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
Since TSI is how the warmists try to discredit Milankovitch I remain skeptical. While total TSI might matter somewhat, it matters more where that energy is striking the Earth. That is why the Earth is colder in January when the Earth is closest to the sun and warmist in July when it is farthest from the sun.
The annual TSI variation is enough to show that location matter more than very small variations in the total amount of energy.
Alistair McKechnie
I suggest you don’t use the word ‘robust’ on this site if you want to avoid ridicule.
However, judging by the rest of your comment that aim does not appear to be high on your list of priorities.
It never ceases to amaze me that CO2 is given every possible route and timeframe by which warming could show itself. Solar influence on the other hand . . . apparently that has to be both immediate and without any complexity attached.
Great that this is beginning to make it into the literature, after we’ve been saying it for several years.
The way Nir Shaviv’s findings have been ignored since 2005 by mainstream climate science is nothing short of shameful.
http://sciencebits.com/calorimeter
John Finn,
“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. ”
Keep in mind that solar activity was still at this unusually high plateau for the latter half of the century, and there is a mid-century cooling that is a problem for the CO2 hypothesis as well. Model diagnostics show that models disagreeing with each other on sensititivity ranging from 2C to 6C can all “match” the observed 20th century climate, because of the uncertainty in aerosols, that same uncertainty in aerosols can aid solar forcing in explaining the mid-century cooling and rapid temperature increases in the 1980s and 90s.
I second Adam at 1:34 am. The conclusion is refreshing.
thingadonta,
“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”
On the contrary, this result works against that “get out of jail free card. We have no model independent estimates of climate sensitivity to CO2 forcing in the current climate regime, so the best model independent attempts have used estimates of the sensitivity to variation in solar and aerosol forcing. Because the estimates of solar variability were low, the required sensitivities solar forcing to explain the medieval warm period and the little ice age had to be correspondingly higher, and based on an invalid assumption of equivilence justified higher sensitivities to CO2. Sensitivity to solar was often in the 2 to 3 degrees C range. A result of higher solar variability like this report, removes one of the model independent justifications for a higher sensitivity, because it is no longer needed for solar. The geographical, vertical and chemical couplings to the climate (including the oceans of course) are quite different for solar and CO2, and the assumption of equivalence in a nonlinear dynamic system was never justified.
This reconstruction is more like the solar variation which would be required to cause the Little Ice Age and some of the other climate cycles we have experienced. I note they have TSI about 8 watts/m2 lower in the late 1400s, 6 w/m2 lower in the late 1600s and 4 watts/m2 lower in 1900.
————–
David Schofield says:
May 10, 2011 at 2:04 am
What would the models produce if that solar forcing variable was multiplied 6 times?
———-
The majority of the warming since 1900 could then be explained by the Sun (in the climate models). They might then better match the 1910 to 1944 warm cycle (which the models cannot do), the 1946 to 1975 down cycle and the 1976 to 2002 up cycle.
(Note the 10be numbers do not match the sunspot cycles exactly in the 20th century. Sunspot levels peaked around 1950, just as temperatures were falling, but the 10be levels seem to peak earlier closer to the 1946 down-step in temperatures).
The sun has risen and the British policy cock crows.
=============
Another reply to John Finn:
I put a pot on the stove, pour soup in the pot, turn the stove burner up to warm and leave it there- there’s no change in burner level over a period of time, yet my soup still warms. Evedently you’ve never warmed soup in a pot.
Maybe I’m misunderstanding something (yet again!) but it seems to me that they are making a massive mistake. Unfortunately I’m not an expert in this area, and I didn’t even fully understand what they were saying (my excuse is that it’s late at night in this part of the globe and I can’t spend any longer on it right now), but this is what I interpreted from it:
They assume that the solar activity indicated by the 10Be records, and which relates to temperature changes, can be interpreted and evaluated as TSI. ie, the assumption is that the temperature changes were caused by direct solar forcing. Hence the TSI variations must have been x times greater than previously thought.
To my simple mind, this is very poor logic indeed. The possibility of indirect effects need to be considered.
Again, the different treatment accorded CO2 and the Sun is striking.
The full dataset of the solar spectral irradiance back to 7000
BC is available upon request.
—-
Now that’s how you do science.
Peter Taylor says:
May 10, 2011 at 3:20 am
I agree.
The main residual factor to be resolved is the correct mechanism for the cloudcover changes.
Svensmark’s cosmic ray effect is certainly a possibility and well thought of by many but I find it implausible for various reasons.
I prefer the idea that more clouds globally result primarily from more air mass mixing from longer air mass boundaries when the jets shift equatorward or become more meridional.
If the solar variations can drive that (and as explained elsewhere I think they can) then we have a suitable amplification mechanism explaining the large energy budget effect from small solar changes.
The cosmic ray changes could just be a coincidental separate effect from reduced solar activity.
The sun has risen.
British policy cock crows.
Cabinet ar’t work.
==========
In the face of the tremendous energy available in Earth’s coupled oceanic/atmospheric natural oscillating variations, as it spins and tilts on its axis, I am unimpressed with the Sun’s relatively tiny changes in available energy to out perform our own Earth. IMHO, the Sun, and dare I say anthropogenic CO2, remain distant cousins in the major Earthly drivers of temperature change.
“I WANT TO BELIEVE”, said the climatologist.
http://oi55.tinypic.com/21lll04.jpg
“How might I explain this article to my young boy?”, he asked himself.
“The sun did it, before, but oh no no not now!”, he said to himself.
“Daddy, what *is* the sun? Why is the sky blue but the sun yellow?”, Xavier asked.
“Well, X, it’s got to do with particles that come in and out of our great universe from nowhere and go back there too, to nowhere.”
“That creates inertia, a sort of soup that other pairs of not-yet-mutually-annihilated particles must always swim in, except in liquid helium.”
“Like balloons?”, X asked.
“Xavier, you will be a lawyer. I’ll pay for that. Science doesn’t fit you. You ask too may questions.”, the climatologist said.
Mike Jonas says:
May 10, 2011 at 6:20 am
“They assume that the solar activity indicated by the 10Be records, and which relates to temperature changes, can be interpreted and evaluated as TSI. ie, the assumption is that the temperature changes were caused by direct solar forcing. Hence the TSI variations must have been x times greater than previously thought.”
I don’t think they have been as simplistic as that:
“Fig. 4 presents a reconstruction of the integrated
flux for several, selected spectral regions. The contrast between
different brightness components of the quiet Sun is especially
high in the UV, which results in a large historical variability of
the UV spectral irradiance. The irradiance in the Schumann-
Runge bands and Herzberg continuum increases from the
Maunder minimum to the present by about 26.6% and 10.9%
respectively, which is much larger than 0.4% for TSI and the
visible region. The variability is also relatively high around the
CN violet system whose strength is very sensitive to even small
temperature differences due to the high value of the dissociation
potential. The large UV variability reported here is especially
of importance to the climate community because it influences
climate via an indirect, non-linearly amplified forcing.”
Thus they seem to be recognising the wavelength variations as a greater contributor to climate forcing than the absolute level of TSI.
My judgement is that those variations alter the vertical temperature profile of the atmosphere to alter surface pressure distribution and cloudiness.
Thus when the sun was more active during the late 20th century the entire atmosphere did not respond in the same way to the solar forcing.
Instead the thermosphere and troposphere warmed but the stratosphere and mesosphere cooled.
Now with a quieter sun the thermosphere has cooled, the troposphere has stopped warming and the stratosphere and mesosphere appear to have stopped cooling.
“John Finn says:
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.”
Well firstly, there is no increasing trend from the higher level plateau reached in 1950 would be a better way of describing it. Your question presupposes that we know how long it takes the Earth to reach an equilibrium temperature following an increase in received solar energy, presupposes that the 17th century temperature measurements are accurate, and reliable, presupposes that the current temperature measurements are accurate and reliable. Lets just say that not all parties are in agreement with those suppositions……:-)
The main problem with the paper is visible in the upper right hand plot of the Figure. It shows a large change in [assumed] TSI from 1900 to 1950 and no change thereafter. All evidence we have from solar indicators is that the sun the last few years have returned to conditions of a century ago. This would seem to include TSI as well, unless they can give a reason for why not [and the paper doesn’t do that]. Since the large increase in their TSI drives the reconstruction back in time, the whole thing becomes dubious. You could contrast this with the conclusion of Schrijver et al.
http://wattsupwiththat.com/2011/03/19/the-minimal-solar-activity-in-2008%e2%80%932009-and-its-implications-for-long%e2%80%90term-climate-modeling/
My money is on Schrijver, but there is a lot of room for confirmation bias with two such disparate papers: you get to choose which ones fits your agenda.
Good grief! I am sure some medieval-declined “scientist” is sneaking out to his climate-Den right now, adding these people to the dreaded BLACKLIST !
And it is all too late anyway;
http://thescotsman.scotsman.com/latestnews/Brown-Fifty-days–to.5747301.jp
Pamela Gray says: May 10, 2011 at 6:49 am
IMHO, the Sun, and dare I say anthropogenic CO2, remain distant cousins in the major Earthly drivers of temperature change.
Agree. Sun provides all the energy but no variability. Oceans and atmosphere are more like two naughty children, while CO2 is a pretentious little upstart; all ‘smoke’ no fire.
References are made to ‘Earth’s thermal equilibrium’. I doubt that such state is ever established. For Earth to do that, first the oceans would have to be in equilibrium; that is highly unlikely since the oceans are continuously perturbed by multiplicity of currents. Among number of other reasons currents are promoted by the lack of equilibrium. Nature’s circular causation.
Is it just my eyes or do the cyan lines end at 1970? Is this “Hide the decline – Part II”?
Patrick M. says:
May 10, 2011 at 10:08 am
Is it just my eyes or do the cyan lines end at 1970? Is this “Hide the decline – Part II”?
No, it is just that the ice core data is not well measured in the upper 30-50 years of the record, because the snow hasn’t yet turned into firm ice.
Leif, it looks like they used data sources from before the decline. Papers cited are from 2004 and 2008, I didn’t read the paper to know if they got updated data.
To the left, resolution in only 22years.
Leif Svalgaard says:
May 10, 2011 at 8:53 am
“My money is on Schrijver, but there is a lot of room for confirmation bias with two such disparate papers: you get to choose which ones fits your agenda”.
____________________________________________________________
21st. Century climate “science” in a nutshell :
Very long on agendas and confirmation biases. Very short on definitive facts.
As compelling a reason as there is for NOT allowing it to drive political policy.