Greenhouse gas levels, surface temperatures, ocean heat and acidification, sea level rise, Antarctic sea ice cover and glacier retreat reached new highs

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The year 2023 smashed multiple climate records with greenhouse gas levels, surface temperatures, ocean heat and acidification, sea level rise, Antarctic sea ice cover and glacier retreat reaching new highs, according to the World Meteorological Organization’s (WMO) State of the Global Climate 2023 report.

“Sirens are blaring across all major indicators… Some records aren’t just chart-topping, they’re chart-busting. And changes are speeding-up,” United Nations Secretary-General António Guterres said in a statement.

The WMO confirmed that the global mean near-surface temperature in 2023 was 1.45 ± 0.12°C above the 1850-1900 average.

This makes it the warmest year in the 174-year observational record, surpassing the previous record holders — 2016 at 1.29 ± 0.12 °C and 2020 at 1.27±0.13 °C — by a clear margin. The past nine years, 2015-2023, were the nine warmest years on record.

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The global average sea-surface temperatures were also at a record level between late spring in the Northern Hemisphere and the end of the year.

In 2022, the three main greenhouse gases — carbon dioxide, methane, and nitrous oxide — reached record-high levels.

Average concentrations for carbon dioxide were 417.9 ± 0.2 parts per million (ppm), methane at 1923 ± 2 parts per billion (ppb) and nitrous oxide at 335.8 ± 0.1 ppb. This is 150 per cent, 264 per cent and 124 per cent of pre-industrial (1750) levels, respectively.

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However, the rate of increase of carbon dioxide was slightly below the 10-year average. This, according to the WMO, typically occurs in years starting with La Nina, as it did in 2022.

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Increase in acidity of the ocean is also increasing. The ocean absorbs around 25 per cent of the annual emissions of anthropogenic carbon dioxide to the atmosphere. The greenhouse gas, in turn, reacts with seawater, resulting in a decrease in acid levels referred to as “ocean acidification”. This has negative consequences for organisms and ecosystem services, including food security, by reducing biodiversity, degrading habitats and endangering fisheries and aquaculture.

The Sixth Assessment Report of the United Nations Intergovernmental Panel on Climate Change noted with high confidence that the acidity in the open oceans is now the lowest it has been for at least 26,000 years.

However, the WMO added that there are regional variations in the rate of change in ocean acidification, its pattern and scale. It called for high-resolution, long-term observation.

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Rohini Krishnamurthy, Down to Earth, 19 March 2024. Article.

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