Two independent studies suggest greenhouse gas emissions are linked to more frequent heavy rainfall.
The studies, which appear today in the journal Nature, highlight the impact humans are having on extreme weather events, and come less than a month after a set of major flooding events around the world.
In one of the studies, scientists from the University of Victoria in Canada and the University of Edinburgh in Scotland, looked at rainfall totals collected between 1951 and 1999 from 6000 rain gauges across the northern hemisphere.
They found extreme rains and floods had increased by 7 per cent in the second half of last century across the Northern Hemisphere.
They then ran computer models with climate change factored in, which correlated with the rainfall pattern they observed.
"We saw that there was a pattern of change that is simulated by the climate models that is detectable in observation. So that suggests that humans influence the intensity of precipitation extremes," says study co-author Dr Francis Zwiers.
Prior to this time there had not been a study that had formally identified this human effect in extreme rainfall events.
"It has often been suggested that the changes in precipitation extremes are likely linked to greenhouse gas increases," says Zwiers.
"Our research provides the first scientific evidence that human-induced greenhouse gas increases have contributed to [more intense rainfall] events over large parts of the Northern Hemisphere."
Rainfall in the Southern Hemisphere
Dr Roger Stone, a professor in climatology and water resources at the University of Southern Queensland says "it's a robust study".
"It's part of the scientific discovery that we're going through with this interesting area of research," he says.
Stone says it is reasonable to assume that if climate change is causing more heavy rainfall in the northern hemisphere, it would also be happening in Australia.
"The CSIRO models have already demonstrated that ... certainly for a region just such as south-east Queensland, that we do get increased, enhanced deep convection under a climate change scenario," he says
In the second study appearing in Nature, an international team of scientists used computer models to replicate the events that led to widespread flooding over parts of the United Kingdom in October-November 2000.
They found that in nine out of ten cases their model suggested human-induced global warming increased the risk of flooding in the region by more than 20 per cent and in two out of three cases by more than 90 per cent.
More work to be done
Professor Roger Pielke Jr of the University of Colorado says: "It is exciting to see the application of innovative approaches to connecting the dots between greenhouse gas emissions and damage from extreme events."
But he warns the methods used in the study are still in their "infancy".
Professor Tim Palmer of Oxford University agrees.
"There remains considerabe uncertainty about the magnitude of future climate change, both regionally and globally, and these results should not be interpreted as implying that the current generation of climate models is good enough," he says.
"Refining our models, in order that we can simulate climate extremes with more fidelity, must be a priority for the future."