Hopes that the rise in average global temperatures by 2100 might be capped below 2.5 degrees Celsius can be all but ruled out if greenhouse gas emissions continue at the current rate, new research reassessing the atmosphere's sensitivity to CO2 suggests.

The study, under the Geneva-based World Climate Research Program, offers the first clear progress in decades toward narrowing the range of temperature rise caused by the doubling of carbon dioxide levels since pre-industrial times...