2015 to 2021 will be the seven warmest years on record. Photo: © SviatlanaLaza / Shutterstock.com

State of the climate in 2021

The World Meteorological Organization’s new analysis reports that in 2020, greenhouse gas concentrations reached new highs. Levels of carbon dioxide (CO2) were 413.2 parts per million (ppm), methane (CH4) at 1889 parts per billion (ppb) and nitrous oxide (N2O) at 333.2 ppb, respectively amounting to 149%, 262% and 123% of pre-industrial (1750) levels. The increase has continued in 2021. The global mean temperature for 2021 (based on data from January to September) was about 1.09°C above the 1850–1900 average and 2015 to 2021 will be the seven warmest years on record. Around 90% of the accumulated heat in the Earth’s system is stored in the ocean, which is measured through Ocean Heat Content. The upper 2000 m depth of the ocean continued to warm in 2019 reaching a new record high. A preliminary analysis based on seven global data sets suggests that 2020 exceeded that record. All data sets agree that ocean warming rates show a particularly strong increase in the past two decades and it is expected that the ocean will continue to warm in the future.

The ocean absorbs around 23% of the annual emissions of anthropogenic CO2 to the atmosphere and so is becoming more acidic. Open ocean surface pH has declined globally over the last 40 years and is now the lowest it has been for at least 26,000 years. Current rates of pH change are unprecedented since at least that time. As the pH of the ocean decreases, its capacity to absorb CO2 from the atmosphere also declines.

The report gives detailed analysis about other key developments during 2020/2021 concerning sea level, sea ice, glaciers and ice sheets, extreme weather, precipitation, socio-economic and environmental impacts.

State of Climate in 2021: Extreme Events and Major Impacts, 31 October 2021,  https://unfccc.int/news/state-of-climate-in-2021-extreme-events-and-majo...


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