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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)

At a glance

Thankfully for us, our Sun is a very average kind of star. That means it behaves stably over billions of years, steadily consuming its hydrogen fuel in the nuclear reaction that produces sunshine.

Solar stability, along with the Greenhouse Effect, combine to give our planet a habitable range of surface temperatures. In contrast, less stable stars can vary a lot in their radiation output. That lack of stability can prevent life, as we know it, from evolving on any planets that might orbit such stars.

That the Sun is a stable type of star is clearly demonstrated by the amount of Solar energy reaching Earth's average orbital position: it varies very little at all. This quantity, called the Total Solar Irradiance, has been measured for around forty years with high accuracy by sensitive instruments aboard satellites. Its average value is 1,362 watts per square metre. Irradiance fluctuates by about a watt either way, depending on where we are within the 11-year long sunspot cycle. That's a variation of no more than 0.15%.

From the early 1970s until today, the Solar radiation reaching the top of Earth's atmosphere has in fact shown a very slight decline. Through that same period, global temperatures have continued to increase. The two data records, incoming Solar energy and global temperature, have diverged. That means they have gone in opposite directions. If incoming Solar energy has decreased while the Earth continues to warm up, the Sun cannot be the control-knob of that warming.

Attempts to blame the sun for the rise in global temperatures have had to involve taking the data but selecting only the time periods that support such an argument. The remaining parts of the information - showing that divergence - have had to be ditched. Proper science study requires that all the available data be considered, not just a part of it. This particular sin is known as “cherry-picking”.

Please use this form to provide feedback about this new "At a glance" section, which was updated on May 27, 2023 to improve its readability. Read a more technical version below or dig deeper via the tabs above!

Further details

Our Sun is an average-sized main sequence star that is steadily using its hydrogen fuel, situated some 150 million kilometres away from Earth. That distance was first determined (with a small error) by a time consuming and complex set of measurements in the late 1700s. It led to the first systemic considerations of Earth's climate by Joseph Fourier in the 1820s. Fourier's number-crunching led him to realise a planet of Earth's size situated that far from the Sun ought to be significantly colder than it was. He was thereby laying the foundation stone for the line of enquiry that led after a few decades to the discovery of what we now call the Greenhouse Effect – and the way that effect changes in intensity as a response to rising or falling levels of the various greenhouse gases.

TSI Solar cycles

Figure 1: Plot of the observational record (1979-2022) on the scale of the TSIS-1 instrument currently flying on the space station. In this plot, the different records are all cross calibrated to the TSIS-1 absolute scale (e.g., the TSIS1-absolute scale is 0.858 W/m^2 higher than the SORCE absolute scale) so the variability of TSI in this plot is considered to be its “true variability” (within cross calibration uncertainties). Image: Judith Lean.

The Sun has a strong magnetic field, but one that is constantly on the move, to the extent that around every 11 years or so, Solar polarity flips: north becomes south, until another 11 years has passed when it flips back again. These Solar Cycles affect what happens at the surface of the Sun, such as the sunspots caused by those magnetic fields. Each cycle starts at Solar Minimum with very few or no sunspots, then rises mid-cycle towards Solar Maximum, where sunspots are numerous, before falling back towards the end. The total radiation emitted by the Sun – total solar irradiance (TSI) is the technical term – essentially defined as the solar flux at the Earth's orbital radius, fluctuates through this 11-year cycle by up to 0.15% between maximum and minimum.

Such short term and small fluctuations in TSI do not have a strong long term influence on Earth's climate: they are not large enough and as it's a cycle, they essentially cancel one another out. Over the longer term, more sustained changes in TSI over centuries are more important. This is why such information is included, along with other natural and human-driven influences, when running climate models, to ask them, “what if?"

An examination of the past 1150 years found temperatures to have closely matched solar activity for much of that time (Usoskin et al. 2005). But also for much of that time, greenhouse gas concentrations hardly varied at all. This led the study to conclude, " that at least this most recent warming episode must have another source."

TSI vs. T
Figure 2: 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 slight decline in Solar activity after 1975 was picked up through a number of independent measurements, so is definitely real. Over the last 45 years of global warming, Solar activity and global temperature have therefore been steadily diverging. In fact, an analysis of solar trends concluded that the sun has actually contributed a slight cooling influence into the mix that has driven global temperature through recent decades (Lockwood, 2008), but the massive increase in carbon-based greenhouse gases is the main forcing agent at present.

Other studies tend to agree. Foster & Rahmstorf (2011) used multiple linear regression to quantify and remove the effects of the El Niño Southern Oscillation (ENSO) and solar and volcanic activity from the surface and lower troposphere temperature data.  They found that from 1979 to 2010, solar activity had a very slight cooling effect of between -0.014 and -0.023°C per decade, depending on the data set. A more recent graphic, from the IPCC AR6, shows these trends to have continued.

AR6 WGI SPM Figure 1 Panel p

Figure 3: Figure SPM.1 (IPCC AR6 WGI SPM) - History of global temperature change and causes of recent warming panel (b). Changes in global surface temperature over the past 170 years (black line) relative to 1850–1900 and annually averaged, compared to Coupled Model Intercomparison Project Phase 6 (CMIP6) climate model simulations (see Box SPM.1) of the temperature response to both human and natural drivers (brown) and to only natural drivers (solar and volcanic activity, green). For the full image and caption please click here or on the image.

Like Foster & Rahmstorf, Lean & Rind (2008) performed a multiple linear regression on the temperature data, and found that while solar activity can account for about 11% of the global warming from 1889 to 2006, it can only account for 1.6% of the warming from 1955 to 2005, and had a slight cooling effect (-0.004°C per decade) from 1979 to 2005.

Finally, physics does not support the claim that changes in TSI drive current climate change. If that claim had any credence, we would not expect to see the current situation, in which Earth's lower atmosphere is warming strongly whereas the upper atmosphere is cooling. That is exactly the pattern predicted by physics, in our situation where we have overloaded Earth's atmosphere with greenhouse gases. If warming was solely down to the Sun, we would expect the opposite pattern. In fact, the only way to propagate this myth nowadays involves cherry-picking everything prior to 1975 and completely disregarding all the more recent data. That's simply not science.

Longer-term variations in TSI received by Earth

It's also important to mention variations in TSI driven not by Solar energy output but by variations in Earth's orbit, that are of course independent of Solar activity. Such variations, however, take place over very long periods, described by the Milankovitch orbital cycles operating over tens of thousands of years. Those cycles determine the distance between Earth and the Sun at perihelion and aphelion and in addition the tilt the planet's axis of rotation: both affect how much heat-radiation the planet receives at the top of its atmosphere through time. But such fluctuations are nothing like the rapid changes we see in the weather, such as the difference between a sunny day and a cloudy one. The long time-factor ensures that.

Another even more obscure approach used to claim, "it's the sun" was (and probably still is in some quarters) to talk about, "indirect effects". To wit, when studies can't find a sufficiently large direct effect, bring even lesser factors to the fore, such as cosmic rays. Fail.

In conclusion, the recent, post 1975 steep rise in global temperatures are not reflected in TSI changes that have in fact exerted a slight cooling influence. Milankovitch cycles that operate over vastly bigger time-scales simply don't work quickly enough to change climate drastically over a few decades. Instead, the enormous rise in greenhouse gas concentrations over the same period is the primary forcing-agent. The physics predicted what is now being observed.

Last updated on 27 May 2023 by John Mason. 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

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Additional video from the MOOC

Expert interview with Mike Lockwood


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Comments 951 to 975 out of 1302:

  1. 950, Tom, For the record he does have a few pages of similar forecasts up to 2055. I just really don't see the point since there's no clue as to what they are forecasts of or how they can be evaluated, let alone of what value they have to anyone, anywhere. Wet... Dry... Wet twice. WTF?
  2. For Tom Curtis (950) The date you seek is 1976.
  3. Don Gaddes @952, as there are editorial comments for 1977, and for 1982, the forecast date is almost certainly after those two years. What was the date of publication of the book so that I can know the true date before which all is hindcast? As an aside, I note that your father considers 1813 to be somehow equivalent to 1982. The two years are separated by 13^2 = 169 years. As neither 13 nor 169 figures on your list of significant periods (post 914), either you have misinterpreted your father's theory, or your father indulged in ad hoc modification of this theory to avoid the appearance of being falsified.
  4. Tom Curtis (950) The date you seek is 1976.
  5. Don Gaddes, the date I am looking for is 1990, the date of first publication of the book (and hence the predictions). It follows that there were only two actual predictions in the section quoted by Sphaerica, one of which was true, and the other false. That means when it comes to predictions (as opposed to retrodictions), your father is as accurate as a coin flip, on the data available to me.
  6. 955, Tom, I'm done with Mr. Gaddes, but to clarify (since he seems unable to articulate things clearly himself)... Don doesn't seem to understand the difference between a hindcast and a forecast. The book was published in 1990 with "forecasts" from 1976 to 2001. My assumption then is that A. S. Gaddes actually performed hindcasts from 1976 to 1990 (which is cheating, because he also used that same data to develop his model, so no surprise there if he achieves some degree of accuracy) as well as true forecasts from 1990 to 2000. Don Gaddes further extended those forecasts through 2055. You can e-mail Don to get a copy of the book, to see his actual forecasts in the Appendices. For my part, I'm only curious as to what figures (both data source and thresholds) you (and he) are using to determine when a period is "wet" or "dry" in order to evaluate the veracity of a forecast. And, with that said, I still see no point to the entire endeavor. Predicting wet/dry cycles based on climastrology has no influence whatsoever on the temperature of the real world, and A. S. Gaddes' prediction of an imminent ice age is clearly not coming to fruition.
  7. dana, Here is a slightly different version of your Figure 3 (in the advanced rebuttal) from a slide talk by Dr. Nathan Schwandron, a professor/researcher in space and plasma physics at the University of New Hampshire. The peak value was in the early 80s. The figure shows a compilation of 45 years of satellite-era total solar magnetic flux (Note: that is not the same usage of flux as in radiative flux (Watts/meter2); it is magnetic field flux, Phi-B = B.A, where B is field strength in Tesla, A is a cross-sectional surface area and . is dot product. Phi-B is thus measured in webers = Tesla meter2). Dr. Schwandron demonstrates that magnetic field flux is an excellent proxy for solar corona temperature - which dropped precipitously during the cycle 23/24 minimum of 2009. The reduced magnetic field flux has also driven the strength of the IMF (inter-planetary magnetic field), as measured at the earth, to a deep low. This point from Dr. Schwandron's talk is very interesting: Space age context shows 1970’s also an era of lower coronal temperatures We know that the 70s was a cool decade (and not just because of all this cool stuff). The reconstructed solar coronal temperature shows 2005-2009 to be even cooler. And yet, and do not show this cooling (on earth) in any way, shape or form. So no, it's not the sun.
  8. I'm a bit confused... isn't this, kind of, the whole point of the Foster and Rahmstorf Measure the Global Warming Signal paper? Separation of the GHG .v. other factors? And, for those who still don't get figure 3... a little video
  9. There is a new paper out by Abdussamatov here, he is claims a total decrease in TSI of 6.8 W/m2 due to a decrease in the bicentennial activity of the sun. Of course this big decrease will cause a new little ice age etc. etc. Only problem I have is that I am not able to find anything on the "Bicentennial Decrease of TSI".
  10. Link to /pub/data/irradiance/composite/DataPlots/composite_d41_62_1110.dat (PMOD) doesn't work.
  11. Notice the somewhat recent topic on the rise of coronal mass ejections. Since the sun has loss heated mass, it has less to burn and therefore less heat
  12. ShadedX - sorry but it doesnt follow. The path for stellar evolution is that heat from the sun will rise very very slowly (and has been doing so through geological time). As fuel is spent, it will expand and eventually engulf the inner planets, including possibly earth. But not for a few billion years.
  13. And as for you scaddnep, I am not talking about a star's lifetime.
  14. ShadedX, coronal Mass Ejection (CME) activity varies with the activity of the Sun in it's approximately 11-year cycle, see for example this SEC plot. The ~2000 peak was reasonably large, and followed by the deepest solar minimum in many decades near 2009. The next peak is forecast to be much smaller, peaking in 2013 or 2014. The cyclicity does not explain long-term global warming, and the past decade has been dominated by the progression from the last solar max to the deep solar min. CMEs themselves have little to do with Earth's climate, except that there are more when the Sun is a bit more active.
  15. ShadedX - sorry, but it not clear what you do mean then. The statement "Since the sun has loss heated mass, it has less to burn and therefore less heat " does not follow. Since the CME happen all the time, if your statement were true, the sun should be gradually cooling which it is not.
  16. Solar activity does not have to increase to cause warming. It has to be at or above a certain level. Approximately 1365.7 seems to be enough to warm. It pretty much held or exceeded that level from 1918 or so on.
  17. Cruzn246 - what is the basis for your statement (ie where is the peer reviewed published research) and how do you explain the cooling since 1918? Other theories match the known data better than the statement "1365.7 seems to be enough to warm". One in particular I would draw your attention to is AGW - it not only incorporate the sun (obviously the primary source of heat energy) but it also includes things like water vapor, CO2, soot pollution, ice cover, volcanoes, etc. Check it out -the good news is the heavy lifting has been done - you can read article on this site that address any question you have.

    [DB] You can peruse Cruzn246's litany of comments here, as he has a long history of posting unsupported assertions at SkS going back about a year and a half.  Note the moderator response to this comment over a year ago. 

    Nor is it the first time he has posted such comments on this very long thread.

  18. Thanks skywatcher. Though seriouly, I don't believe that the sun effects the climate that much. I just wanted to see what you all had to contradict it. Just wondering: Is it me or are some of the "Response" comments bias?
  19. With regards to a comment by one BernhardB here, I am linking to this thread where it is more on topic (at least, I suspect so - if there is a better thread please do point it out). As a response, Bernhard, I am no physicist, but I would say this: We can, when standing at the Earth surface, empirically measure longwave IR backradiation from the atmosphere, and there are posts on this site and elsewhere documenting this. Just as we can empirically measure from orbiting satellites the effect heat-trapping (aka greenhouse) gases in the atmosphere have on outgoing longwave IR. I'm only marginally aware of what a heat sink for a power transistor is, but I gather from your derisive line Then I would like to know why the fins on power transistor heat sinks don`t "back radiate" each other into a China Syndrome melt down. that melt downs are not a common occurence among them. As such, I would suspect the issue is not with either power transistors, their heat sinks, or observed longwave IR backradiation. I would not be surprised if one of the more physics-educated commenters here has more to say.
  20. "We can, when standing at the Earth surface, empirically measure longwave IR backradiation from the atmosphere, and there are posts on this site and elsewhere documenting this." Indeed composer. Martha's Vineyard Coastal Observatory, for instance has an hourly (I think) updated graph of downwelling IR. Just click on the link to Infared radiation. Simple as that. Considering there is always some level of IR, even at night, the GH effect deniers have some seriously contorted explaining to do. No doubt that some will try. I'm waiting for Bernhard's words on these observations.
  21. Philippe - does this mean that down-welling IR can be measured? But if the GHE doesn't exist, how can that be possible? Interesting that they're seeing >300 W/m^2 with an air temperature of 40F. That's after a couple of days of high humidity and relatively low solar input - it's been cloudy. Could clouds be a positive feedback? Note- the linked figures are for 3/23-3/30. They may change to keep current.
  22. From here. "We all know a more active sun means a stronger magnetosphere... up until recently the magnetosphere (a la Sol), was extremely powerful." We all know... not a very scientific argument. Refer to this comment above for some actual data on the sun's mag field. Note the title: Overall Flux Reduction. 45 very flat years. See Arge et al 2002: Lockwood et al. [1999a , 1999b] conclude that the total open solar magnetic flux has increased by 41% from 1964 to 1995 and by 130% over all but the last 5 years of the twentieth century. However, solar data for more than two solar cycles ... show no secular trend in overall photospheric flux. More importantly, the magnetic flux open to interplanetary space ... fails to show evidence of a secular increase over the last two solar cycles. A final point about this vaunted solar 'aa' index increase comes from Russell and Mulligan 1995: -- source It looks like this increase ran during the first half of the 20th century - and then the index went flat. That is entirely consistent with Figure 1 above and the data presented above. This point is very clear: the early 20th century warming was solar in origin. The recent warming is not.
  23. test comment
  24. Hi all, I'm a biochemistry student at the University of Oxford, and some of the stuff I'm finding here is shocking. There's a complete lack of adherence to the scientific method, very few peer-reviewed studies and logical fallacies everywhere. Don't even get me started on the science, either.
    Response: [Rob P] Please note the comments policy. If you're here to discuss actual science, then do so. There are plenty of websites on the internet where empty rhetoric is acceptable. SkS is not one of those sites.
  25. Please, please, please, TheCriticalThinker: don't be a hit and run. Come back and defend your theses, or, rather, engage in a mutually beneficial dialogue using those theses as starting points. It would be lovely, lovely, but, I strongly suspect, highly unlikely.

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