European cities need to adapt now to future drought, floods

European cities in the second half of the century may face significantly worse heatwaves, deepening drought, and more river floods if global temperatures continue to rise - something they need to begin preparing for now, researchers said on Wednesday.

Global temperatures are already 1 degree Celsius above pre-industrial levels, and are projected to rise to 3 degrees or more this century unless emissions are rapidly curbed, according to the United Nations.

If that rise happens, central European cities will see the greatest increase in temperature during heatwaves - of between 2 degrees and 14 degrees Celsius, depending on the rise in global temperatures - researchers from Britain's Newcastle University said.

The researchers, who studied the impact of global temperature hikes of between 2.6 degrees and 4.8 degrees Celsius, said southern European cities will see the biggest increases in the number of heatwave days, however.

Droughts also will become longer and drier and - in the worst-case scenario - will reach northern Europe, they said.

"We are already starting to see an increase in heatwaves and drought and flooding, so cities need to start thinking about adapting now, or even yesterday," said Selma Guerreiro, lead author of a study published in the journal Environmental Research Letters.

Much of southern Europe experienced lengthy droughts last year, which caused widespread fires and decimated crops. Rome turned off its public fountains and only narrowly avoided rationing water supplies to homes.

Britain and Germany have experienced severe flooding in recent years, and Paris was forced to evacuate 1,500 people when the Seine flooded last month.

"There is an awful lot of extreme weather hitting us," said co-author Richard Dawson.

The drought now threatening water supplies in Cape Town is a stark example of how cities need to adapt long before a drought or flood hits.

Once a drought kicks in and the water starts to run dry, it may be too late to build another reservoir or desalination plant, Dawson said. Heatwaves and floods pose similar problems.

"So you have to really start thinking longterm in terms of preparing and adapting cities for any sort of climate event," he told the Thomson Reuters Foundation.

Cities can build large infrastructure such as reservoirs or flood barriers, or can make smaller incremental changes repeatedly, he said.

Buildings also could be designed to be naturally cooler, use less water, or be more resilient to flooding. People, too, can change their behaviour to use less water, he said.

"A combination of all of those things is probably the best way to (adapt)," Dawson said.

If a city can reduce its need for water, or its exposure to climate risks - by cutting the number of people living in flood plains, for example - then its overall vulnerability goes down, he said.

"And if we make buildings more resilient to floods and heat, and more effective at using water resources, then we can create more headroom for adaptation to more extreme events," he said.