Global heating over this millennium could exceed previous estimates due to carbon cycle feedback loops. This is the conclusion of a new study by the Potsdam Institute for Climate Impact Research (PIK). The analysis shows that achieving the Paris Agreement’s aim of limiting global warming to well below 2°C is only feasible under very low emission scenarios, and if climate sensitivity is lower than current best estimates. The paper is the first to make long-term projections over the next 1,000 years while accounting for currently established carbon cycle feedbacks, including methane.