A BLEAK outlook for the world's climate and ecology, with sea levels rising by an average of 50 centimetres over the next 100 years and many species under threat, is predicted by a government report.
Prepared by Sir Robert May, the chief scientific adviser, the study further confirms that humans are slowly but inexorably altering the climate.
Levels of the greenhouse gas carbon dioxide are on course to reach double those of the pre-industrial era by 2050. Even if there is no further change in climate, which would require the equivalent of a 60 per cent reduction in carbon dioxide emissions, sea levels will continue to rise for hundreds of years as the oceans warm up.
The study uses data from the United Nations Intergovernmental Panel on Climate Change and is part of the government's preparations for a UN climate change conference to be held in Kyoto in December.
The IPCC has predicted an average global temperature increase of between 1.5 and 4.5 degrees centigrade. Sir Robert said: "This may sound trivial but the estimated range of variability in global temperature over the past 1,000 years is around one degree centigrade."
Climate change may already have had an appreciable effect on the United Kingdom, said Sir Robert. Of the five warmest years in central England over the past 340 years, three have occurred in the past ten years.
Climate change scenarios suggest the south of the UK will become more windy, hotter and drier with very warm days becoming much more frequent. In contrast the northwest is likely to become wetter. Drought in the southeast and flooding in the northwest are likely to become more common. Storm damage will be frequent and coastal areas will suffer more erosion.
The report says that as temperature increases and precipitation patterns change, natural habitats, wildlife species and farming zones will steadily migrate northwards, in so far as they are able to, by around 50-80 km per decade. Many species and ecosystems will not be able to respond fast enough to the changes.
More generally, Sir Robert said the world may also experience large-scale migration of populations from areas flooded by changes in sea level: "Over six million people in Bangladesh will be displaced and several million in Egypt affected by a one metre rise in sea level, assuming populations do not increase which is unrealistic."
Sir Robert said the world must aim to reduce the emission of greenhouse gases, especially carbon dioxide. "We need to think long term. Whatever target for 2020 is agreed at Kyoto can only be a first step for the international community."