|Jan29-07, 05:22 AM||#52|
Global warming causality
The adventures of physics.
|Jan29-07, 05:25 AM||#53|
The adventures of physics.
|Jan30-07, 06:01 PM||#54|
<Below a quote from a Physics Text book, claiming that human caused carbon-dioxide levels are proven>
Please reread my original post. The question was how much those human caused CO2 levels impact global temperature. The answer appears to around 1K in steady state, as mentioned by Andre. Projections above or below that are the result of feedback factors not well understood.
|Jan31-07, 04:14 AM||#55|
That 1K is a standard basic black body sensitivity for doubling CO2. in the real world things are more complex, it could be more but it's likely far less.
So if we assume 280ppmv preindustrial around 1850AD, and 380 now we are far from doubling yet the temp has already increased 0,6 degrees. Most of that happened however prior to 1940 after which some cycles came in more pronounced. So you cannot attribute that warming to dramatic increase of CO2. It's clear that natural factor play the dominant role at that time, so why not now?
|Jan31-07, 03:16 PM||#56|
And what is more practical as doing an experiment?
The scientific debate (is there a debate? the human-caused carbo levels and global warming effect is not in any doubt any more) can go forever, without resolvin anything.
By the way, so-called "scientists" are paid by oil companies to spread disinformation about the CO2 issue.
By the way.... my post was a bit of cynism of course, as if what I suggested (stopping fossil fuel usage) could be done....
This does not prevent us however for inventing measures that can reduce the problem.
|Feb1-07, 05:32 PM||#57|
Like Nesp, I'm just a guy trying to figure this out. Re the textbook quote:
"CO2 in the atmosphere between 1800 and 2005 has increased from 280 to 380 parts per million. It is known without doubt that this increase is due to human burning of fossil fuels, and not to natural sources such as the oceans or volcanoes."
If the increase is "without doubt" caused by human burning of fossil fuels, does that mean decreased carbon sink capacity from human deforestation is not a factor? If it is a factor, what's the relative contribution of deforestation vs anthropogenic CO2 emissions in increasing CO2 levels?
I often see increasing atmospheric CO2 levels described as a simple imbalance between emission and absorption capacity.
But I read all anthropogenic CO2 output is just about 3% of natural CO2 output. Is that number right? If so, why are atmospheric CO2 levels increasing so rapidly? That implies the biosphere has virtually no adaptability -- no excess carbon sink capacity. If bumping the total CO2 output (natural + anthropogenic) by 3% creates this, doesn't that imply the solution is to reduce it by an almost equal amount?
This may be naive, but if the earth's carbon cycle is that delicate, it seems the required solution is far more drastic than cutting anthropogenic emissions by 20%. Atmospheric CO2 started increasing at the beginning of industrialization when anthropogenic emissions were a fraction of today. If global CO2 emissions were reduced by 70%, the historical graphs I've seen imply atmospheric levels would still be increasing, only slower.
Do we have any idea what reduction in global anthropogenic CO2 emissions is required to achieve equilibrium in atmospheric CO2 levels? If so, what's the basis for and confidence in that number?
I've looked through a bunch of GW stuff, and can't find clear answers to these. Would appreciate any explanations or pointers.
|Feb1-07, 06:12 PM||#58|
A neat little picture here.
The most important part of the carbon cycle is the balance at the sea surface. Changes in ocean - atmosphere fluxes, with an order of magnitude more substance than anthrpogenic CO2, would have a strong effect on the atmospheric CO2. But then again, even before the K/T boundary some more than 65 million years ago the atmospheric the pCO2 (of leaf stomata proxies)was between 300-500ppmv, where it is still today:
|Feb2-07, 10:25 AM||#59|
The argument that increased atmospheric CO2 levels are anthropogenic based on C14/C12 ratios seems pretty good. I'd be interested if anyone has a contrary opinion to that argument.
Re amt of increase from anthropogenic emissions vs reduction in carbon sink capacity due to deforestation, the new IPCC report indirectly addresses this. http://www.ipcc.ch/SPM2feb07.pdf
It says annual anthropogenic emissions are about 7 GtC per year, whereas "land use changes" create about 1.6 GtC per year. Don't know if that's effective creation due to reduction of sink capacity or actual emissions from burning. Either way the % contribution of land use changes vs hydrocarbon emissions seems small.
However -- there may be a fundamental math error in the new IPCC report. Could someone please cross-check me on this?
On page 12, it says "model studies suggest that to stabilize at 450 ppm carbon dioxide, could require that cumulative emissions over the 21st century be reduced from an average of approximately 670 [630 to 710] GtC to approximately 490 [375 to 600] GtC."
I think they forgot to account for the annual increase in hydrocarbon consumption for the nominal "no change" case. Unless I'm mistaken, this is a fundamental error that greatly impacts the calculation of required emission reduction, and any related planning.
E.g, current world anthropogenic CO2 emissions are about 7 GtC per year. If it was capped at that level tomorrow, over the 21st century cumulative emissions would be about what IPCC says: 670 GtC. They apparently just multiplied 93 years by 7 GtC/yr.
However world energy use (of which hydrocarbons make about 85%) increases at about 1.5% to 2% per year, as it's keyed to economic output and development. Like compound interest on a bank account, that makes a vast difference over time.
Thus the baseline number is NOT 670 GtC cumulative emissions over the 21st century, but 7 GtC/yr increasing at a 1.5% to 2% compounded annual rate.
I don't know the formula, but it's the same one to calculate final balance of a non-interest-bearing bank account assuming annual contributions increase at x%. It doesn't matter whether annual growth rate in energy consumption is 1%, 1.5% or 2%. Over a century the difference is vast.
At 1.5% annual growth, the actual "no change" case would be thousands of cumulative GtC released over the 21st century, NOT 670 GtC.
My question is did IPCC model that, or just 670 GtC. This affects everything -- how bad the perceived problem is, amount of required reduction to achieve a given benefit, etc.
It can't be such a simple error. Have I missed something?
|Feb2-07, 05:56 PM||#60|
OK I found the formula. It is:
FV = D * ((1+r)^T - 1) / r , where:
FV = Cumulative carbon emissions in GtC over 93 yrs (2007-2100)
D = 1st yr emissions (7.0 GtC)
r = annual % increase of emissions
T = time in yrs (93 yrs)
So rather than the baseline IPCC number of 670 GtC over the remaining 21st century, the actual baseline emissions would be:
1857 GtC @ 2% annual growth
1396 GtC @ 1.5% annual growth
The EIA projects about an approx. 2% annual growth in hydrocarbon energy consumption over the next quarter century. If that continued over the remainder of the 21st century, the baseline number is 1857 GtC.
Hence the reduction required is NOT from 670 GtC down to 490 GtC, but from 1857 GtC down to 490 GtC.
That is a big difference. I'd be very interested in knowing which input value was modeled -- 1857 GtC or 670 GtC.
This affects everything -- climate modeling, how achievable the needed reductions are, etc.
That superficially looks like a 74% reduction in hydrocarbon energy consumption is required. But it's worse than that. You'd have to virtually eliminate hydrocarbon energy. Why?
Because no matter what technology or how ambitious the plan, it takes time to implement. Hence the 1st few decades you're still burning hydrocarbons at the current rate (inc'l annual increase). All that counts against the IPCC 21st century cumulative limit of 490 GtC.
That means in later decades of the 21st century, much greater reductions are needed than 74%. The entire globe would have to mostly run on fusion or something like that, otherwise you'll go over 490 GtC cumulative emissions. And even that results in atmospheric CO2 increasing to 450 ppm, significantly above current levels.
|Feb2-07, 06:15 PM||#61|
Bottom line is that you'dhave to believe that climate is so sensitive to CO2 radiattive forcing. But it's not. The numbers of IPCC require an amplification of the CO2 greenhouse effect known as positive feedback. Here is the sensitivity at thermal equilibrium, fora US standard atmosphere about 0,97 C increase per doubling with no feedbacks:
but thermal equilibrium is a long lasting process. So you'd need a lot of positive feedback, which is non existent.
|Mar4-07, 01:13 PM||#62|
A) 20 th Century Global Warming
1) 20th Century Solar Changes & Global Cloud Cover
As the thread on clouds notes, the sun is at its highest activity in 8 kyrs, the solar large scale magnetic field has doubled in the last 100 yrs, and in the last 20 years solar coronal holes have began to move towards the solar equator (The solar coronal hole creates a high speed solar wind when it passes in the earth's direction).
The cloud thread in this forum describes a mechanism where rapid increases in the solar wind, causes an increase in the Global Electric Circuit which causes a potential difference between equator and Polar regions. The potential difference it is hypothesized (and data supports) removes atmospheric ions which causes low level clouds to dissipate. As the GCR created ions are removed, electroscavenging makes it appear that the earth's temperature is no longer correlated with the solar cycle and GCR level.
A doubling of the sun's large scale magnetic field will shield the earth from Galactic Cosmic Rays (GCR). Satellite data (See cloud thread, Palle's paper) indicates that there is a 99.5% correlation with changes in GCR and low level cloud level (over a 20 year period). An increase in GCR causes an increase in low level clouds and a decrease in GCR causes a decrease in low level clouds. The correlation between clouds and GCR holds up until 1993 at which time the satellite data indicates that low level clouds start to be reduced, which is consistent with the 'electroscavenging' process.
Palle estimates the warming due to the reduction in cloud cover 1993 to 2001 is 7.5 W/m2 or roughly three times the estimated forcing for CO2 (2.5 W/m2).
Some scientists questioned whether Palle's interpretation of the satellite cloud data was correct. Palle et al, then measured the earth's albedo using telescopes that measured the earthshine reflected off of the moon. The earthshine data supported the satellite data.
2. CO2 and Global Warming
Is it possible that solar changes caused the majority of the 20th century warming? Yes, if Palle's data and analysis is correct. A separate thread should be started to discuss what is know concerning CO2 and its affects on the planet's temperature. Recent data indicates that there have been times in the planets history when CO2 levels have been high and the planet has been cold and visa versa. The relationship between CO2 and planetary temperature is not linear and it appears that there may be a strong negative feedback affect of clouds which regulates planetary temperature (stops the planet from warming when CO2 levels are high) rather than the assumed very strong positive feedback of water vapour with increasing planetary temperature that was assumed by the IPCC and is currently used in the climate models.
B) 21th Century Global Cooling
The 20th century warming (sun at its highest level in 8kyrs, doubling of solar large scale magnetic field, and the coronal holes moving towards the solar equator), seems to be a Henrich event which is named after the climatologist that discovered the semi-periodic event. A Henrich event is a warming of the planet which is then followed by an abrupt cooling (3C drop in temperature, 2C in five years, Younger Dryas, and then roughly 1C drop over a hundred years as the oceans cool.)
There is not consensus as to what causes the observed warming and abrupt cooling, however, there is evidence that the Younger Dryas cooling event could have been caused by a solar event. (i.e. There is a very large increase in cosmogenic nucleons, in the sea sediment data and ice core data which indicates a large increase in GCR flux during the Younger Dryas period.)
Attached is a link to the paper: "Reduced solar activity as a trigger for the start of the Younger Dryas?" that discusses the Younger Dryas Cooling event.
It should be noted that the Younger Dryas paper was written in 2000 before Palle's paper and findings. The Younger Dryas paper assumes the solar event is only a change in solar irradiance, rather than a change in planetary cloud cover which would be consistent with Palle's findings.
All of the public discussion associated with climate change has been concerning global warming and strongly focused on CO2. Attached is a link to lecture material by Strong that shows how the climate has changed over the last 100,000 years. Based on the climatic record interglacial periods are brief and end abruptly.
John Stone, Climate Record Over the Last 100,000 years
When you look at the above climatic record, what do think, is causing the abrupt changes in planetary temperature and the glacial/interglacial cycle?
|Mar4-07, 03:58 PM||#63|
Svensmark, H. 2007. Cosmoclimatology: a new theory emerges. Astronomy & Geophysics 48: 1.18-1.24.
You can take it from me that this was norm rather than anomalous, warm dry Younger Dryas summers. It should also be noted that sea surface temperatures dropped significantly during the preceding "warm" Bolling Allerod. Low SST inhibit cloud forming. The cause of that sequence may have been the Amazon fan clathrate destabilisation event:
|Mar13-07, 02:24 PM||#64|
|Mar16-07, 10:46 PM||#65|
In response to Andre's Comment 63 concerning a request for recent GCR papers.
Svensmark's paper concerns the Antarctic anomaly, which is also called the polar see-saw. The Polar see-saw is the term used to describe the phenomena where when the Atlantic region warms the Antarctic cools and vice versa. While other hypothesis (such as ocean currents) have been proposed to explain the polar see-saw, they cannot explain why the change is simultaneous. (i.e. If the effect has due to ocean currents one would expect a delay from hemisphere to hemisphere, as the ocean currents take time to change) Svensmark's paper provides data (bore hole temperatures, see figure 1, and satellite data figure 2) to support his hypothesis that changes in global cloudiness is causing the polar see-saw.
From Svensmark's paper:
B) Faint Sun
Attached is a link to Shaviv's paper that provides a GCR explanation as to why the earth was warm (not covered in ice) when the sun was younger and fainter.
|Mar17-07, 08:37 AM||#66|
I am curious as to what you meant when you stated:
"Cyclic variation of Earths Geode shape. That's a tough one."
In response to my question what is causing the Glacial/Interglacial cycle and the abrupt climate changes.
I would assume you mean Milankovitch's insolation theory which hypothesizes that variation in the earth's orbit (changes in orbital eccentricity and tilt of the earth's axis which affect relative insolation levels and the relative temperature difference between the seasons) which affect whether summers are relatively warmer and winters relatively colder and visa versa, is the cause for the ice ages.
Based on that theory, the next ice age should be starting now, as the earth is farthest from the sun June 20 and closest to the sun December 20 and the earth's tilt is almost at its minimum. (The glacial period is hypothesized to start when summers are cool and winters are warm.) Insolation at the critical latitude 60N is the same as it was during the last glacial period maximum.
I do not see how changes in insolation could possibly result in Canada, North US States, Russia, and Northern Europe being covered with an ice sheet that is 2 miles thick. Have you read the thread what causes Ice Ages? In that thread there is data that shows an glacial period ending when insolation has close to minimum. What could have caused the planet to warm?
In response to your scepticism to my comments concerning the Younger Dryas: Please click twice on the link to the paper I referenced. You have not read the paper I referred to. The paper I referred to notes cosmogenic isotopes doubled during the Younger Dryas, it also notes that there was ice rafting during the Younger Dryas, the same as occurred during the Henrich events. Data and analysis is provided to substantiate those statements.
|Mar17-07, 10:04 AM||#67|
It's now 8 years ago that I decided to solve the riddle of the Mammoth extinction. I don't think that there are very many studies left with keys words like: "Pleistocene", "Younger Dryas", that I have not read. All those studies that seek to support / explain/ proof a certain part about the hypotheses pertaining the ice age are invariably based on limited information, projecting the unknown as being granted, but most of that unknown is not unknown but actually ïgnored because it completely contradicts the current paradigms. And then there are the studies that are completely unexplained, for instance:
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