| Last week brought the first issue of Bloomberg Green, an attempt by the team behind this newsletter to create a magazine focused entirely on climate change. While making this publication, however, it became clear that other events this year might have distracted even the most ardent trackers of climate science developments. As a service, we included a helpful digest—with links to the original studies—to the biggest findings in recent months. The year 2020 has been all about heat. A deep dive into population data and warming projections suggest that our 6,000-year era of just-right temperatures may be coming to an end. Barring mass migration, a third of humanity may live in Sahara-like conditions by 2070. Lethal combinations of heat and humidity hadn't been projected to appear until after midcentury, but a megastudy of 40 years of hourly weather-station data from all over the world finds that the Persian Gulf and Indus River Valley are already flirting with deadly conditions. The same study shows that episodes of extraordinary humidity and heat have doubled in frequency since 1979. Antarctica saw its hottest day on record, reaching 18.4C on Feb. 6—only days before an iceberg bigger than Tampa broke off the continent. Europe's winter was the warmest it's measured to date. Australia's second-hottest summer caused the Great Barrier Reef its second-worst bleaching in 40 years of observation. And centuries of tree-ring data, combined with water-cycle models, show that human-driven warming transformed what would have been simply another dry spell into the American Southwest's second-worst drought in 1,200 years. It's not the End Times—yet. But scientists analyzing data on environmental change in 42 major ecosystems found that some may be inching closer to collapse than we thought . To make matters worse, a 30-year study of tropical forests indicates trees aren't drawing down our carbon dioxide emissions as well as they used to. In the last decade they absorbed a third less CO2 than they did in the 1990s—a total of 21 billion metric tons less. That's the equivalent of about 10 years of emissions from France, Germany, and the U.K. combined. Meanwhile, clouds remain a puzzle. An unusually cloudless sky above Greenland last summer led to the biggest drop in the ice sheet's mass ever recorded—and yet clouds that did appear over the northern and western parts of the island helped trap heat that would otherwise have escaped, causing even more melting. Climate scientists continue to debate the unusually hot results from the latest generation of climate models, which started producing worrisome forecasts last year. One explanation: The way the models treat clouds may be skewing results hotter. And if all that weren't strange enough, record-breaking rainfall in Hawaii in 2018 may have triggered the eruptions at Kilauea that caused two dozen injuries and $800 million in property damage. It does get happier. Eunice Foote, the amateur American scientist who wrote the first known paper on the heat-trapping potential of CO2 in 1856 and then disappeared from posterity, has been rediscovered and restored to her proper place in climate history. And the ozone hole, which dominated global environmental discussions in the 1980s, has shrunk by about 20% over the past 15 years, which scientists attribute to the landmark 1987 treaty banning the materials that caused it. Don't take that progress for granted, however. In addition to a recent rise in illegal ozone-destroying chemicals, scientists discovered that the substances are also leaking from pre-1987 infrastructure as it ages. Eric Roston writes the Climate Report newsletter about the impact of global warming. | 
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