•  uxbridge, canada
• Thursday, February 17, 2011
• Inter Press Service

Human-induced heating of the planet has already made rainfall more intense, leading to more severe floods, researchers announced Wednesday.

Two new studies document significant impacts with just a fraction of the heating yet to come from the burning of fossil fuels. Fortunately, another new report shows the world can end its addiction to climate-wrecking fossil-fuel energy by 2050. 'Warmer air contains more moisture and leads to more extreme precipitation,' said Francis Zwiers of the University of Victoria.

Extreme precipitation and flooding over the entire northern hemisphere increased by seven percent between 1951 and 1999 as a result of anthropogenic global warming. That represents a 'substantial change', Zwiers told IPS, and more than twice the increase projected by climate modeling.

Zwiers and Xuebin Zhang of Environment Canada used observations from over 6,000 weather stations to measure the impact of climate warming on the intensity of extreme precipitation for the first time. The study was published Wednesday in the journal Nature.

The planet is currently 0.8 degrees C hotter from the burning of fossil fuels. However, global temperatures had not yet started to increase in 1951, the first year of rainfall data Zwiers and Xuebin examined. By 1999, global temperatures had climbed by about 0.6 degrees C. The average temperature increase over that 50-year period is relatively small compared to the present but major impacts have been documented in terms of storm and flood damage even with this small increase in temperatures.

This suggests that the Earth's climatic system may be more sensitive to small temperature increases than previously believed. The global costs of extreme weather events shot up from less than five billion dollars a year during the 1950s to 45 billion dollars a year during the 1990s, according to Munich Re, a major reinsurance company in Germany. Not all of this increase is due to climate change. Some is due to population and infrastructure growth and better disaster reporting. However, the number of significant floods has tripled in the past 30 years.

Those costs came during a time when the planet was cooler than present - a period of 'relatively weak anthropogenic forcing', Zwiers said. But as temperatures climbed, there was a sharp increase in intense rainfall events during the 1990s, suggesting an acceleration in flooding and damaging rainfall. Zwiers said it is too soon to know if the 1990s increase represents a new trend.

Global temperatures are guaranteed to increase further from today's 0.8 degrees C to at least 1.0 degree C by 2020. This will boost the amount of water vapour and heat in the atmosphere, which are the fuel for even more and harder rainfall events.

Scientists have long known extreme events would increase with a hotter planet but have maintained that a single flood or storm could not be explicitly linked to climate change. Now another study published Wednesday in Nature lays odds they've found the 'smoking gun' behind Britain's severe flooding in 2000.

During the fall of 2000, the UK experienced some of its most damaging floods and wettest weather since the first records began in 1766. Using the distributed computing power from thousands of personal computers around the world, researchers at Oxford University and others determined that human emissions of greenhouse gases had more than doubled the odds of the devastating 2000 flood.

'We simulated a parallel world in which there were no greenhouse gas emissions,' said lead researcher Pardeep Pall of Oxford University. Thousand of computer simulations were tested against reality and the results revealed that climate change more than doubled the odds of the 2000 flooding, Pall said at a press conference.

© Inter Press Service (2011) — All Rights Reserved. Original source: Inter Press Service