The scientist who led the international MOSAiC expedition to the North Pole on Tuesday warned that the point could have already been reached at which irreversible global warming is triggered. During its expedition, the German research vessel “Polarstern” drifted through the Arctic on an ice floe for a year to also be able to research the winter at the North Pole, and the effects of climate change. “The disappearance of summer sea ice in the Arctic is one of the first landmines in this minefield, one of the tipping points that we set off first when we push warming too...