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WMO’s State of the Climate report

  • Context (IE | DTE | DTE): On March 19, the World Meteorological Organization (WMO) released its annual State of the Climate report, which highlights significant climate trends and events.
  • 2023 was reported as the hottest year on record, with multiple records broken across various climate indicators.
  • These indicators include greenhouse gas levels (GHGs), surface temperatures, ocean heat, sea level rise, Antarctic Sea ice cover, and glacier retreat.

Greenhouse Gases

  • GHG concentrations reached record-high levels in 2022, based on data from 1984 to 2022.
    • Greenhouse gases such as Carbon dioxide, methane, and nitrous oxide trap solar radiation, contributing to global warming.
  • Among these gases, the rate of increase of methane was the second highest on record and the highest on record for nitrous oxide.

Surface Temperature

  • In 2023, the global average temperature was 1.45 degrees Celsius higher than pre-industrial levels, marking a record high.
  • Higher GHG levels, along with El Nio occurrences, contributed to the rise in temperature.
  • El Nino and La Nina are the warm and cool phases of a recurring climate pattern across the tropical Pacific—the El Nino-Southern Oscillation (ENSO). The year 2023 marked the end of the three-year-long run of La Nina and the beginning of El Nino.

Ocean Heat Content

  • Oceans have absorbed about 90% of the additional heat trapped by GHGs since 1971.
  • This led to a steady increase in ocean temperatures and heat content.
  • In 2023, ocean heat content reached its highest level in the 65-year observational record.

Marine Heat Waves

  • Warmer temperatures caused a significant increase in global ocean heatwaves, with coverage reaching 32%.
  • Marine heatwaves occur when surface temperatures of a particular region of a sea rise 3 or 4 degrees Celsius above average for at least five consecutive days.

Antarctic Sea-Ice Extent

  • Antarctic sea-ice extent hit a record low of 1.79 million km2 in February 2023, the lowest since satellite records began. The extent remained at a record low from June to early November.
  • In September, the annual maximum sea-ice extent was 16.96 million km2, which is 1.5 million km2, well below the average from 1991 to 2020.


  • During the hydrological year 2022-2023, the world’s reference glaciers experienced unprecedented ice loss. Glaciers in North America and Europe were severely affected.
  • The annual mass balance of reference glaciers reached a new low of -1.2 m w.e. in 2022-2023.

Sea-level rise

  • It also reached a record high in 2023 since 1993. This is due to continued ocean warming as well as the melting of glaciers and ice sheets.
  • The rate of increase went up from 2.13 millimetres per year (mm/yr) from 1993 to 2002 to 4.77 mm/yr from 2014 to 2023.

Ocean Acidification

  • The ocean absorbs approximately 25% of the yearly emissions of human-produced carbon dioxide.
  • leading to ocean acidification, which harms marine life and ecosystems.
  • The UN IPCC reported that ocean acidity is at its lowest in 26,000 years, but regional variations exist.
  • The WMO emphasises that long-term, detailed observations are crucial for understanding and addressing ocean acidification‘s impact.

Ocean acidification

Ocean Acidification - PMF IAS

  • It refers to a reduction in the ocean’s pH over an extended period of time, caused primarily by the uptake of carbon dioxide (CO2) from the atmosphere.
  • When CO2 is absorbed by seawater, a series of chemical reactions occur.
    • 1. This results in an increased concentration of hydrogen ions. This increase causes the seawater to become more acidic.
    • 2. This causes carbonate ions to be relatively less abundant. Carbonate ions are an important building block of structures such as seashells and coral skeletons. Decreases in carbonate ions can make building and maintaining shells difficult for calcifying organisms such as oysters, clams, sea urchins, shallow water & deep-sea corals.

pH scale

  • It runs from 0 to 14, with 7 being a neutral pH.
  • Anything higher than 7 is basic (or alkaline).
  • Anything lower than 7 is acidic.
  • The pH scale is inversely proportional to hydrogen ion concentration, so more hydrogen ions translate to a lower pH i.e. higher acidity.
  • The ocean’s average pH is now around 8.1, which is basic (or alkaline).
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