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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

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Comments

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Comments 751 to 775 out of 1288:

  1. Sorry, but it does not. The question was whether solar activity and surface temperatures were always coupled in the holocene, or whether there were other periods of uncoupling. Your graphs do not contain any data of solar energy output at all. So the question was not addressed in your response. I understand you have preented data comparing CO2 to surface temps, but that is not what I asked.
  2. Re: TheCaz (751) Since the Daleks took my time machine back to rescue the Morlocks from the Eloi, from Beer et al, 2006:
    "To date, the only proxy providing information about the solar variability on millennial time scales are cosmogenic radionuclides stored in natural archives such as ice cores."
    Perusual of the various versions of this post, plus the graphs I showed you in My Previous Comment #749 reveal the tight relationship between solar variability, CO2 and temperatures (with temperatures being merely the composite sum of forcings and feedbacks) in the paleo record. The unusual climatic stability of the Holocene: So my questions to you, TheCaz: looking at the record of CO2 over the past 400,000 years or so (here, I'll help with a visual): When did atmospheric concentration jump 40% (which it has over the pre-industrial levels)? At any point? Do you see any uncouplings? Keep in mind that CO2 in the paleo record acted as a lagged feedback to orbital factors and solar irradiance changes. And that it is now acting as a forcing. Or do you have a source for solar activity over the paleo record that materially differs from the information presented in the various iterations of this post, my comments and linked sources? If so, what source is that? Can you furnish a link? The Yooper
  3. Your new post still does not answer the question. I do not see solar activity represented at all, except for the graph in the main article which covers only the past few hundred years. I understand temps and CO2 are uncoupled, but I was asking about solar activity and surface temps. Is the recent uncoupling unique in the holocene? I do not have the data myself. That is why I am asking the question.
  4. Perhaps what you are trying to say is 'we do not know whether solar activity and surface temps were uncoupled prior to the 1800s because the ability to measure solar activity is not able to be calculated prior to that time.' OK. So that is an answer. But repeating the CO2 data is not what I asked.
  5. TheCaz, Daniel gave you an example of solar reconstructions for the Holocene in his link to Beer et al, 2006.
  6. TheCaz, Specifically figure 2 panel c appears to be what you are looking for.
  7. I read the article, but unfortunately, that figure still does not answer the question, for two reasons: (a) the time scale makes it impossible to see the holocene in detail, and (b) it compares temps with insolation (angle and distance from the sun) and assumes a constant solar activity. I was asking specifically about solar activity (not insolation). But the paper does give something of an answer elsewhere. It says before the launching of satellites, solar activity could not be measured. So that is the answer I was looking for - "We do not know." The paper says the sun has activity cycles, but then assumes those cycles are regular. The author uses this to exclude solar activity variation as causative in the long term. We now know this is incorrect. In fact, the graph at the top of this page shows that solar activity (11-year averages) has varied over the past 130 years.
  8. The paper goes on to model solar activity based on proxies, and that is the best we can do right now. OK.
    Response: [Daniel Bailey] Apologies; I thought that the Beer et al quote I cited made that clear. I will try to be more explanatory in the future.
  9. TheCaz, Sorry I pointed you to the wrong section, the paper does go on to detail a solar activity proxy as you discovered.
  10. @TheCaz: in the absence of any evidence that there were similar "uncouplings" in the Holocene, we cannot assume there were. Thus, it's not the sun. It's CO2.
  11. Continuing from a comment here. "Solar variation did not cause the 78 – 98 warming but it can cause the 1880 to 2010 trend" Barring the obvious fact that 78-98 are contained in 1880-2010, there is no evidence for this 'solar cause'. Sunspot numbers correlate well with satellite measures of solar irradiance and the reconstructions of solar output don't support it. If anything, the sun's relatively quiet behavior in recent years should have a cooling effect; yet we know that 2000-2009 was one of the hottest 10 year period in the last 6 decades.
  12. First, "relatively quiet behavior" is not necessarily cooling, the (cooling) low cloud coverage diverged from the higher GCR (quiet sun) cosmic-rays-and-global-warming.htm The quiet behavior (and increased GCR) can certainly change the weather in some cases (e.g. increased blocking). Second, the cooling would not be instant due to thermal inertia (i.e. the ocean is storing the cooling)
  13. #762: Eric, We've been through the cosmic ray discussion many times. There is no consistent evidence of any such effect. "the cooling would not be instant due to thermal inertia (i.e. the ocean is storing the cooling)" The solar max occurred in the late 50s. Sixty years later, still no cooling. And for your own benefit, please don't ever say something 'stores cooling' in any public forum. It's like asking what is the speed of darkness?
  14. Re: muoncounter (763) And you can't have the speed of darkness without the Sound of Silence By 2012, when the sun is really cookin' and the Arctic ice recedes from the pole for the first time in unknown millennia, enquiring minds will want to know: Just how did those Mayans know? I bet this thread hits 1,000 comments before spring... The Yooper
  15. Reminds me of the world's fastest climatologist, Muhammad Ali. Sucker bet on hitting the thou. If I took it, all you'd need to do is drop the words 'climate sensitivity' in here.
  16. Cool Papa Bell was attributed to have said (OK, Satch said it) that Ali quote about a half-century before Ali. If we say "waste heat" we'll draw a cool mill...then John could charge admission & make this site a revenue source instead of sink... The Yooper
  17. Continuing from a comment here. Lockwood 2010 Solar change and climate: an update in the light of the current exceptional solar minimum is an interesting summary paper for the Royal Society. By way of introduction, The Internet has played a useful role in conveying some of the understanding, images and data that lead climate scientists to their conclusions. However, it has also become a haven for un-refereed pseudo-science with dangerously incorrect inference. It has served to give the false impression that there is a serious, widespread academic debate on the basic nature of climate change. The most popular argument runs like this: ‘The Sun drives Earth’s climate system. Therefore changes in the Sun must drive changes in Earth’s climate system’. The first sentence is, of course, absolutely correct; but understanding why the second sentence does not follow from the first requires scientific training and study. --emphasis added The remainder of the paper is a thorough treatment of solar variation, concluding with ... the popular idea (at least on the Internet and in some parts of the media) that solar changes are some kind of alternative to GHG forcing in explaining the rise in surface temperatures has no credibility with almost all climate scientists. Sounds like he's got his head on straight.
  18. Well, the sun isn´t dead yet: A combination of the increased TSI and UV may explain up to 0.44 degrees of the 0.55 degree HADCRU warming - 80%. "A peer-reviewed paper [Krivova et al.] published in the Journal of Geophysical Research finds that reconstructions of total solar irradiance (TSI) show a significant increase since the Maunder minimum in the 1600's during the Little Ice Age and shows further increases over the 19th and 20th centuries.....Use of the Stefan-Boltzmann equation indicates that a 1.25 W/m2 increase in solar activity could account for an approximate .44C global temperature increase.....A significant new finding is that portions of the more energetic ultraviolet region of the solar spectrum increased by almost 50% over the 400 years since the Maunder minimum.....This is highly significant because the UV portion of the solar spectrum is the most important for heating of the oceans due to the greatest penetration beyond the surface and highest energy levels. Solar UV is capable of penetrating the ocean to depths of several meters to cause ocean heating." [N. A. Krivova, L. E. A. Vieira, S. K. Solanki 2010: Journal of Geophysical Research, Vol. 115, A12112, 11 PP., 2010 doi:10.1029/2010JA015431
  19. #768: "shows further increases over the 19th and 20th centuries ..." Figures 5 and 6 in the paper (pdf here) clearly show the solar UV max coincident with the late '50s 'grand maximum'. That suggests that in the 50 years since, the 4 subsequent solar maxima were flat to lower than this well-known peak. That's the key point in this post: between the 1960s and the present day the same solar measurements have shown that the energy from the sun is now decreasing. See the graph at the top of the page. On another note, when I was in the awl bidness, we referred to Mother Exxon as 'the double cross' - and that was before the Valdez.
  20. #769 I´m not sure that the peak values are the most important. The oceans are acting as large integrators and from the diagrams in the article in can clearly be seen that the overall imparted energy has increased (from the UV-band) until about the year 2000. Since UV have a higher penetrability than light in the oceans it is not strange to assume that variations in UV energy fluence may have some impact on the total energy content. The decrease in energy fluence after approx. 2000 is consistent from what is observed, i.e a stable decrease in ocean energy content (since 2002-03). This may eventually have an impact on the surface temperatures as well. (The word "may" should be used more often in climate science considering the uncertainties).
    Response: [Daniel Bailey] Your own linked graphic you provide in 771 below shows the fallacy of focusing on short time scales: Datasets are noisy; the overall trend is up, like global temps.
  21. #770 Update: here is a couple of figures showing the latest (corrected) data on energy content of the oceans (one together with GISS-projections). http://i47.tinypic.com/20kvhwn.png http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/index.html
    Response: [Daniel Bailey] Further discussion on ocean heat content should go on a more relevant page. Use the search function in the upper left corner of every page to find a more appropriate thread if continuing a discussion of OHC is your intent. Thanks!
  22. #770: "not sure that the peak values are the most important. ... from the diagrams in the article in can clearly be seen ..." Figure 5 in the Krivova paper is a graph of UV flux vs. time. In order to represent increasing energy, the area under the curve must increase: either the peaks must be bigger or the width (time duration) of the peaks are broader. The largest peak UV was in 1958 and the time duration of the subsequent cycles is the standard 10-11 years. What part of that is clearly demonstrating your point? If you are saying that the cumulative energy summed over all cycles is increasing, that's obvious. But that sum is not a measure of the energy balance at TOA or in the oceans. Here are the author's conclusions: ... since the LTE approximation underlies the computations of the brightness spectra of different photospheric components, the original version of the model fails in the UV. Although it contributes little to the total irradiance (such that the modelled TSI is nevertheless quite accurate), this wavelegth range on its own is of special interest for climate research due to its important influence on the chemistry and dynamics of the Earth’s atmosphere ... -- emphasis added There is no mention of UV contributing to ocean heating. Their "value of about 1.25 W/m2 as our best estimate for the 11-yr averaged increase in the TSI between the end of the Maunder minimum and the end of the 20th century, compared to 1.3 W/m2 derived by Balmaceda et al. [2007] and Krivova et al. [2007]" doesn't specifically say that it increased through the end of the century. Further discussion specific to ocean heat content should go here.
  23. The current trend in sunspot number Cycle 24 is under the projected trend. NASA's 2006 forecast was ~150. The current predicted maximum of 90, in May 2013, may need further revision downward. I am reminded of the Penn and Livingston 2006 paper that showed a linear decline in umbral magnetic flux, suggesting that a continued decrease below 1500G may result in sunspots disappearing altogether.
    Response: So what? That's not relevant to the point of this post, which is a rebuttal of the skeptic argument that increase in the Sun's irradiation of the Earth is what has and is causing the Earth's temperature rise since about 1850.
  24. My understanding is that solar activity levels have been above the historical norm since the 1940's, See Cycle 21-23, and the correlation between surface temperature anomalies and sunspot cycle length is interesting. A NASA study showed that solar activity influenced the observed warming of the previous century by 25%. But cycle 24 looks similar to cycles 5 and 6, during the Dalton Minumum. It's still too early to say for sure but it is possible that a weak cycle 24 may lead to subsequent global cooling.
  25. Your understanding is incorrect. Please read the article you are replying to. As for a decrease in solar activity trumping the enhanced greenhouse effect, please use the search box to find the article on what would happen if the Sun returned to Maunder Minimum activity levels.

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