Global Cooling

The year 2021 has seen the coldest start to a year that I can remember in the north of England (my memory realistically goes back to the mid-late 1960s). That’s not to say that it has been the coldest start to the year here, since memory is a fickle thing. And of course, weather in one small part of the world does not represent weather globally, nor can a few months of weather be said to be representative of climatic trends.  

That said, is there any significant global cooling going on? I mean, I know it’s cold here – crossing the Pennines the other day, according to my car thermometer, a drop of another 2 or 3C and it could have started snowing. We still have daffodils in full bloom in the second half of May. The trees round here have only really started showing leafage in the last week or so. But that’s here. What’s going on globally?

Fortunately, there is a useful tool at hand for this purpose. The US National Oceanic and Atmospheric Administration (NOAA) devotes a section of its website to “State of the Climate” and provides a monthly global climate report (among many other things). Here is NOAA’s data for the last 12 months, directly compared to its data for the same months one year earlier. And the data tell no lies – yes it has been getting colder globally:

May 2020 -v- May 2019: global land and ocean surface temperature rose by 0.10C.

June 2020 -v- June 2019: global land and ocean surface temperature fell by 0.03C.

July 2020 -v- July 2019: global land and ocean surface temperature fell by 0.03C.

August 2020 -v- August 2019: global land and ocean surface temperature rose by 0.02C.

September 2020 -v- September 2019: global land and ocean surface temperature rose by 0.02C.

October 2020 -v- October 2019: global land and ocean surface temperature fell by 0.13C.

November 2020 -v- November 2019: global land and ocean surface temperature rose by 0.05C.

December 2020 -v- December 2019: global land and ocean surface temperature fell by 0.38C.

January 2021 -v- January 2020: global land and ocean surface temperature fell by 0.34C.

February 2021 -v- February 2020: global land and ocean surface temperature fell by 0.52C.

March 2021 -v- March 2020: global land and ocean surface temperature fell by 0.31C.

April 2021 -v- April 2020: global land and ocean surface temperature fell by 0.27C.

Implications?

Let’s not get excited about this. Data for a two-year period represents nothing of significance in climatic terms. Even if the numbers were significant, they could easily be attributed to La Nina or other factors that bear no relation to anthropogenic global warming. However, there has been a definite cooling trend recently, starting with a plateauing of the rising trend, followed by a decline, which became increasingly marked, and which is perhaps now slowing down.

It is difficult to attribute the cooling trend to the impact of lockdowns responding to the Covid virus, given that although humankind’s greenhouse gas emissions reduced during the pandemic, they still continued, and greenhouse gases in the atmosphere continued to increase. All things being equal, temperatures should be rising, not falling. But all things are not equal. La Nina might explain everything.

Whatever the case, the language adopted by NOAA is interesting. Even as temperatures fell year on year, no reference to this fact is made. Instead, referring to a month which was 0.34C colder than the same month a year earlier, we are regaled with comments like:

The January 2021 global land and ocean surface temperature was 0.80°C (1.44°F) above the 20th century average and ranked as the seventh warmest January in the 142-year global records.

And then, referring to a month which was 0.31C colder than the same month a year earlier, we have this:

“…the eighth highest [temperature departure] for March in the 142-year record

It isn’t a case of cooling, according to these statements. It’s more a case of less warming.

Global Land and Ocean Surface Temperature

By the way, how do you measure global land and ocean surface temperature, and then produce an average of the two?  Not surprisingly it’s complex. But is it meaningful? CarbonBrief has a fascinating section about this on its website. There are four major datasets (of which NOAA’s is one). The four datasets show warming at different rates (so there’s the first query about the accuracy of all this). The explanation for the differences is down to the way the different datasets “deal with having little or no data in remote parts of the world, measurement errors, changes in instrumentation over time and other factors that make capturing global temperature a less-than-straightforward task.” It sounds to me that there’s a lot that can go wrong there. The biggest issue (as CarbonBrief acknowledges) is lack of data in large sections of the world.  

One dataset (HADCRUT) leaves the blanks as blanks, rather than trying to fill them in. The others all use different statistical methodologies to try to fill in the blanks (but the fact remains that they’re still blanks, and however skilled the statistical methods, we can’t know that the blanks have been properly filled in).

Anyway, then they divide the globe into grid boxes (NASA uses different grid boxes to the other three). They also differ in how many land stations they have around the world, and in when their data series commenced. Then they combine the grid boxes to produce average temperatures for the northern and southern hemispheres. That’s a problem in itself, since the northern hemisphere provides more real data. And we haven’t even touched on the Urban Heat Island Effect (UHI), and adjustments made to reflect that.

All of which makes the idea of an average global temperature (on a planet where temperatures can vary on any given day between two extremes by perhaps 100C) pretty meaningless, in my view.   However, (subject to issues such as whether the UHI is being properly adjusted for in an increasingly urbanised world) I do accept that these databases can pick up trends in global temperatures. Which brings me back to the point that NOAA’s database suggests that the world has been cooling for a little while now.

Final Thoughts

Given that the Guardian and the BBC run several climate-related articles a week, it might have been nice if they’d noticed – and mentioned – that it’s been getting colder for a few months now.   But they didn’t (at least not so far as I can see) so I thought I would.

In fact, the mainstream media don’t seem to have picked up on the recent cooling at all (a 0.52C year-on-year fall between February 2020 and February 2021 is apparently not at all newsworthy). Furthermore, in the run-up to COP 26 I don’t expect them to do so. The hysteria will continue, and I will be surprised if any of the media giants will be mentioning falling global temperatures any time soon. I bet they’d have mentioned a year-on-year increase of 0.52C though.

And there’s another thought. There’s lots of talk about the problems associated with global temperatures increasing by 1C, 2C, 3C, or even more, over the course of a century. Who would have thought that temperatures would drop by more than 0.5C in a single year?

And finally: How come the eighth highest temperature departure for March in 142 years felt so ruddy cold?

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May 20, 2021 at 04:12AM

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