And oceans are heating up at a pace not seen since the end of the most recent ice age, 11,000 years ago.īeyond these sobering measurements, the IPCC report emphasizes some of the most significant scientific advances in understanding the regional effects of climate change, including where extreme heat, precipitation and drought have hit hardest. The ongoing global retreat of glaciers is unparalleled in at least 2,000 years. The coverage of sea ice in the Arctic during the late summer has been lower over the past decade than it has been in at least 1,000 years. The report lists a dizzying array of impacts that climate change has had on Earth - and that are already evident from pole to pole. “But unless there are immediate, rapid and large-scale reductions of all greenhouse gases, limiting global warming to 1.5 ☌ will be beyond reach.” Extreme impacts
“Is it still possible to limit global warming to 1.5 ☌? The answer is yes,” says Maisa Rojas, a coordinating lead author on the report and director of the University of Chile’s Center for Climate and Resilience Research in Santiago. Even in a scenario in which governments aggressively cut their greenhouse-gas emissions, the report projects that global temperatures are likely to surpass the 1.5 ☌ threshold in the coming years, before dropping back below it towards the end of the century. This is well above the 1.5–2 ☌ limit laid out as a goal by the nations that signed the 2015 Paris climate agreement. In a moderate emissions scenario that features little change from today’s global-development patterns, for instance, average global temperatures will rise by 2.1–3.5 ☌, according to the IPCC report.
This narrowing of climate sensitivity bolsters scientists’ confidence in their projections for what will happen on Earth in a number of different scenarios. The hard truths of climate change - by the numbers This compares with 1.5–4.5 ☌, the wider range for sensitivity reported in the IPCC’s last climate assessment, released in 2013. Although the IPCC’s best estimate remains at 3 ☌, the report reduces the uncertainty in that figure, narrowing the probable range to 2.5–4 ☌, using evidence such as modern and ancient climate records.
One key metric that researchers use to make their projections is ‘climate sensitivity’, a measure of how much long-term warming would be expected on Earth from a doubling of atmospheric carbon dioxide concentrations compared with pre-industrial levels. The overall assessment underscores efforts to pin down how much more temperatures will rise if atmospheric emissions continue, and provides climate scientists’ most confident projections yet for the twenty-first century. This is just one of the blunt facts appearing in a summary released with the IPCC report that is intended for policymakers. Hotting upĮarth’s global surface temperature has increased by around 1.1 ☌ compared with the average in 1850–1900 - a level that hasn’t been witnessed since 125,000 years ago, before the most recent ice age.
“The climate we experience in the future depends on our decisions now,” she says. If global emissions hit net zero by around 2050 - a target that many countries have committed to over the past year - then the world can achieve the goal laid out in the 2015 Paris accord and limit global warming to 1.5 ☌ above pre-industrial levels over the course of the twenty-first century, says Valérie Masson-Delmotte, a climatologist at the Laboratory of Climate and Environmental Sciences in Gif-sur-Yvette, France, and co-chair of the physical-science working group that produced the current report. There, governments will have the opportunity to make pledges to reverse course and decrease their emissions. The document - part of the IPCC’s sixth climate assessment since 1990 - arrives less than three months before the next major global climate summit in Glasgow, UK. Diagnosing Earth: the science behind the IPCC’s upcoming climate reportĬompiled by more than 200 scientists over the course of several years and approved by 195 governments during a virtual meeting last week, the report is the first in a trio assessing the state of climate change and efforts to mitigate it and adapt to it.
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