ABSTRACT
Humanity is conducting an unintended, uncontrolled, globally pervasive experiment whose ultimate consequences could be second only to a global nuclear war. Climate change impacts are complex in that they can be both direct and indirect. Some of the impacts have been observed over the last several decades, for example changes in the ranges for some already threatened species of plants, animals and birds, retreat of glaciers, shorter duration of river- lake- and sea-ice and melting of permafrost. Increased coral calcification rates at higher temperatures are likely to be outweighed by deaths due to bleaching. The impacts of climate change on food production, prices and numbers at risk of hunger depend on a number of factors. Global aggregate impacts are expected to turn negative at around 2 to 3°C warming, while impacts will hit hardest at poorer countries, thereby increasing international inequity.
