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Do solar cycles cause global warming?

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The skeptic argument...

Solar cycles cause global warming

A new peer-reviewed study on Surface Warming and the Solar Cycle found that times of high solar activity are on average 0.2°C warmer than times of low solar activity, and that there is a polar amplification of the warming. This result is the first to document a statistically significant globally coherent temperature response to the solar cycle, the authors note (source: Mark Morano).

What the science says...

A full reading of Tung 2008 finds a distinct 11 year solar signal in the global temperature record. However, this 11 year cycle is superimposed over the long term global warming trend. In fact, the authors go on to estimate climate sensitivity from their findings, calculate a value between 2.3 to 4.1°C. This confirms the IPCC estimate of climate sensitivity.

The study is Surface warming by the solar cycle as revealed by the composite mean difference projection by Charles D. Camp and Ka Kit Tung. They find a global warming signal of 0.18°C attributable to the 11-year solar cycle. Eg - from solar minimum to solar maximum, global temperatures increase 0.18°C due to an increase in Total Solar Irradiance (TSI). To find the solar signal, they detrended the temperature data by removing the global warming trend. They found the detrended temperature correlated well with the solar cycle.

TSI including 11 year solar cycle vs detrended surface temperature
Figure 1: Detrended temperature (solid) compared to TSI (dotted) (Camp 2007)

However, a fair degree of climate variability contaminated the signal. Volcanic eruptions in 1982 and 1991 coincided with solar maximums. Similarly, the El Nino peak of 1998 occured during low solar activity. Tung and Camp filtered out the noise using various statistical techniques and found an even higher correlation with the solar cycle.

They concluded that from solar minimum to maximum (eg - from 1996 to 2001), the forcing from the sun increases global temperatures by 0.18°C. Conversely, from solar maximum to minimum (eg - from 2001 to 2007), the reduced forcing from the sun cools global temperatures by 0.18°C. This 11 year cycle is superimposed over the long term global warming trend.

Climate Sensitivity

Camp and Tung explore the ramifications further in a follow-up paper Solar-Cycle Warming at the Earth’s Surface and an Observational Determination of Climate Sensitivity. Independently of models, they calculate a climate sensitivity between 2.3 to 4.1°C. Eg - if CO2 levels are doubled, global temperatures will increase around 3.2°C. This confirms the IPCC estimate of climate sensitivity. In Tung's own words, "The finding adds to the evidence that mainstream climate models are right about the likely extent of future human-generated warming. It also effectively rules out some lower estimates in those models."

The other significant finding is that solar forcing will add another 0.18°C warming on top of greenhouse warming between 2007 (we're currently at solar minimum) to the solar maximum around 2012. In other words, solar forcing will double the amount of global warming over the next five to six years.

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It's the sun

Comments

Comments 1 to 7:

ourphyl at 11:15 AM on 21 October, 2007
Very interesting, I'll study your link.

There is much interesting work by UNC prof Jose Rial (and others)on D&O paleoclimate cycles. They need to consider "tipping points" and occasional chaos, extremes that might be of interest. Jose also is a seismic scientist, his abstract re arctic ice follows:

Measurements of seismic activity in Greenland's ice sheet indicate the activity is related to the ice sheet's probable fragmentation due to global warming. Project SMOGIS (Seismic Monitoring of Greenland's Ice Sheet), a collaboration between UNC-Chapel Hill and the University of Colorado at Boulder, has detected intense microearthquake activity throughout the region close to the Jacobshavn glacier, one of the world's fastest moving glaciers. The seismic activity is clearly related to glacial sliding (at the base of the ice sheet) and crevassing, or large fractures expanding under the increased warming. "The area we are inspecting could be seen as belonging to the buttresses of a giant cathedral, which is the Greenland ice sheet," Rial said. "If the buttresses fail, the entire cathedral could collapse, perhaps in just a few years. This may be part of what has been called abrupt climate change."

I don't know where this might fit in your list should it belong.

Thanks and congratulations on a GREAT site.
Mizimi at 05:03 AM on 29 August, 2008
ourphyl:

Have a look at 'It's volcanoes'. Quietman has posted some relevent and interesting information and useful links.
Quietman at 06:24 AM on 18 September, 2008
Camp & Tung assume the IPCC's accepted sensitivity is accurate. If we take their numbers and lower the sensitivity to Spencer's numbers we get a very different result. Their study is on the solar forcing, the feedback is assumed.
chris at 05:21 AM on 7 October, 2008
Re #3

That's incorrect. Tung and Camp derive a value for the earth's climate sensitivity to raised CO2 that is completely independent of the so-called "IPCC's accepted sensitivity". That's the whole point of their work! They analyze the solar cycle contribution to warming and (according to their analysis) derive an INDEPENDENT measure of the climate sensitivity.

Their value is (see equation 2 on line 379 of their manuscript):

2.3 oK < DeltaT(2xCO2) < 4.1 oK

In other words according to Tung and Camp, the Earth warms by around 3 oC (plus/minus a bit) for each doubling of atmospheric CO2 concentration.

The fact that this value is pretty much in line with all of the other scientific analyses of climate sensitivity (as compiled by the IPCC) is interesting and may be taken as further evidence of a consistent arrival at the climate sensitivity using a number of different methods. But it is an ENTIRELY INDEPENDENT measure and doesn't assume anything whatsoever about "the IPCC"!

That's pretty straightforward...
MattJ at 12:48 PM on 8 April, 2009
Isn't there another, longer cycle superimposed over this one? I seem to remember 81 or 181 years, but I can't remember which.

I am surprised that the sunspot cycle could even contribute as much as .18C, seeing that most of the radiation change is in either fairly low RF frequencies or in X-ray spectrum.

Then again, X-rays are well absorbed by the atmosophere, so they really do turn into heat.
MattJ at 12:51 PM on 8 April, 2009
Isn't there another, longer cycle superimposed over this one? I seem to remember 81 or 181 years, but I can't remember which.

I am surprised that the sunspot cycle could even contribute as much as .18C, seeing that most of the radiation change is in either fairly low RF frequencies or in X-ray spectrum.

Then again, X-rays are well absorbed by the atmosophere, so they really do turn into heat.