A host of global climate models developed for the United Nations's next major assessment of global warming, due in 2021, are now showing a puzzling but undeniable trend: They are running hotter than they have in the past. In earlier models, doubling atmospheric carbon dioxide over preindustrial levels led models to predict somewhere between 2 C and 4.5 C of warming once the planet came into balance. But in at least eight of the next-generation models, produced by leading centers in the United States, the United Kingdom, Canada, and France, that "equilibrium climate sensitivity" has come in at 5 C or warmer. Many scientists, including the model developers, are doubtful this increased warming is likely to be real. Over the next year, they will be comparing notes on what happened in their models, which in many cases simulate the Earth system better than ever before.
Climate scientists have been trying to work out why new computer models have begun projecting a potentially much hotter future as CO2 levels rise. A new analysis gives our best idea yet – it seems to be to do with clouds. Ahead of the next major UN climate science panel reports in 2021, researchers have found their sixth generation of climate models show a much wider range for the future temperature than before, up from 1.5 to 4.5 C to 1.8 to 5.6 C. Those estimates are for when "equilibrium climate sensitivity" (ECS) occurs, a theoretical point when the climate system comes into equilibrium after CO2 levels have doubled. "There is definitely not one single common cause. But quite a lot of the models at the high end have introduced new, more sophisticated models of clouds and aerosols. That does seem to be the driver of the new, higher sensitivity," says Catherine Senior at the UK's Met Office.
This story was originally published by Wired and is reproduced here as part of the Climate Desk collaboration. If one is the loneliest number, two is the most terrifying. Humanity must not pass a rise of 2 degrees Celsius in global temperature from pre-industrial levels, so says the Paris climate agreement. The frustrating bit about studying climate change is the inherent uncertainty of it all. Predicting where it's going is a matter of mashing up thousands of variables in massive, confounding systems.
This Report provides results from the Exploratory data analysis done to assess the current state of global warming and climate change and measure their future impacts on the Global temperatures and Rising sea levels. The data analysis performed primarily focus on the answering the three most important questions related to global warming and climate change.