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According to the WMO, the last time the earth had a similar CO2 concentration was 3-5 million years ago, when temperatures were 2-3°C higher and sea levels were 10-20 metres higher than they are now

Key Highlights:

• Record High Greenhouse Gas (GHG) Levels:
  • In 2023, annual mean carbon dioxide (CO2) levels rose by 2.3 parts per million (ppm), reaching a new record of 420 ppm.
  • This marks the 12th consecutive year with an increase of over 2 ppm in CO2 levels.
• Historical Context:
  • CO2 levels not seen in 3-5 million years, when temperatures were 2-3°C higher, and sea levels were 10-20 meters higher than they are today.
• Key GHGs at Record Highs:
  • The globally averaged surface concentrations of CO2, methane, and nitrous oxide all reached new highs in 2023.
• Contributors to the Increase in CO2:
  • Natural Variability: Natural factors such as large vegetation fires and reduced carbon absorption by forests contributed to higher CO2 levels.
  • Human Activity: High fossil fuel emissions from human and industrial activities also played a major role.
  • El Niño Phenomenon: The El Niño event led to higher temperatures and drier conditions, exacerbating the rise in GHG levels through increased wildfires and reduced carbon absorption by land sinks.
• Climate Feedback Loop Concerns:
  • The WMO warned of a vicious cycle:
    • Climate change could cause ecosystems to become larger sources of GHGs.
    • Wildfires could release more carbon, and warmer oceans may absorb less CO2, leading to more CO2 remaining in the atmosphere, accelerating global warming.
• Radiative Forcing:
  • Radiative forcing (the warming effect on climate) from long-lived GHGs has increased by 51.5% from 1990 to 2023, with CO2 contributing 81% of this increase.
• Methane Concerns:
  • Methane saw its largest three-year increase between 2020 and 2022.
  • This increase was linked to warmer temperatures and wetter land conditions during the 2020-2022 La Niña conditions, which caused an uptick in methane emissions from natural wetlands.
• Long-Term Impact of CO2:
  • Given CO2's long atmospheric lifetime, even with rapid emissions reductions, the warming effect will persist for several decades.