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Looking at the Sun

01 Jun 2022 | Backgrounders, Most Watched

Looking at the Sun Transcript

John Robson:

They say you should not look directly at the sun. But when it comes to climate, a lot of people take that advice to ridiculous extremes.


That bright yellow ball in the sky is basically Earth’s only source of energy, though a very small amount radiates from the planet’s hot core. The sun’s output has been measured to a high degree of precision, by satellites in orbit, since the late 1970s and we now know that it varies over time. And since it is our only source of energy, if it gets stronger, it stands to reason that it could warm the climate.

Indeed, there was a time about 20 years ago when many scientists believed that the sun had gotten a bit brighter during the 1980s and 1990s, and they even argued it was enough to explain much of the warming that had taken place. But now, agencies like the UN Intergovernmental Panel on Climate Change, NASA, and others insist the change in solar output never happened, and the warming can only be explained by greenhouse gases. So do not look at the sun.

John Robson:

People, something pretty basic doesn’t add up here. If satellites are measuring the sun’s energy precisely, how could there be disagreement about what it’s been doing?

And the answer, unfortunately, is that there’s a gap in the satellite record, a gap that came about after the 1986 Space Shuttle Challenger disaster. And as happens too much in this field, the gap quickly went from being a scientific problem to a political one. And the way that gap was handled is a story that deserves a little sunlight.

I’m John Robson, and this is a Climate Discussion Nexus backgrounder on the “ACRIM gap” controversy.


The name ACRIM comes from an instrument called the Active Cavity Radiometer Irradiance Monitor that satellites use to measure solar output. And the amount of solar energy that hits the Earth’s atmosphere is called the Total Solar Irradiance or TSI, measured in Watts per square meter. On average the sun provides about one thousand, three hundred and sixty-seven Watts of energy per square meter continuously on the upper atmosphere. For comparison, all the carbon dioxide ever released from using fossil fuels is estimated by the IPCC to have added about 2 Watts per square meter of energy to the atmosphere. And so, given the overwhelming role of solar output in the total, it shouldn’t take much of a change in the sun’s output to have a global influence on the climate.

We also have data on solar output from the pre-satellite era. Astronomers have been keeping track of the number of dark circles or “sunspots” that appears on the surface of the sun for centuries. Galileo even wrote a book about them.

The sunspot count rises and falls on a roughly 11-year cycle, which provides clues to the changing strength of solar energy in the past. Scientists can also use evidence from chemical signatures in the Earth, called cosmogenic isotopes, to reconstruct solar activity. As usual, as you go backward in time on climate, it’s only proxy data and it’s considerably less precise than modern measurements. But by comparing proxies to satellite data since 1979, we get some idea of how to interpret the clues.

In the IPCC’s First Report in 1990, they presented a graph that summarized the prevailing view of the sun’s history over the 19th and 20th centuries. [Source: IPCC FAR p. 62.]

It showed the familiar sunspot cycle, and also suggested average solar output grew stronger in the second half of the century. But they said the changes were not large enough to cause much warming, unless there are positive feedback mechanisms that amplify those changes.

John Robson:

But that qualification is not trivial because, in fact, the notion that carbon dioxide is the driver of warming itself depends on a series of positive feedback mechanisms, because on its own the warming effect of CO2 is quite small. So there have been various proposals for amplifying mechanisms to increase its impact, which we’ll look at in more detail on another day.

When it comes to the sun, basically, the argument is that the sun doesn’t just affect how bright it is outside, it also influences how cloudy it is, and since some kinds of clouds have a major role in reflecting heat back into space, if more solar output not only adds a bit of heat but also suppresses that kind of cloud formation, it can translate into a lot of surface warming.

So, key point here, by the time of the IPCC’s Third Assessment Report in 2001, their views about the sun’s history were getting more uncertain not less uncertain.

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By the time of “AR3” in 2001, instead of just having one reconstruction of solar output, the IPCC now had multiple different ones to choose from. [Source: IPCC TAR p. 382.]

The reconstructions all agreed that solar output followed the sunspot cycle, and they all agreed that solar output had increased over the 20th century. But they disagreed over whether the increase was a lot or a little, and whether it had happened all at once, early in the century, or more gradually over the whole span.

Since these differences arose from statistical estimates using proxy records, it didn’t look as though there would be an easy way to resolve the disagreements.

So attention turned to the modern satellite record. With precise measurements of TSI available since 1978, it should have been possible to compare them with surface temperatures to see if there was any relationship.

Unfortunately, there was the problem we referred to at the outset, a big gap in the data.

The satellites that carried the ACRIM system were first launched in 1978. From time to time, satellites wear out and need to be replaced. A replacement satellite is supposed to be launched early enough so its ACRIM system overlaps with the existing one, allowing the instruments to be calibrated to each other, giving scientists a continuous record. But as you can see, there’s a gap in the ACRIM record from June 1989 to October 1991. [Source: Source: Willson 1997.}

John Robson:

And that gap was a consequence of the Space Shuttle Challenger disaster, in January of 1986, that caused NASA’s satellite launch program to be suspended for several years. By the time a new ACRIM system could be put into orbit, in 1991, the old one had already been offline for two years. And the only data available to fill the gap was from a different monitor called the Earth Radiation Budget System or ERB, which flew on the Nimbus 7 satellite launched in 1978 as part of a separate series, and that satellite didn’t have an ACRIM.


Unfortunately, the ERB system was not meant to monitor solar output with much precision. Its sensors were pointed towards the Earth, so it could monitor the climate system, and it only had a view of the sun during brief intervals of its orbit. Also, it generated two data series, called ERB and ERBS in the diagram, and they disagreed with each other regarding what the sun did during the ACRIM gap.

Still, it was something to work with. In 1997, the lead scientist working on the ACRIM system, Richard Willson of Columbia University, used the satellite data and all available information on the behavior of the onboard sensors in the various satellites to construct a composite ACRIM record.

A comparison of the minimum points in the solar cycle suggested an increase in TSI from the early 1980s through to the end of the 1990s, after which solar output flattened out. Since this broadly matched the progress of temperatures after 1980, it opened the door to the possibility that the sun might be responsible for some, or all, of recent climate changes.

John Robson:

The alarmists didn’t like that result at all. In fact, they reacted like that Far Side cartoon where the astronauts going “Blast. The controls are jammed. We’re headed right [straight] for Mr. Sun.”

So a few years later a different team, led by Claus Frölich and Judith Lean, published a new reconstruction of the same data that showed, voila, no upward step, just the standard solar cycle and a steady downward trend after 1980. Called the PMOD reconstruction, after the name of Frölich’s institute, the Physical Meteorological Observatory in, ahem, Davos, it had the convenient effect of ruling out the sun as a factor in climate change.

And when I say “convenient”, I do mean in the political sense. The authors made no secret of their motivation. In a recent article reviewing the whole episode, scientist Ronan Connolly, of the Center for Environmental Research and Earth Science in Massachusetts, found some telling quotes from the authors and others working in the field.


In a 2003 interview discussing the motivation for their research, author Judith Lean stated “The fact that some people could use Willson’s results as an excuse to do nothing about greenhouse gas emissions is one reason we felt we needed to look at the data ourselves.”

And in a later review published in 2014, Pia Zacharias of the International Space Science Institute in Switzerland conceded that the data adjustments are “still a matter of active debate and have prevented the TSI community from coming up with a conclusive TSI composite so far.”

But, she went on to observe, “A conclusive TSI time series is not only desirable from the perspective of the scientific community, but also when considering the rising interest of the public in questions related to climate change issues, thus preventing climate skeptics from taking advantage of these discrepancies within the TSI community by, for example, putting forth a presumed solar effect as an excuse for inaction on anthropogenic warming.”

We spoke with scientist Ronan Connolly recently to discuss the ACRIM gap and how the IPCC handled the controversy.

Ronan Connolly:

So the PMOD rival group, they took the ACRIM data and they’ve applied a series of adjustments, which kind of got rid of that rise in solar activity in the ’80s and ’90s and replaced it with a decline, that’s a net effect, it shows a declining, it shows effectively that according to the PMOD, solar activity has been generally decreasing since at least in the 1970s.

If the ACRIM composite is correct, then that would be consistent with a solar contribution because the warming, some of the warming in the ’80s and ’90s could be due to the solar activity, and then the reduction in warming, the pause, or even a slight decline depending on the metric, that could be due to a reduction in solar activity. But if PMOD is correct, then solar activity is… it can’t really explain any of the global temperature trends since the… during the satellite era.

John Robson:

Which gives us two things to think about. One is that, if the sun’s output did get stronger over the 1980s and 1990s, that means it bears some of the blame, or gets some of the credit, for warming the planet over that interval. Which is a valid argument for not blaming everything on greenhouse gases, especially since the sun subsequently quieting down coincides with two long pauses in any warming detected by satellites. But the other thing is that we have scientists talking as if their motivation is not just finding the truth, it’s preventing so-called inaction on climate change, and feeling no need to hide such a motive. On the contrary, they seem to be broadcasting it.

And if you’re going to come right out and tell us that your goal is to push a policy agenda whether it’s scientifically justified or not, don’t act surprised when we tell you we’re skeptical about your results.

For our part, we’re not acting surprised that one group that wasn’t skeptical was the IPCC. In their “Fourth Assessment Report” or “AR4” in 2007, they showed both the Willson series, here in violet and the PMOD series which is green. [Source: AR4 Ch 2 Fig 2.16 p. 189.]

But in their next Report in 2013, while they still mentioned the Willson series, they dropped it from their calculations, and said from now on they would only use the PMOD series that told them what they wanted to hear, namely that with no increase in solar output there’s no way to blame the sun for global warming, so it must be all your fault. Which is one way to do science. But what kind of way?

Ronan Connolly:

My own experience, yes, that there’s a lot of scientists that feel a lot of pressure to conform to… their work to the IPCC. The IPCC has become a very dominant political body within the scientific community.


How did the PMOD team come up with a different answer than Willson’s group? By arguing that one of the sensors on the ERB system was defective and experienced an increase in its sensitivity during its time in orbit, adding an artificial upward trend to its readings. The PMOD team corrected this supposed defect by pushing the later part of the data downward, thus erasing the increase and getting the result they were looking for. But did the ERB system actually suffer this malfunction?

John Robson:

In 2008, Richard Willson and another of his coauthors, physicist Nicola Scaffeta of the University of Naples, tracked down Dr. Douglas Hoyt, the scientist who had been in charge of the ERB satellite mission at the time but had since retired, and they asked him. And Hoyt emailed them back the following:


Dear Dr. Scafetta:

Concerning the supposed increase in Nimbus7 sensitivity at the end of September 1989 and other matters as proposed by Frohlich’s PMOD TSI composite:

  1. There is no known physical change in the electrically calibrated Nimbus7 radiometer or its electronics that could have caused it to become more sensitive. At least neither Lee Kyle nor I could never imagine how such a thing could happen and no one else has ever come up with a physical theory for the instrument that could cause it to become more sensitive.
  1. The Nimbus7 radiometer was calibrated electrically every 12 days. The calibrations before and after the September shutdown gave no indication of any change in the sensitivity of the radiometer. Thus, when Bob Lee of the ERBS team originally claimed there was a change in Nimbus7 sensitivity, we examined the issue and concluded there was no internal evidence in the Nimbus7 records to warrant the correction that he was proposing. Since the result was a null one, no publication was thought necessary.
  1. Thus, Frohlich’s PMOD TSI composite is not consistent with the internal data or physics of the Nimbus7 cavity radiometer.
  1. The correction of the Nimbus7 TSI values for 1979-1980 proposed by Frohlich is also puzzling. The raw data was run through the same algorithm for these early years and the subsequent years and there is no justification for Frohlich’s adjustment in my opinion.


Douglas Hoyt

John Robson:

Yeah, “puzzling”. Though we can think of other words, like “suspicious”. So, let’s look again at the various reconstructions of solar output. In the 2007 IPCC Report, here’s the range they admitted was possible from the 1600s to the turn of the century and, typically, the uncertainty increases as you go backwards. [Source: IPCC AR4 p. 190.]

But there are ways to try to decrease it. In that review article I mentioned, by Ronan Connolly and 22 coauthors, when they surveyed the various ways experts have used the satellite and proxy records, they found 16 possible reconstructions of solar activity since 1600, eight yielding fairly low variability and eight fairly high variability.


To illuminate solar influence on temperature, these authors also took a close look at the other side of the equation, surface temperature data, and constructed a new climate record for the Northern Hemisphere, using only rural weather stations and data collected over the sea surface to avoid contamination from urban heat islands. Then they coupled this with tree ring proxy data to assemble a temperature estimate covering the same interval as the solar series.

Putting the solar and temperature data together, depending on which solar reconstruction you pick, the sun turns out to explain either none of the observed warming, or all of it, or somewhere in between.

Ronan Connolly:

So we can get like a result from, we can explain anything from nothing to almost all of the temperature changes since the 19th century in terms of solar activity depending on whether ACRIM is correct or PMOD is correct.

John Robson:

Now that result doesn’t mean we at CDN get to cherry-pick the result we like and say, “Aha! We’ve proven that the sun causes all climate change.” But neither can the alarmists go “Aha! We’ve proven that the sun causes none of it.” And the trouble is, they do. When they put out reports confidently declaring that warming is all due to greenhouse gases, what they don’t tell you is that their calculation is based on using one specific solar reconstruction, and a lot of temperature data from cities that have grown bigger and hotter since the start of the 21st century.

Now, I’m going to leave you here with one more quote from another scientist working in the solar measurement field. In a 2012 review paper, physicist Michael Lockwood discussed all the difficulties in trying to reconstruct solar output, and measure its current effects, and lamented:


“The academic reputation of the field of Sun-climate relations is poor because many studies do not address all, or even some of, the limitations listed above. It is also a field that in recent years has been corrupted by unwelcome political and financial influence as climate change sceptics have seized upon putative solar effects as an excuse for inaction on anthropogenic warming.”

John Robson:

It’s strange when scientists insist that there’s political and financial corruption in their field, but it only ever goes in one direction, and it’s not the direction the funders want, because don’t forget climate research is funded overwhelmingly by governments who believe in a man-made global warming crisis. And it’s also weird when they say that people drawing logical conclusions about the policy implications of the sun having a significant impact on climate are just “making excuses”. I don’t expect these scientists want any advice from me, but I’m going to give it to them anyway.

When you keep telling us that your motivation is to promote a costly policy agenda, whether it’s scientifically justified or not, and you keep getting caught trying to conceal the fact that you’re not nearly as certain about your conclusions as the IPCC keeps claiming, and you keep getting caught fiddling data series, and when challenged you substitute abuse for argument, it makes the general public more skeptical, and not less.

So please look up, because for the Climate Discussion Nexus, I’m John Robson, and I am looking at the sun.

8 comments on “Looking at the Sun”

  1. Using the Precomputed tables - Finding the sun's true bearing published by The Civil Aviation Branch, Department of Transport in Ottawa in 1965. It showed the sunrise and sunset times for Ottawa may 20 as 0320 and 2032. The weatheroffice showed the sunrise and sunset times for Ottawa may 20.2022 as 0527 and 2032, that suggests to me that there is a very significant wobble on earth as the sun is now rising 2 hours later but setting at the same time making up the 2 hour time difference. I live in Ottawa and it seems to be a lot more windy since I moved here 50 years ago. The planet is still spinning at 1670 kilometres an hour and zooming around the sun at 107000 kilometres an hour all this having an effect on the weather.

  2. Svensmark links sun spot rarity periods to enhanced cosmic ray atmospheric penetration and increased cloud cover due to ionization and temperature decline via albedo effect on an 11 year sun spot cycle .
    2020 to 2053 great maunder minimum according to noaa linked to sunspot nosedive and negative irradiance effect of newly discovered double dynamo in solar interior . Plant growth in peril no time to curtail traditional energy.

  3. It goes back to Svensmark's predecessors at the Danish Space Center who published a paper in Science magazine in 1991. Friis-Christensen and Lassen (1991) showed a 95% correlation between solar cycle peak frequency (not the sunspot number) and warming and cooling of the northern hemisphere over 130 years - there are significant deviations from the carbon dioxide trend. It did not take long for ad hominem from alarmists and the trend ended with the eruption of Pinatubo to disrupt the correlation. Since then, Henrik Svensmark has conducted a number of experiments to support the hypothesis. Their work at the Hadron collider in Switzerland was so successful that the Director of Hadron denied permission to publish the conclusions. There are several YouTube presentations by Svensmark that document their experimental follow-up to the Friis-Christensen and Lassen hypothesis. It is now elevated to a theory by experiments.

  4. It is reported that the world uses 100 million barrels of oil per day which flows up from underground.
    50% or so of that is used for fuels and is burnt in engines.
    I wonder what happens to the other 50% which is exhausted as heat, CO2 and H2O.
    Fires and Floods could be a result. And, yes, I am sure varying heat output from the sun is a contributor as well.

  5. Thank you very much for producing these informative videos. This one on the effects of solar activity on the climate is particularly important in understanding that AGW is a political, and in some cases, entirely fraudulent movement.

    Keep up the excellent work. I continue to be a proud monthly sponsor of CDN.

  6. John,
    John, you might want to reference this article: (https://www.msn.com/en-us/news/technology/the-daring-lightsail-2-spacecraft-is-being-sucked-into-fiery-doom/ar-AAZ2LTT?cvid=5e74c34c863d4f3ca9920de95535940d&ocid=winp2sv1plus) in a future Wednesday update.
    "Ironically, the Sun also worked against LightSail 2. When the Sun is more active, it heats Earth’s upper atmosphere, causing it to expand into higher altitudes. At the start of the mission, the Sun was going through some downtime as part of its 11-year cycle, but our host star recently revved up its activity for its solar maximum period. This has caused the atmosphere to be denser at higher altitudes, even reaching the spacecraft, causing LightSail 2 to drag downwards."
    Who knew the solar constant wasn't? I noticed the link is being distorted because of the question mark but I am sure you can search it from the title.

  7. John, you might want to reference this article: (https://www.msn.com/en-us/news/technology/the-daring-lightsail-2-spacecraft-is-being-sucked-into-fiery-doom/ar-AAZ2LTT?cvid=5e74c34c863d4f3ca9920de95535940d&ocid=winp2sv1plus) in a future Wednesday update.
    "Ironically, the Sun also worked against LightSail 2. When the Sun is more active, it heats Earth’s upper atmosphere, causing it to expand into higher altitudes. At the start of the mission, the Sun was going through some downtime as part of its 11-year cycle, but our host star recently revved up its activity for its solar maximum period. This has caused the atmosphere to be denser at higher altitudes, even reaching the spacecraft, causing LightSail 2 to drag downwards."
    Who knew the solar constant wasn't? I noticed the link is being distorted because of the question mark but I am sure you can search it from the title.

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