Is the Faint Young Sun Problem Solved by Increased Greenhouse Gases?

In summary, global warming is considered a fact within the science community. Global surface temperatures and ocean temperatures are rising, while there is a overall melting of ice and permafrost. Sea levels are also rising and the rate of sea level rise has accelerated in the past century. The majority of heat from global warming is going into the oceans, as seen in Figure TS.15 of the IPCC report. The warming is also affecting plant and animal life, causing shifts in climate zones. While there were some discussions of global cooling in the 1970s, it was never a consensus view and there is now ample evidence that the Earth is currently experiencing a warming trend. Some individuals may deny this evidence for political reasons, but the scientific consensus remains that global
  • #106
Xnn said:
Appreciate your feedback and understand that Ruddiman's original hypothesis should not be completely accepted. However, my impression it is accepted that there was a pre-industrial age human contribution of roughly 10 ppm CO2 and 100 ppb CH4 to the atmosphere. In addition, we know that over the last 5000 years orbital changes have lead to a gradual cooling of the arctic that is expected to continue for several thousand years. So, absent human activities, we could have expected an expansion of glacial coverage in the northern hemisphere. This doesn't mean that there should have been a rapid expansion of ice conditions, but rather a continuation of what is known as the little ice age. That is, there would have been an gradual icing of the earth, especially in the northern hemisphere.

Fair enough. 10 ppm CO2 is a forcing of about 0.2 W/m2, and 100 ppb CH4 is a forcing of about 0.06 W/m2, using approximation formulae for estimating forcings from a change in greenhouse gas concentrations. (Formulae are in the http://www.grida.no/publications/other/ipcc_tar/?src=/climate/ipcc_tar/wg1/222.htm [Broken].) If climate sensitivity is sufficiently high, this could make a significant difference. Climate sensitivity is about 0.8 +/- 0.4 degrees per W/m2, so this anthropogenic pre-industrial forcing could drive as much as 0.3 degrees... not much more, I think.

I was reacting to the phrase "the world would be icing up". If you mean a little bit of additional glaciation, then yes; but it could easily be taken as something much more than this; a new ice age. I think that is unlikely. The Holocene would more likely continue mild, with small variations and perhaps a very slow cooling trend of the order of fractions of a degree per century.

An example of Holocene cooling trend estimation is
  • Kullman, L (1993) http://www.jstor.org/pss/2997659, in Global Ecology and Biogeography Letters 2, pp 181-188.

I've only read the abstract. It derives a cooling trend of 0.12 degrees per millenum, a bit less than one hundredth of the current warming trend. The abstract indicates this value is consistent with the work of Berger on a long interglacial, cited previously. This trend is over some 8000 years, and corresponds to a drop in temperatures of about a degree, which seems about right. It would mean current temperatures are not quite as high as at the Holocene thermal maximum as yet, which makes sense to me. So 0.3 degrees off set from that helps.

We came out of the little ice age mainly because of natural variations, I think; it was not part of a longer trend but more of a dip... and mostly regional rather than global.

Unfortunately, I haven't been able to locate copies of the papers criticizing Ruddiman's work to study. However, I notice that a integrated analysis of solar insolation such as that performed by Huyber (figure 2E) appears to distinguish between recent solar forcing and that of 420 Kyrs ago.

http://www.sciencemag.org/cgi/reprint/313/5786/508.pdf [Broken]

Found a freely available preprint of that:
I'll have a look at it. It appears to look at the Early Pleistocene, rather than the current Late Pleistocene. The final sentence of the paper is:
However, the 100-ky glacial cycles of the late Pleistocene have a more complicated relationship with the forcing, and their explanation will require a better understanding of ice sheet–climate interactions.
420,000 years ago is still part of the late Pleistocene. The paper seems to divide early and late at about 1 million years ago, according to figure 2E, which is all labeled as part of the late Pleistocene.

There's another source you might find interesting. Ruddiman has a guest post available at the realclimate blog, which is a deliberate attempt to communicate issues in climate science to a wider general audience. He discusses the contrasts between his ideas and those of Berger and indicates what it would take (in his view) to distinguish them. It is a nice informal and open ended discussion.

Cheers -- sylas
 
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  • #107
Hi eachus. I don't mind if we disagree on general matters such as the quality of climate science generally, or the role of "validation" in science, and so on. I'm content with my perspective as stated previously, particularly in [post=2507536]msg #80[/post] which you have quoted, and don't see much value in expanding on it.

So I'll just comment on a two simpler points that can be resolved more easily.

eachus said:
The other way, of course, to test models is to use them for prediction. Yes, I have seen models which did predict colder temperatures in 2008 and 2009--but they are based on sunspots, and cosmic rays. They are definitely not part of any IPCC consensus.

If you have an actual citation for such predictions, then this could be the basis for an interesting new thread. It would be better as a new thread, it's a bit off topic here. To my knowledge the proposals for sunspots and cosmic rays are nowhere near able to give clear predictions like that, and certainly don't explain the large short term variations. Colder temperatures in 2008 is quite unconventionally recognized as part of the short term ENSO cycle. 2009 is heating up again, and appears to be the fifth hottest year on record. So if anyone was predicting colder temperatures, they've been falsified.

Finally, Bill Illis has linked to some (decent) NOAA data showing CO2 levels over 6000 ppm, or 20 times current levels millions of years ago. The simple application of the Stefan-Boltzman law would call for about 16 degrees C of ratiative forcing, which was clearly not the case.

I think you are mistaken. Bill's links go back some 20 million years, and CO2 levels have remained below 600ppm over that period. Is 6000 a typo?

In any case, the forcing for 600ppm over pre-industrial levels would be around 4 W/m2, and given current best estimates for sensitivity this would give a temperature rise of around 3 degrees, plus or minus 1.5; it is close to double to pre-industrial level.

But even assuming 6000 there still seems to be an error. Using 3*Log2(C/C0) for climate sensitivity of 3 degrees per doubling, this works out to a bit over 13 degrees gain over the pre-industrial levels of 280ppm. Note that this is presuming positive feedbacks to get climate sensitivity of about 3. If you simply ignore feedbacks and use radiative transfers alone, which seems to be what you mean by "Stefan-Boltzman", the temperature effect is less than half this.

I don't know how you got 16, but I think there is an error somewhere in your calculation as well.

Also... the highest CO2 levels in the Cenozoic were during the "Paleocene-Eocene Thermal Maximum" (PETM) about 55 million years ago. This was a short period of greatly elevated temperatures. CO2 levels beyond a million years or so reply on estimates from carbon models and proxies, as we don't have ice cores to give direct readings. Estimates are as high as 3000ppm. You don't get higher than that until you go back more than 400 million years.

Cheers -- sylas
 
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  • #108
Andre said:
The allegations of M&M have been evaluated by two commissions/panels, a ad hoc commision Wegman and the NAS panel of North. Both confirmed the crtique of M&M , despite all attempts to cover that
.This is not correct and I have often seen these Committees mixed up. Wegman was indeed chair of the National Academy of Sciences (NAS) Committee on Applied and Theoretical Statistics, but he produced the non peer-reviewed 'Wegman Report' for the US House Committee on Energy & Commerce.A peer-reviewed 'Committee on Surface Temperature Reconstructions for the Past 2,000 Years' was assembled by the National Research Council (NRC) of the National Academies (Board on Atmospheric Sciences and Climate) under Gerald North, and their report acknowledged that there were statistical shortcomings in the MBH analysis, but concluded that they were small in effect.
http://books.nap.edu/openbook.php?record_id=11676&page=R1"Additionally, the American Statistical Association (ASA), in a session at the Joint Statistical Meetings, 2006 - which included Wegman - came to the same conclusion as the NRC.
http://www.amstat-online.org/sections/envr/ssenews/ENVR_9_1.pdf"
 
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  • #109
JohnMurphy said:
.


This is not correct and I have often seen these Committees mixed up.

and yet another attempt to discredit wegman.

see here
 
  • #110
sylas said:
I think you are mistaken. Bill's links go back some 20 million years, and CO2 levels have remained below 600ppm over that period. Is 6000 a typo?

Cheers -- sylas

The data I linked to sylas goes back 570 million years with the highest CO2 level being 7,069 ppm at 520 million years ago (GeoCarbIII from Berner). There are estimates going farther back with the last solid calculated ones being 12,000 ppm at the end of the last Snowball Earth period 635 million years ago (this wouldn't have been high enough to end the Snowball so it had to be super-continents Rhodinia/Pannotia breaking-up and moving off the south pole) and 4,200 ppm at 770 million years ago. It is inferred that CO2/GHG levels were increasingly higher as we go back farther in time or the Earth would have been a frozen iceball in all earlier time periods due to the Faint Young Sun.
 
  • #111
Bill Illis said:
The data I linked to sylas goes back 570 million years with the highest CO2 level being 7,069 ppm at 520 million years ago (GeoCarbIII from Berner). There are estimates going farther back with the last solid calculated ones being 12,000 ppm at the end of the last Snowball Earth period 635 million years ago (this wouldn't have been high enough to end the Snowball so it had to be super-continents Rhodinia/Pannotia breaking-up and moving off the south pole) and 4,200 ppm at 770 million years ago. It is inferred that CO2/GHG levels were increasingly higher as we go back farther in time or the Earth would have been a frozen iceball in all earlier time periods due to the Faint Young Sun.

Thanks for the correction. I missed that.

These estimates are based on models of the geological carbon cycle (GeoCarbIII), and they do involve very large concentrations many hundreds of millions of years ago, which I did refer to in my post, though I failed to find them in your links. After hunting around, I found the location within the NCDC ftp site: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/climate_forcing/trace_gases/phanerozoic_co2.txt. Values are for RCO2, which is the ratio to present levels (pre-industrial). The dataset reference suggests RCO2 = 1 corresponds roughly to 300ppm.

Of course, going back hundreds of millions of years means we also need to consider changes in the solar output. As you say, the Sun was dimmer but the elevated CO2 levels still meant Earth was warmer than today.

The major reference for this data set proposes the following formulae:
  • Temperature impact of RCO2 is 4*Ln(RCO2).
  • Temperature impact of faint Sun t million years ago is 7.4*t/570

At 520 Mya, with RCO2 = 26.2, we have 13 degree gain from the greenhouse effect, and 6.75 degree loss from the faint Sun. These are very rough estimates, but they are in the ball park for a Cambrian that is about 6 degrees warmer than now, which is about right.

Going back to the snowball/slushball is very interesting; and I know you have done some work on this. Alas, we are going of topic.

Thanks for setting me straight on this.

Cheers -- sylas
 
  • #112
sylas said:
[*]Temperature impact of faint Sun t million years ago is 7.4*t/570
[/list]


Cheers -- sylas

I think it is better to think of it as the Solar Irradiance reaching the Earth was 30% lower 4.55 billion years ago and it has increased in very close to a straight line over time.

So, Solar Irradiance 520 million years ago was = 1366 (0.7*520/4550) = 1319 = 252.8K

or -2.2K change 520 million years ago from lower solar irradiance.

Go back to 4.55 billion years ago and the Te was 233K.

This comes from D. Gough 1981, Kasting 1988 and outlined a little better in a more recent paper by Kasting.

http://geosc.psu.edu/~kasting/PersonalPage/Pdf/annurev_03.pdf [Broken]
 
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  • #113
Bill Illis said:
I think it is better to think of it as the Solar Irradiance reaching the Earth was 30% lower 4.55 billion years ago and it has increased in very close to a straight line over time.

So, Solar Irradiance 520 million years ago was = 1366 (0.7*520/4550) = 1319 = 252.8K

or -2.2K change 520 million years ago from lower solar irradiance.

Go back to 4.55 billion years ago and the Te was 233K.

This comes from D. Gough 1981, Kasting 1988 and outlined a little better in a more recent paper by Kasting.

http://geosc.psu.edu/~kasting/PersonalPage/Pdf/annurev_03.pdf [Broken]


Ahhh! Thanks for the link, I had a copy of this about 2 years ago and lost it, memory wasn't good enough to pull it up in a search.
 
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  • #114
Bill Illis said:
I think it is better to think of it as the Solar Irradiance reaching the Earth was 30% lower 4.55 billion years ago and it has increased in very close to a straight line over time.

So, Solar Irradiance 520 million years ago was = 1366 (0.7*520/4550) = 1319 = 252.8K

or -2.2K change 520 million years ago from lower solar irradiance.

Go back to 4.55 billion years ago and the Te was 233K.

This comes from D. Gough 1981, Kasting 1988 and outlined a little better in a more recent paper by Kasting.

http://geosc.psu.edu/~kasting/PersonalPage/Pdf/annurev_03.pdf [Broken]

Thanks for the link. The calculation you present is better founded on the power law relating temperature to energy; but over the time scales of GeoCarb, this is not actually going to make much difference. A linear approximation works okay.

The real problem is that this calculation ignores all feedback effects, which are actually pretty crucial to the final temperature. Going back 520 Mya, the fractional decrease in insolation is 0.3*520/4550 = 0.0343. Insolation, after allowing for albedo, now about 240 W/m2. The reduction is 0.0343*240 = 8.3 W/m2. Assuming a climate sensitivity of about 0.75 K per W/m2 you get a temperature change at the surface of 6.2K.

This is about what we get also from the numbers in the reference for the GeoCARB III reference, which is

The two papers are consistent with each other, and the factors used for temperature difference over time due to the dimmer Sun take into account both the numbers you have presented for how solar radiance changes, and also the climate feedbacks that affect how the planet responds to that change, which is not simply given by Stefan-Boltzman.

Your latest reference spells this out explicitly. You have cited
On page 442 (my bolding)
If one reduces the value of S by 30% in (1), holding A and ΔTg constant for simplicity, one finds that Te drops to 233 K and Ts = 266 K, well below the freezing point of water. If the calculation is repeated with a climate model that includes the positive feedback loop involving water vapor, the problem becomes even more severe. The dashed curves in Figure 4 show Te and Ts calculated using a one-dimensional, radiative-convective climate model, assuming constant CO2 concentrations and fixed relative humidity (Kasting, Toon & Pollack 1988). The results are remarkably similar to those predicted earlier by Sagan & Mullen: Ts drops below the freezing point of water prior to ~2 Ga. Combined with the snow/ice-albedo feedback loop, this temperature drop would almost certainly lead to a globally glaciated Earth. However, geologic evidence tells us that liquid water and life were both present as far back as 3.5 Ga and maybe longer. The oldest zircons, zirconium silicate minerals that must have formed in liquid water, are dated at more than 4.3 Ga and may indicate the presence of an ocean at that time (Catling & Kasting 2002, Mojzsis, Harrison & Pidgeon 2001, Wilde et al. 2001).

How can the faint young Sun problem be solved? A large decrease in cloudiness would do it (Rossow et al. 1982), but this seems unlikely for reasons mentioned in Section 3.1. Instead, the answer probably lies in increased concentrations of greenhouse gases. Both CO2 and CH4 are plausible candidates. ...

The numbers used in the GeoCARB III reference, which give a temperature difference of about 6 degrees 520 Mya, correspond to estimates that take water vapour and other factors into account, just as Kasting and Catling describe here.

Cheers -- sylas
 
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<h2>What is the Faint Young Sun Problem?</h2><p>The Faint Young Sun Problem refers to the observation that the early Earth received significantly less solar radiation than it does today, yet evidence suggests that the Earth's surface was not frozen over during this time period. This poses a paradox as the Earth's climate should have been much colder in the past due to the lower solar radiation.</p><h2>How is the Faint Young Sun Problem related to increased greenhouse gases?</h2><p>The Faint Young Sun Problem is often discussed in relation to the role of greenhouse gases in regulating the Earth's climate. As the early Earth received less solar radiation, the presence of greenhouse gases such as carbon dioxide and methane may have helped to trap heat and maintain a habitable climate.</p><h2>Has the Faint Young Sun Problem been solved by increased greenhouse gases?</h2><p>While there is still ongoing research and debate on this topic, many scientists believe that increased greenhouse gases played a significant role in solving the Faint Young Sun Problem. However, other factors such as changes in the Earth's orbit and the presence of other greenhouse gases may also have contributed.</p><h2>What evidence supports the role of increased greenhouse gases in solving the Faint Young Sun Problem?</h2><p>Scientists have used a variety of methods to study the Earth's climate in the past, including analyzing ancient rocks and fossils, and running computer simulations. These studies have shown that the Earth's climate was likely kept warm by higher levels of greenhouse gases during the Faint Young Sun era.</p><h2>What are the implications of solving the Faint Young Sun Problem for understanding Earth's climate?</h2><p>Solving the Faint Young Sun Problem can help us better understand the Earth's climate and how it has changed over time. It also has implications for our understanding of how greenhouse gases influence climate, both in the past and in the present day. This knowledge can inform our efforts to mitigate the effects of climate change on our planet.</p>

What is the Faint Young Sun Problem?

The Faint Young Sun Problem refers to the observation that the early Earth received significantly less solar radiation than it does today, yet evidence suggests that the Earth's surface was not frozen over during this time period. This poses a paradox as the Earth's climate should have been much colder in the past due to the lower solar radiation.

How is the Faint Young Sun Problem related to increased greenhouse gases?

The Faint Young Sun Problem is often discussed in relation to the role of greenhouse gases in regulating the Earth's climate. As the early Earth received less solar radiation, the presence of greenhouse gases such as carbon dioxide and methane may have helped to trap heat and maintain a habitable climate.

Has the Faint Young Sun Problem been solved by increased greenhouse gases?

While there is still ongoing research and debate on this topic, many scientists believe that increased greenhouse gases played a significant role in solving the Faint Young Sun Problem. However, other factors such as changes in the Earth's orbit and the presence of other greenhouse gases may also have contributed.

What evidence supports the role of increased greenhouse gases in solving the Faint Young Sun Problem?

Scientists have used a variety of methods to study the Earth's climate in the past, including analyzing ancient rocks and fossils, and running computer simulations. These studies have shown that the Earth's climate was likely kept warm by higher levels of greenhouse gases during the Faint Young Sun era.

What are the implications of solving the Faint Young Sun Problem for understanding Earth's climate?

Solving the Faint Young Sun Problem can help us better understand the Earth's climate and how it has changed over time. It also has implications for our understanding of how greenhouse gases influence climate, both in the past and in the present day. This knowledge can inform our efforts to mitigate the effects of climate change on our planet.

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