Worldwide, more than 145 million people live less than 1 metre above high sea level. As global air and ocean temperatures continue to warm, the combination of melting land-based ice and the water’s thermal expansion causes sea levels to rise. Recent studies suggest global sea level could be about 40 cm higher by 2100 if global temperatures rise by 2 °C, and as much as 80 cm higher for a 4 °C warming. However, there are substantial uncertainties in these predictions, because of the difficulty of estimating the long-term response of major ice sheets. Low-lying densely populated countries such as Bangladesh will be especially vulnerable to coastal flooding.

Higher sea levels provide an elevated platform for storm waves, increasing flood risks for low-lying coastal areas. Changes in storms themselves are harder to predict. An important factor in storm formation is the Equator-to-pole temperature difference. Polar regions are warming faster, reducing the temperature difference – which should reduce the average number of storms. But once a storm system has formed, its growth depends largely on heat drawn from its surroundings. Scientists think overall storm numbers may fall, with fewer weak storms in particular. But storms that do occur could be stronger, with more of them growing into hurricanes. Climate models suggest hurricane rainfall intensity and wind speeds are likely to increase.

Changing geographical patterns of rainfall resulting from higher temperatures are harder to predict than the temperature changes themselves, and there are large uncertainties involved. However, changes in the overall behaviour of the water cycle can be described with more confidence, and scientists can draw on well-understood physical laws as well as climate model results. Scientists expect increased temperatures to result in an increase in global average rainfall and an even greater increase in average rainfall intensity. Much of the additional amount will fall over the oceans, but heavier downpours are also expected over land – putting many regions at greater risk of flash flooding. Areas close to rivers could be especially vulnerable.

In Canada, Alaska and Siberia much of the ground is permanently frozen – ‘permafrost’. Above-average warming is expected in these polar regions and is likely to defrost surface layers of permafrost in many regions. Thawing has already begun in some areas. If global temperatures rise by 4 °C, scientists predict that near-surface permafrost could disappear almost completely from northern Siberia, with reduced areas in Canada and Alaska too. This could threaten the foundations of many homes and buildings, making it more expensive to maintain infrastructure. Reductions in alpine permafrost are also likely, potentially increasing the risk of landslides as sections of mountainside become less stable.

Scientists think climate change could increase the risk of forest fires in many regions of the world. The combination of increased evaporation and more frequent and severe droughts is likely to leave forests and other vegetation with reduced levels of moisture for longer periods of time. This increased availability of dry tinder, together with higher average temperatures and more frequent heat waves, could make forests and shrub land more vulnerable to fire. Scientists estimate that a 2 °C rise in global temperature could increase fire danger in some areas of South America, Africa and Australia, while a 4 °C rise could see danger zones spreading across many populated regions including the US and southern Europe.

Beate Bowron is working with Inuit communities in northern Canada to help them adapt to the impacts of climate change. The Arctic is one of the fastest-warming areas of the world. As temperatures rise, buildings constructed on frozen land will begin to subside and access routes across melting ice will become more perilous.

So Beate talks to community elders to find out how they are adapting. By combining elders’ knowledge with predictions from scientists, she has developed a code of best practice which other communities can use to adapt in the future. It’s chilly work, says Beate: ‘Sometimes I have to tackle temperatures as low as –50 °C.’

• World Meteorological Organisation