2020 is one of the three warmest years on record

2020 was one of the three warmest years on record and challenged 2016 for first place, according to a consolidation of the five main international datasets by the World Meteorological Organization (WMO). The natural weather phenomenon of La Niña, which produces a cooling of temperatures, was able to counteract the heat only very late in the year.

The five datasets studied by WMO agree that the decade from 2011 to 2020 was the warmest on record, and developed against the backdrop of a persistent, long-term trend towards climate change. The six warmest years have all occurred from 2015, occupying 2016, 2019 and 2020 the first three places. The difference in global average temperature between the three warmest years — 2016, 2019 and 2020 — is negligible. In 2020, the global average temperature was about 14.9 °C, or 1.2 ± 0.1 °C above pre-industrial levels (1850-1900).

“The World Meteorological Organization’s confirmation that 2020 was one of the warmest years since records began is a stark reminder that climate change is moving steadily, destroying lives and livelihoods across our planet. There is currently a temperature increase of 1.2 °C and unprecedented extreme weather events are already occurring in all regions and on all continents. We are on track to achieve a catastrophic temperature increase of 3 to 5 degrees Celsius in this century. Making peace with nature is the task that will define the twenty-first century. It must be the top priority for everyone, everywhere,” said UN Secretary-General António Guterres.

“The exceptional heat situation in 2020 occurred even when a La Niña episode occurred, which has a temporary cooling effect on temperature,” said WMO Secretary-General Professor Petteri Taalas. “It is noteworthy that the temperatures of 2020 were practically on par with those of 2016, the year in which one of the most intense El Niño warming episodes was recorded. This clear indication, at the global level, of climate change resulting from human activities is today as powerful as the very force of nature,” Taalas said.

“The classification of temperature by year is only one point element of a much longer-term trend. Since the eighties, each new decade has been warmer than the last. Heat-retaining gases in the atmosphere remain at record levels and the long life cycle of carbon dioxide, the most important gas, subjects the planet to future warming,” Taalas said.

The La Niña episode that began in late 2020 is expected to continue in and out of mid-2021. Typically, the effects of La Niña and El Niño on global average temperature are felt most intensely during the second year of the episode, but it remains to be seen to what extent the continued cooling effects of La Niña in 2021 may temporarily twist the overall long-term warming trend in this new year.

Some of the highlights of 2020 were sustained heat and wildfires in Siberia, a reduced extent of sea ice in the Arctic, and a record hurricane season in the Atlantic.

Temperature is just one of the indicators of climate change. The others are greenhouse gas concentrations, ocean heat content, ocean pH, global mean sea level, glacial mass, sea ice extent and extreme events.

As in previous years, in 2020 the increase in temperatures had important socio-economic repercussions. For example, as a result of weather and climate disasters, the United States suffered record losses of $22 billion in 2020, which was, for that country, the fifth warmest year since records began.

International datasets

WMO uses datasets (which are based on monthly climate data and come from observation sites and from ships and buoys that are part of the global marine networks) developed and maintained by the United States Office of National Oceanic and Atmospheric Administration (NOAA), the Goddard Institute for Space Studies of the National Aeronautics and Space Administration (NASA), the Hadley Centre of the UK Met Office and the Climate Research Unit of the University of East Anglia in the UK (HadCRUT).

It also uses reanalysis datasets from the European Centre for Medium-Range Weather Forecasts (ECMWF), the Copernicus climate change service and the Japan Meteorological Service. The reanalysis combines millions of meteorological and marine observations—including satellite ones—with model results to produce a complete reanalysis of the atmosphere. When observations and model results are combined, temperature can be estimated at any time and place on the globe, even in data-scarce areas, such as the polar regions.

According to estimates by NASA and the Copernicus service on climate change, 2020 is, along with 2016, the warmest year ever recorded. The NOAA and the UK’s HadCRUT dataset shows that 2020 is the second warmest after 2016, with the Japan Weather Service placing 2020 in third place. WMO estimates that the slightest differences between these datasets are all within the margin of error envisaged in calculating the global average temperature.

Recently the UK Bureau of Meteorology and the University of East Anglia updated their HadCRUT dataset that has been in use for several years, and improved, among other elements, coverage in areas where data is scarce, such as the Arctic, a region where temperatures are rising rapidly. This updated version of the dataset provides more accurate estimates of temperature changes at the global, hemispheric, and regional levels. The previous version, HadCRUT4, showed less warming than other global temperature datasets. The HadCRUT5 is more in line with the other datasets regarding the values recorded in recent decades and shows greater warming than most of them for the entire period since 1850.

Projections for the future

The temperature values will be incorporated into the final version of the WMO State of the Climate Report 2020, to be published in March 2021. The report, which is the updated version of the interim report published in December 2020, includes information on key climate indicators and certain climate consequences.

The goal of the Paris Agreement is to keep the global average temperature rise well below 2°C above pre-industrial levels, and to continue efforts to limit that temperature increase to 1.5°C above pre-industrial levels. In 2020, the global average temperature was around 1.2°C above pre-industrial levels (1850-1900), meaning it is approaching the lower limit of temperature rise that the Paris Agreement seeks to avoid. There is at least one in five chances that the global average temperature rise will temporarily exceed 1.5°C by 2024, according to the WMO Global Annual to Decadal Climate Update, which is run by the UK Met Office.

The UK Met Office’s annual global temperature forecast for 2021 suggests that next year will also be part of the series of Earth’s warmest years, even as the temperature will temporarily cool down as a result of La Niña, whose effects are usually most intense during the second year of the BOUT.

Source: WMO