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This year will be among the three hottest on record, the United Nations says, as almost 200 countries started talks in Germany to bolster a global climate accord that the United States plans to quit. Temperatures this year will be slightly less than during a record-breaking 2016 and roughly level with 2015, the United Nations’ World Meteorological Organisation said, part of a long-term warming trend driven by greenhouse gases from burning fossil fuels. “We have witnessed extraordinary weather,” said Petteri Talaas, head of the WMO, pointing to extreme events including a spate of hurricanes in the Atlantic and Caribbean, monsoon floods in Asia and drought in East Africa. The WMO attributed the small dip from last year to the fading effects of a natural El Nino.

With enormous predators such as Tyrannosaurus Rex marching around in the daytime it is not surprising that the first mammals chose to live under the cover of darkness. In fact a study from University College London and Tel Aviv University has found that they did not emerge from the shadows until after the dinosaurs became extinct, around 66 million years ago. Before then, all mammals were nocturnal, sleeping in the daytime and hunting or foraging at night. With the dinosaurs gone, they switched to living in daylight. Researchers used computer algorithms to analyse details from 2415 species of living mammals to reconstruct the activities of their ancestors. They found that when the dinosaurs were wiped out, previously nocturnal mammals shifted to an intermediate stage of mixed day and night living, before changing to live primarily in the daylight. The research is in Nature Ecology and Evolution.