ROGER_WILCO:
Climate change target of 2C is ‘dead’, says renowned climate scientist | Climate crisis | The Guardianhttps://www.theguardian.com/environment/2025/feb/04/climate-change-target-of-2c-is-dead-says-renowned-climate-scientist“The Intergovernmental Panel on Climate Change (IPPC) defined a scenario which gives a 50% chance to keep warming under 2C – that scenario is now impossible,” he said. “The 2C target is dead, because the global energy use is rising, and it will continue to rise.” The new analysis said global heating is likely to reach 2C by 2045, unless solar geoengineering is deployed.
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A key focus has been on emissions from shipping. For decades, the sulphate particles produced by ships burning fuel have blocked some sunlight from reaching the Earth’s surface, suppressing temperatures. But in 2020, new anti-pollution regulations came into force, sharply cutting the level of the aerosol particles. This led to more heat from the sun reaching the surface, which scientists measure as watts a square meter (W/m2).
Hansen’s team’s estimate of the impact of this – 0.5W/m2 – is significantly higher than five other recent studies, which ranged from 0.07 to 0.15 W/m2, but would explain the anomalous heat. Hansen’s team used a top-down approach, looking at the change in the reflectivity over key parts of the ocean and ascribing that to the reductions in shipping emissions. The other studies used bottom-up approaches to estimate the increase in heat.
“Both approaches are useful and often complementary,” said Dr Gavin Schmidt, director of Nasa’s Goddard Institute for Space Studies. “But I think in this case, Hansen’s approach is too simple and doesn’t factor in changes in Chinese emissions, or internal variability.”
The new study also argues that the planet’s climate sensitivity to rising carbon emissions has been underestimated, partly because of the underestimation of the impact of reduced shipping emissions.