Nov 9, 2023 - Energy & Environment

Earth's last 12 months were hottest on record, new study shows

Share of population who experienced temperatures strongly affected by climate change for at least 100 days
Data: Climate Central; Note: A CSI of 3 or higher means human-caused climate change made conditions at least three times more likely; Map: Tory Lysik/Axios Visuals

The past 12 months ending in October was the hottest 12-month period that the planet has seen in at least 125,000 years, a new report finds.

Why it matters: There is ample evidence that climate change significantly shifted the odds of temperature extremes during this period.

The big picture: A Climate Central analysis shows not only how warming is loading the dice for more frequent and severe heat extremes, but also the disproportionate impacts worldwide.

  • The nonprofit organization examined climate change's fingerprints on daily average as well as extreme temperatures worldwide, using the group's Climate Shift Index, a near-real-time climate change attribution system.
  • The index, which has a scale of 0 through 5, is designed to show how human-caused climate change is remaking the climate, both in terms of average daily temperatures and dangerous long-duration extreme heat events.
  • The report shows that November 2022 through October 2023 experienced a global temperature departure from the pre-industrial average of 1.33°C (2.37°F). That is perilously close to temporarily meeting or breaching the Paris Agreement's 1.5°C temperature target.
  • However, that target refers to longer-term temperatures across a few decades, rather than a 12-month period.

Between the lines: Climate Central's report found that over the 12-month period, 5.8 billion people in the 175 countries surveyed experienced more than a month's worth of temperatures that were very strongly affected by human-caused climate change.

  • This is defined as temperatures that climate change made at least three times more likely.
  • The Climate Shift Index also indicates that 1 in 4 people experienced at least a five-day heat wave that was supercharged by climate change, when compared with an atmosphere without the human-caused surge in greenhouse gases from burning fossil fuels.

Zoom in: When looking at the daily average climate shift index for all of the examined countries, the nation with the highest average value was Jamaica, with a 4.5. This means that on a typical day there in the past 12 months, people there experienced temperatures that were 4.5 times as likely to occur due to climate change.

Of note: The new report has not been peer-reviewed, but the methods underlying the index have been and follow some of the approaches other attribution studies have taken.

The intrigue: The data highlights climate change's unequal burden. Many of the developing countries least able to adapt, which contributed relatively few historical greenhouse gas emissions, were hit the hardest during the past 12 months.

  • Meanwhile, larger, industrialized nations that can better withstand climate shocks, and are responsible for the majority of present-day warming, scored far lower on the shift index.
  • Small island countries and least developed nations had some of the highest values, while the 10 countries with the highest historical emissions scored far lower.
  • When looking at 700 cities with at least 1 million people that saw extreme temperatures, the research showed that Houston, Texas, saw the longest streak of climate-driven extreme temperatures, at 22 days.

The report shows that November 2022 through October 2023 experienced a global temperature departure from the pre-industrial average of 1.32°C (2.37°F). That is perilously close to temporarily meeting or breaching the gical Department who conducts climate attribution studies.

  • "It's really affecting every human being in this planet. And it's mostly affecting the vulnerable people."

What's next: The divides between industrialized nations and developing countries will take center stage starting at the end of the month during the COP28 Climate Summit in Dubai.

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