The report – published last week by the IPCC’s working group on climate change impacts, adaptation and vulnerability – charts global warming’s implications for water availability, ecosystems, food, coastlines and health.
The policymakers’ summary was approved by government representatives from around the world following fraught last-minute discussions that led to several sections being dropped.
It notes that some northerly parts of Europe may initially benefit from climate change through reduced demand for heating and increased crop yields. But if it continues unabated, these effects will be outweighed by negative impacts such as heat waves, reduced water availability and species loss.
The panel says ecosystem changes have been recorded on every continent. It also offers more certainty on other impacts. Among the most likely and imminent are worsening drought, increased storm and flood risk, and mass extinction of species.
Low-lying islands vulnerable to sea-level rise, Africa and the highly-populated flood plains of Asia are all expected to be badly hit, as is the Arctic, where warming will be greatest.
The panel puts the total cost of a 4°C temperature rise at 1-5% of global GDP, but says the figure is likely to be much higher in developing countries, which have less potential to adapt.
The report notes that little is being done to mitigate the potential effects of changes despite an inevitable warming of another 0.6°C or so. In the long run, both adaptation and mitigation measures – including technological, behavioural and policy changes – are required, the IPCC says.
The UK Climate Impacts Programme (UKCIP), established in 1997 by the Environment Department (DEFRA) to aid adaptation, has contested what it sees as the report's unjustifiably gloomy view of current adaptation efforts. Its own assessment suggests “a much broader acceptance of the need for, and investment in, adaptation actions”.