1.5 degrees Celsius is here and now

"47% likelihood that the global temperature averaged over the entire five-year 2024-2028 period will exceed 1.5°C above the pre-industrial era”
June 24, 2024
Photo by Javier Miranda / Unsplash

By David Spratt

Summary

  • Former NASA climate science chief James Hansen believes the global warming trend is at 1.5°C or close to reaching that milestone.
  • Global ocean surface temperatures are continuing to break records.
  • New generation climate models project a faster rate of warming, with potential trends of 1.5°C by the mid-2020s and 2°C by the late 2030s.
  • The rate of warming is accelerating, with an increase in ocean heat content and Earth’s energy imbalance driving global warming’s impact.

Has the world already reached a global warming trend of 1.5°C (compared to ~1900 pre-industrial baseline)?

There have been some sharp disagreements between scientists over this question, with former NASA climate science chief James Hansen saying that for all practical purposes the climate system trend is now at the 1.5°C mark, whilst Penn State University’s Michael E Mann and others disagree and say we have up to a decade to go.

In May 2024, Hansen wrote that the 12-month mean global temperature “is still rising at 1.56°C relative to 1880-1920 in the GISS analysis through April. Robert Rohde reports that it is 1.65°C relative to 1850-1900 in the BerkeleyEarth analysis (for the same period).  El Nino/La Nina average global temperature likely is about 1.5°C, suggesting that, for all practical purposes, global temperature has already reached that milestone.”   [El Niño (the warm phase) and La Niña (the cool phase) lead to significant differences from the average ocean temperatures, winds, surface pressure, and rainfall across parts of the tropical Pacific. Neutral conditions are near their long-term average.]

Read the full post at Climate Code Red.

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