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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

Related resource: Myth Deconstruction as animated GIF

MD Sun

Please check the related blog post for background information about this graphics resource.

Denial101x videos

Related lecture-videos from Denial101x - Making Sense of Climate Science Denial

and

Additional video from the MOOC

Expert interview with Mike Lockwood

Comments

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Comments 976 to 1000 out of 1295:

  1. Hello Ladies and Gentlemen. What is the truth to the assertion/hypothesis that the Earth's orbit is degrading by approximately 1 inch per year. I am at a loss for the location of the publication that provided this information. I do find it curious. Have any of you interested parties read about or researched this hypothesis? Although I find myself wondering about the validity of the assertion/hypothesis, it would seem to be a logical,if not complete cause of warming. What would the effects of increased or decreased solar flare activity have on the Earth with this hypothesis. An interesting point for further investigation.
  2. Icyhot @976: If the Earth's orbit decayed by one inch per annum since 1750, it would be 6.65 meters closer to the Sun, on average than in 1750. Incoming solar radiation varies with the inverse square of distance. So, a decay of 6.65 meters in the approx 150 billion meters radius of the Earth's orbit would result in a 0.00000001 increase incoming solar radiation, or a forcing of 0.000000024 W/m^2. This is compared to the approx 1.8 W/m^2 forcing from increased CO2 over the same period. Therefore such a decay in the Earth's orbit would not have a detectable effect the Earth's climate (and probably would not be detectable to begin with). However, that is beside the point. There is, SFAIK, no evidence that the Earth's orbit is decaying. Indeed, if anything the solar tide on the Earth would cause the Earth's orbital distance to increase, just as the Lunar tide result in the measured increase in distance to the moon. The increase in distance, however, is very small so that there is no reason to think the Earth's orbit will increase or decay significantly at any time in the past or future several million years.
  3. Icyhot - in addition to Tom's comments, the beauty of the mainstream climate science view of atmospheric CO2 as Earth's thermostat - is that it has explanatory power. Turn up the CO2 and the Earth gets warmer, turn it down and the Earth cools. Aside from maybe one outstanding complication, the Miocene, this relationship holds true for hundreds of millions of years back in time. There are, of course, other control knobs on Earth's climate - such as the Milankovitch Cycles, but CO2 is very clearly the Big Kahuna. If, as you suggest, the Earth is moving closer to the sun, why then was it much warmer on Earth further back in time?
  4. And as a final point - if we were getting warmer because we were getting closer to the sun, then we should see that in the TSI measurements. As shown in the main article, this is not the case.
  5. My main issue with it is the term: "Total irradience" from which the conclusions are based. It might supprise people to know that the term only includes visible light and does not even include the ultraviolet spectrum. If conclusions are based on less than 10% of the measured EMR emitted from the Sun how realistic are the results ?
    Response: [DB] A prudent person would ensure that they had read both the Intermediate and Advanced versions of this post before making such a strong demurral.
  6. maximo: From what I can see your claim It might surprise people to know the term only includes visible light and does not even include the ultraviolet spectrum. is unequivocally false. One of the sources cited in this article defines TSI in the introduction as: Variations in solar total (i.e. integrated over all wavelengths) and spectral irradiance [...] [Emphasis mine.] This webpage (material taken from what appears to be some form of textbook) defines TSI as: Total solar irradiance is defined as the amount of radiant energy emitted by the Sun over all wavelengths that fall each second on 11 ft2 (1 m2) outside Earth's atmosphere. [Emphasis mine.] Similarly, other discussions of TSI do not discriminate between spectra of radiation emitted by the Sun (e.g. visible light, UV, shortwave IR, &c), such as the IPCC AR4 WG1 Glossary or this University of Colorado solar radiation project site. Do you have sources for your claim about the spectra covered under TSI?
    Response: [DB] Fixed html tag.
  7. This is what I found on the solar irradiance monitor instruments: ERBE 0.2 - 50 micron ACRIM 200-2000 nm SORCE 1-2000 nm (95% of the total) Where did maximo get that information from?
  8. Thanks Riccardo, the information of what actual radiation wavelengths and the definition of "total irradiance" being measured by those satelites can seen on those links you gave. They are measuring in the nano meter range, which is within the visible spectrum though includes some of the Ultraviolet and Infrared wavelengths that are not visible. My issue still stands, 'total irradiance' is not all wavelengths that the Sun radiates. The Sun has microwave emissions and xray emissions and other high energy particles. Clearly not all wavelengths are being measured.. Also note these satelites have only been in orbit for a short period of time and the Temperature versus Solar Activity chart at the beginning of this blog dates back well before 2004 and I wonder how accurate modelling was done before these satelites existed?
  9. maximo I'm glad you admitted you were wrong claiming that TSI only include visible light but still you're missing something. The ERBE mission started somewhere in the late '70s, I'm sure you can easily find the exact date. Apparently you missed that the range 1-2000 nm of the SORCE instruments covers 95% of the total irradiance. I can't quantify how much energy is emitted in the 1-200 nm range and I'm to lazy to check, but I'd expect it's going to be a small part. The same applies to the far infrared and microwave range. There's really no issue with TSI apart from tiny discrepancies between different instruments.
  10. maximo @983, radiation from the Sun follows a black body curve. As such, observations of emissions within a fairly small range of frequencies are enough to quantify its total radiation with a high degree of accuracy. Sufficiently high so that correlating emissions between different instruments is a much larger source of error.
  11. Admitting Ultraviolet and Infrared as being just outside the visible range isn't an incorrect statement. To recognise that as inclusive of the limited range of measurement of the 'visible spectrum' that 95% of coverage is still not measuring the larger proportaion of the non visible Solar emissions. There have been 2 solar storms this year, one just yesterday July 16. The other March 8-10, which hit the earth with 26 million kilowatt hours of thermal energy, enough to power New York for 2 years. NASA have a specially designed satelite to measure those activities, but it is only very recently. http://www.youtube.com/watch?v=EEFQHDSYP1I
  12. maximo @986, do you mean to say that the Earth has been hit with solar storms having an power equivalent of 1.2*10^-8 W/m^2 over the year, and you think that that will massively distort the energy balance equations. Even if we where hit by one of those storms every hour, on the hour, it would only add 0.000005 W/m^2 to the average (after albedo) 240 W/m^2 incoming solar radiation. I am really struggling to see your point here.
  13. Correction it was actually 26 billion kilowatt hours of thermal energy dumped on the earth during the March 8-10 Solar storm, enough to power New York for 2 years. It's from the NASA video on the link I posted, which Tom is nothing to do with what I think. (-Snip-)
    Response:

    [DB] Please refer more closely to the comments policy (linky adjacent to the comments input box) when constructing comments. All-caps contravenes said policy and subjects comments to moderation.

    Converted all-caps to bold.

    Furthermore, please note that repetitive posting constitutes sloganeering, also a CP violation. FYI.

    Snipped repetitive link.

  14. Okay. Big difference. That means one of those storms every hour, on the hour would add 0.0005 W/m^2 to the 240W/m^2 of incoming solar radiation. I think that is considerably less than the error in the observing system.
  15. A simple equation would be 8,244,910 million New York residents x 1000 days = 8 billion persons power usage. Although not everyone on the globe has electricity or uses electrical heating.
  16. maximo @988, you are claiming that satellite sampling of solar radiation is insufficient to constrain TSI. Your evidence is the power of some solar storms which are not sampled by the instruments used to sample solar irradiance. However, even as corrected, one of those storms an hour every hour over the year would only increase solar irradiance by 0.005 W/m^2, well less than the error margin of the 240 W/m^2 we receive from the Sun. During the course of the storm, the power recieved amounted to less than, 0.000002 W/m^2 or less than one ten millionth of a percent of the 240 W/m^2 irradiance from the Sun. What is more, according to the video on which you rely, 95% of that energy was immediately reradiated to space from the thermosphere, with only 5% entering the lower atmosphere and hence effecting the Eearth's energy balance. I have to thank you for this. I did not previously know the relative power received by the Earth from solar storms. Now I do, and it is inconsequential relative to any other source of energy contributing to warming the Earth's surface. As it turns out, it is less than any other source I had previously considered, and on a par with the 0.000003 W/m^2 the Earth receives from the Cosmic Background Radiation.
  17. It's interesting to note that the thermosphere where the greenhouse gases are located subsequently cooled a short time thereafter. Those gases seem to be good at doing their job of reradiating most of that energy back into space. The storm lasted approximately 72 hours and you are right the other instruments do not measure CME's
    Response: [DB] The thermosphere is not the primary location of most of the greenhouse gases. The tropopause is considered the location of the optical depth emission layer.
  18. Solar radiation is not limited to the thermosphere, about half the solar radiation is absorbed by the Earths surface and warms it.
  19. maximo @993, are you still trying to beat your confusion up into an argument against global warming? Consider first your 992: The thermosphere is not "where the greenhouse gases are located". With some exceptions (Ozone, water vapour), greenhouse gases are distributed approximately equally throughout the atmosphere. That happens to mean there are some greenhouse gases (CO2 and NO2) in the thermosphere where they are too thin to have any appreciable effect on the greenhouse effect. However, because the can radiate in the InfraRed spectrum, they are the primary means of radiating away the heat absorbed in the thermosphere by collisions with solar particles. On to 993: Actually about 70% of solar radiation is absorbed by the Earth, lower atmosphere (troposphere) and stratosphere. Virtually none is absorbed by the thermosphere. However, the energy from the solar storms is largely absorbed by the thermosphere, from which 95% is radiated to space, and only 5% radiated towards the surface according to the NASA video you linked to.
  20. Those observed facts from NASA show the atmosphere cools in a short period of time. What exactly is confusing or goes against what you believe?. Atmospheric gases are found high up into the atmosphere 600km and the greatest concentration of them is at 25km. The average density of gases in the atmosphere is log 10 cm -3. http://science.nasa.gov/media/medialibrary/2010/07/15/thermosphere.jpg
  21. maximo, rather than continuing to be cryptic, please concisely make whatever-it-is point you are trying (and failing) to make. Unless your goal is to waste the time of others.
  22. maximo @995: First, the NASA video indicated that the extra energy in the thermosphere accumulated because of the solar storm dissipated in a few days. To dissipate that energy, the thermosphere had to radiate around 0.000002 W/m^2 (or less) over those few days. This has absolutely no bearing on how long it would take to dissipate the approximately 900 thousand times larger energy imbalance in the lower atmosphere due to anthropogenic effects, particularly as that energy imbalance is not a temporary (three day) storm, but an ongoing flux. Second, the graph you show only shows the density of three atmospheric gases, Molecular Oxygen (O2), Nitrogen (N2) and atomic Oxygen (O), along with the density of electrons. The atomic oxygen and electrons are formed by molecular oxygen being split by UV radiation, thereby absorbing the UV radiation. As can be seen, the relative densities of O2 and N2,ie, d(O2)/d(O2+N2) and likewise for N2, where d(x) is the density of x, are near constant in the mesosphere and below. Above the mesophere, the relative density of O2 + O, ie, d(O2 + 0)/d(O2 + O + N2), is also near constant and approximately equal to d(O2)/d(O2 + N2) in the mesosphere and below. In other words, what the graph shows is only that the relative density of O2 is reduced by the splitting of O2 into two oxygen ions by UV radiation. That has no bearing on the densities of CO2 and NO2 which are typically not split by UV radiation. Finally, I grow tired of having a discussion where I have to deduce your implied point, made with irrelevant data, and largely irrelevant to the topic of discussion. There is a name for posting claims containing no clear argument and serving only to identify that you disagree (or agree) with the OP, or subsequent discussion. It is called sloganeering, and is contrary to forum rules. Unless you begin to clearly state not only what evidence you think you are bringing, but how it relates to the thread topic and ongoing discussion, I suggest your posts simply be deleted as being in violation of the comments policy.
  23. (-Snip-) ... (-Snip-)
    Response:

    [DB] Please note that posting comments here at SkS is a privilege, not a right. This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it. Thanks for your understanding and compliance in this matter.

    Inflammatory snipped.

    Sloganeering snipped.

  24. (snip)
    Response: TC: Sabretruthtiger, your post is a gish gallop of off topic claims and bald assertions, none of it backed by evidence from the peer reviewed literature or other reliable source. As such it constituted sloganeering. It contributes nothing more to the discussion than simply typing "You are all wrong" would have. Sloganeering is forbidden by the comments policy. I recommend you read it, and comply with it in future.
  25. Trying for efficient anti denialists argument. Against any thing about present being like med warm period, or the sun being brighter , why does it not suffice to simply state: 1. If the temperature of the earth were increasing since ~1990 only because of the solar flux increasing for any reason whatsoever, then the temperature of the stratosphere would not have been decreasing during this time frame. 2. The temperature of the stratosphere has been decreasing systematically since 1980. Therefore the increased temperature of the surface is due to increased trapping of outgoing IR from greenhouse gases, and can have nothing to do with increasing solar. QED?

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