August 19, 2010

UN: ‘Urgent’ Probe Of Weather Shifts Behind Disasters Needed

UN climate and weather agencies said Wednesday that climate scientists must take an urgent stance on studying the changes in atmospheric currents that have been linked to flooding in Pakistan and wildfires in Russia.

Ghassem Asrar, director of the World Climate Research Program, told AFP that changes -- known as blocking episodes -- in the currents can prevent humidity or hot weather from dispersing as it should.

Those events can lock heavy rain or heat waves over a particular region, in turn potentially growing into extreme weather events that scientists expect to happen more frequently with global warming.

Asrar said that European researchers had constructed a model of the blocking pattern in atmospheric currents and resulting weather behind the Pakistani rains and Russian heat wave a few weeks in advance.

The researchers "clearly flagged this formation and kept track of it," said Asrar. "We know for sure that the two events in Pakistan and Russia are linked," he added.

Asrar's research program is partially linked with the World Meteorological Organization (WMO).

Asrar and the WMO underlined that the intense monsoons in Pakistan, the Russian heat wave, China's rain-induced landslides and giant iceberg that split in Greenland in recent weeks were exceptional even by the standards of naturally-occurring climate extremes.

The WMO said they are an "unprecedented sequence of events" that either compare to, or "exceed in intensity, duration or geographical extent, the previous largest historical events."

"This poses an urgent question for climate science: whether the frequency and longevity of the blocking episodes are going to change," the WMO said in a statement.

Asrar argued that evidence behind the impact and shift in blocking episodes in atmospheric currents as well as the changing role of El Nino and La Nina currents over the Pacific Ocean adds to an urgent need for answers.

"Absolutely, because of the impact on life and property, if you look at what happened in Pakistan and China," he added.

Scientists typically hesitate to blame a single weather event on climate change, which measures longer term shifts over periods of years or decades.

In the past several weeks Moscow was trapped in a record-setting heat wave with temperatures soaring to 104 degrees Fahrenheit and daily highs well above 86 F for over a month. The event triggered a nationwide crisis and destroyed nearly a quarter of the country's crops.

Asrar said the priorities for weather and climate science were "transforming very rapidly."

Experts are predicting that the highly disruptive La Nina pattern would last at least until early 2011.

The La Nina phenomenon lasts, on average, from nine to 12 months, according to Rupa Kumar Kolli, a researcher at the WMO. "At the moment, we don't have really reliable indicators on how long it will last -- at least until the end of this year," Kolli said.

"La Nina conditions are expected to strengthen and last through (the) Northern Hemisphere winter," the NOAA said earlier this month.

The El Nino/La Nina cycle is caused by a buildup of warm water that surges from the western Pacific to the eastern Pacific before cooling. La Nina is associated with greater-than-usual monsoons in south Asia, drought or water stress in South America and increases in Atlantic cyclones. The Last La Nina occurred in 2007-2008