Climate - In-depth/technical discussion

[Iceberg]

Don't get me wrong I am not attacking Arrhenius (SA's) work.

Just like like all simple things such as Newtons gravity theory, it's not ditched, just that it's refined and improved upon, which is what's happened to SA's work.

A very good example is Methane and CFC's, CFC's tend to go to the poles, Methane tends to stay in concentration near source(depending on source location).

Any equation describing a simple log relationship, is just that simple.

A couple of papers that help to build on climate sensitivity.

http://www.agu.org/pubs/crossref/2006/2005JD006713.shtml

http://www.springerlink.com/content/066q0m0m13p26042/

Feel free to post up the none paying versions if they are found.

I have to admit it's not something I've spent alot of time looking at, the assumed forcing of a doubling of CO2 = 1.5C or so of GW I am happy to accept as are most others, even skeptics generally, it tends to be the more contentious WV and feedbacks that effect climate sensitivity.

[Admiral_Bobski]

I haven't read it all yet (!) but here is a link to Frank Very's 1900 work "Atmospheric Radiation: A Research" in PDF format (be warned, it's a scanned-in book and the download is 24MB!!).

http://www.archive.org/details/atmosphericradia00veryrich

[VillagePlank]

Any equation describing a simple log relationship, is just that simple.

I'm afraid I do not agree with that. The reeaon is why does it hold?

Can you please post peer-reviewed papers that show the physical reason with reference to the CO₂/temp relationship?

EDIT: My objection is based on the notion that it is not well known why there is a logarithmic relationship, and it is extremely difficult (it seems to me) to track it down. Nothing personal.

Edited February 19, 2010 by VillagePlank

[jethro]

This isn't peer reviewed but it does a fair job of explaining the basics of why the relationship is logarithmic, it also has some references at the bottom.

http://brneurosci.org/co2.html

[sunny starry skies]

This isn't peer reviewed but it does a fair job of explaining the basics of why the relationship is logarithmic, it also has some references at the bottom.

http://brneurosci.org/co2.html

I'm a bit concerned that one appears to have been written from a certain perspective (particularly in their assertions of linearity for some concepts), though maybe some of the material may be sound. No time (nor probably the ability) to do a proper critique though, so I'll leave any criticisms to others.

Looking around, I found this one, which seems very intuitively right for me and explained a lot of what I didn't get about CO2 concentrations:

http://chriscolose.wordpress.com/2010/02/18/greenhouse-effect-revisited/

It has a rather good explanation of why the effect of CO2 is logarithmic, in relation to the spectrum of outgoing longwave radiation. It thus explains beautifully why methane is far more 'effective' a greenhouse gas by the same principle. It explains why small quantities have such a strong impact, and how the saturation effect does not prevent CO2 from being a continuing effective GHG at ever-increasing quantities.

sss

[Gray-Wolf]

Looking around, I found this one, which seems very intuitively right for me and explained a lot of what I didn't get about CO2 concentrations:

http://chriscolose.w...fect-revisited/

sss

Good find SSS!

Might take me longer to absorb than CO2 does heat though!!!

[jethro]

A step closer to accurately reconstructing past temperatures?

http://www.nature.com/news/2010/100308/full/news.2010.110.html?s=news_rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+news%2Frss%2Fnews_s7+%28NatureNews+-+Earth+and+Environment%29&utm_content=Netvibes

[sunny starry skies]

A step closer to accurately reconstructing past temperatures?

http://www.nature.co...ontent=Netvibes

It's a good technique isn't it! I saw a presentation about it, and the micromilling of the shells required, a few years ago, but it looks like they've made some good progress. I've just had a read of the PNAS paper, and I have some issues with their interpretation of their own graphs. They speak of a 6C drop in winter temperatures post-settlement of Iceland, which is simply not present in their graphs. The 2-3C drop in summer maximum temperatures (not another 6C drop that they talk of) would be quite enough to cause the famine in Iceland however. It's odd, because the data they present in Figures 3 and 4 of the PNAS paper are superb, but their interpretation is poor, but... the outcome of most of their interpretations of that part of their record is the same, despite their own misrepresentation of their figures! I also think they misquote their own data on summer/winter temperatures for their most recent bivalves (they say summer/winter of 8.2 and 5.5C, which is the range of summer temps according to their own graph, winter temps are 1-3C on their graph). Confused yet?? I am!

So it looks like the method has loads of potential, especially with a more detailed dataset, but I wonder if the interpretations of this specific paper will be corrected/criticised in future? Other interesting observations - muted MWP/LIA signal, despite it being most well developed in the North Atlantic, and it will be still more interesting to make comparisons with ice core and tree ring data (but difficult given the lack of either in Iceland, and the challenges of teleconnecting individual temperature series in the North Atlantic).

sss

[sunny starry skies]

A quick last one from me before I go away for a bit (some will be happy to hear ). I stumbled across this - it's a 7-part blog, and may be an accessible walkthrough of CO2 science from the bottom upward, called "CO2 - an Insignificant Trace Gas?". Quite involved, lots of maths, and so perhaps VP in particular will be interested in it (notably parts 3 and 4 perhaps), and the references within.

Other things of note, and I don't have time to reference them entirely, but two interesting posts at RealClimate, covering recent papers discussing sea level rise (underestimated), solar activity influence (around the 10% level), and the scariest of the lot is:

http://www.sciencemag.org/cgi/content/abstract/326/5955/984

Greenland's mass balance looks like it has dropped off a cliff since about 2000, based on GRACE data, and the authors say it would have been 100% worse but for some incresed snowfall. Definitely worrying times. I know some might construe these various papers as 'alarmist', but the data is getting ever more solid, and we are observing the effects all the more each year. I just hope the paper that suggested much higher climate sensitivity was wrong (http://www.sciencemag.org/cgi/content/abstract/1178296)...

sss

[sunny starry skies]

VP asked where on the log curve we were:

If

ΔF = 5.35 * ln(C/Cbase)

ΔT = ΔF * λ.

where ΔF is radiative forcing relative to pre-industrial, C is desired CO2 concentration and Cbase is preindustrial (278ppm), then the forcing can be calculated. This gives us our 3.7W/sq m for a doubling, and a 1.7W/sq m for present concentrations, compared to preindustrial levels.

The equation is from the IPCC AR3 and AR4, derived from Myhre et al (1998). This is directly based on the radiative forcing driven by absorbtion of longwave radiation as described in links I've put up elsewhere (Jethro doesn't like linking to blogs in the technical thread but the relevant blogs are duly referencing the literature on radiative transfer). The relationship is logarithmic because of the gradual saturation of the CO2 absorbtion band.

Temperature change (ΔT) is related to forcing by the variable λ, which is very close to a constant of 0.5.

So to answer VP's question, x = 387ppm, y = 1.77W/sq m. Add another 100ppm and we get to 3W/sq m, demonstrating the logarithmic effect.

sss

[VillagePlank]

VP asked where on the log curve we were:

If

ΔF = 5.35 * ln(C/Cbase)

ΔT = ΔF * λ.

where ΔF is radiative forcing relative to pre-industrial, C is desired CO2 concentration and Cbase is preindustrial (278ppm), then the forcing can be calculated. This gives us our 3.7W/sq m for a doubling, and a 1.7W/sq m for present concentrations, compared to preindustrial levels.

The equation is from the IPCC AR3 and AR4, derived from Myhre et al (1998). This is directly based on the radiative forcing driven by absorbtion of longwave radiation as described in links I've put up elsewhere (Jethro doesn't like linking to blogs in the technical thread but the relevant blogs are duly referencing the literature on radiative transfer). The relationship is logarithmic because of the gradual saturation of the CO2 absorbtion band.

Temperature change (ΔT) is related to forcing by the variable λ, which is very close to a constant of 0.5.

So to answer VP's question, x = 387ppm, y = 1.77W/sq m. Add another 100ppm and we get to 3W/sq m, demonstrating the logarithmic effect.

sss

The lambda variable - how was it derived?

(Thanks for the paper reference)

Edited April 10, 2010 by VillagePlank

[sunny starry skies]

The lambda variable - how was it derived?

(Thanks for the paper reference)

Afraid I won't be at the office for quite a while to check the Myhre paper. Dickinson, 1982; WMO, 1986; Cess et al., 1993 are what the TAR refers to in relation to the second equation, so you could look there.

Dickinson, R.E., 1982: In: Carbon Dioxide Review [Clark, W.C. (ed.)]. Clarendon, New York, NY, USA, pp. 101-133.

WMO, 1986: Atmospheric Ozone: 1985, Global Ozone Research and Monitoring Project, World Meteorological Organization, Report No. 16, Chapter 15, Geneva, Switzerland.

Cess, R.D., M.-H. Zhang, G.L. Potter, H.W. Barker, R.A. Colman, D.A. Dazlich, A.D. Del Genio, M. Esch, J.R. Fraser, V. Galin, W.L. Gates, J.J. Hack, W.J. Ingram, J.T. Kiehl, A.A. Lacis, H. Le Treut, Z.-X. Li, X.Z. Liang, J.-F. Mahfouf, B.J. McAvaney, K.P. Meleshko, J.-J. Morcrette, D.A. Randall, E. Roeckner, J.-F. Royer, A.P. Sokolov, P.V. Sporyshev, K.E. Taylor, W.-C. Wang, and R.T. Wetherald, 1993: Uncertainties in CO₂ radiative forcing in atmospheric general circulation models. Science, 262, 1252-1255.