Is Britain warming? Just look around you

An extraordinary picture of the changing face of our landscape is shown in a special National Trust exhibition. Juliette Jowit looks at the evidence

Shafts of winter sun meekly pierce through a leafy oak tree and light up the frosty grass below. It takes a few minutes to adjust to this beautiful scene before the incongruity begins to jar: the sight of a thick green canopy in mid-winter just doesn't make sense.

The moment is caught in one of 90 photographs to go on show this month in a special exhibition by the National Trust to highlight the strange, visually wonderful and often worrying changes around Britain as a result of global warming and climate change.

From rocky 'snowlines' in winter with no snow to beachgoers running from a summer storm that might be more at home in the tropics, from wind-whipped yew trees to cormorants sheltering on dwindling nesting grounds, these photographs show how global changes could affect Britain's gardens, forests, beaches, rivers, castles and homes.

The scenes might not be as dramatic as the mass migration and wars over diminishing resources that some predict, but they do show changes which are expected to be expensive to adapt to, and sometimes deadly for native wildlife and plants.

The portraits, commissioned by the National Trust and Magnum picture agency, highlight the fact that the impacts of climate change are already visible, said Rob Jarman, the National Trust's head of sustainability. 'It's a here and now issue: it's not some future climate we're going to have to respond to,' said Jarman.

The exhibition, which opens in London and goes on tour to Nottingham, north Wales, Bristol and Belfast, will also include advice on how the National Trust is trying to adapt to the changing environment at its 300 houses and gardens and thousands of miles of coastline and swaths of open countryside - and how visitors can do the same.

The trust has been praised for being more active than most organisations in preparing for change - from the need to plant flowers that need less water and provide new habitats for species forced north to find cooler weather, to improving gutters to cope with heavier rainfall and stamping out pests that thrive in a milder climate.

However, Europe's biggest conservation organisation is taking a controversial stand at a time when some scientists have expressed concern about the 'Hollywoodisation' of climate change and the trend to blame all weather events on the problem.

'What we're saying is we're having to adapt to change,' said Jarman. 'A lot of the things we have taken for granted are proving much more vulnerable to fluctuation than we have experienced before, and we have got to get used to that. We have got to do that almost regardless of global warming and climate change.'

There could also be concern at using snapshots in time to illustrate long-term trends, a problem Jarman acknowledges - particularly with regard to two stunning shots comparing the top of a mountain in Snowdonia, north Wales, which was covered in snow 10 years ago and is shown absolutely bare of snow in a second photograph taken last winter.

'On one day you go up there could be snow, or it could be rocky, but what we can explain is it will be harder and harder to find that day that there's snow,' Jarman said.

This week the United Nations is expected to publish its latest global report on rising temperatures. A separate study by the peace charity International Alert warns that 61 countries, from Egypt and Turkey to the Maldives, are at risk of conflict as crop failures, disease, drought, flooding and other disasters trigger tense battles over precious resources.

· Exposed: Climate Change in Britain's Backyard is at Hoopers Gallery, London EC1, 12 April-11 May; Nottingham Castle, 19 May-1 July; Penrhyn Castle, near Bangor, 7 July-2 September; Bristol Museum and Arts Gallery, 2 November-2 December; and Waterfront Hall, Belfast, January 2008.

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