World - Top climate scientist James Hansen's new climate warning

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.

• The paper lands as the planet endures its warmest year on record, with sizzling new benchmarks set on land and sea. Each month since May has set consecutive new milestones.

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 paper opens the door to endorsing geoengineering, referred to as "climate restoration" in the paper, for a short period of time. This involves deliberately trying to counter warming's effects by modifying the climate in other ways.

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