2011-03-29 00:56:20NEW PAPER: Evolution of the solar irradiance during the Holocene
Spaceman Spiff
Kirk Korista
kirk.korista@wmich...
141.218.60.246

Hi everyone,

This article just appeared on the arXiv preprint service. Being an astronomer, I find the fact that astrophysics is contributing to climate science and that climate science drives advances in astrophysics to be really cool.

From the abstract:

Results. Reconstructions of the TSI over the Holocene, each valid for a di_erent paleomagnetic time series, are presented. Our analysis suggests that major sources of uncertainty in the TSI in this model are the heritage of the uncertainty of the TSI since 1610 reconstructed from sunspot data and the uncertainty of the evolution of the Earth's magnetic dipole moment. The analysis of the distribution functions of the reconstructed irradiance for the last 3000 years indicates that the estimates based on the virtual axial dipole moment are significantly lower at earlier times than the reconstructions based on the virtual dipole moment. Conclusions. We present the first physics-based reconstruction of the total solar irradiance over the Holocene, which will be of interest for studies of climate change over the last 11500 years. The reconstruction indicates that the decadally averaged total solar irradiance ranges over approximately 1.5 W/m2 from grand maxima to grand minima.

2011-03-29 02:59:38
MarkR
Mark Richardson
m.t.richardson2@gmail...
83.150.146.79

Nice!

 

I like some good solid physics. I'll check it out when I get back, thanks for the heads up. :)

2011-03-29 03:32:53interesting
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Yeah, very interesting paper with lots of good TSI plots!

2011-03-29 12:57:41Hockey stick
James Wight

jameswight@southernphone.com...
112.213.158.190

The graph of TSI over the last 2,500 years looks very much like a hockey stick up to circa 1950. That suggests the pre-1950 warming was mostly natural.

2011-03-29 13:29:16Note on hocky stick solar reconstruction
John Cook

john@skepticalscience...
124.185.238.238

Two of the authors, Solanki and Krivova, have published 11,000 year reconstructions of TSI in the past and they too had a slight hockey stick shape - so I gather this work is an improvement on their earlier work. It's one of Solanki's papers Usoskin 2005 where they conclude:

"...during these last 30 years the solar total irradiance, solar UV irradiance and cosmic ray flux has not shown any significant secular trend, so that at least this most recent warming episode must have another source."

2011-03-30 01:20:10
Spaceman Spiff
Kirk Korista
kirk.korista@wmich...
141.218.60.246

Without a physical mechanism, two time-dependent trends with qualitative similarities over narrow time slices ought not be *assumed* to be connected physically.

2011-03-30 05:16:04solar hockey stick
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Note that their solar "hockey stick" only has TSI rising about 1 W/m2 over the past century.  As I showed in a recent blog post, that only corresponds to a temperature increase of about 0.15°C (and is probably less than the early-century CO2 warming).

Maybe I'll do a new one discussing the solar contribution to modern warming, MWP, LIA, Roman, etc. based on their reconstruction.

2011-03-30 06:18:18
Alex C

coultera@umich...
67.149.101.148

Interesting.  It appears that there was a time of similar TSI about 4000 years ago, and another about 8000-10,000 years ago (though more variable).  How did global temperatures respond then?

The MWP also seems to be during a time when TSI was not particularly high.  It seems that the general trend is decreasing from 2000 BC and on, then cutting up about a century ago.  Figures 6 and 11 show this pretty well.  The LIA is clearly during a time of low TSI.

The Roman appears to be during a time of highish TSI, but it was higher before, again during ~2000 BC.

Just observations anyways on trends.

2011-03-31 04:51:36
Spaceman Spiff
Kirk Korista
kirk.korista@wmich...
141.218.60.246

@dana1981 -- one would also need to factor in any feedbacks to that forcing. But point taken -- this (direct) forcing is small.

And in principle there might also be additional, secondary effects on Earth's energy budget associated with the long term solar cycle {e.g., the FUV flux variability and the interaction of the solar wind with Earth's magnetosphere (also time variable) and atmosphere}. The denialist camp would have us believe that these (with little more than hand-waving "arguments" for the physical mechanisms) are the whole ball of wax. This is a silly point of view, yet it would still be a good idea to nail down more precisely their importance.

2011-03-31 05:35:47feedbacks
dana1981
Dana Nuccitelli
dana1981@yahoo...
64.129.227.4

Spaceman - I did factor in feedbacks.  That's what the climate sensitivity parameter is for.  In fact I was quite conservative in using the CO2 climate sensitivity parameter (the direct solar sensitivity parameter is almost certainly lower), just in case there are some other non-TSI effects (like cosmic rays) which amplify the solar effect on global temperatures, which as you noted, is possible.