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Sun & climate: moving in opposite directions

What the science says...

Select a level... Basic Intermediate Advanced

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)

Over the last 35 years the sun has shown a cooling trend. However global temperatures continue to increase. If the sun's energy is decreasing while the Earth is warming, then the sun can't be the main control of the temperature.

Figure 1 shows the trend in global temperature compared to changes in the amount of solar energy that hits the Earth. The sun's energy fluctuates on a cycle that's about 11 years long. The energy changes by about 0.1% on each cycle. If the Earth's temperature was controlled mainly by the sun, then it should have cooled between 2000 and 2008. 

TSI vs. T
Figure 1: 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 solar fluctuations since 1870 have contributed a maximum of 0.1 °C to temperature changes. In recent times the biggest solar fluctuation happened around 1960. But the fastest global warming started in 1980.

Figure 2 shows how much different factors have contributed recent warming. It compares the contributions from the sun, volcanoes, El Niño and greenhouse gases. The sun adds 0.02 to 0.1 °C. Volcanoes cool the Earth by 0.1-0.2 °C. Natural variability (like El Niño) heats or cools by about 0.1-0.2 °C. Greenhouse gases have heated the climate by over 0.8 °C.

Contribution to T, AR5 FigFAQ5.1

Figure 2 Global surface temperature anomalies from 1870 to 2010, and the natural (solar, volcanic, and internal) and anthropogenic factors that influence them. (a) Global surface temperature record (1870–2010) relative to the average global surface temperature for 1961–1990 (black line). A model of global surface temperature change (a: red line) produced using the sum of the impacts on temperature of natural (b, c, d) and anthropogenic factors (e). (b) Estimated temperature response to solar forcing. (c) Estimated temperature response to volcanic eruptions. (d) Estimated temperature variability due to internal variability, here related to the El Niño-Southern Oscillation. (e) Estimated temperature response to anthropogenic forcing, consisting of a warming component from greenhouse gases, and a cooling component from most aerosols. (IPCC AR5, Chap 5)

Some people try to blame the sun for the current rise in temperatures by cherry picking the data. They only show data from periods when sun and climate data track together. They draw a false conclusion by ignoring the last few decades when the data shows the opposite result.


Basic rebuttal written by Larry M, updated by Sarah

Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial


This rebuttal was updated by Kyle Pressler in 2021 to replace broken links. The updates are a result of our call for help published in May 2021.

Last updated on 2 April 2017 by Sarah. 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:


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Comments 1251 to 1295 out of 1295:

  1. The Sun was classified as a G2V main sequence Yellow dwarf star, and oddly it still is. But the fact is it no longer is a yellow star, it's a white star. The once yellowish sun is now a brilliant metallic white, as result of an increase in the average temperature of the photo sphere of approximately 200 degrees kelvin.
    It is possible to actually prove this increase in temperature to yourself.
    The only equipment and materials you need are an astrophysical publication in book form that predates 1980 and gives the photosphere temperature and classification of the Sun , a camera, and a color/temperature star classification chart . All publications no matter where they originate that predate 1980 will say the Sun is a G2V main sequence yellow dwarf star. with a photosphere temperature of 5600-5750 Kelvin. It will also describe the visible overall appearance of the Sun as "pale yellow", which correlates with that temperature color -wise. There may be an image showing you how the Sun appears, usually just a circle of pale yellow. If you reference a star color /temperature chart you will find this to be true, that 5750 correlates with a pale yellow star.. The Sun as a G2 star was on the upper end of the "yellow" classification, but as it gained 200degrees K to 6000K , it's classification changed from G2 to F-9, which is on the lower end of the "white" star classification temperature and color.


    [TD] See MA Rodger's response comment in the Other Planets are Warming thread. Everybody please post further responses here in this It's the Sun thread.

  2. This is a response to MA Rodger's answer in the Other Planets are Warming.

    I failed to finish the comment @1251, but the reason why I found the argument interesting is because everyone can in an easy way, and with rather simplistic material, prove for themselves that the Sun has in a 40 year period gone from being "yellowish" to a pale-white metallic color. This change in color represent a change in temperatur which we can call X. If the data doesn't show X change in temperatur during this period; is the data wrong or is the empiricall method used missleading?

  3. Source,

    An interesting question to post on a scientific blog.  Which is more accurate:

    1)  Carefully calibrated scientific instruments operated by highly trained specialists over a period of decades or

    2) Untrained novices eyeballing 40 year old photographs taken at unknown locations and atmospheric conditions and comparing them to what they see on a randomly selected day outside their home.

    I will note that at my home the color of the sun is different at noon than it is at sunset and differs depending on the clouds and air pollution in the sky at the time of observation.

    I think the readers here at SkS will be able to reach their own conclusions.

  4. michael sweet @1253,

    As you say, the Sun's colour is dependent on what you are looking through to see it. Out in space, where there is nothing in the way, the Sun appears white as the red and blue parts of the spectrum cancel each other out. This German graphic shows how more of the blue part of the visible spectrum is lost in the clear atmosphere, causing the yellowish colour.Sun's spectrum

  5. michael sweet @1253

    In my defence, the photograph(s) were used in the scientific litterature back in the 80's, and I'm pretty sure they were taken out in space. What I am looking for is the color index of the Sun from pre-80's till today, then I would give up the theory.

  6. Sourcer,

    As MA Rodger pointed out to you here, the energy emitted by the Sun has remained in the range 1360-1364 W/m2 since 1975 (longer records are available).  If the temperature of the Sun changed than the energy received on Earth would change.  Ergo the temperature of the Sun has remained constant since 1975 (and actually longer than that).

  7. S0urce @1255,

    You are, I feel, asking for a scientific reference which specifically says the colour of the Sun is changed or unchanged since 1975. If there has been no such colour change, there is hardily likely to be such a reference.

    The NASA Factsheet for the Sun describes its Specral Type as G2V. We can assume this is the current classification, the Factsheet having been last updated February 2018. The Specral Type of a star is defined by its temperature G2. The roman numeral V defines its luminocity (or size). Indeed, The Spectral Type G2V is a direct indicator of a star's colour as it can be determined from ratio of the star's radation flux of in the visible wavebands 500-600nm and 390-490nm, yielding a value (B-V).

    You are asserting up-thread that the Sun's temperature has risen and that it sould now be classified as F9V. The NASA Factsheet says otherwise.

    And the Sun's Spectral Type was G2V according to Gray (1992) 'The Inferred Color Index of the Sun' and if that is not early enough for you, Gray (1992) cites Morgan & Keenan (1973) 'Spectral Classification' who also give the Sun's Spectral Type as G2V.

    This scientific evidence, I would suggest, is quite conclusive.

  8. michael sweet @ 1256, MA Rodger @1257

    Thank you for the answer and linked sources. I've to agree that the scientific evidence is quite conclusive, and that my theory of a color/classification change from yellowish to pale-white metallic or G2 to F-9 doesn't seem to hold.


    [PS] And thank you too for your contribution. Constructive debate happens best when both sides acknowledge errors and misunderstandings, and clearly indicate what they agree with in an opposing argument and what they continue to disagree with.

  9. SOurce's acknowledgment at 1258 is highly commendable. I am tempted to ask: where did this hypothesis of an abrupt and large change in the Sun's photosphere temperature initially come from?

  10. Philippe Chantreau @1259,

    The 'hypothesis' is a little off-stage so not directly linked to climate change, instead appearing within the general conspiracy-theory community. See here or here.

  11. Hi Again,

    I shared the "Sun & climate: moving in opposite directions" link on a public forum with the snipet: In the last 35 years of global warming, the sun has shown a slight cooling trend. Sun and climate have been going in opposite directions. In the past century, the Sun can explain some of the increase in global temperatures, but a relatively small amount.

    A climate denier swooped in all angry and made these comments: As for that 35 year cooling trend, a child can see the fallacy in that arguement.

    Cooling trend from what? The highest cycle in the 400 years observed. Yet this is followed, in your 35 years of "cooling" by the 2nd and 3rd highest cycles is it not? So against the 400 year average output is still greatly higher- why would we expect cooling of any kind, which could only happen if output was LOWER than the 400 year average? (Solar output is still far higher during the entire 35 years than it was for 400 prior so the sun is still forcing warming, not cooling as you claim).

    I am not quite sure how to respond.

  12. "The highest cycle in the 400 years observed"

    Only if you're talking about the 1960s

    Historical TSI

    TSI has dropped off since then while temperatures continue to rise.


    Actual scientists have unpacked the contributions of natural forcings to climate change; only by including the human-caused warming forcing can the upward rise in observed temperatures be explained.

    Natural forcings

    And actual scientists have quantified the warming forcing from the GHG emissions from the human burning of fossil fuels and have found them to be over 50 times greater than the slight extra warming coming from the Sun itself since 1750

    It's not the sun

    Your "friend" is no scientist.

  13. @1262 Daniel Bailey

    Thank you!  I learn so much from you guys when I post the denier claims that I'm not confident in answering. 

    Thank you so much! :)

  14. Hi Daniel @ 1262
    Would you mind explaining how scientists differentiate between human generated and nature generated CO2?

    I've found that there are two different isotopes for the human imprint vs. natural CO2.

    Are there other methods besides the identifying the different isotopes and what methodologies are used to test these different contributors?

    Thank you!


    [PS] that would be offtopic here. Please see this rebuttal for two other methods used to constrain CO2 origins.

  15. Thanks [PS]!

  16. Hello,

    could you explain to me, why "The solar radiative forcing is TSI in Watts per square meter (W-m-2) divided by 4 to account for spherical geometry", when only half of the Earth is being shined on by the Sun? Also why are other Sun cycles being ignored, not to mention galactic rays possibly influencing cloud formation. Thank you


    [PS] Why do you believe that these are "ignored"? Solar influences are discussed in every IPCC report and AR4 Chp 7 examined the science around cosmic rays in some detail.

  17. ThirdStone @1266 ,

    the ratio of area of a disc (receiving sunshine) to the area of a sphere is 1:4 and hence the division by 4  

    The scientists look very carefully at sun activity, and find that the 11-year cycle of solar activity is too slight to produce noticeable cyclic fluctuation in climate.   Or did you have some other factor in mind?

    "Cosmic Rays" are a failed hypothesis for climate change, and can be dismissed.   A triple fail, because (A) CR effects appear non-existent for the period (since mid-20th Century) that CR levels have been measured directly, and (B) likewise the paleological (proxy) measurements of CR variation show no appreciable link to climate changes, and (C) the 2016 experiments at CERN show negligible CR effect on cloud nucleation (negligible in comparison with the nucleation from marine-origin particles).   As they say: Cosmic Rays were a "Nice Try" as an idea for climate influence, but when tested against reality, they were a major fail not just on one way but on three separate ways of testing.


    [PS] Surprising to see cosmic rays still coming up but for more detail (and the papers which tested the hypothesis) see "its cosmic rays" myth.

  18. ThirdStone,

    You should ask yourself how you came to bring the question "why is this being ignored" instead of "is it true that this is being ignored."

    You show very little familiarity with the subject in your disk to sphere comment. It is very likely that you were subject to faulty sources of information, which you nevertheless found credible enough to then come here asking a question indicating you accepted as an established fact that these influences were being ignored, when in fact they have been carefully considered and evaluated. Why did you find the faulty information credible? How much scrutiny did you apply to it?

  19. Can 'the sun' account for as much as 10%?

    “Gavin A. Schmidt, head of the Goddard Institute for Space Studies in Manhattan, a NASA division that studies climate change, said that the sun had probably accounted for no more than 10 percent of recent global warming and that greenhouse gases produced by human activity explained most of it.”

  20. "Can 'the sun' account for as much as 10%?"

    That depends upon where you demarcate your start and end periods.

    Scientists have quantified the warming caused by human activities since preindustrial times and compared that to natural temperature forcings.

    Changes in the sun's output falling on the Earth from 1750-2011 are about 0.05 Watts/meter squared.

    By comparison, human activities from 1750-2011 warm the Earth by about 2.83 Watts/meter squared (AR5, WG1, Chapter 8, section 8.3.2, p. 676).

    What this means is that the warming driven by the GHGs coming from the human burning of fossil fuels since 1750 is over 50 times greater than the slight extra warming coming from the Sun itself over that same time interval.

    Radiative Forcing

  21. This quote from BBC is misleading.  The full quote is:

    "The data suggests that changing solar activity is influencing in some way the global climate causing the world to get warmer.  Over the past 20 years, however, the number of sunspots has remained roughly constant, yet the average temperature of the Earth has continued to increase."

    That's a pretty fair description of the situation in 2004, when the BBC article appeared.  The professor they quote is also right to state that solar activity in the past 60 years exceeds any period of time in the last millennium.

    I suggest you find a skeptic quote that actually does incorrectly atribute recent rises in global average temperature to increases in solar activity.  The BBC quote doesn't.

  22. ricieb1234 @1271,

    Do note that the author of the BBC item quoted in the 'Myth' is David Whitehouse who is now known to be a fully paid-up member of the denialist squad. His take-away message in 2004 was:-

    "This latest analysis shows that the Sun has had a considerable indirect influence on the global climate in the past, causing the Earth to warm or chill, and that mankind is amplifying the Sun's latest attempt to warm the Earth."

    Yet this "latest analysis"  informing the 2004 BBC article by Whitehouse concludes with the warning:-

    "we point out that solar variability is unlikely to have been the dominant cause of the strong warming during the past three decades."

  23. Further to #1272.

    The link to that "latest analysis".

  24. MA Rodger:  Thanks for the additional information.

    My only point is that the "myth" thermometer on the left of the front page is a key part of the SS website's message.  When a viewer clicks on one of those myths, they should find a blatant statement of the myth from a climate denier.   The BBC quote doesn't pass that test.

    The quotes above from Whitehouse also don't show he is claiming that "it's the sun."  In these quotes, Whitehouse is apparently claiming that the sun was a big factor in past climate changes, but not recent changes.  That is an accurate claim.

    I just think there must be a better quote somewhere to illustrate this myth. 

  25. MA Rodger, Tom Dayton and Moderator

    Thanks for the thorough responses to my question about the medieval maximum.  Anyone not using this website is missing out on a treasure trove of information and assistance.

  26. Hi! As mathematician I can't help but wonder about one thing. In advanced section, you compute the possible range of solar contribution to global warming. To do that you use previously computed values for temperature increase for doubling CO_2 (through senstitivity etc). Basically, to compute solar contribution you use computed CO_2 contribution. So the logic goes: if CO_2 contribution is computed correctly, than solar contribution right now is not big enough to explain the current global warming. What I see here is circular logic.

    I would imagine, you want your argument to go something like this: suppose CO_2 contribution is low, then solar contribution is low (in particular, it may not fit the data we have for before 1950s).

    Please correct me if I understood what is going on wrong.

  27. socialfox - estimates of climate sensitivity seek to answer what would the change of temperature for a given effective increase in radiation at TOA. Changes in GHG concentration, albedo are back-calculated to an effective change in TOA radiation. ie. As if the incoming solar radiation was changing. The direct contribution to radiative flux from a change in GHG is a known quantity (~4W/m2 for a doubling, which falls out the Radiative Transfer Equations and has been empirically verified in various ways). It is not something deduced from the temperature response, but resultant feedbacks (water vapour, albedo, cloud cover) that contribute to actual change in temperature are not well known and hence the wide range of estimates for climate sensitivity. Climate sensitivity is estimated from a variety of methods including paleoclimate and models.

    Note that models do not assume a climate sensitivity - it is an emergent property from the model so I dont see the circularity.

  28. As a person concerned about the climatic issue I am trying to understand all the arguments, however this graphic baffles me. Going to the physical foundations of the graph, the temperature is an indicator of the accumulated heat, while solar irradiation is a flow, and by therefore, a contribution of heat. So I don't see any point in looking for a correlation between the two variables (it would be like comparing speed with position). I think that the correlation between temperature variation and irradiation would be more interesting, and that is when these variables not only do not move in opposite directions but do so in parallel.

  29. Reading though the comments, there are mentions of the cooling/warming effects of El Nina/Nino. Looking at this from a marine biologist perspective, I'd like to bring up the effects of climate change on tropical coral, particulary in the indian ocean and south pacific and how examining coral biodiversity records could be used to support AGW. Coral live between a fairly narrow temperature range. Extreme rises in temperature lead to bleaching and usually coincide with el nino events where vast bodies of warmer become trapped in the indian ocean and southern pacific. What we are seeing is a decline in biodiversity and massive bleaching events in the last 30 years, notable events in 1998, 2005 and 2017. Studying in the Maldives, there was evidence of coral recovery but ONLY for a few species compared to what can be found in historical records. Then the whole system got hit again in 2017 so back to square 1. To me, it is apparent that such a delicate ecosystem can be thriving for thousands of years and then hammered by prolonged, frequent, intense  el nino events in a short space of time is a smoking gun. The reversal of trade winds seems to hinge on a delicate energetic balance in the atmosphere. I don't know why it's difficult to comprehend that insulating energy would change the dynamics of a system.

  30. Apology for bothering you, I have misplaced the web path leading to this discussion of the Heinz Hug claim that CO2 absorbs so much of the infrared very close to land surface that more CO2 would not matter. In other words, he claims it is such a potent absorber that the effect is already saturated. There was a nice rebuttal somehere and I could not locate it. The rebuttal included a figure, Australian style, with the planet "upside down". It also mentioned satellite data about infrared emissions over the last decades. Can anyone help me locate this discussion which exists  somewhere in your blogs?


    [DB]  Perhaps this one?

  31. comeaukay @1280: Maybe you are looking for this: Is the CO2 effect saturated?

  32. deucarra @ 1278: You are quite correct.

    I assume that others, as I do, "eyeball" the average incoming irradiation and compare it to the slope of the temperature curve.

  33. Deucarra, sailingfree - remember that outgoing must match incoming for conservation of energy. Perhaps need to look at how the Stephan-Bolzmann law is derived?

    As it is, temperature is function of power. (T4 ~ to incoming energy flux), so the comparison is entirely valid. If energy flux changes, then surface temperature must change to maintain conservation of energy.

  34. Hi All

    I have some questions that I'm sure people here can help me with.

    I read a paper by Ronan Connoly and colleagues:



    They say that the temperature graph on this page above is wrong because it does not take urban heat islands into account.  They seem to show on graphs that rural temperatures are more or less flat since the 1950s.  They seem to have looked very carefully at the data, starting with Valencia in Ireland.  Are they wrong?

    Secondly, I heard a talk by Richard Alley on youtube.  He says that the ice ages were driven by 100,000, 41,000, 23,000 and 19,000-year Milankovitch cycles.  He shows a convincing Fourier transform.  If the sun can drive ice ages (approx 10C change), it should certainly be powerful enough to drive a temperature change of around 1C.

    There seem to be many different models for solar irradiation - see the Connolly article above.  Which one should we pick?  They pick one that almost exactly matches the temperature fluctuations that they report.  Are they wrong?

    Thx to all and I'd be very interested in comments and explanations (but not so interested in assertions that there is "masses of evidence" out there that shows that the Connollys are completely wrong and that I should go and look for it).


    [DB]  Just because the climate changed naturally in the past does not mean that human activities are unable to change the climate today.  Logical fallacy snipped.

    Urban heat islands are dealt with here.  Put all questions and responses to them there, not here.

  35. This particular paper is execrable. You can look at takedown here but also note that Soon simply ignores any dataset that doesnt fit what his fossil fuel funding masters want. eg marine data (no urban heat sources there). Hard to believe this is still circulating in denier land.

    It seems you are frantically on a search for anything that might indicate a problem in the science, no matter what the cesspool. Good luck. Have you actually looked at IPCC WG1 summary of climate science instead?

  36. scaddenp,

    I share your skepticism regarding the motivations of PatrickSS.

    They do not appear to be interested in expanded awareness and improved understanding.

    Instead of starting with a detailed understanding of the subject, they appear to be seeking excuses to not expand their awareness or improve their understanding (though they sound interested by 'asking questions').

    As an example, in previous comments they present their summary understanding of presentations of understanding by "“consensus” climate scientists" (their term of reference) as "...sunlight comes in, heats the Earth, and the heat escapes from the Earth via IR. Increased CO2 absorbs and blocks more IR, so the Earth gets warmer." They then compare that with what they consider to be more believable presentations by Lindzen, Allen and Curry (they are more impressed by these people than they are by the "consensus" climate scientists that they present an extremely poor level of understanding of).

    In addition they appear to have summarized my previous comments to them regarding pursuit of expanded awareness and understanding of climate science matters as "... assertions that there is "masses of evidence" out there that shows that the Connollys are completely wrong and that I should go and look for it":

    "There is a massive diversity of evidence supporting the climate science consensus understanding that human activities, particularly fossil fuel use, are significantly impacting the global climate in ways that are detrimental to the future generations."

    "Seek out detailed explanations of the incorrect aspects of the claims made by Lindzen, Alley and Curry. There are many sources for the corrected expanded understanding (and a vast amount is available right here on the SkS site)."

    I believe you are correct to suspect that PatrickSS has not read, and is unlikely to read, any IPCC document. I would add that I suspect that PatrickSS filters information for its 'ability to impress them, suit their preferred beliefs'. My comments were an attempt to make them aware of that.

  37. Recommended supplemental reading:

    Four graphs that suggest we can’t blame climate change on solar activity by Gareth Dorrian & Ian Whittaker, The Conversation UK, Jan 24, 2020

  38. Recommended supplemental reading:

    Electroverse article incorrectly claims the Sun is behind climate change, Edited by Scott Johnson Climate Feedback, Mar 18, 2020

  39. I appreciate the argument on recent decrease in solar output. But that is the "Gravity doesn't exist" argument. A person tracks a falling ball. Initially, gravity theory and fall rates match. Then they no longer match. So lesser scientists conclude that it's not gravity making the ball fall. "See, if it was gravity, then the ball fall rate would continue to rise." There are good arguments, but that's not a worthy one.

    Scientists have long ago learned to account for fluids. With gravity, it's friction provided by the fluid called air. In climate, it's the fluid called oceans.

    If I turn the stove down, stove element temperature will decrease. But, if the pan still has a temperature lower than the stove element, pan temperature will continue to rise. Oceans are about 7C warmer than the atmosphere.  As sun and ocean temperatures fall, they will continue to increase the temperature of the atmosphere. Oceans will always have a temperature higher than the atmosphere. But, the gap does narrow as oceans cool and the atmospheric temperature continues to rise.

    Think of atmosphere as aluminum foil and think of the oceans as the cast iron pan that is absorbing (and storing) solar heat. This will get you closer to the truth about climate change.

  40. Chuck #1289:

    Your stove analogy fails because the oceans are not cooling. If anything, their warming seems to have accelerated over the last few decades.
    Here's the temperature anomaly of the upper 100 metres:

    Ocean warming upper 100 m











    And here's the change of heat content in the upper 2000 metres:

    Ocean heat content upper 2000 m











    The Sun has cooled, but the atmosphere and the oceans keep warming. The only explanation making sense is that the Earth gives off less heat to space.

  41. HK@1290 -

    "The only explanation making sense is that the Earth gives off less heat to space."

    --- Another additional explanation would be the fact, that the earth absorbs more short-wave solar energy from space, although the solar constant(1360,5W/m²) tends to decrease actually.

    Explained by the cloud and snow / ice albedo that has decreased in the last few decades (0,5W/m² which is a lot).



    [BL] The user cph has been confirmed as a sock puppet of the previously-banned user coolmaster. Until the admins can delete the account of cph, any further posts by cph wll be deleted as soon as moderators find them. Please do not respond to any comments you come across.

  42. "Explained by the cloud and snow / ice albedo that has decreased in the last few decades (0,5W/m² which is a lot)."


    The net forcing from the preindustrial period when counting both the positive forcing from the greenhouse gases and the negative forcing from man-made aerosols is now roughly 2.5–3 W/m².
    Changes in clouds and the snow/ice albedo are positive feedbacks amplifying that warming. The most important and fastest of those is the water vapour feedback which roughly doubles the initial warming.

    BTW, if clouds and snow/ice changed by themselves and not as a feedback to warming caused by GHGs, we wouldn't get a cooling stratosphere or more warming in winter than summer at high northern latitudes.

  43. HK@1292 - "BTW, if clouds and snow/ice changed by themselves and not as a feedback to warming caused by GHGs, we wouldn't get a cooling stratosphere..."

    --- I did not understand your last sentence. I am of the opinion that, for example, a changed cloud albedo cannot be explained by a rise in temperature alone. Changes and anomalies in global mean cloud cover can also be caused by fewer (sulfate) aerosols or expanding deserts (dry regions become drier).

    Timeseries for evapotranspiration (top), precipitation (second from top), discharge (second from bottom) and change in ground water storage (bottom) over 2003-19.

    Evaporation increases by + 2.3 mm / year, which is not fully compensated for by increased precipitation of + 1 mm / year. A decreasing runoff through the rivers of -1.01 mm / year and a falling groundwater level of -0.75 mm / year quantify the drainage of the continents. This drainage (through drained bogs, wetlands, groundwater, aquifers, canalization of rivers and a constantly growing sealing of urban areas) is just as man-made as the CO² emissions, rising temperatures and the resulting higher evaporation. Too little H²O in desert regions and the earth's atmosphere, which in summer extend through droughts up to the Arctic Circle, are a temperature driver. Too much CO² is just as warming as too little H²O. Less evapotranspiration -> less cloud albedo -> higher incoming radiation energy and record temperatures on the earth's surface -> even faster drying out with even higher temperatures - imho, similar to the ice-snow albedo, form a vicious circle.

    The authors estimate a "statistically significant" increase in evapotranspiration of around 10% above the long-term mean (corresponds to a temperature increase over land areas of ~ + 1.44 ° C). During the same period, precipitation only increased by 3% and global river runoff decreased by 6%.


    What is noticeable here is a simultaneous decrease in relative humidity and cloudiness, which certainly correlates with a general increase in the number of hours of sunshine.

    time series sunshine hours germany 1951-2020


    Global time series of annual average relative humidity for the land (green line), ocean (blue) and global average (dark blue), relative to 1981-2010.


    [BL] The user cph has been confirmed as a sock puppet of the previously-banned user coolmaster. Until the admins can delete the account of cph, any further posts by cph wll be deleted as soon as moderators find them. Please do not respond to any comments you come across.

  44. My point in #1292 was that the 0.5 W/m2 of forcing from clouds and snow/ice is small compared to the overall net forcing over the last 150 years or so and that the albedo change brought up by you is at least partly a direct consequence of the warming, i.e., one of the positive feedbacks.

    However, I will admit that clouds and humidity are complex and can be influenced by other factors in addition to the direct result of man-made greenhouse gases. Desertification and deforestation in general and especially cutting down tropical rainforests can have a profound impact on the local hydrological cycle, changing humidity, cloud cover, rainfall and run-off and thus have an impact on the local temperature as well. So yes, man-made climate change isn't only about the greenhouse effect and the warming caused by it, but it's definitely the most important part of it on a global scale.
    It's also worth noting that even if the relative humidity seems to have decreased somewhat for the reasons explained here, the absolute or specific humidity has in fact increased, just as expected in a warming world.

    Specific humidity


    Water has an impact on the temperature not only via its removal of latent heat through evaporation – which has a local cooling impact – but also through its warming impact via its strong greenhouse effect, which is the most important of all the positive (amplifying) feedbacks on a global scale.


    Diagram showing the monthly fluctuations in total global cloud cover since July 1983. During the observation period, the total amount of clouds fluctuated from about 69 percent in 1987 to about 64 percent in 2000. The annual variation in cloud cover follows the annual variation in atmospheric water vapor content, which presumably reflects the asymmetrical distribution of land and ocean on planet Earth.


    Within the still short period of satellite cloud cover observations, global cloud cover reached a maximum of about 69 percent in 1987 and a minimum of about 64 percent in 2000 (see diagram above), a decrease of about 5 percent. This decrease corresponds roughly to a net change in radiation of around 0.9 W / m2 within a period of only 13 years, which can be compared with the total net change estimated by the IPCC 2007 report from 1750 to 2006 of 1.6 W / m2 for all climate drivers including greenhouse gas emissions from fossil fuel burning(cooresponds to your mentioned 2,5-3W/m² in 2021). These observations leave little doubt that cloud cover variations can have a profound impact on global climate and meteorology on almost every time scale considered.

    The total reflectance (albedo) of the planet earth is about 30 percent, which means that about 30 percent of the incident short-wave solar radiation is reflected back into space. If all the clouds were removed, the global albedo would drop to around 15 percent and the short-wave energy available to warm the planet's surface would increase from 239 W / m2 to 288 W / m2 (Hartmann 1994). However, long-wave radiation would also be affected, which emits 266 W / m2 into space compared to the current 234 W / m2 (Hartmann 1994). The net effect of removing all clouds would therefore still be an increase in net radiation of around 17 W / m2. So the global cloud cover has a significant overall cooling effect on the planet, although the net effect of high and low clouds is opposite.

    HK: - "but also through its warming effect through its strong greenhouse effect, which is the most important of all positive (reinforcing) feedbacks on a global level."

    Wild, M., Hakuba, M.Z., Folini, D. et al. The cloud-free global energy balance and inferred cloud radiative effects: an assessment based on direct observations and climate models. Clim Dyn 52, 4787-4812 (2019).
    According to the current status, the net radiation effect of clouds is -19W / m² (Wild 2019) and corresponds very well with + 0.9W / m² per 5% less cloud cover.


    High levels of global cloud cover are associated with low global temperatures, demonstrating the cooling effect of clouds.                        A simple linear fit model suggests that a 1 percent increase in global cloud cover corresponds to a global temperature decrease                        of about 0.07 ° C.


    [DB] You are again off-topic for this post.  Your entire argument revolves around clouds, so if you're going to prosecute that agenda, please take it here (after reading the post and all of the comments in the discussion thread):


    [BL] The user cph has been confirmed as a sock puppet of the previously-banned user coolmaster. Until the admins can delete the account of cph, any further posts by cph wll be deleted as soon as moderators find them. Please do not respond to any comments you come across.


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