This is interesting. This recent paper published in the journal Astronomy & Astrophysics here has done a reconstruction of TSI using Beryllium 10 isotope records combined with sunspot records. The paper suggests that the Total Solar Irradiance (TSI) has increased since the end of the Little Ice Age (around 1850) by up to 6 x more than cited by the IPCC.
Here is how they did it:
For the reconstruction to the past this amplitude is scaled with proxies for solar activity. Two proxies are available for the reconstruction: Group sunspot number, which is available from the present to 1610 AD, and the solar modulation potential extending back to circa 7300 BC. The latter is a measure of the heliospheric shielding from cosmic rays derived from the analysis of cosmogenic isotope abundances in tree rings or ice
cores, and is available with a time resolution of 2-3 solar cycles (Steinhilber et al. 2008). Although sunspot number dropped to zero for a long time during the Maunder minimum, the solar cycle was uninterrupted (Beer et al. 1998; Usoskin et al. 2001) and the modulation potential did not fall to zero. Hence, a reconstruction based solely on sunspot number may underestimate the solar activity during theMaunderminimum. Therefore in our reconstruction we used the solar modulation potential to calculate the long-term variations and sunspot number to superpose them with the 11-year cycle variations (see the Online Section 6.2).
The modulation potential used in the calculations is based on the composite of data determined from the cosmogenic isotope records of 10Be and neutronmonitor. 10Be data are available up to about 1970 (McCracken et al. 2004) and neutron monitor data, which are used to calculate the current solar modulation potential, are available since the 1950s.
A. I. Shapiro, W. Schmutz1, E. Rozanov, M. Schoell, M. Haberreiter1, A. V. Shapiro and S. Nyeki
1 Physikalisch-Meteorologishes Observatorium Davos, World Radiation Center, 7260 Davos Dorf, Switzerland
2 Institute for Atmospheric and Climate science ETH, Zurich, Switzerland
3 Institute for Astronomy ETH, Zurich, Switzerland
Abstract
Context. The variable Sun is the most likely candidate for the natural forcing of past climate changes on time scales of 50 to 1000 years. Evidence for this understanding is that the terrestrial climate correlates positively with the solar activity. During the past 10 000 years, the Sun has experienced the substantial variations in activity and there have been numerous attempts to reconstruct solar irradiance. While there is general agreement on how solar forcing varied during the last several hundred years – all reconstructions are proportional to the solar activity – there is scientific controversy on the magnitude of solar forcing. Aims. We present a reconstruction of the total and spectral solar irradiance covering 130 nm–10 μm from 1610 to the present with an annual resolution and for the Holocene with a 22-year resolution. Methods. We assume that the minimum state of the quiet Sun in time corresponds to the observed quietest area on the present Sun. Then we use available long-term proxies of the solar activity, which are 10Be isotope concentrations in ice cores and 22-year smoothed neutron monitor data, to interpolate between the present quiet Sun and the minimum state of the quiet Sun. This determines the long-term trend in the solar variability, which is then superposed with the 11-year activity cycle calculated from the sunspot number. The time-dependent solar spectral irradiance from about 7000 BC to the present is then derived using a state-of-the-art radiation code.
Conclusions
We present a new technique to reconstruct total and spectral solar irradiance over the Holocene. We obtained a large historical solar forcing between the Maunder minimum and the present, as well as a significant increase in solar irradiance in the first half of the twentieth-century. Our value of the historical solar forcing is remarkably larger than other estimations published in the recent literature.
We note that our conclusions can not be tested on the basis of the last 30 years of solar observations because, according to the proxy data, the Sun was in a maximumplato state in its longterm evolution.All recently published reconstructions agree well during the satellite observational period and diverge only in the past. This implies that observational data do not allow to select and favor one of the proposed reconstructions. Therefore, until new evidence become available we are in a situation that different approaches and hypothesis yield different solar forcing values. Our result allows the climate community to evaluate the full range of present uncertainty in solar forcing.
The full dataset of the solar spectral irradiance back to 7000
BC is available upon request.
Here is the paper, available online in entirety here (PDF) h/t to The Hockey Schtick
“This implies that observational data do not allow to select and favor one of the proposed reconstructions. Therefore, until new evidence become available we are in a situation that different approaches and hypothesis yield different solar forcing values. Our result allows the climate community to evaluate the full range of present uncertainty in solar forcing.”
My! My! What an ingenious escape clause! We don’t claim our results are true because that would undermine the foundations of AGW theory. We merely did all this work to expand the band of uncertainty! We can still maintain that AGW theory is sound, but with the caveat that “the band of uncertainty” is merely expanded.
That kind of equivocation, boys and girls, is what it takes to get such a paper published these days. The fact that such a paper can see the light of day, even with said equivocation, is progress over where things stood only a couple of years ago.
Good to see this paper up at WUWT. I find this an interesting paper in that the authors make no claim that their method is superior or “robust” Rather they highlight the difficulties inherent in all TSI reconstruction attempts, including those that seek to stamp the TSI record flat.
It will be interesting to compare the authors proposed reconstruction to the solar forcing that Willis discovers in his GCM forcing adventure.
Interesting. How do they justify extending the proxy for TSI into a region beyond the level which has been proposed as a stable background level on top of which the solar cycle adds modulation? I think I’m right in saying that there is no evidence yet to directly link the LIA with reduced TSI?
Breaking news on BBC Today
0719: It has emerged that the coalition cabinet is reportedly spit over the government’s policy on climate change. Environment correspondent Roger Harrabin reports.
This marks quite a dramatic shift, because so far the UK politicians have all been on one “consensus” (publicly) and one cannot forget that the Tories were elected by a leader who said they were going to be the “greenest government ever”.
Claude Harvey,
I have to disagree with you. That quote was my favorite part. It means the people who put together this paper are actual scientists. Scientists who recognize the limits of their research and the possibility they can be wrong. As oppose to “scientists” who try to hide their data, or don’t want people to admit the limits of science in public as it could give those “deniers” ammunition.
The main argument against solar forcing being responsible for post 1970-warming still seems valid, i.e. the TSI trend since ~1950 is approximately zero. Also (from the TSI reconstruction since 1600) would we not expect temperatures during the 18th century to be comparable to those in the late 20th century.
Scottish Sceptic says:
May 10, 2011 at 1:12 am
Breaking news on BBC Today
0719: It has emerged that the coalition cabinet is reportedly spit over the government’s policy on climate change. Environment correspondent Roger Harrabin reports.
I think you’ll find that the dissenters want to go further.
What would the models produce if that solar forcing variable was multiplied 6 times?
Anthony,
Is it me or strictly using the Greenland ice core as proxy is a little ridiculous as to the proximity it is away from the rest of the planet for measuring the sun spots using a proxy?
A massive amount of atmosphere and weather conditions to be able to reach that point compared to the equatorial region.
Scottish Sceptic says:
May 10, 2011 at 1:12 am
Breaking news on BBC Today
0719: It has emerged that the coalition cabinet is reportedly spit over the government’s policy on climate change. Environment correspondent Roger Harrabin reports.
It is on Radio 4 listen again;
http://www.bbc.co.uk/programmes/b010xzxh
John Finn says, May 10, 2011 at 1:40 am
the TSI trend since ~1950 is approximately zero
Indeed, but one may not forget that it costs a lot of years to warm the oceans up. Even with a constant high level of TSI, it takes about 30 years (or more) to reach a new high in seawater temperature. The fact that since about 2000 there is no increase in temperature anymore (besides ENSO variability), shows that the new equilibrium is more or less reached. The next decade will show the real impact of the sun, as we currently have a less active sun, which should translate in lower temperatures (or not)…
Solar driven climate? Whatever next?
The evidence is mounting against CO2 as the culprit.
Inability to find the troposphere hot spot.
Ice core data placing temperature rise before CO2 rise.
Now solar variability.
The IPCC will hate this because they refuse to accept any solar variation at all.
Keep the evidence rolling in.
. . .comparable to late 20th Century
yes, if you prefer to ignore sensitivity to initial conditions or assume a straightforward, contemporaneous, purely linear climate response. Doubt it works that way.
Interesting post though. Whilst welcome, I can’t get too carried away, since reading this blog has taught me to treat proxy reconstructions with a pinch of salt.
The TSI trend since 1950 might be close to zero, but the level is high. Bear in mind that no less an authority then James Hansen has pointed out that present levels of CO2 forcing, even if they stayed constant, will have stored up temperature increases for the next 50 years or so. It’s a very big bucket of water, and it’s going to take a long time to warm – or cool.
“The main argument against solar forcing being responsible for post 1970-warming still seems valid, i.e. the TSI trend since ~1950 is approximately zero. Also (from the TSI reconstruction since 1600) would we not expect temperatures during the 18th century to be comparable to those in the late 20th century.”
It is very likely that post 1970 warming is overestimated (anthropogenic local warming).
Even if the solar forcing during the 18th century was comparable to the late 20th century, that still does not mean that the temperatures should be comparable as well. Durin the LIA we had a lot of ice buildup and when the solar forcing increased again, there was a lot of thermal inertia. A lot of heat is needed to melt the ice.
But I still think that the temperatures during ~40s were comparable to the ~80s/90s.
John Finn says:
May 10, 2011 at 1:40 am
Try reading the paper.
It’s the UV range (175-242 nm) of the Solar Spectra that comprises most of the change in TSI and SSI.
I would not put too much money on it. Beryllium records from Greenland ice cores, are highly unreliable, I would say border on useless.
Antarctic records I am not familiar with, I would think that they should be far more reliable.
Why do I question Greenland’s 10Be?
See here: http://www.vukcevic.talktalk.net/CET&10Be.htm
Can someone answer: how is past TSI estimated and how it is now measured, at the surface or by satellite?
Should point out the item is 1 hour 20mins 30 secs.
There are two or three factors involved during solar max and minimums – one is the TSI, the others are cloud cover and UV displacement effects on the jetstream (which also affects cloud cover) – these lead to ‘pulsed’ warmings of the ocean surface waters to 200m and time lags that redistribute that heat to land – these latter are complex teleconnections from ocean basin to basin – and this determines the global average temperature. From 1980-2001 low level reflective cloud cover decreased by 4-5% – quite enough to account for ‘global warming’. After 2001 it came back by about 2% and the oceans soon afterwards stopped accumulating heat.
If we focus on one factor alone, we get a distorted picture.
Interesting study but although I scoured it most carefully to see if their findings could correlate with the warming over the last ten years, it actually seemed to have a negative correlation – quieter sun, more warming. So when they use the word ‘historical’ in the title of the report, they obviously do mean ‘historical’.
So as a scientifically robust counter to the IPCC argument, this is very far from doing the job.
Yeah ,but the AGW crowd have a get out of jail free card. They say that if the climate is very sensitive with regards to the sun, it must be very sensitive for everything else as well, so the C02 greenhouse effect increases even more if the sun’s effects are larger. This is a false equivalence, or rather, a tendancy to lump all climate effects together, rather than to recognise that nature genearlly doesnt follow patterns in a linear or predictable form, which I hesitate to say, tends to be a socialist assumption (.i.e evenness and equivalence).
Alistair McKechnie says:
May 10, 2011 at 3:24 am
Interesting study but although I scoured it most carefully to see if their findings could correlate with the warming over the last ten years,
What warming over the last 10 years?
Why is it ” Hydrothermal Vent Complexes Causing Global Warming”is ignored or seldom entered into the equation??
http://tinyurl.com/3gowq2j
Peter Taylor
hi Peter
I am somewhat ambivalent about the notion that there is a wholseale transfer of heat from Ocean to land which sems to be the generally agreed maxim.
i live 100 yards from the South coast of England. The warming effect of the gulf stream is easily overcome by the wind direction and the nature of the weather fronts they bring. For example we would normally reckon that in a ‘normal’ year (which rarely seems to happen) the warmth of the gulf stream will just about keep frosts away from our garden until February. 2 miles inland the warming effect has been lost all through the winter. Cloud cover will have a considerable effect on keeping the sea warm, especially at night.
During the last few winters, when we had strong easterlies and high pressure, the intense cold and lack of cloud they brought meant we had frosts even in November and the gulf stream had a marginal effect.
Whether the warming effect of the oceans can therfore be said to affect the whole of the UK or by inference entire continental land masses i would be dubious. Wind direction and the effects of weather systems are to my mind every bit as important.
tonyb