Information about solar irradiance measurements sought


Planetary science at The Shard: How soon is the sun’s radiation going to be destructive? (apart from the effect on the CCD chip)

This blog post is based on a thread in the Azimuth forum.

The current theories about the sun’s life-time indicate that the sun will turn in about 5 billion years into a red giant. How and when this process is going to be destructive to earth is still debated. Apparently according to more or less current theories there has been a quasi linear raise in luminosity, quoting from p. 3 “Distant future of the Sun and Earth revisited” by K.-P. Schröder and Robert Connon Smith, 2008:

The present Sun is increasing its average luminosity at a rate
of 1% in every 110 million years, or 10% over the next billion years.

Unfortunately I feel a bit doubtful about this, in particular after I looked at some irradiation measurements.
But let’s recap a bit.



In the Azimuth forum I asked for information about solar irradiance measurements. Why I was originally interested in how bright the sun is shining is a longer story, which includes discussions about the global warming potential of methane. For this post I prefer to omit this lengthy historical survey about my original motivations (may be I come back to this later) – meanwhile (see above) there is an also a newer reason why I am interested in solar irradiance measurements, which I want to talk about here.

Strictly speaking I was not only interested in knowing more about how bright the sun is shining, but how bright each of it’s “components” is shining, i.e. I liked to see spectrally resolved solar irradiance measurements and in particular measurements from a range between roughly the frequencies* 650nm and 950nm.

So I had found the Sorce mission, which is a NASA sponsored satellite mission, whose website is located at the University of Colorado. The website provides very nicely an interactive part with a fairly clear and intuitive LISIRD interactive app with which the spectral measurements of the sun can be studied.

As a side remark I should mention that this NASA mission belongs to the NASA Earth Science mission, which is currently threatened to be scrapped.

By using this app I found in the 650nm and 950nm range a very strange rise in radiation between 2003 and 2016 which happened mainly in the last 2-3 years. Here you can see this rise:


spectral line 774.5nm from day 132 to 5073, day 132 starting Jan 24 in 2003, day 5073 is end of 2016

Now, fluctuations within certain spectral ranges within the sun spectrum are no news, however here it rather looked as if a rather stable range suddenly started to change rather “dramatically”.

I put the word “dramatically” in quotes for a couple of reasons.

Spectral measurements are complicated and prone to measurement errors. Alone the subtle issue of dirty lenses etc. suggests that this is no easy feat and that so this strange rise might easily be due to a measurement failure. Moreover as said it looked as this was a fairly stable range over the course of ten years, but maybe this new rise in irradiation is part of the 11 years sun cycle, i.e. a common phenomenom. In addition, although the rise looks big it may overall still be rather subtle.

But so – how subtle or non-subtle is it then?

In order to assess that question I made a quick estimation (see forum discussion) and found that if all the additional radiation would arrive on soil (which of course it doesn’t due to absorption) than on 1000 sqm you could easily power a lawn mower with that subtle change! I.e. my estimation was 1200 W for that lawn patch. WOA!

That was disconcerting enough to download the data and linearly interpolate it and calculate the power of that change. I programmed a calculation program in javascript for that. The computer calculations revealed 1000 W, i.e. my estimation was fairly close. WOA again!

How does this translate to overall changes in solar irradiance? Some increase had already been noticed. NASA wrote 2003 on it’s webpage:

Although the inferred increase of solar irradiance in 24 years, about 0.1 percent, is not enough to cause notable climate change, the trend would be important if maintained for a century or more.

That was 13 ys. ago.

I now used my program to calculate the irradiance for one day in 2016 between the frequencies 180.5nm and 1797.62nm, i.e. about a quite big part of the solar spectrum and got the value \(627 W/m^2\) and computed the difference to one day in 2003 and got \(0.61 W/m^2\), which is 0.1% in 13 years, rather then 24 years. But of course this is no average and fluctuations play a big role in some parts of the spectrum, but well – this may indicate that the overall rate (!) of rise in solar radiation may have doubled. And concerning the question of the sun’s luminosity: for assessing luminosity one would need to take the concrete satellite-earth orbit at the day of measurement into account, as the distance to the sun varies or at least average – but still, on a first glance this appears disconcerting.

Moreover for this specific range I mentioned above I calculated the value \(192 W/m^2\) for day in 2016 (day 5073), so this would mean for this frequency range the increase in 13 ys was about 0.5% and most of it in the last 2-3 years.

Given that this spectral range has e.g. an overlap with the absorption of water (clouds!) this should at least be discussed.

And indeed one can even see the rise in this range within the solar spectrum without zooming in. See how the spectrum splits into a purple and dark red line in the lower circle?


Difference in spectrum between day 132 and 5073

The upper circle display another rise, which is discussed in the forum.

So concluding all this looks as if this needs to be monitored a bit more closely. Finally the theories about the lifetime of the sun are only theories.
In particular it would be important to see wether these rises in irradiance are also displayed in other measurements, so I asked in the Azimuth Forum, but sofar got no answer.

The russian wikipedia site about solar irradiance contains unfortunately no links to russian satellite missions (if I haven’t overseen something) and there exists no chinese or indian wikipedia webpage about solar irradiance. I also couldn’t find publicly accessible spectral irradiance measurements on the ESA website (although they have some satellites out there) and wrote in December an email to the head of the section solar radiometry of the World Radiation Center (WRC) Wolfgang Finsterle with no answer yet.

In short if you know about publicly available solar spectral irradiance measurements other than the LISIRD ones then please let me know.

update Jan 15, 2017: This post appeared also as a guest post on John Baez blog Azimuth with minor modifications, in particular the english was polished by John.

correction Feb, 3, 2017: * frequencies should read inverse spatial frequencies or simply wavelength

9 Responses to “Information about solar irradiance measurements sought”

  1. Dr. Penn Says:

    Why I was originally interested in how bright the sun is shining is a longer story, which includes discussions about the global warming potential of methane.

    I have heard that you were about to publish a blog post about the role of methane in global warming with new scientific findings, which indicate that the earth climate situation is way worse than assumed.

    This would imply that the Paris climate summit agreement is rather a minimal consensus than a sufficient measure to avert catastrophical consequences for mankind. As you may know US President Trump may announce today that he may not even support this minimal Paris consensus. Don’t you think its time to publish your findings immediately? Eventually some people could fastly initiate a Twitter campaign that may raise awaremenss for that pressing issue.

  2. nad Says:

    I don’t know how you acquired this information, but yes I was preparing a blogpost which concerns in some way the gobal warming potential of methane which offers rather gloomy interpretations. I hesitate to publish it, as the scientific finding -if it holds valid under scrutiny- is clearly a political minefield.

    At this point the finding is rather a half-bred theory with very,very large error bars, that is even if the argumentation would be right then the given finding is still vague enough to allow for not so bad or worser projections and I fear too emotional reactions might arrise from this interpretational freedom.
    Moreover as a fact and by all what I know the finding seems to differ from the current scientific paradigms, because -as I think- a major component had been forgotten in those. But maybe I am wrong – I am not involved in the corresponding scientific circles and the probability that I don’t know about certain scientific developments is of course rather big.

    But yes if the finding would be more investigated and then indeed point towards the worser projections then it seems that the Paris agreement would definitely be not enough as a regulatory measure for curbing greenhouse gas emission. In fact the Paris agreement would look like a “minor regulation” in the wake of what kind of regulatory framework one would need to establish for fully adressing the problems. I just say: rice fields.

    In mid march I had sent a copy of the blog post to John Baez and to Gunnar Myhre who is the coordinating Lead Author of the chapter on Anthropogenic and Natural
    Radiative Forcing.
    They are both very busy men. John had also problems with the 3D Javascript graphics, which I had included as an illustration and I haven’t heard of Gunnar Myhre since then. I hope that they realized what this post is about but then the blog post is not so easy readable with all those HTML commands interspersed.

    So in short: I fear to put this blogpost up. Not because I might be wrong but because of all that commotion that might arise from it. The blog post is written in a very technical manner so hopefully it will reach only an audience which is capable to sort in accordingly -but who knows. I currently don’t have enough means and support to deepen and defend the findings and engage in larger discussions. I would like to point out that I did this scientific work as a more or less voluntary “hobby.” And as one knows especially internet discussions can easily get very ugly. I am in my daily life already under too much other pressures that I might cope with a shit storm.

    So thanks for your interest. I would though be interested to hear from you from whom you had acquired the information, because I had expected that since I haven’t heard of John Baez or Gunnar Myhre that the blog post is just among the 3 of us. I hope that in this comment I made now clear that I think that a broader dissemination of the research in the global warming potential of methane is very problematic and has to be done very carefully if at all. I might also change the text. So if you should hold copies of the blog post I kindly ask you to keep these confidentally.

  3. nad Says:

    As you may know US President Trump may announce today that he may not even support this minimal Paris consensus…Eventually some people could fastly initiate a Twitter campaign that may raise awaremenss for that pressing issue.

    By the way I don’t think that any argumentation would have changed that current US attitude. The US decision to withdraw from the Paris agreement makes things even more difficult and hopeless, but I fear one can’t do much about it.

  4. Dr. Penn Says:

    The US decision to withdraw from the Paris agreement makes things even more difficult and hopeless, but I fear one can’t do much about it.

    I think if you would have had published your post than eventually this would have made a difference, finally as far as I can tell the consequences would mean that CO2 emission from cars and planes would be less a driver of climate change than CH4 emissions, so maybe you would have got even support from the oil industry! They might like your findings!

    Anyways maybe things are not so bleak:
    Luke Kemp on WEForum argues:

    “…a US withdrawal would minimise risks and maximise opportunities for the climate community. “

    Nonetheless I think that you should publish your post, if your finding is right then the world certainly needs to know about it and experts have to take care of it.

    I am in my daily life already under too much other pressures that I might cope with a shit storm.

    Come on! Do you know the amount of hatespeech comments that are loaded on people like Kim Kardashian? And real threats! Why should there be a special safe space for you? And then finally aren’t you living about 10kms away from Merkels office? I could imagine there is an immense amount of executive forces in this area.

  5. nad Says:

    Why should there be a special safe space for you?

    I am irreligious, but if I would be religious than I could interprete an event yesterday as a sign from god(s) that I should better keep away from that ugly internet and that some godly creature tries to keep me safe. That is yesterday there was here not even a thunderstorm but suddenly a giant superloud lightning stroke down on our living place or at least our vicinity. It was just this one unique lightening. No other lightenings, no thunderstorm -just rain. And nothing happened apart from the fact that the rooter was destroyed and that we were cut off from the internet.

  6. Dr. Penn Says:

    I had written:

    if your finding is right then the world certainly needs to know about it and experts have to take care of it.

    It seems I have to insist on reminding you that you can’t just withheld that information. If you don’t change your mind then accept – you are a LIAR, that is – read the Stanford Encyclopedia 1.5.1:

    Lying to others may be defined as “any form of behavior the function of which is to provide others with false information or to deprive them of true information” (Smith 2004, 14)

    And your motivation for lying is well-known according to the American Psychological Association:

    Martin found that of the 37 percent who reported lying, most did so “to protect themselves in some way-mostly to avoid shame or embarrassment, to avoid painful emotions and to avoid being judged or rejected by the therapist,” she says.

    and I think you should be aware of the risks of lying:

    In cases of nondisclosure, we suggest that people infer withholders to be untrustworthy. Because trustworthiness is a desirable trait, we predict that those who divulge information—even extremely unsavory information—will be liked more than those who conceal.

  7. nad Says:

    I think it is not helpful to water down the definition of lying that is “handing out wrong information while knowing better” is very different from simply “not handing out information” and why put both under the umbrella of the term “lying” ? Especially since most people reserve the term for the former. Withhelding information can be necessary. Like I was more or less withhelding information or rather obscuring what I thought in the days after the Fukushima disaster. That is despite the fact that the reasoning was based on very incomplete information, I got rather fast the impression that -even if some will say otherwise- the Fukushima nuclear accident clearly endangered the living space of over 30 million people but -apart from the problem of my incomplete information (which makes stating opinions always problematic)- even if I would have had more information: it would have made no sense to invoke a mass panic, by telling people about the potential dangers, while there was still hope to avoid such a disaster.

    In the case of the CH4 blog post: the information which I have is so incomplete that I haven’t even myself formed an opinion about whats really going on.

  8. cough prevention Says:

    I agree with Dr. Penn that you should disseminate your findings. Finally don’t you think that it is important to make the failures of climate science (in particular if they are as big as the discussion above suggests) public and thus initiate an important public discussion ?

  9. Ni-Sue E. Taarovet Says:

    it would have made no sense to invoke a mass panic, by telling people about the potential dangers, while there was still hope to avoid such a disaster.

    Your arrogance is unbelievable and unbearable. People have a right to be properly informed about the potential dangers they are going to face. The information policy during the Fukushima accident was completely inappropriate, patromizing and undemocratic. How could you and also those self-acclaimed “people in the know” get at all the idea that their reasoning and their decisions are “right”? These are peoples lives! People have to be informed! I hope you are at least aware that this is one of the worst rightwing views in a while.

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