Even a slight rise in global temperatures may lead to extreme weather conditions, say scientists who found that just half a degree Celsius of warming has led to an increase in heat waves and heavy rains across the planet.

Researchers compared two 20-year periods 1960-79 and 1991-2010 between which average global temperatures jumped 0.5 Celsius. They found that several kinds of extreme weather gained in duration and intensity.

The hottest summer temperatures increased by more than 1 degree Celsius across a quarter of Earth's land areas, while the coldest winter temperatures warmed by more then 2.5 degree Celsius, researchers said.

Researchers also found that the intensity of extreme precipitation grew nearly 10 per cent across a quarter of all land masses, and the duration of hot spells-which can fuel devastating forest fires-lengthened by a week in half of land areas.

“We have to rely on climate models to predict the future,” said lead author Carl-Friedrich Schleussner, a researcher at the Potsdam Institute of Climate Impact Research in Germany.

“But given that we now have observational evidence of around one degrees Celsius warming, we can also look at the real-life impacts this warming has brought,” he added.

Global warming caused mostly by the burning of fossil fuels began slowly in the early 19th century with the onset of industrialisation, but has accelerated rapidly over the last 50 or 60 years.

“With the warming the world has already experienced, we can see very clearly that a difference of 0.5 degrees Celsius really does matter,” said Erich Fischer, a scientist at Swiss Federal Institute of Technology in Switzerland.

Earlier researches had also concluded that two degree Celsius of warming would – compared to 1.5 Celsius – double the severity of crop failures, water shortages and heat waves in many regions of the world.

It also found that holding the rise in temperature to 1.5 degrees Celsius would give coral reefsthe cornerstone of ecosystems that sustain half-a-billion people and a quarter of marine wildlife – a fighting chance of adapting to warmer and more acidic seas.