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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

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MD Sun

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Denial101x videos

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Additional video from the MOOC

Expert interview with Mike Lockwood

Comments

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Comments 701 to 725 out of 1037:

  1. KL #700: "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." The Sun is constantly 'adding energy to the system'. However, if solar activity remained constant then it would obviously not cause any change to the climate. It is only when there is a change in solar activity (that is, a "forcing") that there is a corresponding change in climate... and then only until a new equilibrium is reached. The same is true of all climate forcings. So no, KR probably 'does not get' that flat forcing factors do not change the climate. Because they don't.
  2. Two things: first, blatant denier spam such as Howard at 697 should be deleted. Second: KL, I get what you're saying, I guess I just don't see the point you are trying to make. It seems you've lost yourself in your own arguments.
  3. Ken Lambert - Your hypothesis appears to be that an unmeasured amount of TSI, one mis-calculated since the beginning of TSI measurements, is providing a dominant effect on global temperatures rather than CO2 and greenhouse gas accumulation. In other words, that it's the sun, not CO2. The satellite TSI readings appear to have cross-platform calibration issues, as each is self-calibrated to internal standards. This has improved over the years, not to say that it's not a work in progress, but it's improving. Note that the precision, the repeatability of these measures, is extremely good - the accuracy may be off a bit. But high precision means excellent tracking of changes, of deltas in TSI forcing. Now, if there's a linear offset in TSI measures (direct or using sunspots as proxies), as you have argued, there would be a difference in slope between measured TSI responses and temperature over the entire temperature/TSI record, not just the last 60 years. One look at the Temperature vs. Solar Activity chart on the Basic version of this thread will disprove that. I certainly know that all forcings are part of the picture; I'm not certain from your statements that you do. The two lines have separated. The temperature changes correspond to changes in GHG forcings, they do not correspond to changes in TSI. That is entirely supported by the numbers you presented here, as kdkd pointed out statistically - you've just disproven your hypothesis again. You are incorrect on the basis of correlation of ΔT versus ΔForcings, on the magnitude of the TSI changes, and on somehow not crediting the forcings of GHG's. You've repeated the same arguments over and over despite multiple corrections. At this point I'm out of this discussion.
  4. @KR: "You've repeated the same arguments over and over despite multiple corrections. At this point I'm out of this discussion." I think this is Ken's strategy: obfuscate, reiterate and ignore other arguments until people are fed up with him and leave, at which point he claims victory. Better to ignore him. It's not as if his arguments will be reused by other "skeptics" anyway...
  5. CBD #701 KR #703 archiesteel #704 "So no, KR probably 'does not get' that flat forcing factors do not change the climate. Because they don't" Flat forcing is not 'zero' forcing CBD & KR. The numbers I presented show a F.Solar of about 0.4W/sq.m from the IPCC Fig 613 Chart which is also available in numerical form (worked elsewhere by kdkd)from AD1950 onward, and 0.1-0.2W/sq.m before that. A 'flat' 0.4W/sq.m integrated wrt time will give you a linearly increasing number of Joules/sq.m - the unit of energy. Energy is what you need to heat mass. Note the units of specific heat of water (or other mass)are Joules/kG-degC - NOT Watts/kG-degC Linearly rising energy in Joules will linearly raise the temperature of a given mass (without phase change). Hence rising temperatures with 'flat' non-zero forcing are quite consistent with the 'Temperature vs. Solar Activity chart on the Basic version of this thread' Add to that a 'theoretical' roughly linearly rising forcing F.CO2 and you will get a squared function non-linear rising curve of energy wrt time. This is Grade 11 maths. What counts is the sum of and proportions of the energy added by the two sources. I calculated previously that on the IPCC data the energy proportions were about 55/45 CO2GHG/Solar since AD1750. The question then becomes how reliable and accurate are these forcings. We have some proxy and direct measurement for TSI and F.Solar. KR: "Now, if there's a linear offset in TSI measures (direct or using sunspots as proxies), as you have argued, there would be a difference in slope between measured TSI responses and temperature over the entire temperature/TSI record, not just the last 60 years" Wrong - see above. Non-zero constant forcing produces linearly rising temperature for a given mass. How long do we have Satellite TSI data? - since 1978? Again high precision - low accuracy. Will tell you the deltas within an individual satellite record - maybe spliced together between satellites (maybe not too) - but no good for accurately measuring absolute TSI (SORCE TIMS is a good example). Archiesteel - don't know what your technical training or background is - but kdkd will tell you that it is risky to call me on the sums.
  6. @KL: I don't dispute your capacity to make mathematical operations. I simply think you're not very apt at clearly presenting your arguments, hence the impression that you obfuscate issues by throwing around of math. Your inability earlier to understand such as simple matter as relative deltas instead of absolute values seems to confirm this hypothesis. If you truly understand an issue, you should be able to explain it to non-technical people like me. The fact you cannot seem to make a clear argument with all those equations is telling, and that's all I'll say on the matter before getting even more off-topic.
  7. KL #705 "Hence rising temperatures with 'flat' non-zero forcing are quite consistent with the 'Temperature vs. Solar Activity chart on the Basic version of this thread'" That may be the case, if we didn't have additional data showing that the role of CO2 has been strong for the past 60 years. However we do. If you omit key information, then your hypothesis would appear credible. However omitting key information is not justified, so your hypotheis is not credible.
  8. kdkd #707 We should have a beer together someday kdkd. I have a sudden feeling of kinship with you after a night listening to Ziggy Switkowski. KL: "What counts is the sum of and proportions of the energy added by the two sources. I calculated previously that on the IPCC data the energy proportions were about 55/45 CO2GHG/Solar since AD1750. The question then becomes how reliable and accurate are these forcings. We have some proxy and direct measurement for TSI and F.Solar." I have not ignored the theoretical contribution of F.CO2 - I have said that the two main positive forcings add together - F.Solar a linear function - and F.CO2 a squared function. It all depends on the magnitude of the forcings and the elapsed time - ie the area under the curves. This only represents the available positive (warming) forcings. The main negative forcings are cloud and aerosol albedo, and S-B radiative cooling. I shall run some numbers on these and try for a net forcing since say AD1750 in 50 year tranches. Had a late night so look for this tomorrow.
  9. archiesteel #706 Forgive my lack of communicative skills - but I only felt knowledgeable enough to enter this blog after a year or so jousting with the likes of kdkd and reading Dr Trenberth, IPCC reports etc. The most imformative paper I have read is: http://www.cgd.ucar.edu/cas/Trenberth/trenberth.papers/EnergyDiagnostics09final2.pdf
  10. KL #708 I should have prefixed this with 'the energy from" "I have not ignored the theoretical contribution of F.CO2 - I have said that the two main positive forcings add together - F.Solar a linear function - and F.CO2 a squared function. It all depends on the magnitude of the forcings and the elapsed time - ie the area under the curves."
  11. @Ken >- I have said that the two main positive forcings add together - F.Solar a linear function - and F.CO2 a squared function. It all depends on the magnitude of the forcings and the elapsed time - ie the area under the curves. Taking the area under the curves ignores the tendency of the system towards thermal equilibrium. A flat forcing does not produce a linear increase in the net energy of the system, since the energy emitted by the system also rises proportionally to the energy absorbed. What it will produce is an increase with its slope tapering towards zero. Now the operative question is: how long does the system take to reach equilibrium given a flat forcing? This question (and the general claim you are making) was addressed in one of John's posts a while back. In short, there is no evidence that the flat solar trends are having a significant influence on recent temperature increases. >in fact all charts show increasing temperatures since 1850. No they don't. Temperatures were stable if not cooling slightly from 1850-1915. I believe what you are thinking of are charts showing overall temperature increase from 1850 to today, not the actual trends during those particular decades.
  12. @KL: It's not about being knowledgeable, it's about making a cogent argument. Even after all these messages I still don't get what you're driving at. Talk about a colossal waste of time...
  13. Responding to oxymoron, who in another thread argued that "Certainly before 2000 the correlation between TSI and temperature is obvious" Well, as this article shows, it's not 2000, it's 1980. Also, note that temperatures actually *lead* TSI from about 1925 to 1950. So, what can we conclude? Solar forcing does have an impact, but in the past 30-35 years it has been completely overpowered by anthropogenic greenhouse gases.
  14. e #711 I covered this point about areas under curves viz: KL : "This only represents the available positive (warming) forcings. The main negative forcings are cloud and aerosol albedo, and S-B radiative cooling. I shall run some numbers on these and try for a net forcing since say AD1750 in 50 year tranches." There will be a S-B negative curve and cloud albdo and aerosol negative curves - with the sum of all being the net energy added or lost to the Earth system. According to Hansen the thermal lag of the system is about 25 - 50 years, so we should see a temperature response which follows the net energy balance - lagging by some similar time period. Certainly if you take decadal sections of the post AD1850 temperature curves there are flat periods or slightly cooling periods - just like the one we have had for the last 10 years. This is consistent with the net area of Total forcing curves shown here : http://www.brighton73.freeserve.co.uk/gw/GISS_forcings.gif PROVIDED you add the correct Solar forcing of about +0.1 - 0.2/sq.m on the positive side which has been wrongly set to zero in this Total forcing chart. ie: The period 1850 - 1915 should be cooling because all the area under the Total Forcing chart is negative -but the temperature record shows flat (or very slight cooling) which indicates that positive Solar forcing at was offsetting the negative area.
  15. archiesteel #712 "Even after all these messages I still don't get what you're driving at. Talk about a colossal waste of time... " Your failure to understand might not be within my power to explain archiesteel.
  16. @KL: "Your failure to understand might not be within my power to explain archiesteel." Oh, I *understand* what you're saying (with a measured IQ of 150, I should be able to understand basic math and science even though my training in those areas stopped after high school). I just don't get what you're driving at. I'm sure it has something to do with trying to disprove AGW, but your argument is so buried in obfuscating jargon it's hard to tell anymore. Please come down your high horse and state your argument clearly, or we'll be forced to conclude all you're doing is trying to muddy the waters. Here, I'll help you, since that task seems above your abilities: Do you think the sun is responsible for the current warming trend?
  17. Ken, Did you take a look at the post I linked? It addressed essentially exactly what you are claiming, that solar forcings have a more long term effect then currently understood. Anyways, Hansen 2005 already "ran the numbers" as you are attempting to do. The net radiation and temperature data produced as a result is consistent with the temperature record and inconsistent with the idea that solar forcing is having any significant effect on recent warming.
  18. KL #715 I can assure you that it's your argument that is unclear, and that it leads to conclusions that you do not state explicitly, but instead expect the reader to infer themselves. Not good enough I'm afraid.
  19. archiesteel #713: I don't know if I will be successful in posting this chart (from Soon), but it shows the strong correlation between TSI and arctic air temperature from 1880 to 2000. Again, CO2 levels have been steadily rising, yet temperatures fell between (roughly) 1940 and 1965. To have gone from a sun-dominated system to a CO2-dominated system so quickly seems to be an extraordinary claim, requiring extraordinary evidence.
  20. May as well just provide a link to the entire paper, oxymoron, always better than a disconnected graph orphaned from its parent. Here: Variable solar irradiance as a plausible agent for multidecadal variations in the Arctic-wide surface air temperature record of the past 130 years (full text, pdf)
  21. @oxymoron: temperature mid-century fell mostly because of aerosols, not a drop in solar energy. CO2 and aerosol forcing are an order of magnitude larger than solar variations. Don't get hoodwinked by scientists-for-hire like Willie Soon.
  22. e #717 This is the introduction to your cited Hansen paper: "Our climate model, driven mainly by increasing humanmade greenhouse gases and aerosols among other forcings, calculates that Earth is now absorbing 0.85 ± 0.15 W/m2 more energy from the Sun than it is emitting to space. This imbalance is confirmed by precise measurements of increasing ocean heat content over the past 10 years." I don't think so. OHC content measurement debated at great length elsewhere on this blog eg; "Robust warming of the global upper oceans" has shown that OHC measurement is everything but precise. Even Dr Trenberth who would be on the same side of the debate as Hansen can only find 60% of the OHC increase posed by the 0.9W/sq.m imbalance. Will post my numbers when completed and checked. You all can be my peer review.
  23. archiesteel #721: Thanks. You've given me all the evidence I need.
  24. @oxymoron: you're welcome. I knew sooner or later you'd come around to the side of reason. :-)
  25. Gentlemen Regarding the numbers I am currently crunching (Ref #651)- could anyone point me to some historical data on Wate Vapor + Ice Albedo feedback - currently quoted by Dr Trenberth at +2.1W/sq.m in AD2005. I could assume linearity back to zero in AD1750 but this is a very significant component, and this could widely affect the result of the Total forcing sum.

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