Increase in deadly rains caused by global warming – ‘If extreme rainfall events continue to intensify, we can expect to see floods occurring more frequently around the world’

Desdemona Despair

By Tim Wall
4 February 2013

(Discovery News) – Don’t let the drought in the U.S. fool you, intense rainfall around the world has been causing deadly floods in the past few years. Several have died in the current flooding in Queensland, Australia. In July 2012, the heaviest rain in decades left 37 dead in Beijing, China. More than 400 Pakistanis died in floods in September 2012. The now shriveled Mississippi River was a raging flood in 2011, killing 24 Americans in associated flash floods.

Recent extreme rains may have been intensified by the rising global average temperature, according to a recent study in the in the Journal of Climate, which examined data from more than 8,000 weather stations around the planet. The study looked for correlations between atmospheric temperature and extreme rainfall between 1900 to 2009.

“The results are that rainfall extremes are increasing on average globally,” lead author Seth Westra of the University of Adelaide said in a press release. “They show that there is a 7% increase in extreme rainfall intensity for every degree increase in global atmospheric temperature.

“If extreme rainfall events continue to intensify, we can expect to see floods occurring more frequently around the world.

“Assuming an increase in global average temperature by 3 to 5 degrees Celsius by the end of the 21st century, this could mean very substantial increases in rainfall intensity as a result of climate change,” Westra said. [more]

Increase in Deadly Rains Linked to Climate Change

ABSTRACT: This study investigates the presence of trends in annual maximum daily precipitation time series obtained from a global dataset of 8326 high quality land-based observing stations with more than 30 years of record over the period from 1900 to 2009. Two complementary statistical techniques were adopted to evaluate the possible non-stationary behaviour of this precipitation data. The first was a Mann-Kendall non-parametric trend test, and was used to evaluate the existence of monotonic trends. The second was a non-stationary generalised extreme value analysis, and was used to determine the strength of association between the precipitation extremes and globally averaged near-surface temperature. The outcomes are that statistically significant increasing trends can be detected at the global scale, with close to two-thirds of stations showing increases. Furthermore, there is a statistically significant association with globally averaged near-surface temperature, with the median intensity of extreme precipitation changing in proportion with changes in global mean temperature at a rate of between 5.9% and 7.7% per degree, depending on the method of analysis. This ratio was robust irrespective of record length or time period considered, and was not strongly biased by the uneven global coverage of precipitation data. Finally, there is a distinct meridional variation, with the greatest sensitivity occurring in the tropics and higher latitudes, and minima around 13°S and 11°N. The greatest uncertainty was near the equator due to the limited number of sufficiently long precipitation records, and there remains an urgent need to improve data collection in this region to better constrain future changes in tropical precipitation.

Global increasing trends in annual maximum daily precipitation