New Climate Report Will Detail Grim Future of Hotter, Extreme Weather and Rising Seas

The United Nations is poised to release the most confident and comprehensive assessment yet of global warming, including detailed estimates of how continued greenhouse-gas emissions will increase Earth’s sea levels and drive extreme weather in the coming years. Compiled by more than 200 scientists and approved by government representatives from 195 countries, the report from the Intergovernmental Panel on Climate Change (IPCC) will leave little doubt that humans are altering the way the planet functions — and that things will get much worse if governments do not take drastic action, say climate researchers interviewed by Nature.

Many hope that the report, which covers the latest advances in climate science, will galvanize action at the UN climate summit in Glasgow, UK, this November, where world leaders will make fresh commitments to curbing greenhouse-gas emissions. Scientists say that on the basis of current policies, governments will fail to meet the goals they set in the 2015 Paris climate accord to limit global warming to 1.5–2 °C above pre-industrial levels.

“This report will make it absolutely clear what is the state of the science, and throw the ball back in the camp of the governments for action,” says Corinne Le Quéré, a climate scientist at the University of East Anglia in Norwich, UK.

It is the first in a trio of reports that will comprise the IPCC’s sixth major climate assessment since 1990: a second report, on climate impacts and adaptation, and a third, on mitigation efforts, will follow next year. In anticipation of the first report’s release next week, Nature previews what researchers say are some of the most significant advances in climate science conducted since the last IPCC assessment eight years ago.

High confidence, hot models

After several decades of research, climate scientists have no doubt that greenhouse-gas emissions cause global temperatures to rise. Concentrations of these gases have risen by around 50% since pre-industrial times, and the planet has warmed by more than 1 °C (see ‘Warmer worlds’). By some estimates, the world is on track for nearly 3 °C of warming unless governments do more to curb these emissions.

Researchers have grown more confident in such projections as climate science has advanced — a point that the IPCC report will emphasize. One way in which scientists have assessed their climate projections is through a metric known as climate sensitivity. This is a measure of the projected long-term warming that would occur if the planet’s atmospheric carbon dioxide (CO₂) level.