Posted on 11 April 2023 by John Mason, BaerbelW

On February 14, 2023 we announced our Rebuttal Update Project. This included an ask for feedback about the added "At a glance" section in the updated basic rebuttal versions. This weekly blog post series highlights this new section of one of the updated basic rebuttal versions and serves as a "bump" for our ask. This week features "Sun & climate: moving in opposite directions". More will follow in the upcoming weeks. Please follow the Further Reading link at the bottom to read the full rebuttal and to join the discussion in the comment thread there.

At a glance

Thankfully, our Sun is a very average kind of star, meaning that it behaves stably on a multi-million year timescale, steadily consuming its hydrogen fuel in the nuclear reaction that produces sunshine. That stability, in conjunction with the Greenhouse Effect provided by Earth’s atmosphere, gives Earth a habitable range of surface temperatures. In contrast, the radiant energy output of less stable stars often varies too much to enable life - as we know it - to evolve on any planets that orbit them.

That the Sun is a stable type of star is clearly demonstrated by the value for 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, fluctuating by about a watt either way depending on where we are in the approximately 11-year long sunspot cycle. That's a variation of no more than 0.15%.

From the early 1970s until recently, the Solar radiation reaching the top of Earth's atmosphere has in fact shown a very slight overall decline as the Sun’s 11-year activity cycle decreased in amplitude. Through that same multi-decadal period, however, global temperatures continued to increase. The two datasets, incoming Solar energy and global temperature, have diverged – they have gone in opposite directions. That incoming Solar energy has decreased while the Earth continues to warm up shows that the Sun cannot possibly be the control-knob of that warming.

Conversely, attempts to blame the sun for the rise in global temperatures have had to involve the dubious practice of taking the data and 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. This particular fact-twisting sin is known as “cherry-picking”. 

Please use this form to provide feedback about this new "at a glance" section. Read a more technical version via the link below!

Click for Further details

In case you'd like to explore more of our recently updated rebuttals, here are the links to all of them: