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Do solar cycles cause global warming?

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.

Climate Myth...

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).

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.

Last updated on 9 July 2010 by John Cook.

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Comments 1 to 25 out of 60:

  1. 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.
  2. ourphyl: Have a look at 'It's volcanoes'. Quietman has posted some relevent and interesting information and useful links.
  3. 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.
  4. 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...
  5. 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.
  6. 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.
  7. There is a widespread belief that global warming is caused by sunspots. This is the result of a 2006 NASA prediction that near the end of 2010 there would be a higher than normal solar maxima. We have to be more careful with our predictions. This was picked up by a TV station which specializes in potential disasters. Dire predictions of super solar storms which could shut down our electrical power distribution network indefinitely. The reality is that the newest NASA predictions are for a solar maxima in 2013 and that this will be a mild maxima. As of November 1, the sunspot number was 30 whereas the 2006 prediction called for a sunspot number as high as 175 at this time. The problem was that they hadn't waited for the true minima which occurred late 2008 and early 2009. The problem is that few people are aware of the truth that we have been in an extended quiet period of the sun for close to 7 years.
  8. The statement "This confirms the IPCC estimate of climate sensitivity" is incorrect. The level trend (maybe even slightly declining trend) from 1 January 2003 until the present (July 2011) places serious questions upon the IPCC guesses because CO2 has continued to rise linearly and they cannot blame the 11 year cycle any longer. Where they went wrong was in not recognising the 934 year cycle and the 59.6 year cycle which wer both rising 1970 to 2000. See for much mre detail.

    [DB] Climastrological attempts to explain away the known radiative physics of CO2 warming due to semimythical cycles can be aptly described as "Mathturbation".

  9. "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." 2011 is already the costliest year for natural disasters Well, I feel really cheerful now! ;)
  10. The link under the figure above is broken. The paper can be found (at least today) at This is the first paper I've seen that successfully shows the correlation between the solar cycle and surface temperature. Lean and Rind [Geophys. Res. Letts 35, L18701 (2008)] certainly suggest that it's been true from 1600 to 1995 or so, and get similar numbers for the size of the effect. I'm one of those people on the wrong side of the paywalls, and I'd be very interested to know how well this work has been found to hold up. Since it's in the same direction as any effects due to cosmic rays, I think it might well mask those effects entirely.

    [DB] Fixed link.

  11. A new paper by Kristoffer Rypdal demonstrates that the cycles in the temperature series found by Camp and Tung are caused by volcanic eruptions, not the solar cycle. Citing from the paper: "In particular, the cyclic GMST variations reported by Camp and Tung [2007] is naturally explained as a result of a succession of volcanic eruptions, ending with Mount Pinatubo in 1991." Reference: Rypdal, K. (2012), Global temperature response to radiative forcing: Solar cycle versus volcanic eruptions, J. Geophys. Res., 117, D06115, doi:10.1029/2011JD017283.
  12. Two links with some differing findings, namely increasing TSI activity since 1850. What is wrong here? (found matching with with USA daily max temp!) and (see figure "historical TSI reconstruction"-> TSI increase!)
  13. Falkenherz - The Washington Times article (not a peer-reviewed paper, mind you) authored by Soon and Briggs did not identify their source of TSI data, making it extremely difficult to evaluate. The second TSI estimate is based on Lean 2005 - Knopp and Lean 2011 downgrades recent forcings based on corrected satellite calibrations, noting that "Climate change studies that use published TSI time series to accredit solar responses must be cognizant of the possible errors in the record; otherwise climate variability is incorrectly attributed to solar variations that are in fact instrumental drifts." Finally, there are multiple papers indicating, as with Lockwood and Frohlich 2007, Recent oppisitely directed trends in solar climate forcings and the global mean surface air temperature, that:
    ...the observed rapid rise in global mean temperatures seen after 1985 cannot be ascribed to solar variability, whichever of the mechanisms is invoked and no matter how much the solar variation is amplified.
  14. Note that I've contacted both Soon and Briggs asking about the source of their TSI data. Neither has responded. Note also that the Colorado/Lean 2005 reconstruction shows no TSI increase on average over the past ~50 years.
  15. From the William Briggs blog, a rather curious statement: Luis Dias on 7 September 2012 at 11:34 am said:
    "Leif Svalgaard [refers to posts on WUWT] seems to take great exception to your solar radiation curve." He’s extremely up in arms about it. What do you have to say about what he says, mr Briggs?
    Briggs on 7 September 2012 at 2:07 pm said:
    Luis, Asked Soon. He said “we can make this independent of any TSI curve. I really meant it when I said, we got evidence for Arctic, China and USA temperatures to very co-varying somewhat similarly.” I’ve seen several of these other plots and can verify. For instance, we sent four to the Washington Times; they printed just the one. Willie and I are hunting around for other outlets (with more exposure than this small blog) to show the others. Willie also asks, in the proper spirit, “Svalgaard knew his curve is correct?”
    (Emphasis added) I find it quite odd, in an article on the relationship between TSI and temperature, to state that "we can make this independent of any TSI curve". Regardless of the (as yet not provided) provenance of their TSI data, that statement seems to call into question the entire Soon and Briggs article...
  16. Willie and I are hunting around for other outlets (with more exposure than this small blog) to show the others.
    Why? Have we grown tired of publishing scientific papers in science journals?
  17. Now if Phil Jones had said something like that . . .
  18. KR @15 - the correlation between local temps and TSI is independent of TSI? I think the 'statistician to the stars' may be losing it. I'm also glad that reputable media outlets have not published this utter nonsense.
  19. #15 KR - very interesting statement. I have to wonder if Soon and Briggs' graph at Washington Times is hand-drawn. Two graphical things lead towards that conclusion, one noticed by somebody else, the second by me (full resolution source, from newspaper article): 1: First, it is apparent that lines on the graph do not always join up smoothly, always progressing forwards in time, as they would if they were generated by a plotting program from a single series of data. This is most apparent around 1935 and 1953 in the "solar radiation" curve. In both cases, the line appears to go "backwards", or is not joined, and so is not a normal single time series. It may suggest multiple data sources, or poor tracing of a single data source; either is very poor practice. 2: Second, several of the line segments are perfectly vertical, despite both series being ostensibly continuous time series, and the resolution of the plot being sufficient (580 pixels/180 years) that lines of a year's length should all be non-vertical. Again, data should always progress forwards in time. No automatic plotting pachage that I am aware of would produce a plot like the one above. Examples are in the temperature plot around 1850 and 1895, and in the solar radiation plot at about 1960. The line segments frequently cover many years, and are clearly smoothed data, so there is no reason to think that what is being presented is monthly data (which would be of a resolution to allow vertical segments). These very strongly suggest to me that the plot, uness it can be shown otherwise by the authors, is traced by hand, using a package such as Illustrator. The only other explanation is that there are multiple points for the same year, or even two points which go back in time, neither of which should exist in a timeseries plot like this. These features, along with the lack of a source for the solar data, make me very suspicious indeed of the graph's provenance. It may just reflect poor practice (though what user of climate data cannot plot data from a spreadsheet?). The Comments Policy forbids me from speculating on other possible motives.
  20. Andy S noted to me the possibility that the drafting was done by the Washington Times. That is a reasonable explanation for the poor plotting, but why on earth would they plot reverse slopes? Very poor plotting/tracing whoever did it! What remains are the substantive questions as to the source of the "solar radiation" curve. It is clearly plotted poorly, and does not appear to relate to other estimates (proxy or direct) of solar irradiance. Adding that to the cherry-pick of US land daytime temperatures (rather than global, or full daily, ie day and night), and this graph is very poor indeed. Soon and Briggs, show your working please!
  21. The closest match to the curve Soon & Briggs posted (that I've seen) is Hoyt & Schatten 1993, Fig. 10. The S&B graph differs in that it extends later (with the odd issues of verticals and doubled lines) than H&S, and is offset by ~10 W/m^2, but the overall shape is strikingly similar. The H&S graph was an 11-year running mean of multiple solar models including solar cycle length. A H/T to Leif Svalgaard on WUWT, who noted:
    ...looks like the discarded 20-yr old Hoyt & Schatten data, which today is not generally accepted...
    Again, as others have noted - Soon and Briggs simply have not sourced their TSI data, which doesn't match any current TSI record I am aware of.
  22. Thanks for taking up my question. IMO, this is the first real observation which I found and could finally lead to a sound sceptical argument about AGW. I think we can agree that, no matter how accurate that graph in the WP is drawn, it does match the generally observable trend from other TSI records: No matter how we might find issues with the WP-graph, the graph "historical TSI reconstruction" on does also show a correllation of TSI and global (not only USA) rising temperature trend. Now, if I understand correctly, that correllation is not really being challenged as concerning the first half of the 20th century, right? According to what KR did quote, we look merely at the time since 1985, where TSI goes downwards. Others say we need to look at the time since about 1960. So, it is only from that point of time that GHG could really take over as a driver, right? But, atmospheric temp seems again to align to the weaker TSI, by keeping moreless its level since 1998. However, we then argue that it is the global oceanic temp, which continues to rise. Correct? If I go by simplified logic, it should be like that: +TSI +GHG = strong raise of global temperature -TSI +GHG = weaker raise of global temperature (if at all, if you look at the lag at the climax shown by the ice core curves...) If we observe merly atmospheric global temperature, this simplified logic seems to apply and our AGW Theorie seems to fail. Atmospheric temperatur does indeed not rise for about 10 years! But if we put emphasis on the oceanic global temperature, we instead observe a continued strong raise of global temperature, right? Which is odd, too. If it should be mainly GHG as responsible factor, could that raise really be that strong? It should be weaker than a bundled raise of TSI and GHG together, right? Or do we commit an error by taking into account oceanic temperature somehow in a wrong way? Or do we still not understand TSI, or other influences and its effects on earth correctly? This seem at least to be possibilities. Along these lines, another observation: I always understood IPCC arguing that climate is a long term issue, and that we observe a rather strong raise of 0,8 degree since 1850. But suddenly, I see here that most of the raise can be aligned with historical TSI-data (as far as we know...) and it is only 1960 or 1985 where GHG really could kick-in. This does not seem consistent, do we have AGW by GHG emissions since 1850 or since 1960/1985??? I am confused.
  23. Falkenherz - Actually, the differing recent behavior of TSI and temperature are a very strong argument for anthropogenic global warming. In the past solar variations (and volcanic aerosols, with an overlay of ENSO) has been one of the biggest drivers of varying climate. That's no longer the case. Since mid-century the rising influence of anthropogenic greenhouse gases has been statistically separable from natural drivers. And hence solar cycles do not cause recent global warming. To quote a popular TV show, "...that myth is busted!" Source: "Comparison between global mean surface temperature anomalies (°C) from observations (black) and AOGCM simulations forced with (a) both anthropogenic and natural forcings and (b) natural forcings only..."
  24. And for yet another paper on the decoupling of solar and surface temp, see Pasini et al. (2012). That paper finds the departure date at around 1960.
  25. KR, DSL, thanks again. So, taking into account of what we think we know about TSI, we are basically not talking about a GHG-attributed warming of 0,8 Degree increase in 100 Years, but about a 0,2 Degree increase in 50 Years. I looked up the 4th IPCC report summary to confirm this, here: (the average from the table should be around said 0,2 Degree) 0,2 Degree is something very different to 0,8 Degree. Nevertheless IPCC includes the latter in its summary here (first bulletpoint): This is for me a serios and intentional miscommunication from IPCC. So, setting things straight, the current models take those 0,2 Degree and extrapolate from it a future GHG-induced rise of 3 Degrees for 100 Years. I must admit that makes me now much more sceptical than I was before. How can this possibly fit to the icecore-data, where CO2 lags behind (=still rises up) and temperature nevertheless is falling in accordance with the TSI, maybe even with a lag to declining TSI which would correspond to what we observe today? Where can I find more information on TSI data related to the icecore-data?

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