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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

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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

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Denial101x videos

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Additional video from the MOOC

Expert interview with Mike Lockwood


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Comments 801 to 825 out of 1295:

  1. Ok, I am caught up with the discussion. I disagree that this is a sun discussion because my point is the temperature of the Earth changes separate from the energy from the sun for the exact reasons that Tom states in #798. The SH varies less because there is more ocean and less land. The NH drives the global temperature because it has more land. As he also pointed out it is simply inaccurate to apply the insolation of London as a global change in energy. Rob and Muon continue to miss my point (but deride me anyway). My point is that the Earth's geography plays a very important factor in the Earth's temperature. If the Earth's orbit was a perfect circle, but with the same tilt. The Earth as a whole would receive the exact same energy every day of the year. The temperature would vary based on the geography of the land that was receiving the direct and indirect energy. Winters would be colder than they are now and summers would be hotter than they are now. I am baffled at the deriding discussion between Rob and Muon when they are ignoring the point of discussion.
  2. John (TIS) @ 801... The problem with your analysis here is that what you're saying doesn't allow a mechanism for current warming. Look at the overall temperature trend of the Holocene (even per your Penny ice cap chart). Compare it with the Holocene shown in the Vostok record and the Byrd ice core. All these put together you can see that over the Holocene we are in a slow cooling trend that is orbitally forced (Miller 2010). But we are now seeing nearly all indicators of temperature pointing one direction. Up. The planet is warming. The entire planet. That is clearly not being cause by the difference in land mass between NH and SH. John, the whole reason all the temperature data sets use an anomaly is because you have to look at the overall trend, not the annual signal. The annual signal tells you very little, if anything, about any kind of forcing.
    Response: [DB] Fixed date. Rob, we've been hearing a lot of conflation by commenters between temperatures and anomalies lately. It's probably time to put together a post on the subject. I can do one later this week unless someone has more time before then.
  3. TIS: "I am baffled ..." I'm baffled at this whole question. To that extent, I guess I am missing your point. You stated "In January the Earth gets ~7% more energy than it does in July, but July is also ~4C warmer. Explain the warmer July to me without using geography." If I am not mistaken, the 7% in question is the % difference between the Jan and July average solar radiation at TOA, as described in my comment and in this graphic. I checked the values, averaging all latitudes over each day; it is indeed 7% more in January and I agreed with that. Forgive the ghastly colors, it was the first one I found. By your 'July is 4C warmer,' I naturally took that to be in reference to the NH. The graph for London bears out the point that temperature follows net radiation. I'm baffled at how you missed that I mentioned the cited source had several other examples. Here's one from the SH, specifically Bulawayo, Zimbabwe, 20S 29E: -- Once again, temperature follows net radiation, even in the SH. I don't deny that geography has a moderating influence, but it is certainly not a driving factor. Differential heating of land vs. ocean is in response to solar input, is it not? But your original question said 'explain the warmer July without geography'. Your question made no mention of the difference between incoming and net radiation and that was the focal point of my response.
  4. Rob (802), I understand the reason why anomaly is used. Ignoring the actual temperature is not useful though. For instance. During the NH summer the Earth radiates away more energy than it does during the NH winter. That is because RHT is dependent on actual temperature. Snow, ice, humidity are all determined by the actual temperature. During the NH summer the average temperature of the Earth is at it's warmest. Enormous amounts of energy go into increasing the total water vapor in the atmosphere. Latent energy transfers to the atmosphere increase as does RHT and convective heat transfer. The behavior of the Earth is different at the two ends of the temperature extremes. Geography is the reason why those differences are real. These annual cycles are likely drivers of events like the ENSO that does show up in the anomaly charts that you are so concerned about. I pay attention to the trend in the anomaly, but I don't give it the overwhelming weighted importance that you do. The global anomaly for February is basically zero for both the UAH and RSS sets, but I don't think that is very important. That temperature of the Earth for February was right at 12.1 °C tell more about how the Earth is behaving than saying the anomaly is zero. I do think it is worth considering that over the next three months that will increase to ~16°C while the energy the Earth gets from the sun will decrease by several percent. Saying that this effect is not important is... rather incoherent.
  5. Muon (803), If the two hemisphere's had equal geography then January would be warmer than July with the current orbital parameters. The NET energy you refer to is local. Picking London explains why that location is cooler in winter, but does nothing for why the entire hemisphere reacts more strongly than the SH. That is where geography enters into the equation. Please see #802 for why I say the actual temperature matters. None of what I am saying actually goes against global warming, but for some reason when I say something people tend to disagree anyway. I of course understand that, but it is nonetheless an interesting effect by my choice of name.
  6. PS... I meant #804. This discussion is kinda long.
  7. John @ 804... It's not incoherent at all! It's expected. It's understood. It has absolutely no net forcing effect over the natural annual cycle. This is just not a mechanism that is driving any warming or cooling trend. When you start focusing on the temperature cycle rather than the trend you are completely missing the point of global climate. If you ignore the trend you are just closing your eyes to any potential forcing mechanisms. So, that would be my question to you. How would a natural annual cycle drive the trend one way or the other? How would this annual cycle drive ENSO?
  8. TIS @805, people tend to disagree with what you are saying because they try to interpret it as being relevant to the debate. Because it is irrelevant to the debated, they end up misinterpreting you. Perhaps you can point out why you think this fact is relevant, bearing in mind that geography has not changed over the last century, but temperatures (and temperature distributions) have. For those trying to understand where Inconvenient Sceptic is coming from, this appears to be a lead in to George White's much refuted nonsense.
  9. TIS: "why the entire hemisphere reacts more strongly than the SH." This is, of course, an entirely different question, one that leads to Arctic amplification. Yes, the geography of the hemispheres produces different thermal responses. One might suspect that it also has something to do with the fact that there is a very large ice cube down there in the basement. I looked again at TOA insolation figures: on an annual basis, the southern hemisphere actually 'receives' ~2% more than the northern. Hardly a significant difference. "over the next three months that will increase to ~16°C while the energy the Earth gets from the sun will decrease" Yes, that's been going on for a very long time. To what point?
  10. Rob(807) I am not ignoring the trend, I am trying to get to the relevance, but you are still stuck on anomaly. Tom(808), It isn't irrelevant and it has nothing to do with that guy who I have not heard of before, but I will take a look since you linked. Muon(809), Thank you for discussing. If there was no CO2 in the atmosphere, how would an identical Earth be different without CO2 in the atmosphere (plants breathe O2 so even plant coverage is identical). The geography of the Earth would force the same type of temperature cycle that the Earth currently experiences. NH winter would cause the Earth average to be colder and the NH summer would cause it to be warmer. The greater effect would be in the winter when there was less water vapor in the atmosphere. So the Earth would be colder by some value. The summer would have a lesser effect because there would be more water vapor that would compensate for the lack of CO2. The Earth would still not behave like a blackbody (i.e. there would still be a GHE) because there would still be convection and latent heat transfer to the atmosphere that would keep the atmosphere warmer than 254K. So the anomaly difference from normal earth would be greater cooling in the winter, but less of a difference in the summers, but still cooler. I am sure we won't agree on the magnitude, but even if the winter difference was 5 °C, then the summer difference would be less than 5 °C. If the summers were 2.5 °C cooler, then on average the Earth would be 3.5-4°C cooler than now. One helping factor would be a cooler Earth would need less energy because it would radiate away less energy. In this case boundaries of response can be established by looked at the seasonal temperature and atmospheric behavior. Would you agree that the summer effect would be lesser than the winter effect?
  11. TIS, How is an unchanging cycle relevant to the trend? Plants require atmospheric CO2 for production of food, i.e. photosynthesis.
  12. TIS... You are still failing to explain how this could possibly explain the warming trend. My next question is, why do you think even Spencer and Christy present their data as anomaly?
  13. TIS... As to me being stuck on the anomaly, well, everyone is stuck on the anomaly because that is how you see the trend. The trend and related mechanisms driving the trend are what it's all about (Alfie).
  14. Going back to the original premisen that because solar radiation has reduced since 1960, the sun has nothing to do with global temperature rise - this agument is flawed. The reason being that according to Wein's Distribution Law for black body radiation, if the sun has cooled such that its total radiation has reduced, then the radiation peak will have also shifted towards the infra red. These means that the Earth is likely to receive more insolation because we know the Earth absorbs radiation in the infra red region than at higher frequencies ( shorter wavelengths )due to the greenhouse ( and other effects ). Hence the rise in global temperatures. Global warming occurs for complex reasons ( and not that well understood by the so-called experts)and attributing it to man made pollution (alone) is nonsense. It has occurred in the past and will occur again in the future. Our contribution to CO2 etc is nothing compared to that produced by vulcanism.


    [DB] Welcome to Skeptical Science!  There is an immense amount of reference material discussed here and it can be a bit difficult at first to find an answer to your questions. 

    That's why we recommend that Newcomers, Start Here and then learn The Big Picture.

    I also recommend watching this video on why CO2 is the biggest climate control knob in Earth's history.

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    Remember to frame your questions in compliance with the Comments Policy and lastly, to use the Preview function below the comment box to ensure that any html tags you're using work properly.

    With that out of the way, there is much indeed wrong with your comment, more than can be summed up by just one thread post.  Please break up your many objections into their individual parts and post them on the appropriate thread (that's where the Search function will help you).  Thanks!

  15. John. Nope. Spectral signature in IR range is insignificant. We measure spectra at TOA and earth-bound and what we see is consistent with GHE, not your idea. "Our contribution to CO2 etc is nothing compared to that produced by vulcanism." This is false. See Volcanoes and global warming Global warming occurs for complex reasons ( and not that well understood by the so-called experts)and attributing it to man made pollution (alone) is nonsense. Care to support that assertion with some science? You might also like to look at Climate has changed before
  16. Whew! I have just finished reading this entire thread. The reason the stratosphere is stratified as opposed to the convective trophosphere below is that the lapse rate is "inverted" and begins warming, forming a stable lid just like the adiabatic inversion that traps smog in the LA basin. The stratospheric inversion is probably not adiabadic, but is thought to result from the absorbtion of UV photons by oxygen, forming ozone. The top of the stratosphere where the oxygen becomes "saturated" with photons approaches the temperature of the earth's surface during solar maxima. Above the top of the stratosphere the lapse rate becomes normal again but there is another or two poorly understood (at least by me) inversions before the TOA. Question: what does a satellite measuring the temperature of the earth from space (255K?) really see? Can it distinguish between the spectrum of CO2 absorbtion at the top of the troposphere and the spectrum of ozone absorbtion (approximately half of which should be radiated back to space), or does it see just the triple net of all the refracted, reradiated, conducted, convected energy from the earth atmosphere system?
  17. Hi. First Post, please be nice :) Can someone (anyone?) explain why in this graph we are comparing TSI Actuals against Temperature Anomalies? I've done a (very little) bit of stats and one thing I remember is that if you want to compare things you have to get those things onto the same playing field. On the whole, SkS does a great job helping me to understand what's going on. Sometimes (like this for example) I'm left wondering why the author didn't do the proper job... Thanks.
    Response: Using the anomaly instead of the raw temperature merely is a good way of reducing noise. An example of another way of reducing noise is to smooth a curve with a moving average. The anomaly still addresses our question: Does temperature change across time correlate with TSI? Temperature anomaly change mirrors raw temperature change. Think about what the raw temperature curve would look like next to the anomaly curve. A very rough analogy: It doesn't matter whether you plot the temperature in degrees Farenheit or degrees Celsius, if what you are interested in is the shape of the curve across time.
  18. For me, it's just a simple way of showing that TSI and Temp have come completely unhinged in the last 35 years.
  19. Also, what the various temperature system do is determine a global temperature anomaly, (that is, a spatial average of anomalies because these are strongly correlated). It is extremely difficult to determine a global average absolute temperature that has any meaning. See Hansen 2008 for detail. However TSI is just a number. You can determine an anomaly if you like by subtracting from an arbitary baseline. It cannot change the shape of the curve however.
  20. Thanks, that's helpful. :) AMF
  21. This paper shows the Models underestimate solar forcing by up to six times. It makes perfect sense for us to take time to cool the oceans are vast and deep so 30 years of lag time are more than exeptable.
  22. Cole -
    "This paper shows the Models underestimate solar forcing by up to six times."
    It does no such thing. The paper suggests that other TSI reconstructions underestimate the amplitude of TSI changes in the past. It has very little to do with climate models, and in fact specifically notes that their TSI estimates over recent decades, during which we have good measurements, are no different than previous TSI reconstructions.
  23. Cole, Dana's right. I'm not sure you read that paper. In fig 4 there no net change in solar forcing since 1950. And why is the 30 year lag relevant? And what justification for 30 year lag other than " the oceans are vast and deep" do you have?
  24. I'll probably do a post on this paper. To be fair, if the reconstruction is correct (which I don't think is plausible), it does suggest a very low climate sensitivity, so you could argue that climate models are wrong in that sense. Sensitivity would have to be in Spencer/Lindzen territory, below 1°C for 2xCO2 if this reconstruction is right. I don't think it's plausible, but should make for an interesting post.
  25. Cole, your linked paper starts : The variable Sun is the most likely candidate for natural forcing of past climate change on time scales of 50 to 1000 years. And ends : We note that our conclusions can not be tested on the basis of the last 30 years of solar observations because, according to the proxy data, the Sun was in a maximum plato state in its longterm evolution. All recently published reconstructions agree well during the satellite observational period and diverge only in the past. This implies that observational data do not allow to select and favor one of the proposed reconstructions. Therefore, until new evidence become available we are in a situation that different approaches and hypothesis yield different solar forcing values. Our result allows the climate community to evaluate the full range of present uncertainty in solar forcing. Can you explain in your own words (i.e. not from WUWT) what you get from that paper ?

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