Climatologist Hansen warns less particle pollution to fuel 2°C warming

A team of scientists led by world-known climatologist and former NASA researcher James Hansen is working on a new study that warns of a possible short-term spike of planetary heating 2 degrees Celsius above pre-industrial levels by 2050.

Ironically, the sudden surge of warming – predominantly since 2010 – is driven mainly by the steep reduction of climate-cooling particles in the past 10 to 20 years, as new regulations limited emissions from the biggest sources, including the burning of coal and heavy ship fuels.

Shielding the planet

Hansen was one of the first scientists to formally raise the alarm about climate change to the US Congress in 1988. According to Hansen and his team, the climate responds much more strongly to CO2 than previously assumed. “The influence of CO2 on the climate is one and a half times stronger than expected,” the man says.

Hansen’s previous warning about short-term heating due to emission reductions was in 2021, when he said the drop in sulfate aerosol pollution could double the rate of global warming during the next 25 years. Sulfate aerosol particles have been shielding the planet’s surface from some of the sun’s heat for decades, and cutting them is removing the shield, leading to a rapid warm-up.

Reflection of heat

He explained that sulfate aerosols cause microscopic water droplets in the atmosphere to multiply, which brightens clouds to reflect heat away from the Earth. The reduced amount of sulfates in the atmosphere allows more heat from the sun to warm ocean and land surfaces. As a result, global warming will likely pierce the 1,5°C ceiling in the 2020s and 2°C before 2050.”

However, not everyone agrees. “Warming of 2°C by 2050 is unlikely,” says climate scientist Michael Mann, director of the Center for Science, Sustainability & the Media at the University of Pennsylvania.

Methane emissions

Mann doesn’t think the findings in Hansen’s paper will withstand peer review because the research doesn’t adequately account for the cooling effects of cutting other short-lived climate-warming pollutants. For instance, black soot, which absorbs heat from the sun, can warm the atmosphere in the short term and have an outsized climate heating effect.

Projections of the Intergovernmental Panel on Climate Change (IPCC) include big cuts in methane emissions as another key to offsetting the spike in warming from the reduction of atmospheric sulfates. But methane emissions are not declining; they’ve accelerated sharply over the past five years, data from the National Oceanic and Atmospheric Administration show.

Surface temperature

Hansen and his team will not answer questions or do interviews until their paper has been peer-reviewed. He says his research is focused on real-world data and comparison with models, with the hope of gaining insights into how the climate system works and where the real world is headed.

If the average global temperature warms 2°C above pre-industrial times by 2050, it means that temperatures over land will likely increase double that amount, by 4°C, because land surfaces have less heat capacity than the oceans, where some of the heat goes deep down and isn’t immediately expressed as a rise of surface temperature.

Food and water supply

This year’s IPCC 6th Assessment Report shows that level of warming rapidly increases the odds of massive, widespread droughts that could wipe out food production in key global crop areas at the same time, as well as severe water shortages and fierce heat waves that would displace millions of people. The combined physical and social impacts would destabilize some regions and possibly stir up conflicts over food and water supplies.