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

[sylas]

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 .) 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

Found a freely available preprint of that:

• Huybers, P.J. (2006) Early Pleistocene glacial cycles and the integrated summer insolation forcing in Science 313(5786): pp 508-511.

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

 

[sylas]

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.

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

 

[JohnMurphy]

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"

 

[Andre]

.


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

and yet another attempt to discredit wegman.

see here

 

[Bill Illis]

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.

 

[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.

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

 

[Bill Illis]

[*]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

 

[Trakar]

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

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.

 

[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

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

• Berner, R.A. and Z. Kothavala(2001) GEOCARB III: A Revised Model of Atmospheric CO2 over Phanerozoic Time, American Journal of Science, v.301, pp.182-204, February 2001.

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

• Kasting, J.F. and Catling D. (2003) Evolution of a Habitable Planet, in Annual Review of Astronomy and Astrophysics, Vol. 41, No. 1. pp. 429-463.

On page 442 (my bolding)

If one reduces the value of S by 30% in (1), holding A and ΔT_g constant for simplicity, one finds that T_e drops to 233 K and T_s = 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 T_e and T_s 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: T_s 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