Nov 2, 2023 - Energy & Environment

New study warns climate is warming even faster than some think

Global ocean heat content anomaly
Data: Cheng, et al., 2023, "Another year of record heat for the oceans"; Note: For the upper 2,000 meters of ocean; Chart: Axios Visuals

A new study warns the Earth's climate is on track to warm significantly more than shown by the U.N. Intergovernmental Panel on Climate Change's (IPCC) projections.

Driving the news: The paper, published Thursday in the peer-reviewed journal Oxford Open Climate Change, is a synthesis of new and previous discoveries across multiple fields. It is peppered with policy prescriptions, unusual for a scientific paper.

  • The stark warning comes from ex-NASA scientist James Hansen, who is the lead author of the report. In 1988, he famously and accurately warned that human-caused warming would soon emerge from the background noise of natural variability.

Why it matters: Should the paper's authors be proven correct this time, the globe can expect more severe extreme weather events, species losses and sea level rise than currently projected.

Yes, but: Hansen has long straddled the line between scientist and activist. In the new paper, he recommends pursuing a range of policy options, from putting a price on carbon to geoengineering.

  • In this study, he calls on climate scientists to embrace the responsibilities medical professionals have to their patients. He argues they have been too reticent and conservative to lay out the full ramifications of warming.
  • "We are in the early phase of a climate emergency," Hansen writes.

What they found: The study finds that the warming resulting from doubling carbon dioxide levels in the atmosphere, also known as equilibrium climate sensitivity, is higher than the current consensus view.

  • The authors calculated a total warming of 4.8°C (8.6°F) for a doubling of CO2, above the IPCC's most recent estimate of 3°C (5.4°F), though not discordant with some previously published work.
  • The paper finds that global warming has been accelerating since 2010 and that this will soon become clear in the data. Specifically, it notes that a warming rate of 0.18°C (0.32°F) per decade, recorded between 1970-2010, will spike to 0.27°C (0.48°F) per decade after 2010.
  • It concludes the quickening pace of warming is not well-handled by computer models.

Between the lines: Climate scientist Zeke Hausfather, who was not involved in the new study, told Axios that research varies on estimating the amount of warming the world would see due to a doubling of CO2 concentrations.

  • He adds the new study's estimate is on the high side of previous research.
  • Hansen's findings also put forward that the planet's energy imbalance is growing, with more and more heat trapped in Earth's atmosphere.

The intrigue: Hansen and his coauthors argue that immediate and deep cuts in greenhouse gas emissions alone won't be sufficient to forestall dangerous levels of climate change.

The other side: While there are indications that climate change has sped up, some scientists disagree quite strongly with Hansen's findings.

  • Hausfather wrote this week that although the warming rate has clearly sped up since the 1970s, it is within the range anticipated by climate models.
  • Model simulations, he found, depict warming to be about 40% faster in the 2015-2030 period, compared to 1970-2014.

What they're saying: Michael Mann, a climate researcher at the University of Pennsylvania, told Axios via email that he doesn't believe the authors "have made the case for any of the major claims...or that climate models are getting this wrong."

  • He noted that ocean heat content, a key indicator of the planet's heat budget, "shows a very steady, rather than accelerating, increase."

Yet Katharine Hayhoe, a climate researcher and chief scientist at the Nature Conservancy, told Axios the study is an effective communications tool, since it tells people not only how serious things are, but also some possible solutions.

  • She noted reservations about his endorsement of solar radiation management, a geoengineering technique that could decrease the amount of solar radiation coming into the atmosphere.

The bottom line: "The fact that he puts the solutions right there in the abstract is actually exactly what needs to be done psychologically in the way that we communicate about climate change," Hayhoe said in an interview.

  • "If we tell people how bad it is, which it is, but we don't tell people what to do about it, then you can have the whole world worried and nothing will happen.
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