Ordinary citizens sometimes wonder: How serious is a global warming of 2 or 3°C? The answer is: It would be very serious.

The planet has already warmed by about 1 °C, and the harmful effects are already being experienced worldwide. Record breaking monthly heat occurs five times as often as it would without global warming - this includes heat waves causing many thousands of fatalities. Drought and extreme rainfall, leading to floods, are also on the rise. Almost half of the summer sea ice cover on the Arctic ocean is gone. The huge ice sheets on Greenland and Antarctica are melting at an accelerating rate, contributing to rising sea levels worldwide. Coastal cities -- like Boston and Miami -- are flooding more frequently. Coral reefs are dying. And this is only the beginning.

With further global warming the weather will become increasingly unpredictable and dangerous. Droughts and crop failures will become more frequent, making it more and more difficult to feed all of Earth’s people. Many coastal cities and island nations will become uninhabitable. Conflicts and refugee movements on an unprecedented scale will become ever more likely. And the risk of crossing critical “tipping points” in the climate system -- where major and devastating, irreversible changes in the functioning of the Earth system occur, such as a breakdown of the Gulf Stream System or the Amazon rainforest, or the complete destabilisation of the 3-km-thick Greenland ice sheet – becomes ever more likely.

An overview over critical tipping elements of the climate system. Source: Potsdam Institute for Climate Impact Research


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Prof. Stefan Rahmstorf
Potsdam Institute for Climate Impact Research

Prof. Edward Maibach
George Mason University