Context: From registering the hottest summer on record to some significant steps at the yearly United Nations climate summit, 2023 was a year of extremes. Here are some climate-related milestones from this time.
Hottest year:
- The global mean near-surface temperature in 2023 (to October) was around 1.40 (± 0.12) °C above the 1850–1900 average. Based on the data to October, it is virtually certain that 2023 will be the warmest year in the 174-year observational record, surpassing the previous joint warmest years, 2016 at 1.29 (± 0.12) °C above the 1850–1900 average and 2020 at 1.27 (±0.13) °C.
Highest sea surface temperature ever:
Marine heat waves - periods when ocean temperatures are warmer than 90% of prior observations for a given time of year - were widespread in 2023.
- According to the U.S. National Ocean and Atmospheric Administration (NOAA), 48% of global oceans experienced them in August 2023.
Global sea surface temperatures (SST) are usually highest in March. But as per data, global average SSTs remained at record highs throughout April, May, June, and July 2023.
Sea level rise
In 2023, global mean sea level reached a record high in the satellite record (since 1993), reflecting continued ocean warming as well as the melting of glaciers and ice sheets. The rate of global mean sea level rise in the past ten years (2013–2022) is more than twice the rate of sea level rise in the first decade of the satellite record (1993–2002).
A graph showing the number of satellites.
Lowest Antarctic Sea ice extent: Sea-ice extent is the area of ice covering the Antarctic Ocean at a given time. In 2023, Antarctic Sea ice had record low ice growth from April.
- According to NOAA, sea ice in the Antarctic reached an annual maximum extent of 16.96 million sq. km on September 10, 2023, the lowest since 1979. This year’s maximum was 1.03 million sq. km, below the previous record low set in 1986.
Record carbon dioxide levels: Global carbon dioxide emissions are expected to have hit a new high in 2023, up 1.1% from 2022. The Global Carbon Budget Report, published in December 2023, said overall CO2 emissions, which climbed to a record last year, had plateaued in 2023 due to a slight drop in deforestation.
Ocean Acidification:
The ocean absorbs around one quarter of the annual emissions of anthropogenic CO2 to the atmosphere. CO2 reacts with seawater and alters the carbonate chemistry, resulting in a decrease in pH referred to as ‘ocean acidification’.
- Ocean acidification affects organisms and ecosystem services, including food security, by reducing biodiversity, degrading habitats, and endangering fisheries and aquaculture.
- The IPCC AR6 concluded that “There is very high confidence that open ocean surface pH is now the lowest it has been for at least [thousand years] and current rates of pH change are unprecedented since at least that time”.
Loss and damage fund: The world’s first loss and damage fund for the impacts of climate change was created in 2023, at the start of the COP28 climate talks in the U.A.E. in early December. This money is meant to help countries trying to recover from climate induced disasters.
The fund will be based at the World Bank but managed by an independent secretariat.
- According to a senior U.N. official, it has received pledges of $792 million from governments, which is a lot but still well short of the billions required to fulfill its purpose.
Impact of food systems: For the first time in the history of climate summits, 134 countries at COP28 pledged to tackle the climate impact of the food industry.
- These countries represent over 5.7 billion people, 70% of the food we eat, nearly 500 million farmers, and 76% of total emissions from the global food system. But observers noted the declaration doesn’t include quantitative targets.