Climate trends/events

HBS Guy

Head Honcho 💉💉
Staff member

Dr. Zeke Hausfather@hausfath

·
Jan 18

Our State of the Climate 2021 is out! https://carbonbrief.org/state-of-the-climate-how-the-world-warmed-in-2021… 5th or 6th highest surface temps Warmest summer on land Warmest year for 25 countries + 1.8 billion people Record ocean heat Record high GHGs Record high sea levels Record low glacier mass 1/18

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We saw the 5th warmest (
@CopernicusECMWF
) or 6th warmest year on record (
@NASAGISS

@NOAANCEI

@BerkeleyEarth
). Temperatures were 1.1C to 1.2C above preindustrial levels in 2021:
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2021 was a bit cooler than the last few years due to a moderate La Nina event. La Nina tends to result in cooler temps globally, though the global response tends to lag 3-4 months after peak conditions. Here is what global temps look like since 1970 with and without ENSO removed:

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The years since 2015 – 2021 included – are quite a bit warmer than any years that came before. Barring a Pinatubo-sized eruption in the next few years, its exceedingly unlikely we will ever see a year as cool as 2014 again:
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HBS Guy

Head Honcho 💉💉
Staff member
From the Carbon Brief paper cited above:

  • Ocean heat content: It was the warmest year on record for ocean heat content, which increased markedly between 2020 and 2021. Due to the La Nina
  • Surface temperature: It was between the fifth and seventh warmest year on record for surface temperature for the world as a whole, the fifth warmest for the world’s land regions, and the seventh warmest for the oceans. Despite the La Nina
  • Warming over land: It was the warmest year on record in 25 countries, and in areas where 1.8 billion people live.
  • Extreme weather: 2021 saw the warmest northern-hemisphere summer (June, July, and August) on record over the world’s land, along with extreme heatwaves, wildfires, and rainfall events.
  • Comparison with climate model data: Observations fall well within the range of CMIP5 climate model projections over the past 70 years. CMIP6 models not yet going long enough for use as yet.
  • Warming of the atmosphere: It was the sixth or eighth warmest year in the lower troposphere – the lower part of the atmosphere – depending on which dataset is used.
  • Sea level rise: Sea levels reached new record-highs, with notable acceleration over the past three decades.
  • Greenhouse gases: Concentrations reached record levels for CO2, methane and nitrous oxide.
  • Sea ice extent: Arctic sea ice was well below the long-term average for most of the year, though relatively few daily records were set. The summer Arctic sea ice minimum was the 12th lowest since records began in the late 1970s.
  • Looking ahead to 2022: Carbon Brief predicts that global average temperature in 2022 will be similar to 2021. Not going by what Perth has gone through :)
(I have added some comments in red italic text.)
 
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