The evolution of the evidence base for observed impacts of climate change

Natural and human systems are increasingly affected by climate change. A synopsis of the documentation of scientific evidence for the observed effects of climate change in the third, fourth and fifth assessment reports of the Intergovernmental Panel on Climate Change shows that the amount of evidence available, the range of impacts observed and their geographical scope has expanded rapidly. Fifteen years ago, robust evidence for observed climate change impacts was almost exclusively available for the cryosphere and terrestrial ecosystems in mid to high northern latitudes or mountain regions. By contrast, the effects of climate change are now documented for all land areas and oceans, for both natural and human systems. Over the last decade, evidence has increased especially for impacts on marine ecosystems, food production and wildfire regimes. No recent progress has been found in the documentation of impacts of climate change related sea level rise. Though the evidence base has improved substantially for regions in the Southern hemisphere and developing countries, the global distribution of observed impacts remains uneven.