Is cleaner air with accelerating global warming more than we expected?

James Hansen, the climate scientist best known for warning the US Congress of global warming in the 1980s, has doubled his warnings that we are underestimating the climate impact of decline air pollution.

“Humanity entered into a bad deal, a Faustian trade, when we used aerosols to equalize general most half of the greenhouse gas heating,” said Hansen by a briefing hosting the united nations’ sustainable development solutions networks.

But other researchers say this conclusion is based on appalling foundations and we still do not know how much reductions in air pollution contribute to global warming. Hansen’s conclusions “Hovering surrounds the top end of what we consider to be plausible,” says Michael Diamond at Florida State University, who was involved in the research.

Record tips in global average temperatures by 2023 and 2024 have spurred the debate over whether the pace of global warming accelerates faster than expected. Rising levels of greenhouse gases and a heating Pacific Ocean drove most of the temperature rise, but other unknown contributors pushed average temperatures even higher than can be explained by these factors alone.

Hansen and his colleagues previously connected the accelerating warming rate with a reduction in air pollution. Now they offered a new analysis that argued that a decrease in air pollution can explain the tip of temperatures in the last two years. Aerosols in air pollution can both reflect sunlight away from the soil directly and affect the reflective properties of clouds – changes in cloud covering have also been implicated as a factor in the heat.

In particular, the researchers focus on the effect of a 2020 regulation cut down to harmful sulfur used in shipping fuel. The sudden fall in air pollution over the world seas has gained researchers an unintended experience that they determine the climate effects of aerosols with more precision.

Hansen and his colleagues looked at busy shipping corrodes in the Pacific Ocean to estimate this effect and measure the change in solar radiation, which was absorbed by the planet in these areas as air pollution declined. From this, they estimate that the decrease in shipping aerosols increased the heat that reached the soil by 0.5 watts per day. Square feet. This corresponds to the heating effect of a decade of global carbon dioxide emissions at today’s levels.

This additional heating would be enough to explain the non -classified part of the heat seen in the last two years, they found. But the consequences are wider: It would also mean that the cooling effect of the air pollution has masked the full extent of the greenhouse gas heating effect – in other words, the heating that has so far been experienced does not resume the full influence of our emissions.

Hansen and his colleagues warn that this means that the climate is much more sensitive than expecting to increase levels of greenhouse gases. As a result, they claim that the world is faster to approve climate points, such as slowing down key Atlantic currents and the collapse of the Western Antarctic ice sheet. To fight this, they say that we need to consider more seriously how to cool the planet with interventions such as Solar Geoengineering.

However, 0.5 watts per Square meter number at the core of the new analysis far higher than other estimates of the heating effect of the change in shipping emissions, says Tianle Yuan at the University of Maryland Baltimore County. But he knows he is not completely impossible.

Gavin Schmidt at NASA says the number is “very likely an overestimation” because it assumes that all the change in absorbed sunlight is due to the change in shipping aerosols rather than other changes as minor air pollution from China or natural variability.

A change in aerosols may not even be necessary to explain the temperature stand in 2023, says Shiv Priyam Raghuraman at the University of Illinois Urban-Champaign-He previously found that it can be explained by changes in the pacific temples alone. He says that more work is down to unite different estimates of the warming effects of aerosols.