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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Sun & climate: moving in opposite directions

What the science says...

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The sun's energy has decreased since the 1980s but the Earth keeps warming faster than before.

Climate Myth...

It's the sun

"Over the past few hundred years, there has been a steady increase in the numbers of sunspots, at the time when the Earth has been getting warmer. The data suggests solar activity is influencing the global climate causing the world to get warmer." (BBC)

Over the last 35 years the sun has shown a cooling trend. However global temperatures continue to increase. If the sun's energy is decreasing while the Earth is warming, then the sun can't be the main control of the temperature.

Figure 1 shows the trend in global temperature compared to changes in the amount of solar energy that hits the Earth. The sun's energy fluctuates on a cycle that's about 11 years long. The energy changes by about 0.1% on each cycle. If the Earth's temperature was controlled mainly by the sun, then it should have cooled between 2000 and 2008. 

TSI vs. T
Figure 1: Annual global temperature change (thin light red) with 11 year moving average of temperature (thick dark red). Temperature from NASA GISS. Annual Total Solar Irradiance (thin light blue) with 11 year moving average of TSI (thick dark blue). TSI from 1880 to 1978 from Krivova et al 2007. TSI from 1979 to 2015 from the World Radiation Center (see their PMOD index page for data updates). Plots of the most recent solar irradiance can be found at the Laboratory for Atmospheric and Space Physics LISIRD site.


The solar fluctuations since 1870 have contributed a maximum of 0.1 °C to temperature changes. In recent times the biggest solar fluctuation happened around 1960. But the fastest global warming started in 1980.

Figure 2 shows how much different factors have contributed recent warming. It compares the contributions from the sun, volcanoes, El Niño and greenhouse gases. The sun adds 0.02 to 0.1 °C. Volcanoes cool the Earth by 0.1-0.2 °C. Natural variability (like El Niño) heats or cools by about 0.1-0.2 °C. Greenhouse gases have heated the climate by over 0.8 °C.

Contribution to T, AR5 FigFAQ5.1

Figure 2 Global surface temperature anomalies from 1870 to 2010, and the natural (solar, volcanic, and internal) and anthropogenic factors that influence them. (a) Global surface temperature record (1870–2010) relative to the average global surface temperature for 1961–1990 (black line). A model of global surface temperature change (a: red line) produced using the sum of the impacts on temperature of natural (b, c, d) and anthropogenic factors (e). (b) Estimated temperature response to solar forcing. (c) Estimated temperature response to volcanic eruptions. (d) Estimated temperature variability due to internal variability, here related to the El Niño-Southern Oscillation. (e) Estimated temperature response to anthropogenic forcing, consisting of a warming component from greenhouse gases, and a cooling component from most aerosols. (IPCC AR5, Chap 5)

Some people try to blame the sun for the current rise in temperatures by cherry picking the data. They only show data from periods when sun and climate data track together. They draw a false conclusion by ignoring the last few decades when the data shows the opposite result.


Basic rebuttal written by Larry M, updated by Sarah

Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial


This rebuttal was updated by Kyle Pressler in 2021 to replace broken links. The updates are a result of our call for help published in May 2021.

Last updated on 2 April 2017 by Sarah. View Archives

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Further viewing

Related video from Peter Sinclair's "Climate Denial Crock of the Week" series:

Further viewing

This video created by Andy Redwood in May 2020 is an interesting and creative interpretation of this rebuttal:

Myth Deconstruction

Related resource: Myth Deconstruction as animated GIF

MD Sun

Please check the related blog post for background information about this graphics resource.


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Comments 876 to 900 out of 1304:

  1. Eric (skeptic) @875, first, I think there may be a difference in definition. Specifically, when talking about thermal lag for CO2, we are talking about the period of time to reach 60% (or there about) of the equilibrium response. When we talk about thermal lag for seasonal temperature changes, we are talking instead about the time difference between the peak (minimum) insolation and the peak (minimum) temperature response. That is because the oscillating insolation does not leave enough time for 60% of the equilibrium response to be reached. Rather, the insolation falls below the equilibrium level of the current temperature long before it reaches that point. The same is certainly true for the solar cycle, and probably true for changes in TSI over the 20th century in general, which first fell, than rose to about 1950, then fell again, then rose almost as far, and then fell gradually. Consequently thermal lag for insolation probably measures the period to peak measurable response rather than the period to a certain percentage of equilibrium response as with CO2. The difference is not because of the different source of forcing, but because the CO2 forcing is increasing monotonically (note: CO2 forcing, not total or total anthropogenic forcing). Second, the level of the forcing for changes in TSI and especially for the solar cycle are not large, and certainly not nearly the same size as the CO2 forcing. Remember that the greatest change in TSI in the twentieth century (from 1910 to 1950) accounted for approximately a third of a slower warming than that at the end of the twentieth century which can be attributed exclusively to CO2 (but only in that the other factors canceled out). Consequently the peak solar forcing is at most a third of the peak CO2 forcing in the twentieth century, which means the resulting decadal temperature change from solar alone is not greatly different from the annual variation in mean global temperature. If the temperature is rising then falling due to an oscillating forcing, it will approximate to a sine wave. It will first rise slowly, then quite rapidly, and then slow down again. For a weak forcing, it is probable that only the change in temperature during the rapid rise will be statistically detectable, particularly if the forcing is very weak (solar cycle) or there are only one or two examples to test against (major TSI changes). Consequently the end of the peak measurable change of temperature will coincide with the end of that rapid rise rather than the actual peak which will be obscured by year to year temperature variations. Third, and particularly for the the solar cycle, because annual temperature fluctuations are large compared to those induced by the solar cycle, it is probable that after a short period of time a random fluctuation will bring the temperature up to the peak response point. From that point the higher (or lower) insolation will be acting to dampen departures from that temperature rather than lifting (or lowering) the temperature to that point. And as we have established, there is no thermal lag for that. Consequently the two month lag (which I and, more importantly as he has reasonable claim to expertise in this area, Tamino find surprising) may just be the average period until a random fluctuation shifts the temperature towards the effective equilibrium temperature. My point is not that any of these factors is shortening the "thermal lag" period for TSI variations including the solar cycle. It is that there are good reasons to expect weak, and fluctuating forcings to exhibit a reduced lag response both because their full response is never exhibited due to lack of time, and because noise can swamp out the more subtle parts of the signal. I do not suppose these are the only ways that can happen, and nor can I claim to know how much each factor is relevant in particular cases. But I do know that the difference between the thermal lag duration for CO2 and solar forcings is a function of characteristics of those forcings, not special pleading.
  2. Eric (skeptic) In comparing the lag of decades for CO2 and months for the 11 year solar cycle you appear to be confusing "equilibrium" and "instantaneous" responses of the climate. Think of the thermal inertia of the oceans as acting like a damper in a car suspension system; if you increase the weight of the car, it will slowly sink on its suspension at a rate depending on the damping. If you put a 100kg weight in the car, it doesn't immediately sink an inch, it takes a fraction of a second. If you fit stiffer dampers, it will take longer. So there is an "equilibrium" response of the suspension that is larger than the "immediate response" (it starts settling immediately, but it takes time to get to its equilibrium position). Now consider what happens if you drive down a cobbled street (i.e. a cyclic forcing), the damper then will attenuate the oscillation in ride height, and you will find there will be lag introduced in the ride height relative to the road surface, but there is no "equilibrium response" as the cobbles don't change the equilibrium ride height.
  3. Tom, I must take issue with your statement "Second, the level of the forcing for changes in TSI and especially for the solar cycle are not large, and certainly not nearly the same size as the CO2 forcing." Please double check these numbers, but 11 year TSI amplitude is 0.1% or 1366/1000/4 or 0.34 W/m2. For CO2 over 11 years it is 22 ppm or (22/280)*3.7 or 0.29 W/m2. That means they are roughly the same amplitude over that phase of the solar cycle. Dikran, perhaps you can check those numbers too, I don't see how the damping on the CO2 rise can be any different than the damping on the TSI oscillation. Aren't they exactly the same?
  4. Eric, the point is that you are confusing the instantaneous response with the equilibrium response. The climate starts responding to CO2 rapidly just as it does the 11 year solar cycle, but in the case of CO2 it eventually overcomes the inertia (as it is monotonically rising) but the 11 year solar cycle doesn't as it alternates phase far earlier than thermal inertia is overcome. If TSI gradually increased (rather than oscillated) it too would have an equilibrium response that would only be fully realised after several decades, but temperatures would start to rise immediately. I don't know if you have an engineering background, but it is the difference between the equilibrium response and transient response of a system described by differential equations. They are not the same thing.
  5. Eric, I think your comparison is apples and oranges. First, as to the cycle, while the change in amplitude could be 0.34 W/m2, it's not really fair to treat the minima as the baseline, so you're really talking about +/- 0.17 W/m2. It's also not a square cycle, jumping from minimum to maximum in one leap, so the duration of time spent at that full increase or decrease is low, with the majority of the cycle spent within 0.09 W/m2 or even less. Also, every positive swing has the negative swing, so any lag at all is going to be very muddled (with the counter/braking action starting before the original action is able to take effect). Second, for changes between cycles, the difference is even less than 0.34 W/m2, much less. In the past three cycles, the variation from the first to the third maximum (eyeballing it) looks to be less than one one hundredth of one percent, while the minima have no apparent change.
  6. Eric, Just to make it a little clearer, no net change in minima, and a net change in maxima of about 0.03 W/m2 i the past 33 years, would net out (since most of the time is spent in the basically unchanged ups and downs of the cycle) to probably an addtional 0.03 W/m2 for maybe 6 or 9 of those 33 years, or at best 1/4 of the time, meaning a net of 0.0075 W/m2... a completely inconsequential number.
  7. Eric, Whoa! Lastly, I just noticed that you bumped the CO2 forcing down to only consider the change in forcing, i.e. in the increase during an 11 year period. But the CO2 forcings are cumulative, where the TSI changes are not. It's hardly a fair argument to compare 11 years of TSI changes (which net to zero!) to 11 years of CO2 changes which pile on top of decades of previous change in the value. Those are not the two values under discussion (11 year change in CO2 versus 11 year change in TSI, which itself is probably less than 0.0025 W/m2 anyway -- you have to measure the areas under the two curves to get a true number).
  8. Sphaerica, your first post didn't really address my concern because you turned the 11 years of increase into a shorter interval of high solar. Then your second post changed the topic to secular solar changes and I have no argument with it (they are small). In your third post you resumed the original topic but missed my point which is quite simple: there is an interval of 11 years in which the TSI forcing increases roughly the same amount as CO2 does during that same interval. It is then balanced by the next 11 years of decreasing TSI forcing. Dikran, you are suggsting that the earth has a different thermal intertia to TSI changes than to CO2 changes. I don't see how that can be true. Tom, regarding your statement "Second, the level of the forcing for changes in TSI and especially for the solar cycle are not large certainly not nearly the same size as the CO2 forcing" would make sense if it was simply appended with "in total" or "since preindustrial" or "ongoing long term". Then we would all be able to violently agree.
  9. Eric (skeptic) @883, first, Sphaerica's 880 and 881 are I believe restatements of my first point in 886. So are Dikran's 877 and 879, though he states it with greater clarity and economy than I do. Second, I think the best way to state it is that the unrealized instantaneous forcing is very much larger for CO2 than for TSI changes associated with the solar cycle, and significantly larger than for TSI changes at any time in the twentieth century. By "unrealized instantaneous changes" I mean the change in total forcing due to a given factor at anytime minus the change in OLR due to changes in surface temperature at the same time. I take it that is what you mean by "ongoing long term forcing", and also what Sphaerica was describing in his 882. That being the case, we can all now agree furiously together on this point.
  10. Eric (skeptic) wrote: "Dikran, you are suggsting that the earth has a different thermal intertia to TSI changes than to CO2 changes. I don't see how that can be true." No, I am not suggesting any such thing. The thermal inertia of the earth has the same effect on warming due to TSI changes as it does on CO2 changes. The point is that you are comparing the equilibrium response to CO2 forcing with the transient response for TSI, so you are not comparing like with like. If TSI forcing was steadily rising just as CO2 radiative forcing is, then there would be a transient response (the Earth would start warming essentially immediately), but the full warming would not be realised for some decades (the equilibrium response). However, TSI is not steadily rising, it is oscillating, which is why the delay being discussed in relation to the 11-year solar cycle is not the delay before equilibrium is reached, it is a phase shift caused by the thermal inertia of the oceans. Until you understand the difference between a transient and an equilibrium response in a dynamical system, you are unlikely to resolve your confusion.
  11. Dikran, I think Tom explained it pretty well in 884. Past CO2 forcing plus thermal intertia (to warming) have produced an unrealized forcing which exceeds any natural forcing since secular natural forcings are all very small. Thus the GAT effect of such a forcing is much larger than the GAT effect of any cyclical natural forcing like TSI.
  12. Great Post! It's 2011, and we in the US are in the middle of another Summer heat wave and severe drought. I used a few arguments from this post to totally debunk someone in my office who was trying to use the "11-year solar cycle" argument to explain this drought.
  13. gcdem, The solar cycle has nothing to do with the Southern (especially Texan) drought. The main culpret has been the strong La Nina. Areas to the north experienced above normal precipitation (rain and snow), whereas southern areas were rain-starved. Similar occurrances accompanied past strong La Ninas, many of which were more severe than the current situation, particularly the mid 1950s.
  14. Hi all, Do you have a page dedicated to the Denialist claim that the IPCC itself admits it doesn't know what's happening with solar forcings at the following 2007 report page. IPCC 2.9.1 Uncertainties in Radiative Forcing
  15. Um, it's rather a long stretch from quantifying the uncertainties as of 2007 to "it doesnt know whats happening". As that reference points out, solar forcing is extremely well measured for last 25 years (direct measurement by satellite) but is "B" because of reliance on proxies prior to that. For more up to date look at the solar proxy uncertainties see this . Note that all forcings (indeed all scientific measurements) have uncertainties. What's important is the extent to which these can be quantified.
  16. I am not sure if any of you notice this or not, but the PMOD link goes to a data set that is a little too small of deviation for solar data collected in Earth orbit with daily entries. That is to say, the Earth's orbit is elliptical. For part of the year we are closer and the other half farther away. This results in a difference of about 90 W/m^2 between minimum and maximum. The data on PMOD at most varies by a few W/m^2 in a year. If you are measuring values on 22DEC2009 that are within 1 W/m^2 of values on 22JUN2010, then you have some issues with your data. That difference should be pushing 90 W/m^2. The difference in r value for the intensity calculations is about 5 million km. So, maybe the sources for this article should be revised.
  17. Thanks Scaddenp. One query regarding the forum software: every thought of switching to Wordpress? Wordpress is great software and has BBpress forums as a plug-in now. Commenting could have all the power of BBpress (or SMF or Phpbb3 or whatever other open source forum software you want).
  18. Disregard the last comment about Wordpress... I just realised how much work you've already put into the ipad and iphone apps and would hate to put you through all that again. (Not sure if Wordpress has simple translation into these formats but there you go). I just love powerful forum software, because... well... I didn't even get an email last time someone replied?
  19. This next argument seems to be another version of "It's the sun" that good old Willie Soon (and his $million from Exxon) have written. New Willie Soon paper Does anyone know any peer-review work on this yet? Is the journal it is in actually an authentic climate journal? Is it legitimate science about a LOCAL Chinese phenomenon or a hyped up local phenomenon that fraudster Denialists are using to try and confuse people about GLOBAL climate change?
  20. I've read the abstract of the Soon paper you linked to Eclipse. The temperature trends observed in China seem consistent with what is known about the 20th Century temperature trends in general IIRC - as a result of global brightening and dimming. So he may have that part right at least.
  21. And besides,the paper was about *China* and about the 20's and 40's for some reason. It's not as if he's discovered something controversial about the *globe now* is it? Cheers.
  22. Soons paper sounds to me like the results of a search for statistically significant trends and association with solar forcing region by region - which of course invalidates the test of statistical significance (unless multiple hypothesis testing issues are properly dealt with).
  23. Continuing from here. EtR's sunspot graph clearly shows the 1950s solar maximum; since then solar activity has in fact declined (hence the descriptive term maximum). A simple straight lines fit doesn't capture that important detail and is therefore irrelevant.
  24. To illustrate Muoncounter's point @898:
  25. Muon, Yes, solar cycle 19 was definitely the highest of the 20th century. However, cycles 21 and 22, in the 1980s and 1990s, were the next two highest, significantly surpassing anything during the early 20th century. The point is that sunspot activity was still high during the last portion of the 20th century. To expect temperatures to decrease based on the drop from a very high to just a high value would be comparable to expecting temperatures to drop because we added less CO2 to the atmosphere this year than last. A straight line fit does not capture the temperature profile of the 20th century, but does that negate the fact that an increase has occurred?
    Response: [Dikran Marsupial] Re your second paragraph, it is well know that there are multiple forcings that affect climate, hence nobody would expect a straight line fit. Please be less opaque in your posts as such obfuscation gives the impression of trolling.

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