2020, climate statistics and all that
There has been no significant warming trend for 5 years.
Every year in the middle of January various organisations, The UK Met Office, NASA, NOAA, etc. release their estimates of the annual average global temperature of our planet.
This year the conclusion is that 2020 is statistically identical to 2016. Some have placed it the second whereas the Japanese Meteorological Agency has it as the third warmest of the modern era. The overall conclusion to be drawn however is the misunderstanding of statistics used to support a predetermined opinion.
To illustrate the point let’s just look at NOAA’s data. This has a temperature anomaly for 2020 of 0.98 +/- 0.15 °C compared to 1.00 +/- 0.15 °C for 2016 (which was the year with the strongest recorded El Nino). The difference is trivial, especially since the precision of the mean is reported to thousandths of a degree. Looking at NOAA’s data for previous years you can see that every year since 2015 falls within one standard deviation of the mean.
Such a simple and unbiased view of the data leads to a much more justifiable headline for the data: There has been no significant warming trend for 5 years, as NOAA has confirmed.
NOAA’s conclusion is also confirmed by the Met Office’s own data set.
Looking at the global heat map based on HadCRUT5 data from the UK Met Office published by the BBC it is quite apparent that the warming that was recorded in 2020 was not global but regional, primarily in parts of the Arctic around Siberia.
This way of looking at the observational data provides a broader context for a few of the comments have been made.
“The exceptional heat of 2020 is despite a La Niña event, which has a temporary cooling effect,” said WMO Secretary-General, Prof Petteri Taalas.
“It is remarkable that temperatures in 2020 were virtually on a par with 2016, when we saw one of the strongest El Niño warming events on record. This is a clear indication that the global signal from human-induced climate change is now as powerful as the force of nature.”
Actually, it is the opposite, as I pointed out in a previous post. A number of months in early 2020 were affected by El Niño conditions, very different from what the WMO Secretary-General has claimed.
It is true that 2016 would have been cooler but for the El Nino and 2020 warmer but for the La Nina. However, as I pointed out in my previous post, the El Nino effect can be seen over several years making estimates for greenhouse gas forcing problematic.
That can been seen in a claim by Gavin Schmidt, director of the Nasa Goddard Institute for Space Studies, who told BBC News, “We’re still putting our foot on the accelerator of climate change.”
How does his acceleration claim square with the fact that the increase in atmospheric CO2 between 2015-2019 made no difference to global temperatures and neither has the 7% fall in global CO2 emissions observed in 2020?
The global annual average temperature dataset is a fascinating one. It can be interpreted in many ways, looking at short- and long-term trends to a better understanding of what seems to be a ever changing El Nino and La Nina phenomena.