Two thousand people killed during a summer heatwave; mosquitoes at Heathrow carrying malaria parasites picked up from infected holidaymakers; road-builders switching to a melt-resistant tarmac.

If anyone is in any doubt that climate change is already affecting the UK, this is your answer. "It's not just a question of impacts in the future. We are actually looking at impacts right now," said Chris West, director of the UK Climate Impacts Programme. His job is to advise the government, private and voluntary sectors on how changes to the UK's climate will affect how they operate.

The most severe and immediate impacts of climate change will hit developing countries. But the rich, developed world will also be affected, and adapting to the changes will be extremely expensive.

The Intergovernmental Panel on Climate Change's (IPCC) Fourth Assessment report last year included a detailed breakdown of impacts for regions around the world. Europe must prepare for warmer, wetter winters in the north and hotter, drier summers in the south. That is going to put severe demands on water in southern Europe and will mean more crop failures due to drought. Also, people will suffer directly. The 2003 summer heatwave killed 2,000 people in the UK alone. Winter floods will increase in maritime regions and flash floods will be more common across the continent. Coastal flooding linked to sea-level risk will threaten up to 1.6 million more people each year by 2080.

Like Europe, the US will experience the greatest warming in winter at high latitudes and hotter summers in the south-west, according to the IPCC. Climate modellers expect extremes of hot weather, wildfires, water stress, insect outbreaks and a range of health problems to increase; but there will also be benefits. Crop yields will rise 5-20% during the next few decades as the warming climate opens up more land for cultivation.

But probably the hardest hit of the developed regions will be Australia. In temperate regions, the IPCC climate models predict up to 32 more days in a year over 35°C (95F) by 2020 and up to 84 more by 2050. Water security will become a major concern with prolonged droughts a regular feature, while extreme weather and sea-level rise will cause problems for Australia's predominantly coastal population. Water flow in the Murray-Darling river basin - Australia's largest, which accounts for around 70% of irrigated crops and pastures - is expected to fall by between 10 and 25% by 2050.