Climate scientist Prof James Hansen says the 2C target is “dead” due to significantly underestimated global heating. A new analysis by Hansen and colleagues concludes that recent cuts in sun-blocking shipping pollution have raised temperatures more than thought, and the sensitivity of the climate to increasing fossil fuel emissions are also greater than assumed.
The study’s results are at the high end of estimates from mainstream climate science but cannot be ruled out, independent experts said. If correct, they mean extreme weather will come sooner, and there is a greater risk of passing global tipping points, such as the collapse of the Atlantic ocean currents.
Hansen predicts global heating will reach 2C by 2045 unless solar geoengineering is deployed. The world’s nations pledged to keep global temperature rise below 2C in 2015, but climate crisis has already supercharged extreme weather across the world with just 1.3C of heating on average in recent years.
Hansen’s team used a top-down approach, looking at changes in ocean reflectivity and ascribing that to reduced shipping emissions. Their estimate of 0.5W/m2 is significantly higher than other studies, which would explain anomalous heat. However, other experts noted the simplicity of Hansen’s approach and the need for more detailed analysis.
The study also argues that climate sensitivity has been underestimated due to reduced shipping emissions. Climate scientists define this as the temperature rise resulting from a doubling of CO2 levels in the atmosphere. Hansen’s team estimated 4.5C, higher than IPCC’s range of 2.5C to 4C.
Hansen calls for urgent action, including a carbon fee and dividend policy, rapid development of nuclear power, and research on cooling techniques like geoengineering. He argues that political change is needed to achieve these measures, saying special interests have too much power in democratic systems.
Source: https://www.theguardian.com/environment/2025/feb/04/climate-change-target-of-2c-is-dead-says-renowned-climate-scientist