The Sun and Global Warming

So this morning, I checked out the July satellite temperature record and made a short post about it. I then hopped into my boat (a carefully crafted replica of Lookfar) and quickly circumnavigated the Puppy seas checking on various blogs to see what was what. Coincidentally, Accordingtohoyt had a guest post on climate! Stephanie Osborn is an astronomer who write occasional science essays for Sarah Hoyt and this one was an update on solar activity entitled ‘A Solar Activity Update’ (https://accordingtohoyt.com/2018/08/01/a-solar-activity-update-by-stephanie-osborn/ ) that seems sensible enough.

The premise of the post was two fold:

• Current solar activity seems to be winding down towards some sort of minimum.
• Past solar activity has been related to cooler periods.

Sensible enough. It ends on a rhetorical question:

“But how many correlations does it take before we need to sit up and take notice? Before we seriously start to wonder what is really going on?”

So let’s pick up where that essay leaves off. The sun and solar activity are certainly interesting as far as global warming go and certainly on longer timescales it’s an obvious factor. The Earth is warmed primarily by the Sun, so variations in the Sun should connect with variations in surface temperatures – all else being equal.

All else is not currently equal.

Those who would rather not believe that put a lot of hope in the Sun. Maybe, as the essay partly implies, recent changes in climate are not due to human activity but due to solar activity. Neat question…but also one that climatologists have been thinking about for decades. I’m not a climatologist but it isn’t hard to have a look see at some data to at least get a sense of whether more experienced scientists have somehow missed this connection.

I’m going to make use of the graphic and data set tools at the marvellous Wood For Trees website (http://www.woodfortrees.org/ ) The site is clear about its sources and if readers want to do things the hard way and check original data then you can.

I’ll start with sunspot activity. This is one of the indicators the author of the essay pointed at. People have been tracking sunspot activity for hundreds of years, so there is heaps of data and the site has data back to 1750ish. Unfortunately, there’s not a good instrumental record for temperature for that long but HADCRUT4 does go back to 1850. Here’s a graph of sunspots and temperature anomaly for a hundred years 1850 to 1950. The data has been normalised for both sets so that they can be seen together on the same axes.

http://www.woodfortrees.org/plot/sidc-ssn/normalise/from:1850/to:1950/plot/hadcrut4gl/normalise/from:1850/to:1950

Interesting enough I guess. Not a slamdunk relationship just using eyeballs to judge but you wouldn’t dismiss it.

Now keep going.

http://www.woodfortrees.org/plot/sidc-ssn/normalise/from:1850/plot/hadcrut4gl/normalise/from:1850

Wham.

The essayist is quite right about that sunspot decline but note what has been happening with temperatures? That’s not because she is wrong about solar activity being related to global temperatures but rather that the current global warming is NOT due to solar activity and worse, it is still going DESPITE reduced solar activity.

It’s not that solar activity is irrelevant to global temperatures — there is a solar signal in that data — it’s just that it can’t explain current global warming. Now I don’t know enough to know whether a sufficiently low solar minimum would put a break on the effects of anthropogenic global warming but even if it did and we used that as an excuse to do nothing about greenhouse gas emissions, the problem would still be waiting for us when the solar cycle ticked up again.

It is literally wishing on a star to think that solar activity will make global warming go away. In the meantime, I have to worry that the dry winter means my water tanks are low for the coming bushfire season which may be a month earlier this year in New South Wales were farmers are already suffering from the impact of a sustained drought.