importance.”

Evidence that Milankovitch forcing ‘‘controls’’ the records, in particular the 100 ka glacial/interglacial, is very thin and some what implausible, given that most of the high frequency variability lies elsewhere.

www.soest.hawaii.edu/GG/FACULTY/POPP/Lecture14.pp[/URL][url]http://en.wikipedia.org/wiki/Milankovitch_cycles[/url][QUOTE]100,000-year problem

[B]The 100,000-year problem[/B] is that the eccentricity variations have a significantly smaller impact on solar forcing than precession or obliquity and hence might be expected to produce the weakest effects. However, observations show that during the last 1 million years, the strongest climate signal is the 100,000-year cycle. In addition, despite the relatively large 100,000-year cycle, some have argued that the length of the climate record is insufficient to establish a statistically significant relationship between climate and eccentricity variations.[6] Some models can however reproduce the 100,000 year cycles as a result of non-linear interactions between small changes in the Earth's orbit and internal oscillations of the climate system.[7][8][/QUOTE]

[QUOTE][B]The 400,000-year problem[/B] is that the eccentricity variations have a strong 400,000-year cycle. That cycle is only clearly present in climate records older than the last million years. If the 100 ka variations are having such a strong effect, the 400 ka variations might also be expected to be apparent. This is also known as the stage 11 problem, after the interglacial in marine isotopic stage 11 which would be unexpected if the 400,000-year cycle has an impact on climate. The relative absence of this periodicity in the marine isotopic record may be due, at least in part, to the response times of the climate system components involved — in particular, the carbon cycle.[/QUOTE][QUOTE][B]The stage 5 problem[/B] refers to the timing of the penultimate interglacial (in marine isotopic stage 5) which appears to have begun 10 thousand years in advance of the solar forcing hypothesized to have been causing it. [B]This is also referred to as the causality problem.[/B] Effect exceeds cause 420,000 years of ice core data from Vostok, Antarctica research station.[/QUOTE]

[QUOTE]The effects of these variations are primarily believed to be due to variations in the intensity of solar radiation upon various parts of the globe. Observations show climate behaviour is much more intense than the calculated variations. Various internal characteristics of climate systems are believed to be sensitive to the insolation changes, causing amplification (positive feedback) and damping responses (negative feedback).

[B]The unsplit peak problem[/B] The unsplit peak problem refers to the fact that eccentricity has cleanly resolved variations at both the 95 and 125 ka periods. A sufficiently long, well-dated record of climate change should be able to resolve both frequencies [5], but some researchers interpret climate records of the last million years as showing only a single spectral peak at 100 ka periodicity. It is debatable whether the quality of existing data ought to be sufficient to resolve both frequencies over the last million years.
[/QUOTE]

[QUOTE][B] The transition problem[/B]

[B]The transition problem[/B] refers to the change in the frequency of climate variations 1 million years ago. From 1-3 million years, climate had a dominant mode matching the 41 ka cycle in obliquity. After 1 million years ago, this changed to a 100 ka variation matching eccentricity. No reason for this change has been established.[/QUOTE]

 

[Skyhunter]

OK, Making eyeball guesstimates is not very accurate so let me get more exact numbers.

http://www.imcce.fr/Equipes/ASD/insola/earth/online/index.php

65N summer insolation peaked 17,000 years ago.

http://www.imcce.fr/tmp/insola/insolaoutKWaaCo

The coldest point of the last glaciation was ~25,000 years ago and 65N 360L was about -6Wm² less than the present.

But there are other factors besides orbital forcings and NH summer insolation at any given period. I was not arguing that 65N insolation was the only forcing involved, I was simply pointing out your error. Since your argument was based on bad information, your conclusion is suspect.

 

[Xnn]

Xnn,
This is not religious studies where one can appeal to some sacred book that has a higher status or democratic where if 10 people agree with your statement and only 9 agree with what my statement, you win.

Saul;

The problem is that there are a number of quacks around when it comes to science.
The way to avoid being mislead, is to refer to reputable sources and journals that employ the peer review process. It not, then this may just as well be a political or religious belief forum.

I agree with you that the Sun is in an exceptional period which may continue. There has been very few sunspots for the last 2 years. It's about as big a lull and what occurred in 1910 to 1913. This means the solar forcing for the climate is about as low as it was way back then. However, last I checked, global surface and land temps are both near record highs. It's far warmer now than it was back then and I think we both know why.

Here's a link to the latest National Climate Data Center summary:

*The combined global land and ocean average surface temperature for August 2009 was 0.62°C (1.12°F) above the 20th century average of 15.6°C (60.1°F). This is the second warmest such value on record, behind 1998. August 2009 was the 31st consecutive August with an average global surface temperature above the 20th century average. The last August with global temperatures below the 20th century average occurred in 1978.
*The combined global land and ocean average surface temperature for June-August 2009 was the third warmest on record for the season, 0.59°C (1.06°F) above the 20th century average of 15.6°C (60.1°F).
*The worldwide ocean surface temperature for August 2009 was the warmest on record for August, 0.57°C (1.03°F) above the 20th century average of 16.4°C (61.4°F).
*The seasonal (June-August 2009) worldwide ocean surface temperature was also the warmest on record, 0.58°C (1.04°F) above the 20th century average of 16.4°C (61.5°F).
*In the Southern Hemisphere, both the August 2009 average temperature for land areas, and the Hemisphere as a whole (land and ocean surface combined), represented the warmest August on record.

Now, this does not mean we can not discuss the influence of the Sun on the climate. However, I'm not interested in being mislead by outrageous over hyped claims.

 

[Evo]

Science is the analysis of observation data to validate or invalidate hypotheses.

There is a significant solar event underway. How has the solar magnetic cycle changed?

Are there any unexplained climatic events or changes that correlate with the recent solar changes? Note the mechanism has solar wind bursts removing the ions that are hypothesized to increase planetary cloud cover, therefore the planet will not cool (planetary clouds increased due to high levels of GCR) until the the solar wind bursts abate and then stop.

As shown in the solar links below, the solar wind bursts are starting to abate. GCR is 19% higher than any period in the last 40 years.

Ocean heat content is starting to trend down. Why?

edit: removed link

This set of links shows the progress of the solar magnetic cycle.

The sun is spotless for this day in 2004 however there is significant magnetic activity.

edit: removed links
The solar magnetic cycle has not restarted. There continues to be coronal holes in low latitude locations on the sun, however, the affect on the geomagnetic field is less and less as the coronal holes are stripping of the sun's magnetic flux and the solar magnetic cycle has not restarted. (See coronal hole CH382.)

Today. (See coronal hole CH382.)

edit:deleted links

Saul, those links are not to valid sources. Some even say that they are made by the person from other sources. Since we can't validate every graph that every person puts together, we have to insist on only the original data.

 

[Saul]

OK, Making eyeball guesstimates is not very accurate so let me get more exact numbers.

http://www.imcce.fr/Equipes/ASD/insola/earth/online/index.php

65N summer insolation peaked 17,000 years ago.

http://www.imcce.fr/tmp/insola/insolaoutKWaaCo

The coldest point of the last glaciation was ~25,000 years ago and 65N 360L was about -6Wm² less than the present.

But there are other factors besides orbital forcings and NH summer insolation at any given period. I was not arguing that 65N insolation was the only forcing involved, I was simply pointing out your error. Since your argument was based on bad information, your conclusion is suspect.

"Skyhunter 1st Quote:"No it isn't. 20,000 years ago was the coldest part of the last glacial period and insolation at 65N was ~20Wm² less than it is today.

"Skyhunter 2nd quote:"65N summer insolation peaked 17,000 years ago.

The coldest point of the last glaciation was ~25,000 years ago and 65N 360L was about -6Wm² less than the present.

Skyhunter,

You contradict yourself in the above quotes.

No it isn't. 20,000 years ago was the coldest part of the last glacial period and insolation at 65N was ~20Wm² less than it is today.

This interglacial period began roughly 20,000 years ago. The past six interglacial periods have been around 15,000 years long. The glacial periods are 100,000 years long. Do we agree what has happened before? i.e. I am not stating a theory I am stating the what the paleoclimatic data indicates. i.e. The mechanism must explain what has happened before.

The current interglacial period started about 20,000 years ago. As you note the coldest period of the last glacial period was about 25,000 years ago. Solar insolation in the summer has become progressive less at the 65N. When the interglacial started 20,000 years ago the Earth was closest to the sun in June. Now 20,000 years later the Earth is closest to the sun in January, which makes summers colder now then they were 20,000 years ago.

We both agree and multi papers state something else besides solar insolation is abruptly forcing the planet's climate. When you look at the peculiar saw shaped glacial/interglacial cycle there is obviously some massive forcing function at work.

Suddenly in the middle the current warming "Holocene interglacial" 12,900 years ago, the planet abruptly returns to glacial cold for a 1000 years. (The abrupt cooling period is called the Younger Dryas cooling period named after an alpine flower that suddenly appears in the fossil record in mid latitudes in Europe.)

My point is the Younger Dryas abrupt cooling event is one of a series of abrupt cooling events in the paleoclimatic record. There are cosmogenic isotope changes that are concurrent with the abrupt cooling events. Cosmogenic isotope changes are caused by interruptions in the solar magnetic cycle and geomagnetic field changes which then causes a massive increase in GCR.

 

[Saul]

As I said, there is a massive cosmogenic isotope change that is concurrent with a massive 1000 year abrupt cooling event which paleo climatologists have called the "Younger Dryas" cooling event.http://cio.eldoc.ub.rug.nl/FILES/root/2000/QuatIntRenssen/2000QuatIntRenssen.pdf

Reduced solar activity as a trigger for the start of the Younger Dryas?

The Younger Dryas (YD, 12.9-11.6 ka cal BP, Alley et al., 1993) was a cold event that interrupted the general warming trend during the last deglaciation. The YD was not unique, as it represents the last of a number of events during the Late Pleistocene, all characterised by rapid and intensive cooling in the North Atlantic region (e.g., Bond et al., 1993; Anderson, 1997). During these events, icebergs were common in the N Atlantic Ocean, as evidenced by ice-rafted sediments found in ocean cores. The most prominent of these episodes with ice rafting are known as Heinrich events (e.g., Bond et al., 1992, 1993; Andrews, 1998). A Heinrich-like event (H-0) was simultaneous with the YD (Andrews et al., 1995). Moreover, the YD seems to be part of a millennial-scale cycle of cool climatic events that extends into the Holocene (Denton and KarleHn, 1973; Harvey, 1980; Magny and Ru!aldi, 1995; O'Brien et al., 1995; Bond et al., 1997). Based on analysis of the 14C record from tree rings, Stuiver and Braziunas (1993) suggested that solar variability could be an important factor a!ecting climate variations during the Holocene (see also Magny, 1993, 1995a), possibly operating together with oceanic forcing.

Evidence for solar variations in the geological past may be inferred from cosmogenic isotope records (Hoyt and Schatten, 1997). The two most important of these isotopes are carbon-14 (14C) and beryllium-10 (10Be),... Estimates for the increase in 14C at the start of the YD all demonstrate a strong and rapid rise: 40-70 %/% within 300 years (Goslar et al., 1995), 30-60 %/% in 70 years (BjoK rck et al., 1996), 50-80%/% in 200 years (Hughen et al., 1998) and 70%/% in 200 years (Hajdas et al., 1998). This change is apparently the largest increase of atmospheric 14C known from late glacial and Holocene records (Goslar et al., 1995). Hajdas et al. (1998) used this sharp increase of atmospheric 14C at the onset of the YD as a tool for time correlation between sites.

There is evidence is the sun is moving to a complete solar magnetic cycle interruption, not a slow down.

The magnetic field strength of newly formed sunspots has been linearly decreasing with time. It is believed sunspots are created at interface of the convection zone and the radiative zone (the tachocline). The sunspot requires a minimum field strength of around 1500 gauss to avoid being torn to pieces as it moves up to the surface of the sun through the turbulent convection zone.

Sunspots from the previous cycle are believed to move back down to tachocline to form the seeds for the next cycle, which explains why there is some periodicity between every second cycle. (The period of the convection motion motion is 22 years.). An interesting and unanswered question is how does the solar magnetic cycle re-start after being interrupted?

http://www.leif.org/EOS/2009EO300001.pdf

Are Sunspots Different During This Solar Minimum?

But something is unusual about the current sunspot cycle. The current solar minimum has been unusually long, and with more than 670 days without sunspots through June 2009, the number of spotless days has not been equaled since 1933 (see http:// users . telenet .be/ j . janssens/ Spotless/ Spotless .html). The solar wind is reported to be in a uniquely low energy state since space measurements began nearly 40 years ago [Fisk and Zhao, 2009].

The same data were later published [Penn and Livingston, 2006], and the observations showed that the magnetic field strength in sunspots were decreasing with time, independent of the sunspot cycle. A simple linear extrapolation of those data suggested that sunspots might completely vanish by 2015.

Yet although the Sun’s magnetic polarity has reversed and the new solar cycle has been detected, most of the new cycle’s spots have been tiny “pores” without penumbrae (see Figure 1); in fact, nearly all of these features are seen only on flux magnetograms and are difficult to detect on whitelight images.

 

[Andre]

The problem with the Younger Dryas is that if you really research it meticulously, checking out a couple of hundred studies on methodology, especially on dating calibration, the cold image crumbles. One example:

http://geology.geoscienceworld.org/cgi/content/abstract/30/5/427

Anomalously mild Younger Dryas summer conditions in southern Greenland

abstract

The first late-glacial lake sediments found in Greenland were analyzed with respect to a variety of environmental variables. The analyzed sequence covers the time span between 14 400 and 10 500 calendar yr B.P., and the data imply that the conditions in southernmost Greenland during the Younger Dryas stadial, 12 800–11 550 calendar yr B.P., were characterized by an arid climate with cold winters and mild summers, preceded by humid conditions with cooler summers. Climate models imply that such an anomaly may be explained by local climatic phenomenon caused by high insolation and Föhn effects. ... cont'd

Note that model speculations don't count as evidence.

 

[Saul]

The problem with the Younger Dryas is that if you really research it meticulously, checking out a couple of hundred studies on methodology, especially on dating calibration, the cold image crumbles. One example:

http://geology.geoscienceworld.org/cgi/content/abstract/30/5/427

Note that model speculations don't count as evidence.

Andre,

A melting ice in Greenland during the Younger Dryas does not mean the has not an abrupt cooling climatic climate change during the Younger Dryas that lasted a 1000 years.

If we understood the mechanism then interpreting the paleoclimatic record would be easier.

The Younger Dryas was the strongest climatic event in the Holocene, interglacial period. It was an abrupt climate event, not a gradual cooling. It lasted for 1000 years. During the Younger Dryas the North Atlantic froze each winter to a latitude of around mid-Spain.

There is a 6 fold increase in dust deposited on the Greenland ice sheet during the Younger Dryas cold period which indicates a massive increase in desertification due to abrupt cooling. As noted below the ice sheet dust changes occurs in less than 10 layers of ice. There is cycles of the abrupt increases in the dust deposited on the Greenland ice sheet.

Due to insolation, summers should have been warmer 12,900 years ago than now. Melt water in the Greenland region during the summer does not disprove an abrupt climatic cooling event occurred.

http://www.agu.org/revgeophys/mayews01/node6.html

The Younger Dryas (YD) was the most significant rapid climate change event that occurred during the last deglaciation of the North Atlantic region. Previous ice core studies have focused on the abrupt termination of this event [ Dansgaard et al., 1989] because this transition marks the end of the last major climate reorganization during the deglaciation. Most recently the YD has been redated--using precision, subannually resolved, multivariate measurements from the GISP2 core--as an event of 1300 70 years duration that terminated abruptly, as evidenced by an 7 C rise in temperature and a twofold increase in accumulation rate, at 11.64 kyr BP [ Alley et al., 1993] (Figure 2). The transition into the Preboreal (PB), the PB/YD transition, and the YD/Holocene transition were all remarkably fast, each occurring over a period of a decade or so [ Alley et al., 1993]. Fluctuations in the electrical conductivity of GISP2 ice on the scale of <5-20 years have been used to reveal rapid changes in the dust content of the atmosphere during the same periods and throughout the last glacial [ Taylor et al., 1993b]. These rapid changes appear to reflect a type of ``flickering'' between preferred states of the atmosphere [ Taylor et al., 1993b], which provides a new view of climate change. Holocene climates are by comparison stable and warm.

High resolution (mean: 3.48 years/sample), continuous measurements of GISP2 major anions (chloride, sulfate and nitrate) and cations (sodium, magnesium, potassium, calcium and ammonium) were used to reconstruct the paleoenvironment during the YD because these series record the history of the major soluble constituents transported in the atmosphere and deposited over central Greenland [ Mayewski et al., 1993c]. These multivariate glaciochemical records provide a robust indication of changes in the characteristics of the sources of these soluble components or changes in their transport paths, in response to climate change. A dramatic example is provided by the calcium series (Figure 2) covering the last 10-18 kyr BP. Prominent periods of increased dustiness have been observed in the record, peaking approximately every 500 years (see figures in Mayewski et al. [1993c]): during the early PB at 11.4 kyr BP; throughout the YD at 11.81, 12.22 and 12.64 kyr BP; during the Bolling/Allerod (B/A) at 13.18, 13.65, and 14.02 kyr BP; and during much of the Glacial. Such events have been attributed by Mayewski et al. [1993c] to changes in the size of the polar atmospheric cell and in source regions (e.g., growth and decay of continental biogenic and terrestrial source regions).

The climate change that accompanied the YD was not restricted to Greenland. The record of variations in the CH concentration of trapped gases in the GRIP ice core [ Chappellaz et al., 1993] shows that tropical and subtropical climates were colder and drier during the YD and also earlier cold events. The major natural source region of CH is low-latitude wetlands [ Chappellaz et al., 1993]; higher atmospheric concentrations are presumably due to the greater areal extent of tropical and subtropical wetlands [ Chappellaz et al., 1993].

 

[Andre]

No Saul, the Bjorck et al paper is just an example.

Another example, starting with the A:

http://esp.cr.usgs.gov/research/alaska/PDF/Ager2003QR.pdf

..A brief invasion of Populus (poplar, aspen) occurred ca.11,000–9500 14C yr B.P., overlapping with the Younger Dryas interval of dry, cooler(?) climate...

and in the discussion:

...At Zagoskin Lake, the time interval for the Populus-Salix assemblage overlaps with the Younger Dryas interval of colder, drier climate that has been documented in several areas of Alaska (e.g., Peteet and Mann, 1994). It is unclear why an interval of apparently colder, drier climate might favor the expansion of Populus and Salix populations, even into areas beyond the present day range of Populus trees...

How many more shall I present?

 

[Saul]

No Saul, the Bjorck et al paper is just an example.

Another example, starting with the A:

http://esp.cr.usgs.gov/research/alaska/PDF/Ager2003QR.pdf

and in the discussion:

How many more shall I present?

Andre,

I am not sure what your point or mechanism is. The paper you quote above discusses a microclimatic region (Bering Straight) where the Pacific Ocean significantly moderates the climate. i.e. That area and similar microclimate regions could be less cold than the Northern Hemisphere as a whole.

The Younger Dryas Greenland Ice sheet cooling occurred in less than a decade. Your paper does challenge the observation of rapid and extreme cooling on the Greenland Ice sheet.

The Greenland Ice Sheet temperatures dropped -15C as compared today. The Northern Atlantic ocean froze to the latitude of mid Spain. Why? What planetary or external change caused the planet to change.

As I note there are cosmogenic isotope changes that are concurrent to the planetary temperature changes.

There is a cycle of warming and abrupt cooling periods throughout the glacial and interglacial period which show evidences of an external forcing function. The forcing occurs regardless of surface events. Its effect (the external forcing function) depends on surface events at the time of the occurrence.

 

[Saul]

http://en.wikipedia.org/wiki/Milankovitch_cycles

People have been silent on the list of paradoxes concerning Milankovitch's theory.

Milankovitch's theory does not explain the observations. There is evidence of abrupt warmings and coolings that do not correlate with any surface events.

The 100,000 year problem
The 100,000-year problem is that the eccentricity variations have a significantly smaller impact on solar forcing than precession or obliquity and hence might be expected to produce the weakest effects. However, observations show that during the last 1 million years, the strongest climate signal is the 100,000-year cycle. In addition, despite the relatively large 100,000-year cycle, some have argued that the length of the climate record is insufficient to establish a statistically significant relationship between climate and eccentricity variations.[6] Some models can however reproduce the 100,000 year cycles as a result of non-linear interactions between small changes in the Earth's orbit and internal oscillations of the climate system.[7][8]

The 400,000 year problem
The 400,000-year problem is that the eccentricity variations have a strong 400,000-year cycle. That cycle is only clearly present in climate records older than the last million years. If the 100 ka variations are having such a strong effect, the 400 ka variations might also be expected to be apparent. This is also known as the stage 11 problem, after the interglacial in marine isotopic stage 11 which would be unexpected if the 400,000-year cycle has an impact on climate. The relative absence of this periodicity in the marine isotopic record may be due, at least in part, to the response times of the climate system components involved — in particular, the carbon cycle.

The Stage 5 Problem
The stage 5 problem refers to the timing of the penultimate interglacial (in marine isotopic stage 5) which appears to have begun 10 thousand years in advance of the solar forcing hypothesized to have been causing it. This is also referred to as the causality problem. Effect exceeds cause 420,000 years of ice core data from Vostok, Antarctica research station.

The effects of these variations are primarily believed to be due to variations in the intensity of solar radiation upon various parts of the globe. Observations show climate behaviour is much more intense than the calculated variations. Various internal characteristics of climate systems are believed to be sensitive to the insolation changes, causing amplification (positive feedback) and damping responses (negative feedback).

The unsplit peak problem
The unsplit peak problem refers to the fact that eccentricity has cleanly resolved variations at both the 95 and 125 ka periods. A sufficiently long, well-dated record of climate change should be able to resolve both frequencies [5], but some researchers interpret climate records of the last million years as showing only a single spectral peak at 100 ka periodicity. It is debatable whether the quality of existing data ought to be sufficient to resolve both frequencies over the last million years.

The transition problem
The transition problem refers to the change in the frequency of climate variations 1 million years ago. From 1-3 million years, climate had a dominant mode matching the 41 ka cycle in obliquity. After 1 million years ago, this changed to a 100 ka variation matching eccentricity. No reason for this change has been established.

 

[Saul]

The following is additional evidence that indicates Milankovitch's theory is not correct and there is an external mechanism that is forcing the planet's temperature.

http://earthobservatory.nasa.gov/Newsroom/view.php?id=24476

Glacial Records Depict Ice Age Climate In Synch Worldwide

An answer to the long-standing riddle of whether the Earth's ice ages occurred simultaneously in both the Southern and Northern hemispheres is emerging from the glacial deposits found in the high desert east of the Andes.

"The results are significant because they indicate that the whole Earth experiences major ice age cold periods at the same time, and thus, some climate forcing mechanism must homogenize the Earth's climate system during ice ages and, by inference, other periods," says Michael R. Kaplan, a postdoctoral fellow at the University of Edinburgh who conducted the work in a postdoctoral position at UW-Madison

"During the last two times in Earth's history when glaciation occurred in North America, the Andes also had major glacial periods," says Kaplan.

"Because the Earth is oriented in space in such a way that the hemispheres are out of phase in terms of the amount of solar radiation they receive, it is surprising to find that the climate in the Southern Hemisphere cooled off repeatedly during a period when it received its largest dose of solar radiation," says Singer. "Moreover, this rapid synchronization of atmospheric temperature between the polar hemispheres appears to have occurred during both of the last major ice ages that gripped the Earth."

This is evidence that the short term planetary temperature changes in this interglacial period are global and synchronous. The synchronicity rules out ocean current as a possible mechanism as the time for ocean currents changes in the Northern Hemisphere to affect the Southern Hemisphere is theoretically around 1000 years.

A second as serious issue with the ocean current mechanism (likely a show stopper) is the recently confirmed finding that the deep ocean conveyor does not exist. There is therefore no ocean current mechanism to teleconnect the two hemispheres even with a time delay.

http://geology.geoscienceworld.org/cgi/content/abstract/33/3/237

Evidence of early Holocene glacial advances in southern South America from cosmogenic surface-exposure dating

Cosmogenic nuclide surface-exposure dating reveals that glaciers in southern South America (46°S) advanced ca. 8.5 and 6.2 ka, likely as a result of a northward migration of the Southern Westerlies that caused an increase in precipitation and/or a decrease in temperature at this latitude. The older advance precedes the currently accepted initiation of Holocene glacial activity in southern South America by 3000 yr. Both of these advances are temporally synchronous with Holocene climate oscillations that occurred in Greenland and the rest of the world. If there are causal links between these events, then rapid climate changes appear to be either externally forced (e.g., solar variability) or are rapidly propagated around the globe (e.g., atmospheric processes).

 

[Andre]

Andre,

I am not sure what your point or mechanism is. The paper you quote above discusses a microclimatic region (Bering Straight) where the Pacific Ocean significantly moderates the climate. i.e. That area and similar microclimate regions could be less cold than the Northern Hemisphere as a whole.

The Younger Dryas Greenland Ice sheet cooling occurred in less than a decade. Your paper does challenge the observation of rapid and extreme cooling on the Greenland Ice sheet.

The Greenland Ice Sheet temperatures dropped -15C as compared today. The Northern Atlantic ocean froze to the latitude of mid Spain. Why? What planetary or external change caused the planet to change.

As I note there are cosmogenic isotope changes that are concurrent to the planetary temperature changes.

There is a cycle of warming and abrupt cooling periods throughout the glacial and interglacial period which show evidences of an external forcing function. The forcing occurs regardless of surface events. Its effect (the external forcing function) depends on surface events at the time of the occurrence.

I know, it's a bit weird to challenge the cold of the Younger Dryas and oppose all parties in the climatology, "warmers" and "deniers", but it's just the outcome of my years of research into that direction as I shall prove. There is no other option than to be absolutely accurate about the data before the suppositions can start and we are far away from that.

So, I'm afraid, it's all a bit different. and I still have dozens of "micro" climates on my sleeve. After the B of Bjorck, we now have the C for Columbia.

Van’t Veer R., G.A. Islebe, H. Hooghiemstra, 2000; Climate change during the Younger Dryas chron in Northern South America: a test of the evidence. Quartenary Science Review Vol 19 (2000) pp 1821 - 1835

Abstract

New AMS and palynological data are presented from the Colombian Andes to assess vegetational and climatic change during the Lateglacial-Holocene transition, with special emphasis on the Younger Dryas (YD) chronozone.

...From ca. 11,000 to ca. 10,500 14C yr BP there is a sharp increase of subparamo and paramo pollen, reflecting a relatively cool phase during the YD chronozone (zone Y1). After ca. 10,500 14C yr BP, a slight increase of arboreal pollen and the presence of Cactaceae (zone Z1) point toward a relatively milder but drier phase extending to ca. 9000 14C yr BP in the earliest Holocene...

The sharp boundary at 11,000 and 10,500 year 14C BP, carbon dated, convert to 12,920 and 12,600 calendar years BP using the INTCAL04 calibration table so that cooling period is mosty before the beginning of the Younger Dryas that started about 12680 "varve" counted years ago (http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6R-4CWBMMN-2&_user=10&_coverDate=08%2F19%2F2004&_alid=1045205706&_rdoc=1&_fmt=high&_orig=search&_cdi=5821&_sort=r&_docanchor=&view=c&_ct=5&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=88acc331cfe014c99e4b2d3fa69e7c56)

So the warm period after 10,500 carbon years is actually in the middle of the Younger Dryas. Furthermore, peek at Lucke and Brauer again:

High lacustrine primary production was further favored by relatively warm YD summer temperatures.

so we have yet another micro climate here, but now in Germany, Europe.

So if you find all these discrepancies, are these all micro climates? or is something more seriously wrong with our interpretations?

 

[Skyhunter]

Skyhunter,

You contradict yourself in the above quotes.

What part of:

OK, Making eyeball guesstimates is not very accurate so let me get more exact numbers.

didn't you understand?

Since my second post was specifically to offer more precise numbers... why are you accusing me of contradicting myself?

This interglacial period began roughly 20,000 years ago. The past six interglacial periods have been around 15,000 years long. The glacial periods are 100,000 years long. Do we agree what has happened before? i.e. I am not stating a theory I am stating the what the paleoclimatic data indicates. i.e. The mechanism must explain what has happened before.

The current interglacial period started about 20,000 years ago. As you note the coldest period of the last glacial period was about 25,000 years ago. Solar insolation in the summer has become progressive less at the 65N. When the interglacial started 20,000 years ago the Earth was closest to the sun in June. Now 20,000 years later the Earth is closest to the sun in January, which makes summers colder now then they were 20,000 years ago.

The current interglacial is known as the http://www.ucmp.berkeley.edu/quaternary/hol.html" and it began ~10,000 years ago, not 20,000.

We both agree and multi papers state something else besides solar insolation is abruptly forcing the planet's climate. When you look at the peculiar saw shaped glacial/interglacial cycle there is obviously some massive forcing function at work.

Suddenly in the middle the current warming "Holocene interglacial" 12,900 years ago, the planet abruptly returns to glacial cold for a 1000 years. (The abrupt cooling period is called the Younger Dryas cooling period named after an alpine flower that suddenly appears in the fossil record in mid latitudes in Europe.)

My point is the Younger Dryas abrupt cooling event is one of a series of abrupt cooling events in the paleoclimatic record. There are cosmogenic isotope changes that are concurrent with the abrupt cooling events. Cosmogenic isotope changes are caused by interruptions in the solar magnetic cycle and geomagnetic field changes which then causes a massive increase in GCR.

The Younger-Dryas preceded the Holocene. One theory is that a http://www.sciencemag.org/cgi/content/abstract/323/5910/94" and caused the abrupt cooling, but the more likely cause was a Dansgaard/Oeschger event. Here are two recent papers that synchronize the Antarctic and Greenland ice cores.

Do you have a link showing the cosmogenic isotope proxies that coincide with the 100,000 year glaciations?

It is my understanding that they isotope proxies reveal a 2500 year cycle.

How does the GCR theory explain the tropical Earth and snowball Earth events?

How do you explain the anti-correlation with low clouds and medium altitude clouds?

 

[Skyhunter]

Here is a comparison of the Delta ¹⁸O ice core records.

The Y-D event was not globally synchronous.

 

[Saul]

Here is a comparison of the Delta ¹⁸O ice core records.

The Y-D event was not globally synchronous.

Skyhunter if you look at this graph there is abrupt interglacial warming that began 15,000 years ago, not 10,000 years ago. The start of the warming is the start of the interglacial. Your comment is correct, the Holocene period is defined as the warming that occurs after the Younger Dryas event. Interglacial periods are typically 15,000 years long.

The Younger Dyras cooling affected the tropics in addition to the Northern Hemisphere. I believe there was cooling in the Southern Hemisphere however not a 1000 year cooling period as occurred in the Northern Hemisphere.

What is key (to explain in terms of mechanism) about the Younger Dryas event is the rapidity and magnitude of cooling event. Also note the North Hemisphere was cold for a 1000 years. Impacts to the planet or volcanic eruptions cool the planet for a few years. Those how appeal to impacts and volcanic eruptions cannot explain the duration of the cooling event. Insolation at 65N is at maximum during the Younger Dryas cooling event, the oceans will retain there heat and will not cool based on increased cloud cover for a couple of years.

Thinking in terms of mechanism what is required is a mechanism that can abrupt cool one hemisphere and regions in a hemisphere more than others in addition to a mechanism that can cool the entire planet.

The were other cooling events, as per my comments in links, that concurrently effected both hemispheres. Including the long term cooling glacial cycle for the last two glacial cycles.

The problem of course with the finding of long term glacial cooling occurring in both hemispheres at the same time is insolation can only cool one hemisphere based on insolation at 65 degree latitude. The other hemisphere is 180 degrees out of phase and will be receiving maximum insolation in the summer. If both hemispheres abruptly cool something else is forcing the planet's climate.

Everyone that is interested in Milankovitch's theory look closely at this link that shows how the planet's temperature has changed vs insolation for the last 800,000 years.

Look closely at this comparison of insolation at 65N Vs planetary temperature. Skyhunter, how do explain the planet becoming colder and colder over 100,000 years and then 15,000 years ago abruptly warming? Also if you look at insolation at 65N compared to past glacial/interglacial cycles, there is a lack of proportional change. Insolation is has become less and less in the last 15,000 years.

http://upload.wikimedia.org/wikipedia/commons/5/53/MilankovitchCyclesOrbitandCores.png

This also is interesting. Using ocean floor sediments this graph shows how planetary temperature has changed over the last 5 million years. You can see the evidence of the abrupt forcing function in the plot. What is confusing the researchers is they initially selected the incorrect mechanism.

As Jasper Kirkby notes in his review paper, the geomagnetic field intensity now peaks during the interglacial and is stronger in intensity than during normal periods. There is also a cycle of 41 kyrs in the geomagnetic field.

http://upload.wikimedia.org/wikipedia/commons/6/60/Five_Myr_Climate_Change.png

 

[Saul]

What part of:


Do you have a link showing the cosmogenic isotope proxies that coincide with the 100,000 year glaciations?

This is the paper that shows there is 100,000 period for geomagnetic field intensity changes. (The geomagnetic field intensity is 5 to 6 times greater during the interglacial period. For the last 40 kyr lava flows can be used to determine geomagnetic field intensity quite precisely. All accept that the geomagnetic field intensity has increased 5 to 6 times from the cold glacial period to the warm interglacial period. Jasper Kirkby discusses the correlation of geomagnetic field intensity with planetary climate.) The GCR is modulate by the geomagnetic intensity in terms of the intensity of the GCR that strikes the planet and the latitudes the GCR can reach.

The 100kyr magnetic cycle paper's hypothesized mechanism for what is modulating the geomagnetic field intensity is not correct. The eccentricity of the planet's orbit changes how the periodic solar event affects the planet. The effect is greater when the orbital eccentricity is greater. The effect is also greater when the orbital tilt is greater. Based on the timing of abrupt cooling event the solar event occurs with periodicity of roughly 8000 to 12,000 years.

So if you have a solar event that is semi periodic and its effect on the geomagnetic field depends on the planetary orbital changes (tilt, timing of aphelion, and orbital eccentricity) and also on the amount of the planet's surface that is covered with ice sheets, a person is not going to understand what is happening (the observations) without a correct strawman mechanism. Picking an incorrect mechanism will force other assumptions to be incorrect in an attempt to try to match the paleo record. (Look at the paleo record of temperatures for the last 5 million years.)

http://www.geo.uu.nl/~forth/people/Hirokuni/Hiro2002a.pdf

Orbital Influence on Earth’s Magnetic Field: 100,000-Year Periodicity in Inclination

A continuous record of the inclination and intensity of Earth’s magnetic field, during the past 2.25 million years, was obtained from a marine sediment core of 42 meters in length. This record reveals the presence of 100,000-year periodicity in inclination and intensity, which suggests that the magnetic field is modulated by orbital eccentricity. The correlation between inclination and intensity shifted from antiphase to in-phase, corresponding to a magnetic polarity change from reversed to normal. To explain the observation, we propose a model in which the strength of the geocentric axial dipole field varies with 100,000-year periodicity, whereas persistent nondipole components do not.

 

[Skyhunter]

Thanks I will try and read it today.

 

[Skyhunter]

I could find no validation for the intensity of the magnetic field intensity being 5-6 times stronger than during the last glaciation. In fact what I read offered evidence that overall it remains fairly constant over time, weakening during reversals.

http://www.terrapub.co.jp/e-library/ecp/pdf/EC0075.PDF

 

[Saul]

I could find no validation for the intensity of the magnetic field intensity being 5-6 times stronger than during the last glaciation. In fact what I read offered evidence that overall it remains fairly constant over time, weakening during reversals.

http://www.terrapub.co.jp/e-library/ecp/pdf/EC0075.PDF

Check figure 9 and compare to paleoclimatic data.

Time Variations in the Geomagnetic Intensity

http://www.eos.ubc.ca/~mjelline/453website/eosc453/E_prints/2001RG000104.pdf

Figure 9. (a) Field variations during the past 75 kyr (North Atlantic paleointensity stack (NAPIS-75)) generated by stacking six independent records from the North Atlantic Ocean [Laj et al., 2000a] plotted with the most recent version of the Sint-200 database (error bars are drawn from the standard deviation around the mean value). These stacks are compared to the composite record of the volcanic database [Perrin and Shcherbakov, 1998] obtained after averaging VADMs within 500- and 1000-yr-long time intervals [Yang et al., 2000] for the past 45 kyr. (b)

The discovery of fast millennium spaced geomagnetic field intensity changes is fairly recent.

http://www.dstu.univ-montp2.fr/LGHF/equip/gaillot/PDF/6_EPSL184.PDF

Wavelet analysis of relative geomagnetic paleointensity at ODP Site 983

As I noted, it appears the solar magnetic field is periodically interrupted. When it restarts a series of massive coronal mass ejections occur. The region of the planet where these CME strike is dependent on planetary tilt and the timing of aphelion (I believe the seasonal timing of aphelion controls which hemisphere the strikes occur in.)

The effect is significantly amplified when the Earth's orbit is more eccentric.

There appears to be a permanent charge difference from the solar core to solar surface. The sunspots help equalize the solar core charge build-up. Evidence to support this statement would be an increase in volcanic activity during solar minimums and super volcanic eruptions during deep solar minimums. What is happening is the planets also become charged and as there is a significant time delay for the planet's core to equalize with the surface of the planet.

When there is a deep solar magnetic cycle interruption, there is a change in the solar system charge balance at the orbit of each planet. As the charge balance on the surface of the planet has changed there is charge movement from the core to the planet's surface to try to equalize. There are multiple solar system observations to support this statement as well as many anomalous terrestrial observations.

 

[Saul]

Something that I found interesting (see papers below) is the inverse relationship of sunspot number and volcanic eruptions. During Maunder and Dalton minimums there are significantly more and larger volcanic eruptions. When the sunspot activity is high there is less volcanic activity.

There is also correlation with earthquakes, however, the paleo earthquake data is difficult to data so the relationship has only been shown for human record history.

The paper at the end of this comment notes the volcanic eruptions are following a millennium periodicity. The paper provided above notes that geomagnetic field intensity also varies with a millennium periodicity.

The paper linked to above showed a set of volcanoes that do not share the same magna chamber yet that erupted within a sort period of time together and that all recorded a geomagnetic excursion when the lava cooled. This finding shows a link between what is causing the geomagnetic field excurion and what is causing a simultaneous volcanic eruption from a set of volcanoes that do not share the same magna chamber.

What it appears is happening is the solar magnetic cycle is interrupted and when it restarts there are very large coronal mass ejections. The CME create a space charge differential in the ionosphere which then creates a potential difference between the planet and the earth. There is a strike from the planet to the Earth which disrupts the geomagnetic field. Depending on the hemisphere where the strike is the geomagnetic field is either strengthened or weakened.

As the core magnetic field time constant is around 3000 years, initially the strike always weakens the geomagnetic field in the region of the strike.

In paleo past the super volcanic eruptions have also correlate with deep solar minimums.

http://adsabs.harvard.edu/abs/1989JGR...9417371S

“Volcanic eruptions and solar activity” by Richard Stothers

The historical record of large volcanic eruptions from 1500 to 1980 is subjected to detailed time series analysis. In two weak but probably statistically significant periodicities of about 11 and 80 yr, the frequency of volcanic eruptions increases (decreases) slightly around the times of solar minimum (maximum). Time series analysis of the volcanogenic acidities in a deep ice core from Greenland reveals several very long periods ranging from about 80 to about 350 yr which are similar to the very slow solar cycles previously detected in auroral and C-14 records. Solar flares may cause changes in atmospheric circulation patterns that abruptly alter the Earth's spin. The resulting jolt probably triggers small earthquakes which affect volcanism. (My comment. This mechanism guess is not correct.)

http://adsabs.harvard.edu/abs/2002AGUFMPP61A0298A

The Role of Explosive Volcanism During the Cool Maunder Minimum

The Dalton Minimum was a period of low solar activity, named for the English meteorologist John Dalton, lasting from about 1790 to 1830.[1] Like the Maunder Minimum and Spörer Minimum, the Dalton Minimum coincided with a period of lower-than-average global temperatures. The Oberlach Station in Germany, for example, experienced a 2.0° C decline over 20 years.[2] The Year Without a Summer, in 1816, also occurred during the Dalton Minimum. The precise cause of the lower-than-average temperatures during this period is not well understood. Recent papers have suggested that a rise in volcanism was largely responsible for the cooling trend.[3]

http://www.pnas.org/content/101/17/6341.full#otherarticles

Analyzing data from our optical dust logger, we find that volcanic ash layers from the Siple Dome (Antarctica) borehole are simultaneous (with >99% rejection of the null hypothesis) with the onset of millennium-timescale cooling recorded at Greenland Ice Sheet Project 2 (GISP2; Greenland). These data are the best evidence yet for a causal connection between volcanism and millennial climate change and lead to possibilities of a direct causal relationship. Evidence has been accumulating for decades that volcanic eruptions can perturb climate and possibly affect it on long timescales and that volcanism may respond to climate change. If rapid climate change can induce volcanism, this result could be further evidence of a southern-lead North–South climate asynchrony. Alternatively, a volcanic-forcing viewpoint is of particular interest because of the high correlation and relative timing of the events, and it may involve a scenario in which volcanic ash and sulfate abruptly increase the soluble iron in large surface areas of the nutrient-limited Southern Ocean, stimulate growth of phytoplankton, which enhance volcanic effects on planetary albedo and the global carbon cycle, and trigger northern millennial cooling. Large global temperature swings could be limited by feedback within the volcano–climate system.

 

[Saul]

The papers in the above comment show there is correlation with solar magnetic minimums with volcanic activity.

This is the paper that provides evidence of multiple volcanoes with different magma chambers all erupting in a short time period and all capturing a geomagnetic excursion.

http://www.agu.org/pubs/crossref/2006/2006GL027284.shtml

Geomagnetic excursion captured by multiple volcanoes in a monogenetic field

Five monogenetic volcanoes within the Quaternary Auckland volcanic field are shown to have recorded a virtually identical but anomalous paleomagnetic direction (mean inclination and declination of 61.7° and 351.0°, respectively), consistent with the capture of a geomagnetic excursion. Based on documented rates of change of paleomagnetic field direction during excursions this implies that the volcanoes may have all formed within a period of only 50–100 years or less. These temporally linked volcanoes are widespread throughout the field and appear not to be structurally related. However, the general paradigm for the reawakening of monogenetic fields is that only a single new volcano or group of closely spaced vents is created, typically at intervals of several hundred years or more. Therefore, the results presented show that for any monogenetic field the impact of renewed eruptive activity may be significantly under-estimated, especially for potentially affected population centres and the siting of sensitive facilities.

 

[Saul]

This is an interesting discussion concerning "Courtillot et al's paper: Are there connections between the Earth's magnetic field and climate?"

The geomagnetic data indicates that something is forcing the geomagnetic field changing the tilt of the geomagnetic field in relationship with the Earth's axis of rotation as well as modulating the intensity of the geomagnetic field. As the planet's core is conductive, currents are induced in the conductive core which work to return symmetry of the geomagnetic field and the Earth's axis of rotation.

The geomagnetic field deflects galactic cosmic radiation (GCR). With strongest GCR deflection at 90 degrees to the magnetic field poles and the weakest GCR deflection at the magnetic poles.

Tilting the geomagnetic field and the creation of large geomagnetic field anomalies brings the magnetic pole down to lower latitudes where there is warmer moist air. GCR has been shown to increase planetary cover and increase rainfall. The increase in planetary cloud cover cools the planet.

The discussion explains both the mechanism and the periodicity of the forcing event. The forcing events vary in magnitude and correlate with solar magnetic cycle minimums. It appears the forcing event is related to the restart of the solar magnetic field mechanism. The paleoclimatic shows immediate cooling when the solar magnetic cycle is interrupted which creates a weak solar heliosphere. (The solar heliosphere also deflects GCR.)

Then when the solar magnetic cycle restarts there is this sudden geomagnetic forcing event that tilts the geomagnetic field and creates a geomagnetic field anomaly which is a region of stronger or weaker field. Whether the forcing event constructively or de-constructively reinforces the geomagnetic field depends on the orientation of the geomagnetic field at the time of event and the hemisphere where the strike occurs.

There is correlation of geomagnetic field intensity with both the amount of tilt of the planet and with eccentricity of the planet's orbit. So if you can imagine the strike event which is controlled by a solar process, its affect on the geomagnetic field depends on the Earth sun distance (orbital eccentricity) and tilt of the planet.

The time constant of the geomagnetic field is 1000s of years, so the affects of a significant geomagnetic field forcing change can persist as opposed to the solar magnetic cycle minimum which is less than 100 years.

The paleoclimatic data shows evidence of multiple forcing events with varying magnitudes of temperature changes. The strongest events are called Henrich events which have a periodicity of 6000 years to 8000 years. There is also a strong cycle with a periodicity of the 1470 years. There is correlation of cosmogenic isotope changes with both the 1470 cycle and the Henrich events.

http://geosci.uchicago.edu/~rtp1/BardPapers/responseCourtillotEPSL07.pdf

Also, we wish to recall that evidence of a correlation between archeomagnetic jerks and cooling events (in a region extending from the eastern North Atlantic to the Middle East) now covers a period of 5 millenia and involves 10 events (see f.i. Figure 1 of Gallet and Genevey, 2007). The climatic record uses a combination of results from Bond et al (2001), history of Swiss glaciers (Holzhauser et al, 2005) and historical accounts reviewed by Le Roy Ladurie (2004). Recent high-resolution paleomagnetic records (e.g. Snowball and Sandgren, 2004; St-Onge et al., 2003) and global geomagnetic field modeling (Korte and Constable, 2006) support the idea that part of the centennial-scale fluctuations in 14C production may have been influenced by previously unmodeled rapid dipole field variations. In any case, the relationship between climate, the Sun and the geomagnetic field could be more complex than previously imagined. And the previous points allow the possibility for some connection between the geomagnetic field and climate over these time scales.

Point 4: We first reiterate the fact that the “claims” made in our paper regarding correlations between cooling periods and archeomagnetic jerks were actually put forward by Gallet et al (2005, 2006). We do note that the causal relationship between cosmic ray flux and cloud cover suggested by Marsh and Svensmark (2000) would result in a correlation opposite to the one we find if the field geometry were axial and dipolar and this is precisely why we propose a mechanism of dipole tilt or non dipole geometry to interpret our observations. Gallet et al (2005) write: “ Another hypothesis is to assume that the incoming charged particles are deflected towards the poles, where the overall low humidity level due to cold temperatures limits cloud formation. If archeomagnetic jerks indeed correspond to periods of strongly inclined dipole, then the charged particles would interact with more humid air from lower latitude environments, leading to significantly larger cloud production and cooling.” And if this happens, there is no need to “overcome the more direct effect", as (mis)understood by BD07 (who seem to understand that a growing axial dipole is superimposed on a tilted dipole, which is not the case).

It is therefore not surprising that the tuned curve should reveal the link between solar activity and O18. It is moreover interesting to note that this correlation, obtained on an Alpine stalagmite, and therefore evidence of the influence of solar variability on climate, is also found in proxies from other regions around the globe: correlation between times of solar minima and cold episodes in western Europe (Magny, 1993; Holzhauser et al, 2005), modulation of precipitation in the tropics in Northern South America and Yucatan (Haug et al, 2001), in Eastern Africa (Verschuren et al, 2000), and Arabia (Neff et al, 2001); influence on droughts in North America (Yu and Ito, 1999).

This is a link to the original paper.

Are there connections between the Earth's magnetic field and climate?

http://sciences.blogs.liberation.fr/home/files/Courtillot07EPSL.pdf

 

[Xnn]

About this paper:

It suggests that solar irradiance could have been a major forcing function of climate until the mid-1980s, when “anomalous” warming becomes apparent.

So, only greenhouse gases can explain the warming of the last 25 years.

 

[mheslep]

About this paper:

So, only greenhouse gases can explain the warming of the last 25 years.

That does not logically follow from the statement in the Courtillot et al abstract you quoted.

 

[Xnn]

There has been a lot of warming over the last 25 years.
However, the paper does not come up with a solar explanation for it.

We know that greenhouse gases have been rising steadily for over a hundred years.
Initially, the influence of rising greenhouse gases were small compared to short term fluctuations such as those from solar changes. However, over time, the influence of greenhouse gases have accumulated and are now dominating climate change. Short term fluctuations still exist, but the overall warming trend is unmistakable.

Solar influences are at nearly a 100 year minimum and should be leading to significant global cooling. However, the last 2 months have both been the 2nd warmest months (September & October) since 1880. So, again we see that solar theories cannot explain current climate change.

I'm open minded about solar theories, but nothing in this thread has shown that they could reasonably be used to dismiss the influence of greenhouse gases.

 

[seycyrus]

Are you guys aware that the American Physical Society is now emailing its members to see how they feel about their official statement regarding AGW, and a proposed revised statement offered by some of its fellows?

 

[Xnn]

No, but if this is the "Official" statement, then I can see why.
IMO, it's a stretch to state that security and human health will be impacted by climate change more so than from routine population increases or all the wars that we have.

Emissions of greenhouse gases from human activities are changing the atmosphere in ways that affect the Earth's climate. Greenhouse gases include carbon dioxide as well as methane, nitrous oxide and other gases. They are emitted from fossil fuel combustion and a range of industrial and agricultural processes.

The evidence is incontrovertible: Global warming is occurring. If no mitigating actions are taken, significant disruptions in the Earth’s physical and ecological systems, social systems, security and human health are likely to occur. We must reduce emissions of greenhouse gases beginning now.

Because the complexity of the climate makes accurate prediction difficult, the APS urges an enhanced effort to understand the effects of human activity on the Earth’s climate, and to provide the technological options for meeting the climate challenge in the near and longer terms. The APS also urges governments, universities, national laboratories and its membership to support policies and actions that will reduce the emission of greenhouse gases.

 

[Wagmc]

So, only greenhouse gases can explain the warming of the last 25 years.

TSI is not the only component of solar forcing. You continue to ignore indirect (magnetic) effects as well as the recent discovery that UV modulates ozone production over the poles, which is an exothermic reaction.


http://www.iop.org/EJ/abstract/0004-637X/705/1/926/"

New study confirms that solar magnetic activity drives the solar wind, which, if Svensmark is correct (and we'll soon know) modulates cloud cover and Earth temperatures.

And solar magnetic activity continues to decline even as cycle 24 ramps up.
http://www.swpc.noaa.gov/ftpdir/weekly/RecentIndices.txt"

 

[Xnn]

I'm not ignoring the other components of solar forcing. UV modulation of ozone does impress me as a plausable mechanism. However, I haven't see a peer reviewed paper that quantifies it or an paper that quantifies any solar mechanism for the last 25 years of warming.

We are also about 2 years into the most significant solar minimum since 1912, and yet global temperatures are very near all time instrumented highs.

 

[Saul]

A significant portion of the 20th century warming is hypothesized to be caused by solar wind bursts. Solar wind bursts remove cloud forming ions and hence makes it appear increases in GCR does not cause an increase in planetary cloud cover.

The solar wind bursts were created by coronal holes that moved down to lower latitudes of the sun late in the cycle of cycles 22 and cycle 23. As noted below, although cycle 24 appears to be a rump or abrupt Maunder minimum, there are three times as many solar wind bursts being produced.

Solar wind bursts remove cloud forming ions by a process that is called "electroscavenging".
This paper explains how GCR and solar magnetic cycle changes are hypothesized to change planetary climate.

See section 5a) Modulation of the global circuit in this review paper that explains how solar wind bursts increases in the global electric circuit hence removing cloud forming ions. Somewhat interesting solar wind burst increased by a factor of 2.5 in the later part of the 20th century in a manner that directly correlates with the warming and cooling of the later part of the 20th century.

http://www.utdallas.edu/physics/pdf/Atmos_060302.pdf

The solar wind bursts are now starting to abate, so we should and are seeing increased colder weather in both hemispheres.

The same review paper summarizes the data that does show correlation between low level clouds and GCR.

http://sait.oat.ts.astro.it/MSAIt760405/PDF/2005MmSAI..76..969G.pdf

Once again about global warming and solar activity K. Georgieva, C. Bianchi, and B. Kirov

We show that the index commonly used for quantifying long-term changes in solar activity, the sunspot number, accounts for only one part of solar activity and using this index leads to the underestimation of the role of solar activity in the global warming in the recent decades. A more suitable index is the geomagnetic activity which reflects all solar activity, and it is highly correlated to global temperature variations in the whole period for which we have data.

In Figure 6 the long-term variations in global temperature are compared to the long-term variations in geomagnetic activity as expressed by the ak-index (Nevanlinna and Kataja 2003). The correlation between the two quantities is 0.85 with p<0.01 for the whole period studied. It could therefore be concluded that both the decreasing correlation between sunspot number and geomagnetic activity, and the deviation of the global temperature long-term trend from solar activity as expressed by sunspot index are due to the increased number of high-speed streams of solar wind on the declining phase and in the minimum of sunspot cycle in the last decades.

If the Sun is so quiet, why is the Earth ringing? A comparison of two solar minimum intervals (Cycle 24 and Cycle 23/22)

Observations from the recent Whole Heliosphere Interval (WHI) solar minimum campaign are compared to last cycle's Whole Sun Month (WSM) to demonstrate that sunspot numbers, while providing a good measure of solar activity, do not provide sufficient information to gauge solar and heliospheric magnetic complexity and its effect at the Earth. The present solar minimum is exceptionally quiet, with sunspot numbers at their lowest in 75 years and solar wind magnetic field strength lower than ever observed. Despite, or perhaps because of, a global weakness in the heliospheric magnetic field, large near-equatorial coronal holes lingered even as the sunspots disappeared. Consequently, for the months surrounding the WHI campaign, strong, long, and recurring high-speed streams in the solar wind intercepted the Earth in contrast to the weaker and more sporadic streams that occurred around the time of last cycle's WSM campaign.

 

[Wagmc]

I haven't see a peer reviewed paper that quantifies it or an paper that quantifies any solar mechanism for the last 25 years of warming

I'll post you some references. There are several.

We are also about 2 years into the most significant solar minimum since 1912, and yet global temperatures are very near all time instrumented highs.

Only if you look at the contaminated surface record. Satellites don't show that "all time" high.

As for "where's the cooling?" Ha. Where's the warming? If CO2 is such a significant driver of temps, they why no warming since 2000?

This is a water planet. Lots of studies put the solar lag at 5 to 15 years due to the huge ocean sinks. Even as we speak a little el nino is transferring heat to air, where it will be convected away. The planet is cooling.

 

[mheslep]

I'll post you some references. There are several.



Only if you look at the contaminated surface record. Satellites don't show that "all time" high.

1998 aside, sure they do, at least over the three decades of satellite records.
http://upload.wikimedia.org/wikipedia/commons/7/7e/Satellite_Temperatures.png

 

[Saul]

I'm not ignoring the other components of solar forcing. UV modulation of ozone does impress me as a plausable mechanism. However, I haven't see a peer reviewed paper that quantifies it or an paper that quantifies any solar mechanism for the last 25 years of warming.

We are also about 2 years into the most significant solar minimum since 1912, and yet global temperatures are very near all time instrumented highs.

Yes, however, as noted solar wind bursts continue to be produced by the sun even though the solar magnetic cycle is at a 100 year minimum.

(See Paper: If the Sun is so quiet, why is the Earth ringing? A comparison of two solar minimum intervals (Cycle 24 and Cycle 23/22)).

http://www.agu.org/pubs/crossref/2009/2009JA014342.shtml

The solar wind bursts remove cloud forming ions by the process of electroscavenging which results in a decrease in low level clouds and an increase in high level clouds. See Tinsley's paper below.

The solar wind bursts are starting to abate. Based on the mechanisms what should be observed now is an increase in low level clouds and a decrease in high level clouds due to the increased GCR, at latitudes from 40 degree to 60 degree both hemispheres.

The decrease in high level clouds will result in exceptionally cold nights in the higher latitude regions which should result in increased sea ice both hemispheres.

In addition as the global electric circuit will be reduced it is expect that there will be increased cloud cover in the tropics.

The cooling will be moderate by the El Nino event, so the full effect of the cooling may not be expected until the winter of 2010/2011.

http://upload.wikimedia.org/wikipedia/commons/7/7e/Satellite_Temperatures.png

http://www.utdallas.edu/physics/pdf/Atmos_060302.pdf

4b. Altitude and solar cycle dependencies

Ambient ions are continuously generated by galactic cosmic rays as noted earlier, with the magnitude of the ionization rate variations being a function of latitude and altitude. During a solar cycle, the values of Q vary by ~ 20 -25% in the upper troposphere and ~5-10% in the lower troposphere for high latitudes, and by ~4-7% in the upper troposphere and ~3-5% in the lower troposphere for low latitudes [Ney, 1959]. The effect of such systematic change in ionization rate on the altitude profile for the production of ultrafine particles has been studied by Yu [2002].

Figure 4.2 shows the total condensation nuclei bigger than 3nm (Nd>3 nm) after three hours of simulations at different altitudes. The line with open circles is for the baseline Q values while the line with filled circles is for Q values 20% over the corresponding baseline values. ….The neutralization by ion-ion recombination will make the growing charged clusters lose their growth advantage and the resulting neutral clusters may dissociate if smaller than the critical size. At typical [H2SO4] where significant nucleation has been observed, for very low Q most of the ion clusters have sufficient time to reach the larger stable sizes prior to recombination and the nucleation rate is limited by Q. As Q (or altitude) increases, ion concentration increases but the lifetime of ions decreases and hence the fraction of ions having sufficient time to grow to the stable sizes decreases. As a result, the total number of particles nucleated first increases rapidly but later on decreases as Q (or altitude) increases. The altitude of the turning point is around 4 km under the vertical profiles assumed in this study.

It is clear from Figure 4.2 that an increase in GCR ionization rate associated with solar activity leads to an increase in the ultrafine production rate (i.e., dN/dQ > 0) in the lower troposphere (as indicated by the arrows) but a decrease in the ultrafine production rate (i.e., dN/dQ < 0) in the upper troposphere (as indicated by the arrows). In the middle troposphere, dN/dQ changes sign and the average value of dN/dQ is small compared to that of lower and upper troposphere.

5. The Global Electric Circuit and Electroscavenging

5a. Modulation of Jz in the global circuit.

The global electric circuit was illustrated pictorially in Figure 3.1, and a schematic circuit diagram is given in Figure 5.1. General properties of the circuit have been reviewed by Bering et al. [1998[. Earlier comprehensive reviews have been given by NAS [1986] and Israël [1973]. The polar potential pattern is superimposed on the thunderstorm-generated potentials. In a given high latitude region the overhead ionospheric potential, Vi is the sum of the thunderstorm-generated potential and the superimposed magnetosphere-ionosphere generated potential for that geomagnetic latitude and geomagnetic local time. During magnetic storms the changes in Vi from the mean can be as high as 30% within regions extending up to 30km of latitude out from the geomagnetic poles [Tinsley et al.1998].

As indicated in Figure 5.1, horizontal potential differences of order 100 kV are generated, high on the dawn side and low on the dusk side, producing corresponding changes in Vi and Jz. The dawn-dusk potential difference has a strong dependency on the product of the solar wind velocity, vsw, and the Bz(GSM) north-south solar wind magnetic field component [Boyle et al., 1997].

 

[mheslep]

...The solar wind bursts are now starting to abate, so we should and are seeing increased colder weather in both hemispheres...

All else remaining the same, i.e., ONLY if all other forcings were to remain a net constant, which they never do.

 

[Wagmc]

1998 aside, sure they do, at least over the three decades of satellite records.

Uhm...no. I see a plateau since 2000, and the most recent temps are NOT record highs.

Just because you read it in the news does not make it a fact.

This was in response to the statement:

We are also about 2 years into the most significant solar minimum since 1912, and yet global temperatures are very near all time instrumented highs.

your lovely chart makes my point nicely, although the clever use of scaling makes temps looks like...uhm...a hokey stick. Here's another view direct from UAH that puts it in a little better perspective.

http://www.drroyspencer.com/wp-content/uploads/UAH_LT_1979_thru_Oct_09.jpg

I'm still seeing a plateau after 2000. No record-breaking warming in the last two years. This in spite of continuing increases in CO2, but I digress...

 

[mheslep]

Uhm...no. I see a plateau since 2000, and the most recent temps are NOT record highs.

Just because you read it in the news does not make it a fact.

[...]
your lovely chart

Its not mine.

makes my point nicely, although the clever use of scaling makes temps looks like...uhm...a hokey stick.

The attitude doesn't help. Please check it at the door.

Here's another view direct from UAH that puts it in a little better perspective.

http://www.drroyspencer.com/wp-content/uploads/UAH_LT_1979_thru_Oct_09.jpg

Same data. So what?

I'm still seeing a plateau after 2000.

Yes temperatures are at plateau for the last few years. A HIGH plateau.

No record-breaking warming in the last two years.

So? The statement was "temperatures are very near all time instrumented highs."Indeed they are. Nobody said new records. Please don't attribute that which was not said. A plateau maintains the highs.

 

[Xnn]

https://www.physicsforums.com/attachment.php?attachmentid=21606&stc=1&d=1257469597

The above image of Arctic temperatures over the last 2000 years is based on a very recent study.

Observe that over the fist 1900 years, there were indeed several ~100 year long periods of
warming and cooling that might be attributed to changes in solar forcing. There is also a
clear overall cooling trend attributed to changes in Earth's orbit (gradually lowering of solar
insolation at 65N; AKA Milankovitch theory).

If one looks closely, the Maunder Minimum (1645 to 1715) is discernible. There is also the
Dalton Minimum (1790 to 1815), but I can't clearly pick it out in the temperature record.
However, what really sticks out is that there really are no good solar theories that can
explain the last 100 years and especially the last 25 years of warming.

I'm trying to be open minded here!The source document is found at the following:

http://www.ucar.edu/news/releases/2009/arctic2k.jsp

 

[Saul]

The above image of Arctic temperatures over the last 2000 years is based on a very recent study.

Observe that over the fist 1900 years, there were indeed several ~100 year long periods of
warming and cooling that might be attributed to changes in solar forcing. There is also a
clear overall cooling trend attributed to changes in Earth's orbit (gradually lowering of solar
insolation at 65N; AKA Milankovitch theory).

If one looks closely, the Maunder Minimum (1645 to 1715) is discernible. There is also the
Dalton Minimum (1790 to 1815), but I can't clearly pick it out in the temperature record.
However, what really sticks out is that there really are no good solar theories that can
explain the last 100 years and especially the last 25 years of warming.

I'm trying to be open minded here!

The source document is found at the following:

http://www.ucar.edu/news/releases/2009/arctic2k.jsp

Xnn,
How did planetary temperature or temperature in the Northern Hemisphere change during the same period?

Why do you believe that graph corresponds to actual arctic temperatures. What proxy did the authors use to determine arctic temperatures for the period?

 

[Saul]

If the GCR theory is correct, then the planet must start to cool, as GCR is 19% higher than past periods and the solar wind bursts are starting to abate.

There is starting to be some observational evidence that the planet is cooling such as the coldest US October in 110 years and the coldest New Zealand October in 45 years. When the current El Nina dissipates perhaps there will be more observational evidence. November appears to be warmer, however, the warmer November is likely El Nina.

A significant portion of the 20th century warming is hypothesized to be due to solar wind bursts removing cloud forming ions by the process called "electroscavenging". Even though GCR is high if the solar wind bursts remove the cloud forming ions then the affects of GCR will not be observed.

Planetary temperature is closed correlated with the parameter Ak which is a measure of the solar wind and solar wind bursts. (See my comments above for links to papers.)


http://www.agu.org/pubs/crossref/2009/2009JA014342.shtml

If the Sun is so quiet, why is the Earth ringing? A comparison of two solar minimum intervals (Solar Cycle 24 compared to past solar cycles.)

Observations from the recent Whole Heliosphere Interval (WHI) solar minimum campaign are compared to last cycle's Whole Sun Month (WSM) to demonstrate that sunspot numbers, while providing a good measure of solar activity, do not provide sufficient information to gauge solar and heliospheric magnetic complexity and its effect at the Earth. The present solar minimum is exceptionally quiet, with sunspot numbers at their lowest in 75 years and solar wind magnetic field strength lower than ever observed. Despite, or perhaps because of, a global weakness in the heliospheric magnetic field, large near-equatorial coronal holes lingered even as the sunspots disappeared. Consequently, for the months surrounding the WHI campaign, strong, long, and recurring high-speed streams in the solar wind intercepted the Earth in contrast to the weaker and more sporadic streams that occurred around the time of last cycle's WSM campaign. In response, geospace and upper atmospheric parameters continued to ring with the periodicities of the solar wind in a manner that was absent last cycle minimum, and the flux of relativistic electrons in the Earth's outer radiation belt was elevated to levels more than three times higher in WHI than in WSM.

 

[mheslep]

If the GCR theory is correct, then the planet must start to cool, as GCR is 19% higher than past periods and the solar wind bursts are starting to abate.

Saul, for that statement to hold, you'd have to show, at a minimum, what fraction GCR contributes to planetary energy budget. I have no idea, but if its impact is, say, 5% of albeto based radiation return to space then a 200% increase in GCR won't mean the planet as a whole will 'start to cool'.

There is starting to be some observational evidence that the planet is cooling such as the coldest US October in 110 years and the coldest New Zealand October in 45 years. When the current El Nina dissipates perhaps there will be more observational evidence. November appears to be warmer, however, the warmer November is likely El Nina.

What's the point of saying, aha, there's some cooling (or warming) at some localized point on the planet, in isolation from the rest of planet?

 

[Saul]

Saul, for that statement to hold, you'd have to show, at a minimum, what fraction GCR contributes to planetary energy budget. I have no idea, but if its impact is, say, 5% of albeto based radiation return to space then a 200% increase in GCR won't mean the planet as a whole will 'start to cool'.

What's the point of saying, aha, there's some cooling (or warming) at some localized point on the planet, in isolation from the rest of planet?

mheslep,
Based on the mechanisms and past cooling events the planet will overcome the current El Nina and start cooling this winter. The cooling will continue reaching the new equilibrium low in about 5 years.

The cloud data indicates as much as 75% of the planet's 20th century warming was due to solar wind bursts that created a space charge in the ionosphere that removed ions from the atmosphere by the mechanism that is called electroscavenging which resulted in less clouds which caused the planet to warm.

Electroscavenging was stopped (coronal holes are starting dissipate), the solar heliosphere is at its lowest level in almost 50 years, GCR has increased by 19% and based on past solar magnetic deep minimums, GCR will increase to around 30%.

So as there is both a cessation of electroscavenging and an increase in GCR there will be an increase in low level planetary cloud cover which will cause increase planetary low level planetary cloud cover and cooling.

Higher GCR also causes a reduction in high level cloud cover. High level clouds warm the planet particularly at high latitudes in the winter.

The net result will be record cold winter temperatures at high latitudes and more clouds over the oceans as the atmosphere over the oceans is ion poor.

The geomagnetic changes later, perhaps a number of decades later based on the paleoclimatic record.

I am saying the planet has in the past abruptly cooled when the sun went into a deep solar minimum. I have provided a series of paper that show there are abrupt changes to the geomagnetic field inclination and magnitude that correlate with the abrupt cooling event. The hypothesized mechanism is the sun goes into a deep solar magnetic cycle minimum. When the sun restarts there are a series of massive coronal mass ejections which create a space charge differential in the ionosphere which cause a flash over from the ionosphere to the planet's surface.

The paper copied above shows evidence of 10 such events in the last 10,000 years. Geomagnetic specialists have coined the term archomagnetic jerks for the observations.

The paper I linked to above shows 5 New Zealand volcanoes that do not share the same magma chamber that suddenly erupted within a period of 100 years and that all capture in their magma flow evidence of a geomagnetic field direction excursion that occurs with in the period.http://www.esd.ornl.gov/projects/qen/transit.html


Sudden climate transitions during the Quaternary

Until a few decades ago it was generally thought that all large-scale global and regional climate changes occurred gradually over a timescale of many centuries or millennia, scarcely perceptible during a human lifetime. The tendency of climate to change relatively suddenly has been one of the most suprising outcomes of the study of Earth history, specifically the last 150,000 years (e.g., Taylor et al., 1993). Some and possibly most large climate changes (involving, for example, a regional change in mean annual temperature of several degrees celsius) occurred at most on a timescale of a few centuries, sometimes decades, and perhaps even just a few years. The decadal-timescale transitions would presumably have been quite noticeable to humans living at such times,

Initial evidence from the GRIP ice core evidence (Dansgaard et al., 1993; Taylor et al. 1993) indicated that the Eemian (My comment last interglacial period) was punctuated by many short-lived cold events, as shown by variations in electrical conductivity (a proxy for windblown dust, with more dust indicating colder, more arid conditions) and stable oxygen isotopes (a proxy for air temperature) of the ice were used by these workers infer the climatic conditions during the Eemian. The cold events seemed to last a few thousand years, and the magnitude of cooling was similar to the difference between glacial and interglacial conditions; a very dramatic contrast in climate. Furthermore, the shifts between these warm and cold periods seemed to be extremely rapid, possibly occurring over a few decades or less.

http://www.geo.arizona.edu/palynology/geos462/8200yrevent.html

The 8200 B.P. event, "lasted four hundred years (6400-6000 B.C.) and, like the Younger Dryas, generated abrupt aridification and cooling in the North Atlantic and North America, Africa, and Asia (Alley et al. 1997; Barber et al. 1999; Hu et al. 1999; Street-Perrot and Perrot 1990). This event is well-known from the GISP2 analyses, within which it is second only to the Younger Dryas in magnitude of some measurable variables (Alley et al. 1997; Figure 22). The pronounced West Asian signal for the 8200 B.P. event is present in Soreq Cave speleothem records (Bar-Matthews et al. 1999), Negev snail isotope variability (Goodfriend 1991, 1999), low Dead Sea levels (Frumkin et al. 1994), and the geochemistry of stage E to stage F transition at Lake Van (Lemcke and Sturm 1997). . .

."

 

[mheslep]

The cloud data indicates as much as 75% of the planet's 20th century warming was due to solar wind bursts that created a space charge in the ionosphere that removed ions from the atmosphere by the mechanism that is called electroscavenging which resulted in less clouds which caused the planet to warm.

Okay, sorry, what cloud data? I've missed the link.

I am saying the planet has in the past abruptly cooled when the sun went into a deep solar minimum. I have provided a series of paper that show there are abrupt changes to the geomagnetic field inclination and magnitude that correlate with the abrupt cooling event. The hypothesized mechanism is the sun goes into a deep solar magnetic cycle minimum. When the sun restarts there are a series of massive coronal mass ejections which create a space charge differential in the ionosphere which cause a flash over from the ionosphere to the planet's surface.

Okay, but the Adams-Maslin-Thomas paper you referenced proposes no hard connection with these changes. It widely discusses, or even simply muses about, only possibilities as I read it, of a dozen different long term climate effects.

 

[Xnn]

Data currently available for the Southern Hemisphere is too sparse to allow for construction of a temperature timeline with similar resolution to that in message #138.

https://www.physicsforums.com/showpost.php?p=2429570&postcount=138

Notice that the graph in message #138 is one of the newest reconstructions with much higher resolution than previously found for the Arctic. It's based on sediments in lakes.
What's remarkable about the graph is that one can pick out a cooling period concident with the Maunder Minimum. So, sunspots and solar changes related to sunspots probably did have a noticeable influcence global temperatures. However, due to their cyclic nature, we can't say that they drove climate over periods greater than ~100 years.

What has happened over the last century in the Arctic is unprecidented over the last 2000 years. The chances of it being caused by changes in sunspots, solar winds, UV spectrum shifts, cosmic rays and everything related is zilch.

Prior to 1910, solar and orbital changes were driving the climate over ~100 years time scales with El Nino/La Nina over time scales of <10 years. Since about 1950, changes in greenhouse gases are dominating climate change. Solar and orbital changes still exist and play a role, but are probably about an order of magnitude smaller than those from greenhouse gases.