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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, "...so 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

Related resource: Myth Deconstruction as animated GIF

MD Sun

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

Denial101x videos

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Additional video from the MOOC

Expert interview with Mike Lockwood

Comments

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Comments 51 to 75 out of 1288:

  1. Quietman Flawed logic! IF what you say were true and it's a BIG IF, then it becomes even MORE important to reduce CO2 emissions to even LOWER levels than if CO2 was the primary cause of warming, because it's fairly impossible to do anything about the sun. I'm surprised that you weren't smart enough to spot that! Of course in the topsy-turvy world of AGW denial things that make sense don’t and things that don’t make sense, do. The next time you meet Alice in Wonderland, say hi! The tipping points remain waiting and at some stage they will be triggered. It matters not one jot to the clathrates or the permafrost where the heat is derived from. The ocean too is warming and that will mean outgassing. BTW Your link was corrupted and did not work. [hhttp protocol] I looked at the site you recommended and it's not science, it's not even peer reviewed but it's garbage and of no relevance. Not a single peer reviewed reference. But I noticed the Exxon funded Hoover Institute! Don't you just love the smell of that oil money! You will have to try harder, much harder. Try some real objective peer-reviewed science - you know the stuff that doesn't smell of oil or coal. Your argument gets even more unbelievable with every post.
  2. ScaredAmoeba It would be silly to try to do something about the sun now would it not? Perhaps since we actually have no control over climate change we should put our effort into ways that we can live with it?
  3. ScaredAmoeba And I do not intend to make an argument, my intent is to learn more about climate change by questioning the points that I do not understand. The articles and papers that I have read all seem to be conflicting and I want to know why. The most logical statements I have seen all agree that we need to plan for a changing climate. Cleaner resources are a given, that is common sense. But putting the effort into controlling CO2 does not seem sensible given that we can have so little effect by following that route.
  4. Quietman Definition of Argument 1'A connected series of statements intended to establish a position; a process of reasoning or disputation..,' NSOED 1993
    Response: I'm having a deja vu of a Monty Python sketch :-)
  5. John Me too.
  6. ScaredAmoeba Definition of Argument UN food chief urges crisis action Still don't think greens kill out of ignorance?
  7. ScaredAmoeba Call for delay to biofuels policy This is why I said that drastic measures without thinking things through could kill us all.
  8. "Environmentalist Groups Say Tech Firms Get Great Publicity from Their Green PR Efforts, But They Wonder How Deep the Commitment Really Is" But eho are the real Hypocrites? I am now seeing things that I have been afraid of for 40 years.
  9. I believe in taking care of the environment, buying only efficient products and recycling. But these alarmists and violent greens that burn other peoples Hummers really get me. Greenpeace is the worst of all, even one of its founders will have nothing more to do with them. They make me ashamed to say I am an environmentalist because it makes me part of the problem rather than part of the solution. Can't anyone see where rash actions lead? The blame for this is squarely on the UN itself for pushing Algorism and punishing skepticism and the green alarmists pointing fingers at oil companies instead of thinking things out rationally. Come on people, wake up, get off the bandwagon and start using constructive criticism.
  10. John No offense, but this is an issue that true environmentalists need to take a strong stand on.
  11. I have, so far, only determined that CO2 does not cause Global Warming and that there is no such thing as ‘water vapor feedback’. To my knowledge the combination of factors that contribute to climate has still not been sorted out. The reason why increased greenhouse gas level has no influence on average global temperature is proven at http://www.ruralsoft.com.au/ClimateChange.doc . See more at response 16 to Climate’s changed before.
  12. "The blame for this is squarely on the UN itself for pushing Algorism and punishing skepticism and the green alarmists pointing fingers at oil companies instead of thinking things out rationally." How many times have I seen this argument? Thousands of scientists follow wacky environmentalists, worship at the Church of Gore and push "Algorism". This is a general attempt to marginalize the overwhelming consensus view among scientists into a right vs left thing, in order to rally strong opposition through the political sphere. I don't think Gore has done much to affect views. Those who could use convincing are those who would, if anything, want to believe the opposite of what Al Gore says. There's a genuine difference between skeptics and contrarians. All scientists consider themselves skeptics. Contrarians seek to argue a particular point of view, the way a lawyer might.
  13. NewYorkJ As you are replying to a statement I made I would like to reply. I agree with you, scientists need to be skeptical. My point was that by turning this issue into politics by a movie aimed at inciting the more volatile environmental groups Mr. Gore has created a schism, isolating one group into alarmists and another into deniers. Any skepticism is now viewed as a denial and natural occurrences are blamed on global warming. The alarmisim has done more to hurt the science than help it, pushing govenments into rash actions that are backfiring. In science it is a scientists duty to challenge a new hypothesis and the current CO2 hypothesis is no different. That is how it works. The hypothesis must answer all challengers. The general public does not understand this and calls for action in fear.
  14. SA When you talk about "tipping points" you are taking yourself very far beyond the idea of science. Carbon Dioxide levels have been many times what they are today without ever finding this supposed point so I'm not too concerned with it. I think it is nearly certain that the overall feedback effect is not a positive number, that is kept very quiet because it blows an enormous hole in the panic. I have no trouble with "oil money" if you have no trouble with the IPCC. Which owes it's entire existence to the pre-formed conclusion that CO2 causes warming. Or to the more than 100 times greater money, usually tax money, spent on the other side of the issue. This is a log in your own eye issue if ever there was one. I also don't quite follow how evidence that CO2 does not cause the problem you fear is reason to control it even more tightly. Ignored in all of this of course are all the questions that should probably come first like is warming good or bad or would greater CO2 benefit the biosphere?
  15. Good article, but I'd suggest augmenting it with two other points showing that the recent warming is not due to the sun: 1) If the surface warming was due to the sun, you'd expect the entire depth of the atmosphere to be warming. However if the surface warming is due to the release of anthropogenic greenhouse gases, you'd expect the stratosphere to cool, partly due to decreasing stratospheric ozone (which heats the stratosphere by absorbing incoming solar UV radiation) but more because increasing GHGs in the stratosphere more efficiently radiate that ozone-absorbed heat, leading to a net cooling above the tropopause. Observations from satellites show that the stratosphere is cooling, which directly contradicts the hypothesis that the warming is coming from the sun, but agrees with the hypothesis that the warming is coming from greenhouse gases. 2) If the warming were due to the sun, you'd expect the increased shortwave input to the Earth to result in more warming during the day than at night. If the warming were due to anthropogenic greenhouse gases, you'd expect nighttime temperatures to increase more than daytime, since nighttime temperatures are more directly influenced by downward longwave radiation emitted by the atmosphere (as greenhouse gas concentrations increase, they warm and emit more downward longwave radiation, warming the surface). Observations in fact show more nighttime warming than daytime warming. Keep up the good work.
    Response: DWP, find me some peer reviewed studies highlighting point 2 and I'll be more than happy to do a post on the topic. As for point 1 on the cooling stratosphere, that's another topic on the to-do list :-)
  16. Well it's a complicated topic, as usual in climate, and I was skipping over most of that complexity above (especially the important role of clouds!). It's fascinating though, espeically as it is a way of probing how the models are simulating climate versus reality. The canonical reference is Easterling et al., Science, 1997 (p. 364-367). However, anyone who looks into this should also look at the updated work. For example, I'd suggest Stone and Weaver, Geophys. Res. Lett. 2002, v. 29, p. 1356; Braganza et al., Geophys. Res. Lett. 2004, v. 31, L13217; and the summary in the 2007 IPCC report of Working Group 1, in particular, Figures 3.2 and 3.11 and the discussion of those.
  17. John You might find this NASA clip interesting: A shock wave following a flare
    Response: That's an awesome animation - just imagine the size of that shockwave, the magnitude many times the size of the Earth!
  18. And the latest ideas on Solar Inluence in climate change.
    Response: The idea of global dimming is covered somewhat here. The most disturbing element of global dimming is expressed well on the PBS page: "Is global dimming masking the full impact of global warming? Some climate experts worry that it is, with the possible consequence that as we reduce pollution, the climate will heat up to unprecedented levels."
  19. 2007 global cooling continues into 2008: http://wattsupwiththat.wordpress.com/2008/05/31/globally-2008-significantly-cooler-than-last-year/ And the sun is still blank: www.solarcycle24.com I'm looking forward to this coming winter (but then I don't live in Canada). By next spring, the debate (which is far from over), will "heat" up.
  20. http://www.spaceandscience.net/siteb...eport12008.doc John L. Casey “The existence of ‘relational cycles’ of solar activity on a multi-decadal to centennial scale, as significant models of climate change on Earth.” Research Report 1-2008 http://www.spacecenter.dk/publications/scientific-report-series/Scient_No._3.pdf/view Svensmark, H. and Friis-Christensen, E. Danish National Reply to Lockwood and Fröhlich –“The persistent role of the Sun in climate Forcing” Danish National Space CenterScientific Report 3/2007 http://www.sciencedaily.com/releases/2007/08/070801174450.htm Charles D. Camp and Ka Kit Tung Geophysical Research Letters (GRL) paper 10.1029/2007GL030207, 2007 http://www.sciencedaily.com/releases/2007/08/070801175711.htm Anastasios A. Tsonis, Kyle Swanson, and Sergey Kravtsov: Synchronized Chaos: Mechanisms For Major Climate Shifts Geophysical Research Letters (GRL) paper 10.1029/2007GL030288, 2007 http://www.fel.duke.edu/~scafetta/pdf/2007JD008437.pdf N. Scafetta e B.West : Phenomenological reconstructions of the solar signature in the Northern Hemisphere surface temperature records since 1600 JOURNAL OF GEOPHYSICALRESEARCH, VOL.112D24S03,doi:10.1029/2007JD008437, 200
  21. clayco Very interesting links but I cant get the top one to work, seems to be something missing.
  22. John I am not sure of the relevance but How Plasma From Superstorms Affects Near-Earth Space from ScienceDaily (May 31, 2008) represents another unfactored aspect of the irregularity of output from the sun.
  23. Hi Quietman, John, New studies show it's not just about TSI: See: “Is Climate Sensitive to Solar Variability?”, March 2008 “Physics Today”, provided the graph of Phenomenological Solar Signal (PSS) from 1950 to 2007 http://i27.tinypic.com/1zbavyo.jpg CERN's CR & cloud machine: http://aps.arxiv.org/PS_cache/arxiv/pdf/0804/0804.1938v1.pdf FWIW the Aurorae rain hot particles emitting IR & NIR, there's a So. Atlantic Anomaly weakness in the magnetosphere where the radiation belt descends into the ionosphere, and cosmic rays over the Antarctic may cause regional warming via NO2 formation.
  24. John, The question of global dimming is a tricky mess and b/c of the heretofore lack of solid field data, a big "known unknown," largely misunderstood & relegated to a "masking" function. V. Ramanathan (Scripps, INDOEX) has consistently found that in the case of aerosols there's a net heating effect, despite the surface dimming. Instead of easing or masking CO2's effect, mid-tropospheric brown clouds ladened with soot & sulfates are driving temperatures up, creating bigger temperature anomalies. The effect is as high as 40% over the vast Pacific region. He's claiming that the window of opportunity can be stretched to 20 years via simple soot mitigation. C. Zender is saying similar things re: soot deposition in the Arctic & Subarctic. There's also a documented cloud-seeding effect of winter storms in the N. Pacific that in turn loft soot into the stratosphere to be borne into the Arctic, eventually causing black icebergs (yes, black icebergs). The odds that we can curtail CO2 fast enough against even the mid-case scenarios are low, so subsuming the evidence against soot under the rubric of "carbon emissions" for fear of diluting the message about CO2 seems to me a mistaken approach. see: http://www.scientificblogging.com/blog/258
  25. John, The question of global dimming is a tricky mess and b/c of the heretofore lack of solid field data, a big "known unknown," largely misunderstood & relegated to a "masking" function. V. Ramanathan (Scripps, INDOEX) has consistently found that in the case of aerosols there's a net heating effect, despite the surface dimming. Instead of easing or masking CO2's effect, mid-tropospheric brown clouds ladened with soot & sulfates are driving temperatures up, creating bigger temperature anomalies. The effect is as high as 40% over the vast Pacific region. He's claiming that the window of opportunity can be stretched to 20 years via simple soot mitigation. C. Zender is saying similar things re: soot deposition in the Arctic & Subarctic. There's also a documented cloud-seeding effect of winter storms in the N. Pacific that in turn loft soot into the stratosphere to be borne into the Arctic, eventually causing black icebergs (yes, black icebergs). The odds that we can curtail CO2 fast enough against even the mid-case scenarios are low, so subsuming the evidence against soot under the rubric of "carbon emissions" for fear of diluting the message about CO2 seems to me a mistaken approach. see: http://www.scientificblogging.com/blog/258

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