Leaked UN climate report underscores growing risk, need for fast action

The world’s top climate scientists are preparing to issue their starkest warning yet about the dire consequences of global warming, including the imminent risk that the world is about to crash through irreversible tipping points that will permanently affect the liveability of the planet.

According to news reports, a leaked draft from the Sixth Assessment Report (AR6) by the UN’s Intergovernmental Panel on Climate Change (IPCC) reports that climate change is happening now, is accelerating and posing unprecedented threats to human and natural systems — and that taking fast action can still avoid the worst economic and ecological impacts.

The IPCC’s report pulls together published research so we can see and assess the broader picture, which will soon look like a ruined landscape of a Hieronymus Bosch painting if we don’t act fast. The scientific research based on real-world measurements has been telling us with increasing confidence that the impacts of climate change are being felt sooner and more intensely than anticipated. Most Americans can now sense it from the changes they can see in their daily lives, including the growing weather extremes, as the U.S. West is currently experiencing.

Most disturbing, some of today’s impacts are setting off self-reinforcing feedbacks where the Earth is starting to warm itself. This includes the melting of the Arctic sea ice, which in normal times was acting as a reflective shield that bounced incoming solar radiation safely back to space. This warming in turn is accelerating release of carbon dioxide, methane and nitrous oxide from thawing permafrost in the Arctic. Canadian permafrost thaw is already exceeding earlier projections. Siberia’s ice-rich permafrost also is thawing at higher rates than expected as hard to kill zombie fires continue to smoulder.

These self-reinforcing feedbacks, including the loss of reflective Arctic sea ice, are among the most vulnerable links in the chain of climate protection. Last week, a new study by NASA and NOAA scientists found that the Earth is trapping twice as much heat as it did in 2005, with loss of reflective sea ice contributing significantly to the extra heat the planet is now retaining. The Arctic Ocean could lose all of its reflective ice in late summer within the next decade; its strong multi-year ice is already down to just a few percent. The thin first year ice not only melts faster, it also is broken up more easily by wind and waves. In the extreme case where we lose the Arctic’s reflective sea ice for multiple summer months, we’ll experience additional warming equivalent to adding a trillion tons of carbon dioxide to the atmosphere on top of the 2.4 trillion tons human activity has emitted since the Industrial Revolution.

Perhaps most dangerous of all, the self-reinforcing feedbacks can interact, with each one accelerating others, and together they will soon push the planet past irreversible tipping points. Warming is likely to cross the major threshold of 1.5 degrees Celsius by 2030. Many of these feedbacks and tipping points are projected to be tripped between today’s 1.2 degrees of observed warming and 1.5 degrees —  and many more beyond 1.5 and 2 degrees of warming.

The good news is that world leaders are starting to wake up to the climate emergency and recognize the need to take urgent action today, and throughout the decade to 2030, to keep the temperature goal of 1.5 degrees Celsius within reach, thanks in large part to the leadership of President Biden and his climate envoy John Kerry.

Numerous studies — including the 2018 IPCC Special Report on 1.5 degrees Celsius and the Global Methane Assessment from the Climate and Clean Air Coalition — show that the fastest way to slow warming in the near-term is by cutting emissions of super-climate pollutants: methane, hydrofluorocarbons, black carbon soot and precursors of ozone. Because these are short-lived pollutants, cutting their emissions will slow the rate of global warming by half and the Arctic by two-thirds in the coming decades. Just cutting methane emissions from the fossil fuel, agricultural and waste sectors could avoid up to 0.3 degrees of warming by the 2040s.

Black carbon soot, a major constituent of particulate air pollution from burning fossil fuels, is both a super-climate pollutant and an air pollutant that kills millions of people every year. In the Arctic, black carbon not only warms the atmosphere but also causes extra warming by darkening the snow and ice, allowing the darker surface to absorb more solar radiation and cause still more melting. Cutting black carbon and tropospheric ozone can save up to 2.4 million lives every year and increase annual crop production by more than 50 million tons, worth up to USD $33 billion a year.

The final report from AR6 will tell this story in more compelling detail. But we don’t need to wait for the official draft or final report to realize that we need to get out of the blocks and start the race to win the ten-year sprint to 2030 by cutting short-lived super-pollutants. This is the only way to keep 1.5 degrees Celsius within reach, while we also decarbonize our energy systems to deliver net-zero climate emissions by 2050.

Durwood Zaelke is president of the Institute for Governance & Sustainable Development (IGSD) in Washington, D.C. and Paris, as well as adjunct professor at the University of California, Santa Barbara. He is co-author of “Cut Super Climate Pollutants Now!: The Ozone Treaty’s Urgent Lessons for Speeding Up Climate Action” (2021).

Gabrielle Dreyfus, Ph.D., is senior scientist at IGSD and has been an adjunct professor at Georgetown University.

Both Zaelke and Dreyfus are peer reviewers for AR6.