Brief Answers to the Big Questions

by Stephen Hawking

The danger is that global warming may become self-sustaining, if it has not become so already. The melting of the Arctic and Antarctic ice caps reduces the fraction of solar energy reflected back into space, and so increases the temperature further. Climate change may kill off the Amazon and other rainforests and so eliminate one of the main ways in which carbon dioxide is removed from the atmosphere. The rise in sea temperature may trigger the release of large quantities of carbon dioxide. Both these phenomena would increase the greenhouse effect, and so exacerbate global warming. Both effects could make our climate like that of Venus: boiling hot and raining sulphuric acid, with a temperature of 250 degrees centigrade (482 degrees Fahrenheit). Human life would be unsustainable. We need to go beyond the Kyoto Protocol, the international agreement adopted in 1997, and cut carbon emissions now. We have the technology. We just need the political will.