UK's 'sobering' climate forecast

Low-lying areas of the UK would be threatened by a sea level rise

The UK could face major flooding and tropical temperatures by the year 3000 if greenhouse gas emissions are not sharply reduced, a new study says.

The report, from the Tyndall Centre for Climate Change Research, claims Britain could look radically different with sea levels rising as much as 11.4m.

The study was commissioned by the Environment Agency.

However, other researchers cautioned that it was extremely difficult to make climate forecasts so far in advance.

The study, which was led from the University of East Anglia (UEA), modelled the climate impacts of three possible scenarios:

• What would happen if our emissions were "minimised", meaning that they were decreased steadily to zero between 2020 and 2200
• What would happen if we took no action to reduce our emissions and continued to burn our remaining reserves of conventional fossil fuels by the year 3000
• What would happen if our emissions increased by burning not just conventional fossil fuels but by exploiting unconventional reserves as well, such as methyl hydrates and oil shales

Sobering outcomes

The only scenario that avoided "dangerous climate change" was the minimum emissions scenario, allowing for one-quarter of known reserves of fossil fuels to be used.

This would result in a small increase in emissions up to 2025 before emissions were then phased out by 2220.

The other scenarios produced much more sobering outcomes.

The worst-case scenario would see global and regional warming, raising the world's average surface temperature by 15C and lifting sea levels by more than 11m.

Even in the "business as usual", middle scenario, increased emissions would probably precipitate abrupt climate change events, such as the weakening and shifting of currents in the Atlantic Ocean.

Sea water acidity would also increase dramatically, posing a major threat to marine organisms.

Dr Tim Lenton, the UEA lead author on the paper and a climate change modeller, said: "If we follow business-as-usual then we will commit future generations to dangerous climate change, and if we exploit unconventional fossil fuels we could return the Earth to a hot state it hasn't seen since 55 million years ago.

"The best-case scenario, keeps the temperature rise in the year 3000 at 1.5 degrees of warming and sea level rise to under a metre, because it has avoided the Greenland ice sheet melting."

The choices we make in the coming decades have implications that play out over the next thousand years and beyond that Dr Lenton, UEA

Barbara Young, the chief executive of the Environment Agency, commented: "We are running out of road on decision-making - unless we dramatically change the use of fossil fuels then we will be committing future generations to the most severe impacts of climate change."

This is one of the first projects to look at possible climate impacts well into the next century. The current projections used by the UN's Intergovernmental Panel on Climate Change go no further than 2100.

'No economic data'

Professor Geoff Jenkins, formally of the UK's Met Office, told the BBC News website about the difficulties of making very long-term projections.

"The greatest uncertainties are the ones about predicting emission use in the future. We don't know how populations are going to grow, how energy use will grow, whether that will be increasingly reliant on fossil fuels, or whether we'll be smart enough to find some good alternatives," he said.

Those openly sceptical of this type of modelling find little merit at all in the exercise.

"I would describe this as garbage in, garbage out," said Julian Morris, director of the International Policy Network.

"There is no attempt to take into account actual economic circumstances that might pertain in 2100. Perhaps that isn't surprising since trying to estimate what is going to happen by 2100 is going to be very difficult, let alone imagining what might happen by the end of the millennium. We really are way out into 'terra incognita'."

But Dr Lenton countered that there were real merits to this type of study.

"What we are trying to do is project where the Earth's system would be heading if we chose to use a certain amount of fossil fuel," he explained.

"The main result is that the choices we make in the coming decades have implications that play out over the next thousand years and beyond. If we start to make a serious reduction in emissions, then we could avoid dangerous climate change thresholds and leave a stable climate in the year 3000."