Four Key Climate Change Indicators Break Records in 2021

Four Key Climate Change Indicators Break Records in 2021

Yet another clear sign that human activities are causing planetary scale changes

Four key climate change indicators – greenhouse gas concentrations, sea level rise, ocean heat and ocean acidification – set new records in 2021.

This is yet another clear sign that human activities are causing planetary scale changes on land, in the ocean, and in the atmosphere, with harmful and long-lasting ramifications for sustainable development and ecosystems, according to the World Meteorological Organization (WMO).

Extreme weather – the day-to-day “face” of climate change – led to hundreds of billions of dollars in economic losses and wreaked a heavy toll on human lives and well-being and triggered shocks for food and water security and displacement that have accentuated in 2022.

The WMO State of the Global Climate in 2021 report confirmed that the past seven years have been the warmest seven years on record. 2021 was “only” one of the seven warmest because of a La Niña event at the start and end of the year.

This had a temporary cooling effect but did not reverse the overall trend of rising temperatures. The average global temperature in 2021 was about 1.11 (± 0.13) °C above the pre-industrial level.

WMO Secretary-General Prof. Petteri Taalas said: “It is just a matter of time before we see another warmest year on record.

“Our climate is changing before our eyes. The heat trapped by human-induced greenhouse gases will warm the planet for many generations to come. Sea level rise, ocean heat and acidification will continue for hundreds of years unless means to remove carbon from the atmosphere are invented.

"Some glaciers have reached the point of no return and this will have long-term repercussions in a world in which more than 2 billion people already experience water stress.”

“But much more needs to be done, as we are seeing with the drought emergency unfolding in the Horn of Africa, the recent deadly flooding in South Africa and the extreme heat in India and Pakistan."

The WMO State of the Global Climate report complements the IPCC Sixth Assessment report, which includes data up to 2019.

The new WMO report provides information and practical examples for policy-makers on how the climate change indicators outlined in the IPCC reports played out during the recent years globally and how the associated implications on extremes have been felt at national and regional level in 2021.

The report was released just ahead of the World Economic Forum Davos 2022 Annual Meeting.

Global annual mean temperature difference from pre-industrial conditions (1850–1900) for six global temperature data sets (1850–2021). Source: Met Office, United Kingdom of Great Britain and Northern Ireland.
Global annual mean temperature difference from pre-industrial conditions (1850–1900) for six global temperature data sets (1850–2021). Source: Met Office, United Kingdom of Great Britain and Northern Ireland.

Key Messages

Greenhouse gas concentrations reached a new global high in 2020, when the concentration of carbon dioxide (CO2) reached 413.2 parts per million (ppm) globally, or 149% of the pre-industrial level.

The global annual mean temperature in 2021 was around 1.11 ±0.13 °C above the 1850-1900 pre-industrial average, less warm than some recent years owing to cooling La Niña conditions at the start and end of the year. The most recent seven years, 2015 to 2021, are the seven warmest years on record.

Ocean heat was record high. The upper 2000m depth of the ocean continued to warm in 2021 and it is expected that it will continue to warm in the future – a change which is irreversible on centennial to millennial time scales.

Ocean acidification. The ocean absorbs around 23% of the annual emissions of anthropogenic CO2 to the atmosphere. This reacts with seawater and leads to ocean acidification, which threatens organisms and ecosystem services, and hence food security, tourism and coastal protection. As the pH of the ocean decreases, its capacity to absorb CO2 from the atmosphere also declines.

The IPCC concluded that “there is very high confidence that open ocean surface pH is now the lowest it has been for at least 26,000 years and current rates of pH change are unprecedented since at least that time.

Global mean sea level reached a new record high in 2021, after increasing at an average 4.5 mm per year over the period 2013 -2021. This is more than double the rate of between 1993 and 2002 and is mainly due to the accelerated loss of ice mass from the ice sheets.

Source: AVISO altimetry

Cryosphere: Although the glaciological year 2020-2021 saw less melting than in recent years, there is a clear trend towards an acceleration of mass loss on multi-decadal timescales. On average, the world’s reference glaciers have thinned by 33.5 meters (ice-equivalent) since 1950, with 76% of this thinning since 1980.

Exceptional heatwaves broke records across western North America and the Mediterranean. Death Valley, California reached 54.4 °C on 9 July, equalling a similar 2020 value as the highest recorded in the world since at least the 1930s, and Syracuse in Sicily reached 48.8 °C.

Flooding induced economic losses of $17.7 billion in Henan province of China, and Western Europe experienced some of its most severe flooding on record in mid-July associated with economic losses in Germany exceeding $20 billion. There was heavy loss of life.

Drought affected many parts of the world, including the Horn of Africa, Canada, the western United States, Iran, Afghanistan, Pakistan and Turkey.

Hurricane Ida was the most significant of the North Atlantic season, making landfall in Louisiana on 29 August, with economic losses in the United States estimated at $75 billion.

The ozone hole over the Antarctic was unusually large and deep, reaching its maximum area of 24.8 million km2 (the size of Africa) as a result of a strong and stable polar vortex and colder than average conditions in the lower stratosphere.

Food security: The compounded effects of conflict, extreme weather events and economic shocks, further exacerbated by the COVID-19 pandemic, undermined decades of progress towards improving food security globally.

Displacement: Hydrometeorological hazards continued to contribute to internal displacement. The countries with the highest numbers of displacements recorded as of October 2021 were China (more than 1.4 million), the Philippines (more than 386 000) and Viet Nam (more than 664 000).

Ecosystems: including terrestrial, freshwater, coastal and marine ecosystems – and the services they provide, are affected by the changing climate and some are more vulnerable than others. Some ecosystems are degrading at an unprecedented rate.

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