Year 2020 is now the warmest year on record, tying with 2016, the World Meteorological Organization (WMO) has said. And, it was only at the end of the year that a La Niña effect — a naturally occurring cooling climate phenomenon — put a brake on the heat.
The WMO compiles data from five climate monitoring centers — NASA, NOAA, the UK Met Office Hadley Centre and the University of East Anglia’s Climatic Research Unit (HadCRUT), European Centre for Medium Range Weather Forecasts (ECMWF) and its Copernicus Climate Change Service, and the Japan Meteorological Agency (JMA) to create a central annual global mean temperature estimate.
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According to WMO, the warmest six years have all been since 2015, with 2016, 2019 and 2020 in the top three, with very small differences in average global temperatures among the three — the average global temperature in 2020 was about 14.9 degree Celsius, which is roughly 1.2 degree Celsius above the pre-industrial (1850-1900) level.
Why it is all the more alarming
The news is all the more alarming because 2020 also saw significantly lower human-induced activities due to the ongoing pandemic — first, the complete lockdowns and even afterwards, a lower industrial activity. Further, the exceptional heat of 2020 is also despite a La Niña event that had a temporary cooling down effect. In contrast 2016 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,” WMO Secretary-General Prof. Petteri Taalas, said in a statement.
“The temperature ranking of individual years represent only a snapshot of a much longer-term trend. Since the 1980s each decade has been warmer than the previous one. Heat-trapping gases in the atmosphere remain at record levels and the long lifetime of carbon dioxide, the most important gas, commits the planet to future warming,” he added.
The finer details
NASA and Copernicus Climate Change Service estimate that 2020 was jointly the warmest year on record together with 2016. NASA analysis in fact stated 2020 just exceeded the record set in 2016 by less than a tenth of a degrees. NOAA and the UK’s HadCRUT dataset, on the other hand, ranked 2020 as the second warmest behind 2016, while Japanese Meteorological Agency (JMA) Reanalysis ranking 2020 as the third warmest. The small differences among these datasets are all within the margin of error for calculating the average global temperature according to WMO.
NASA incorporates surface temperature measurements from over 26,000 weather stations and thousands of ship- and buoy-based observations of sea surface temperatures for its analysis. It then uses an algorithm to analyze these raw measurements that considers the varied spacing of temperature stations around the globe and urban heating effects that could skew the conclusions if not taken into account. The result of these calculations is an estimate of the global average temperature difference from a baseline period of 1951 to 1980.
The satellite surface temperature record from the Atmospheric Infrared Sounder (AIRS) instrument aboard NASA’s Aura satellite confirms the GISTEMP results of the past seven years being the warmest on record. Measurements from satellites of air, sea surface and sea level temperatures, and other space-based observations also reveal how extreme climate events shaped 2020 and added to fast warming and changing world.
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Notably, NOAA use much of the same raw temperature data in their analysis, but have a different baseline period (1901-2000) and methodology. Also, unlike NASA, NOAA does not infer temperatures in polar regions lacking observations, which accounts for much of the difference between NASA and NOAA records.
The UK Met Office and the University of East Anglia recently upgraded the HadCRUT dataset. This includes better coverage in data-sparse areas such as the rapidly warming Arctic, and will provides more accurate estimates of global, hemispheric and regional temperature changes.
According to the UK Met office, notable regional warmth was observed in northern Asia extending into the Arctic, parts of eastern Europe and Central America.
“The confirmation by WMO that 2020 was one of the warmest years on record is yet another stark reminder of the relentless pace of climate change, which is destroying lives and livelihoods across our planet. Today, we are at 1.2 degrees of warming and already witnessing unprecedented weather extremes in every region and on every continent,” United Nations Secretary-General António Guterres, said in a statement.
He added that the world was headed for a catastrophic temperature rise of 3 to 5 degrees Celsius this century, and that must be the “top priority for everyone, everywhere”.