Do solar scientists STILL think that recent warming is too large to explain by solar activity?

Guest post by Alec Rawls

Study of the sun-climate link was energized in 1991 by Friis-Christensen and Lassen, who showed a strong correlation between solar-cycle length and global temperature:

This evidence that much of 20th century warming might be explained by solar activity was a thorn in the side of the newly powerful CO2 alarmists, who blamed recent warming on human burning of fossil fuels. That may be why Lassen and Thejll were quick to offer an update as soon as the 1997-98 El Nino made it look as if temperatures were suddenly skyrocketing:

The rapid temperature rise recently seems to call for a quantitative revisit of the solar activity-air temperature association …

We conclude that since around 1990 the type of Solar forcing that is described by the solar cycle length model no longer dominates the long-term variation of the Northern hemisphere land air temperature.

In other words, there was now too much warming to account for by solar cycle length, so some other factor, such as CO2, had to be driving the most recent warming. Of course everyone knew that the 1998 warming had actually been caused by ocean oscillations. Even lay people knew it. (El Nino storm tracks were all the news for six months here in California.)

When Lassen was writing his update in mid ’99, temperatures had already dropped back to 1990 levels. His 8 year update was outdated before it was published. 12 years later the 2010 El Nino year shows the same average temperature as the ’98 El Nino year, and if post-El Nino temperatures continue to fall off the way they did in 99, we’ll be back to 1990 temperatures by mid-2011. Isn’t it about time Friis-Cristensen, Lassen and Thejll issued another update? Do they still think there has been too much recent warming to be accounted for by solar activity?

The most important update may be the discovery that, where Lassen and his colleagues found a correlation between the length of a solar-cycle and temperatures over that cycle, others have been finding a much stronger correlation to temperatures over the next cycle (reported at WUWT this summer by David Archibald).

This further correlation has the advantage of allowing us make projections. As Archibald deciphers Solheim’s Norwegian:

since the period length of previous cycle (no 23) is at least 3 years longer than for cycle no 22, the temperature is expected to decrease by 0.6 – 1.8 degrees over the following 10-12 years.

Check out this alarming graphic from Stephen Strum of Frontier Weather Inc:

The snowed in Danes might like to see these projections, before they bet the rest of their climate eggs on a dangerous war against CO2.

From sins of omission to sins of commission

In 2007, solar scientist Mike Lockwood told the press about some findings he and Claus Frohlich had just published:

In 1985, the Sun did a U-turn in every respect. It no longer went in the right direction to contribute to global warming. We think it’s almost completely conclusive proof that the Sun does not account for the recent increases in global warming.

Actually, solar cycle 22, which began in 1986, was one of the most intense on record (part of the 20th century “grand maximum” that was the most active sun of the last 11 thousand years), and by almost every measure it was more intense than solar cycle 21. It had about the same sunspot numbers as cycle 21 (Hathaway 2006):

Cycle 22 ran more solar flux than cycle 21 (via Nir Shaviv):

Cycle 22 was shorter than cycle 21 (from Joseph D’Aleo):

Perhaps most important is solar activity as measured (inversely) by the cosmic ray flux (which many think is mechanism by which solar activity drives climate). Here cycle 22 is THE most intense in the 60 year record, stronger even than cycle 19, the sunspot number king. From the Astronomical Society of Australia:

Some “U-turn in every respect.”

If Lockwood and Frohlich simply wanted to argue that the peak of the modern maximum of solar activity was between solar cycles 21 and 22 it would be unobjectionable. What difference does it make exactly when the peak was reached? But this is exactly where their real misdirection comes in. They claim that the peak of solar activity marks the point where any solar-climate effect should move from a warming to a cooling direction. Here is the abstract from their 2007 Royal Society article:

Abstract There is considerable evidence for solar influence on the Earth’s pre-industrial climate and the Sun may well have been a factor in post-industrial climate change in the first half of the last century. Here we show that over the past 20 years, all the trends in the Sun that could have had an influence on the Earth’s climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures.

In order to assert the need for some other explanation for recent warming (CO2), they are claiming that near peak levels of solar activity cannot have a warming effect once they are past the peak of the trend—that it is not the level of solar activity that causes warming or cooling, but the change in the level—which is absurd.

Ken Gregory has the most precise answer to this foolishness. His “climate smoothing” graphic shows how the temperature of a heat sink actually responds to a fall-off in forcing:

“Note that the temperature continues to rise for several years after the Sun’s forcing starts to decrease.”

Gregory’s numbers here are arbitrary. It could be many years before a fall off in forcing causes temperatures to start rising. In the case of solar cycle 22—where if solar forcing was actually past its peak, it had only fallen off a tiny bit—the only way temperature would not keep rising over the whole solar cycle is if global temperature had already equilibrated to peak solar forcing, which Lockwood and Frohlich make no argument for.

The obvious interpretation of the data is that we never did reach equilibrium temperatures, allowing grand maximum levels of solar activity to continue to warm the planet until the sun suddenly went quiet. Now there’s an update for Lockwood and Frohlich. How about telling the public when solar activity really did do “U” (October 2005).

Usoskin, Benestad, and a host of other solar scientists also mistakenly assume that temperature is driven by trend instead of level

Maybe it is because so much of the evidence for a sun-climate link comes from correlation studies, which look for contemporaneous changes in solar activity and temperature. Surely the scientists who are doing these studies all understand that there is no possible mechanism by which the rate of change in solar activity can itself drive temperature. If temperature changes when solar activity changes, it is because the new LEVEL of solar activity has a warming or cooling effect.

Still, a remarkable number of these scientists say things like this (from Usoskin et al. 2005):

The long term trends in solar data and in northern hemisphere temperatures have a correlation coefficient of about 0.7 — .8 at a 94% — 98% confidence level. …

… Note that the most recent warming, since around 1975, has not been considered in the above correlations. During these last 30 years the total solar irradiance, solar UV irradiance and cosmic ray flux has not shown any significant secular trend, so that at least this most warming episode must have another source.

Set aside the other problems with Usoskin’s study. (The temperature record he compared his solar data to is Michael Mann’s “hockey stick.”) How can he claim overwhelming evidence for a sun-climate link, while simultaneously insisting that steady peak levels of solar activity can’t create warming? If steady peak levels coincide with warming, it supposedly means the sun-climate link is now broken, so warming must be due to some other cause, like CO2.

It is hard to believe that scientists could make such a basic mistake, and Usoskin et al. certainly have powerful incentive to play dumb: to pretend that their correlation studies are finding physical mechanisms by which it is changes in the level of solar activity, rather than the levels themselves, that drive temperature. Just elide this important little nuance and presto, modern warming gets misattributed to CO2, allowing these researchers to stay on the good side of the CO2 alarmists who control their funding. Still, the old adage is often right: never attribute to bad motives what can just as well be explained by simple error.

And of course there can be both.

RealClimate exchange on trend vs. level confusion

Finally we arrive at the beginning, for me anyway. I first came across trend-level confusion 5 years ago at RealClimate. Rasmus Benestad was claiming that, because post 1960’s levels of Galactic Cosmic Radiation have not been trending downwards, GCR cannot be the cause of post-60’s warming.

But solar activity has been well above historical norms since the 40’s. It doesn’t matter what the trend is. The solar-wind is up. According to the GCR-cloud theory, that blows away the GCR, which blows away the clouds, creating warming. The solar wind doesn’t have to KEEP going up. It is the LEVEL that matters, not the trend. Holy cow. Benestad was looking at the wrong derivative (one instead of zero).

A few months later I took an opportunity to state my rebuttal as politely as possible, which elicited a response from Gavin Schmidt. Here is our 2005 exchange:

Me: Nice post, but the conclusion: “… solar activity has not increased since the 1950s and is therefore unlikely to be able to explain the recent warming,” would seem to be a non-sequitur.

What matters is not the trend in solar activity but the level. It does not have to KEEP going up to be a possible cause of warming. It just has to be high, and it has been since the forties.

Presumably you are looking at the modest drop in temperature in the fifties and sixties as inconsistent with a simple solar warming explanation, but it doesn’t have to be simple. Earth has heat sinks that could lead to measured effects being delayed, and other forcings may also be involved. The best evidence for causality would seem to be the long term correlations between solar activity and temperature change. Despite the differences between the different proxies for solar activity, isn’t the overall picture one of long term correlation to temperature?

[Response: You are correct in that you would expect a lag, however, the response to an increase to a steady level of forcing is a lagged increase in temperature and then a asymptotic relaxation to the eventual equilibrium. This is not what is seen. In fact, the rate of temperature increase is rising, and that is only compatible with a continuing increase in the forcing, i.e. from greenhouse gases. – gavin]

Gavin admits here that it’s the level of solar activity, not the trend in solar activity, that drives temperature. He’s just assuming that grand maximum levels of solar forcing should have bought the planet close to equilibrium temperature before post-80’s warming hit, but that assumption is completely unwarranted. If solar activity is driving climate (the hypothetical that Schmidt is analyzing), we know that it can push temperatures a lot higher than they are today. Surely Gavin knows about the Viking settlement of Greenland.

The rapid warming in the late 90’s could easily have been caused by the monster solar cycle 22 and there is no reason to think that another big cycle wouldn’t have brought more of the same. Two or three more cycle 22s and we might have been hauling out the longships, which would be great. No one has ever suggested that natural warming is anything but benign. Natural cooling bad, natural warming good. But alas, a longer grand maximum was not to be.

Gavin’s admission that it is level not trend that drives temperature change is important because ALL of the alarmist solar scientists are making the trend-level mistake. If they would admit that the correct framework is to look at the level of forcing and the lapse to equilibrium then they would be forced to look at the actual mechanisms of forcing and equilibration, instead of ignoring key forcings on the pretense that steady peak levels of forcing cannot cause warming.

That’s the big update that all of our solar scientists need to make. They need to stop tolerating this crazy charade that allows the CO2 alarmists to ignore the impact of decades of grand maximum solar activity and misattribute the resulting warming to fossil fuel burning. It is a scientific fraud of the most disastrous proportions, giving the eco-lunatics the excuse they need to unplug the modern world.