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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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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


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Comments 676 to 700 out of 971:

  1. KL #673 "Again the absolute values need to be used above a theoretical 'zero' equilibrium to quantify the energy gain or loss from each forcing." You appear to have the concept of a 'baseline' confused - it is not the same thing as a 'theoretical zero equilibrium' whatever that means. This is perhaps the root of the problems you are having with your illogical and confused argument.
  2. KR #674 Here is the link - have a look for yourself. Seems that the Monitoring community has been stumped over this -4.5W/sq.m discrepancy since 2005.
  3. KL #677 Pray please explain your interpretation of the phrase "There remains an unresolved 4.5 W/m^2 difference between the TIM and other space-borne radiometers, and this difference is being studied by the TSI and radiometry communities" from the link that you provided. Personally I feel more comfortable with the empirical surface data, which shows pretty clear anthropogenic warming from multiple angles. If you can explain the TIM/TSI issue in layman's terms (i.e. no jargon) without attempting to overlay your own preconceptions/interpretations on what's happening, that would be useful and valuable. The value will decrease if you use it to promulgate your sceptical agenda though - save that for a different post.
  4. archisteel #675 Here is the Wiki chart for CO2 concentration for the last 1000 years and last 400000 years: When was it last at 180ppmv archisteel? Looks pretty close to 280ppmv for the last 1000 years or so. Happy to argue on a baseline which gives no warming or cooling of the Earth for any forcing. Warming and cooling in pre-industrial times was caused by Solar variation - output and orbital exposure of the Earth to the sun. CO2 lagged Solar warming as a feedback mechanism on interglacial time scales. Of course at some point warming was arrested by IR radiative cooling and a cooling phase followed.
  5. kdkd #678 "The value will decrease if you use it to promulgate your sceptical agenda though - save that for a different post." Is that a banned political comment kdkd? May I only play in this sandpit with you as gatekeeper of pure AGW thought? Regarding TIMS - this illustrates the point that BP has made many times - satellites have high precision but low accuracy. Good for day to day or month on month variation but not for absolute values. The earlier satellites were reading TSI at around 1366W/sq.m - TIMS is 1361.5W/sq.m. Which is right? Now notice how no-one is trying to splice TIMS to the earlier satellites because the TSI would have a huge offset correction yet SLR satellites are being spliced eg TOPEX-Jason with a claimed zero offset due to extensive intercalibration. The TIMS people also produced an energy balance based on 1361.5W/sq.m which Dr Trenberth said was wrong in spades. It does seem strange that while up to date TSI charts are on the SORCE website - the comment on the minus 4.5W/sq.m discrepancy has not been updated since 2005. 5 years seems a long time for the "difference being studied by the TSI and radiometry communities" without some resolution.
  6. I found an interesting comparison at the Active Cavity Radiometer Irradiance Monitor (ACRIM) site of various TSI's over time, using different satellites: This states that: "The results of TSI monitoring experiments are reported on their 'native scales' as defined in SI by the ‘self-calibration’ features of their sensor technologies. Systematic uncertainties in the metrology used to relate their observations to SI caused the ± 0.25 % spread of results during the first decade of monitoring. The tighter clustering of results after 1990 is attributable to dissemination of more accurate sensor metrology among the various experiments and national standards labs. The causes of the ~ -0.35 % difference between the ACRIM3 and VIRGO results and the SORCE/TIM results are not presently understood in this context." It does appear that different satellites measuring TSI have inter-platform calibration issues, Ken - you are correct in that. I would encourage you to look at that site, though, and consider the work done on composite TSI time series, where this is addressed to some degree. So perhaps an absolute TSI number is not as fixed as we would like. A major question here, though: Do the absolute value of TSI, IR radiation, etc., matter? Or can we determine what's having an effect by looking at well established changes of these values? We know the history of TSI changes pretty well over the last 800,000 years, between satellite measurements, sunspot observations, isotopic analysis of ice cores, etc. - the correlation of these measures to absolute values isn't as good as we would like, but the ability to track changes is excellent. The situation is rather a lot like tracking the carbon cycle. We have a rough idea of total carbon sources (natural and manmade), we have a rough idea of carbon sinks (ocean/vegetation/weathering), but we have a really really accurate measure of how atmospheric CO2 changes, and how that relates to man-made CO2. Thus we can state that man-made CO2 is contributing ~2ppm/year to atmospheric CO2. We know how it's changing. So, while we may not know absolute TSI as accurately as we like, we know how it has changed, and it's clear that it has not changed in a manner sufficient to account for late 20th century warming. We know accurately how the inputs to the climate system have changed over quite a long period. We also know accurately how the outputs (temperature) have changed as well. Even the simplest black-box model of climate will then tell us which stick has poked the box inducing those correlating changes. Your "absolute value" issues are really not valid.
  7. One more note from the Active Cavity Radiometer Irradiance Monitor (ACRIM) website: " The de-facto redundant, overlap TSI monitoring approach that has provided a contiguous record since 1978 resulted from the deployment of multiple, overlapping TSI satellite experiments. The traceability of this database is at the mutual precision level of overlapping experiments. ... A carefully implemented redundant, overlap strategy should therefore be capable of producing a centennial TSI record with traceability of ~ 500 ppm, providing a useful signal to noise ratio for assessing climate response to TSI variation. • A redundant, overlapping TSI measurement strategy using existing ‘ambient temperature’ instrumentation can provide the long term traceability required by a TSI database for climate change on centennial time scales." They seem very confident in their ability to establish accurate TSI information. And even more confident in their ability to measure changes in TSI.
  8. @Ken: "Looks pretty close to 280ppmv for the last 1000 years or so." I'm sorry, were we only talking about the last 1000 years? I must have missed that in your latest attempt at obfuscation. The point is that climate is not static, and there is no ideal reference point. You still miss the most basic element: the graph you have wasted so much time talking about shows relative values, not absolutes. But please go on imagining, you actually have a solid argument...
  9. @Ken: Also, aerosols and land use also had an impact. The forest that once covered much of Europe was more than half gone by 1750. This likely had an impact, even if it was relatively small. I still fail to see what the point is of this entire discussion.
  10. KL #680 Limitations for accuracy of absolute measurements across different measurement systems and or devices is pretty much universal, although we do an OK job with things like thermometers in the lab these days. Anyway, it's a problem that limits our ability to make conclusions, it's not evidence showing falsification. "The TIMS people also produced an energy balance based on 1361.5W/sq.m which Dr Trenberth said was wrong in spades." Could you explain this in a little more detail please.
  11. archisteel #683 Oh - you mean THAT chart KL....the one for the last 1000 years. I find no problem with the concept of looking at each forcing component separately in order to ascertain the importance of each. We know that they all act in concert at any point in time. I am perfectly happy with GISS Fig. 613 reproduced from #631 in the absence of something better. Where the Solar irradiance forcing crosses the axis is where TSI is neither warming or cooling the planet, in the absence of other forcings. Any disagreement with that? This is what KR said at #650: "Ken Lambert - I would agree, there is one TSI for one equilibrium temperature of the Earth, with all other variables held constant" You have my permission to leave now archisteel if that is your desire.
  12. Ken Lambert - "Where the Solar irradiance forcing crosses the axis is where TSI is neither warming or cooling the planet, in the absence of other forcings. Any disagreement with that?" In short, Ken, I absolutely disagree with that. You seem to have missed what I (and others) have said in many ways, on many posts. In particular, "with all other variables held constant". Is the temperature the same as the baseline starting point? Was the temperature trajectory at the start of this baseline period zero, with sufficient time at zero for time constants of ocean heating and secondary feedbacks to stabilize? (No on the last two points, incidentally.) Let alone the question on the other forcings, which have not held completely constant over this period. This is not a single variable system! Ken, do you understand that the GHG forcing changes over the last 150 years are an order of magnitude greater than the TSI changes over that period? Please answer that question.
  13. KR #687 "with all other variables held constant" This is something you get for free in multiple regression models - you can examine the predictive ability of individual variables by holding all other variable constant - that 's what the various R2 values and other diagnostics give you. Ken didn't seem to get this when I went through this with him many aeons ago (using temperature anomaly as the predictor variable rather than TSI, but same diff ...).
  14. KR#687 So what do you find wrong with the baselines in GISS Fig 613 from Post #631 KR? I thought we agreed that circa AD 1700 - 1750 was a 'low temperature trajectory' - a Maunder Minimum in fact. Anyway kdkd seems to have no problem with 'holding all other variables constant' in order to ascertain the contribution of each. If one variable did depend on another in an identifiable relationship (lets say CO2 positive forcing is directly related to cloud cooling negative forcing) then the two variables could be treated as one with a known equation for the combined forcing. Go look at the CO2 forcing via the IPCC equation and tell me what the relative forcings are with Solar in say 1800, 1850, 1900, 1950 and 2005. In 2005 you can find Solar at about 0.3 - 0.4W/sq.m and CO2 at 1.66W/sq.m - hardly an order of magniude difference and only at the most recent end of the time scale.
  15. kdkd #688 You are actually looking sensible among some of this lot kdkd. I'm interstate for a few days - will catch up with you Monday. Maybe time to re-visit the karaoke and look for that CO2 saturation again.
  16. @Ken: why would I leave? I enjoy seeing you squirm around while trying to defend illogical points. Your arrogance only compounds the farcical nature of your arguments. "Where the Solar irradiance forcing crosses the axis is where TSI is neither warming or cooling the planet, in the absence of other forcings. Any disagreement with that?" TSI is warming the planet. How could radiated energy cause the planet to cool? Again, you're confusing absolute values with deltas. You have failed to successfully argue your point. You can stick around if you want, but you'll only make yourself look more foolish. Your choice.
  17. Ken Lambert - my apologies, I was thinking about the UV issue (several orders of magnitude insignificance), which apparently wasn't being brought up. Too many threads... The greenhouse gas forcing is only 4-5 times the TSI forcing, and the TSI change is currently going in the opposition direction from the temperatures. Not an order of magnitude - I was off by a factor of two. But it's still 4-5x the TSI forcings! It's really, really not the sun. TSI changes have not correlated with temperature changes over the last 40 years, GHG forcing changes have. Unless you somehow disagree with this basic and quite provable point?
  18. KR #692 I pulled out a chart of CO2 concentration from AD1750 and used the IPCC quoted equation to calc the forcing F.CO2 for a range of dates: F.CO2 = 5.35ln(CO2*conc/280) W/sq.m where CO2*conc is the well mixed global concentration in ppmv at any point in time. F.Solar in W/sq.m is from IPCC 2007 Fig 613. Here are the numbers: Date/CO2*conc/F.CO2/F.Solar AD1850 / 290 / 0.18 / 0.2 AD1900 / 295 / 0.28 / 0.1 AD1950 / 310 / 0.54 / 0.4 AD1975 / 335 / 0.96 / 0.4 AD2000 / 370 / 1.50 / 0.45 AD2005 / 382 / 1.66 / 0.4 (estimated) Until circa AD1950 the F.CO2 did not overtake the F.Solar and in AD2000 it was 3x and only in AD2005 had it reached 4x. Again it is the area under the curve which represents the total available energy from both sources and both add together as I have calculated elsewhere back to AD1750. S-B radiative cooling has grown to -2.8 W/sq.m to date as a climate response to 0.75 degC warming.
  19. archisteel 3691 "TSI is warming the planet. How could radiated energy cause the planet to cool?" Its called IR cooling from S-B equation proportional to T^4. In 2005 at about minus 2.8W/sq.m. due to a 0.75degC warming since AD1750. IR radiating temp is currently about 255degK. Which was 254.25 degK in AD1750. The sum is roughly (255/254.25)^4 x 240 = 242.8W/sq.m where 240W/sq.m is the original IR outgoing from the planet. Hence IR outgoing increases proportionally with (T2/T1)^4.
  20. I'm sorry, Ken, can you explain this to me in layman's terms? This site does a great job at explaining concepts in everyday language, you should follow that example.
  21. KL #693 The multiple regression on the climate karaoke confirms your analysis rather nicely - after the mid-20th century, co2 is the main driver of warming (as expressed in that case by temperature anomaly as the dependent variable). I can't remember offhand what the precision of the prediction is, but it was reasonable, although regression assumptions were violated somewhat. Who'd have thought - convergent evidence. I can't see this supporting your 'sceptic' argument at all though. It more confirms the opposite.
  22. If you want to know the answer to sun spot production and the link to global temperature variation, then see this site, the answer will surprise you!!
  23. I wouldn't waste your time with Howard's site. An example of its 'thinking' : "Ever so Clever Alarmist Tricks of Trade There seems no end to the assemblage of clever tricks and blockades which the bretheren of the alarmist church can dream up. And since they hold pretty much all the top jobs all over their global diocese they for the most part go undetected and unreported." Hm, nice...
  24. archiesteel #695 As the planet warms from a forcing imbalance, it emits black body radiation in proportion to the fourth power of the absolute temperature (degK) via the Stefan-Boltzman equation. The forcing imbalance gap then closes and a new equilibrium temperature is approached. The 'emitting temperature' is quoted as about 255degK which is the temperature that space sees the Earth. The average surface temperature is about 15 degC or 288degK. The difference of 33degK is the 'greenhouse effect' of the atmosphere which slows down the heat transfer like an insulating blanket.
  25. KR #692 and kdkd #696 Two points: Firstly - KR seems to still not get the fact that a forcing component does not have to be rising to be adding energy to the system. A steady or roughly constant forcing such as F.Solar (say S) will add energy over time as St - a linear increase. Lets say that F.CO2 is linearly rising wrt time (over a short period of say 25 years). Therefore F.CO2 = Kt where K is a constant. F.CO2 will add energy over time as Kt^2/2 - a squared function increase. Both are adding energy. Secondly, the F.CO2 and other component forcings are theoretical and not directly measured - only the combined imbalance is directly measured at TOA. This is supposed to be +0.9W/sq.m. In fact the CERES satellites are measuring +6.4W/sq.m. So this is 'corrected' down by -5.5W/sq.m to the theoretical imbalance. The problem is that not even the 0.9 is being observed in OHC. The wide error bars on aerosol cooling, and other forcing components mean that the mix of components is not really known accurately. I would like to see a combined forcing chart including S-B cooling over time to see what the energy balance is as well. Anyway - I think my point is made - the Solar forcing component 1950 - now is about 0.4W/sq.m - not 0.12W/sq.m as the IPCC chart implies.

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