The 2020-2022 La Nina events had a temporary cooling effect on global temperatures. 2021 has still emerged as one of the seven warmest years on record
After consolidating six leading international datasets, World Meteorological Organisation (WMO) has gone on to call 2021 as one of the seven warmest years on record. Even though 2020-2022 La Nina events temporarily cooled the average global temperatures, 2021 still emerged as quite a warm year.
La Nina refers to the large-scale cooling of the ocean surface temperatures in the central and eastern equatorial Pacific Ocean, coupled with changes in the tropical atmospheric circulation. It usually has the opposite impacts on weather and climate as El Nino. La Nina has a temporary global cooling effect, which is typically strongest in the second year of the event.
The average global temperature in 2021 was recorded to be 1.11 degrees Celsius above the pre-industrial (1850-1900) levels. According to all datasets compiled by WMO, 2021 is the 7th consecutive year (2015-2021) where the global temperature has been recorded to be over 1 degrees Celcius above pre-industrial levels.
Since the 1980s, each decade has been warmer than the previous one but some of the warmest years were recorded after 2014. The seven warmest years began with the year 2015. Then came the El Nino event in 2016 which contributed to record global average warming. Out of these 7, 2016, 2019, and 2020 have been the warmest.
In its press release, the WMO has said that global warming and other long-term climate change trends are expected to continue as a result of record levels of heat-trapping greenhouse gases in the atmosphere. The organisation uses six international datasets to ensure the most comprehensive, authoritative temperature assessment. The same data are used in its annual State of the Climate reports, which inform the international community on global climate indicators. The rankings of individual years should be considered in the long-term context, especially since the differences between individual years are sometimes marginal.
"Back-to-back La Nina events mean that 2021 warming was relatively less pronounced compared to recent years. Even so, 2021 was still warmer than previous years influenced by La Nina. The overall long-term warming as a result of greenhouse gas increases is now far larger than the year-to-year variability in global average temperatures caused by naturally occurring climate drivers," said WMO Secretary-General, Professor Petteri Taalas.
He added, "The year 2021 will be remembered for a record-shattering temperature of nearly 50 degrees Celsius in Canada, comparable to the values reported in the hot Saharan Desert of Algeria; exceptional rainfall, and deadly flooding in Asia and Europe as well as drought in parts of Africa and South America. Climate change impacts and weather-related hazards had life-changing and devastating impacts on communities on every single continent."
Even the India Meteorological Department (IMD) had last week announced that the year 2021 was the fifth warmest year for India since nationwide records commenced in 1901.
The Paris Agreement aims to contain the increase in the global average temperature to well below 2 degrees Celsius above pre-industrial levels while pursuing efforts to limit the temperature increase to 1.5 degrees Celsius above pre-industrial levels. At 1.11 degrees Celsius above the pre-industrial (1850-1900) levels, the global average temperature in 2021 is already approaching the lower limit of temperature increase the Paris Agreement seeks to stop.
Temperature is just one of the indicators of climate change. Others include greenhouse gas concentrations, ocean heat content, ocean pH, global mean sea level, glacial mass, and sea ice extent.
The temperature figures will be incorporated into the final WMO report on the State of the Climate in 2021 which will be issued in April 2022.