The latest scientific projections launched by Environment Secretary, Hilary Benn, provide the most detailed picture to date of the threat facing Britain from soaring summer temperatures, more extreme weather and rising sea levels.

The UK Climate Projections 2009, based on Met Office science, illustrate the extent of the changes the UK might face in the absence of global action to cut emissions - warmer and wetter winters, hotter and drier summers, increased risk of coastal erosion and more severe weather.

The projections show a range of climate change scenarios up until the end of the century, based on three possible greenhouse gas emissions pathways - high, medium and low. Broadly speaking the world's emissions are currently equivalent to the medium pathway, although there is a risk we could still be heading for the high scenario. While we cannot be absolutely certain what will happen in the future, these projections show the probabilities of potential changes for the UK.

These projections show a future that must be avoided. The medium emissions scenario shows that within the lifetimes of our children and grandchildren - by the 2080s - we could be faced with:

-       An increase in average summer temperatures of between two and six degrees Celsius in the south east with a central estimate of four degrees
-       A 22 percent decrease in average summer rainfall in the south east  - which is already water stressed - and an increase of 16 percent in average winter rainfall in the north west, with increases in the amount of rain on the wettest days leading to a higher risk of flooding
-       Sea level rise of 36 centimetres
Temperatures would rise even more under a high emissions scenario and could be up to 12 degrees Celsius warmer on the hottest summer days, with peak summer temperatures in London regularly hitting over 40 degrees.

These findings are sobering.  Without decisive action there will be an increase in water shortages, heat stress and floods. All of these would have a severe impact on people's health and quality of life, the economy and the natural environment.

The message is clear that to avoid dangerous levels of climatic change in the second half of this century, we need a strong global deal to restrict global temperature rises to less than two degrees (above pre-industrial levels). This would mean reducing emissions below those in the projections.

At the same time the projections show that some climate change is now inevitable whatever we do.  Past emissions are likely to make summers over two degrees hotter in southern England by the 2040s (compared to the 1961-1990 average). Even at a two degree global temperature increase we would need to adapt the way we live and work - for example the 2003 heatwave saw an increase of two degrees above average temperature and caused 35,000 deaths across Northern Europe.

Environment Secretary, Hilary Benn said: 'There is no doubt about it, climate change is the biggest challenge facing the world today. Climate change is already happening. The hottest ten years on record globally have all been since 1990. This landmark scientific evidence shows not only that we need to tackle the causes of climate change but also that we must deal with the consequences. The projections will allow us to make sure we have a resilient infrastructure to cope - whether it's the design of school buildings or protection of new power plants, maintaining the supply of drinking water, adjusting ways of farming for drier summers or understanding how our homes and businesses will have to adapt.'

Energy and Climate Change Secretary, Ed Miliband said: 'The science is pushing us harder than ever towards an ambitious global deal in Copenhagen this December.  These projections add to the overwhelming body of scientific evidence that says mankind must cut carbon emissions now to prevent a future of extreme weather patterns which could threaten the livelihoods of people across the world as well as put plants, animals and sea life in peril. Now is the time to act.'

The UK Climate Projections 2009 are available on the web and will be used as part of risk-based planning for local government, utilities and other organisations. Defra is rolling out an extensive training programme to help organisations make best use of the projections. It has also launched a consultation  on the use of its new Adaptation Reporting Power, which will require over 100 organisations  providing a public service to report on the risks climate change poses to their operations and the plans they have in place to respond. For the first time Government departments will have to publish their plans to adapt by spring 2010.