The World Meteorological Organization on "Unprecedented sequence of extreme weather events"

The World Meteorological Organization (WMO) issued a statement yesterday (11 August 2010) saying that "the sequence of current events matches IPCC [Intergovernmental Panel on Climate Change] projections of more frequent and more intense extreme weather events due to global warming."

After a section on "Unprecedented sequence of extreme weather events," the WMO said in its statement on Current Extreme Weather Events (emphasis added):

"Several diverse extreme weather events are occurring concurrently around the world, giving rise to an unprecedented loss of human life and property. They include the record heatwave and wildfires in the Russian Federation, monsoonal flooding in Pakistan, rain-induced landslides in China, and calving of a large iceberg from the Greenland ice sheet. These should be added to the extensive list of extreme weather-related events, such as droughts and fires in Australia and a record number of high-temperature days in the eastern United States of America, as well as other events that occurred earlier in the year.

The heatwave in the European part of the Russian Federation is associated with a persistent pressure ridge that appeared in June 2010. Initially, it was associated with the Azores high, but later was reinforced by a strong inflow of warm air from the Middle East. More than 20 daily temperature records were broken including the absolute maximum temperature in Moscow. The high temperatures triggered massive forest and peat fires in the European part of the country. Some villages were burned completely, with smoke and smog adversely and greatly affecting the health and well-being of tens of millions of people.

The floods in Pakistan were caused by strong monsoon rains. According to the Pakistan Meteorological Department, the instant rain intensity reached 300 mm [11.8 inches] over a 36-hour period. The strong monsoon rains led to the highest water levels in 110 years in the Indus River in the northern part of the country, based on past records available from 1929. More areas in central and south Pakistan are affected by the floods. The death toll to date exceeds 1 600 and more than 6 million people have been displaced. Some reports indicate that 40 million citizens have been affected by the floods.

China is also experiencing its worst floods in decades. The recent death toll due to the mudslide in the Zhouqu county of Gansu province on 7 August 2010 exceeded 700, with more than 1 000 people missing. In addition, 12 million people are reported to have lost their homes owing to the recent floods.

On 5 August 2010, the MODIS sensor on NASA’s Aqua satellite detected calving from the Petermann Glacier in northern Greenland. The largest chunk of ice to calve from the glacier in the past 50 years of observations and data (since 1962) measures more than 200 sq. km. Tens of thousands of icebergs calve yearly from the glaciers of Greenland. However, this one is very large and because of its size more typically resembles icebergs in the Antarctic.

Climate extremes have always existed, but all the events cited above compare with, or exceed in intensity, duration or geographical extent, the previous largest historical events. According to Roshydromet, studies of the past climate show no record of similar high temperatures since the tenth and eleventh centuries in Ancient Russia.

The occurrence of all these events at almost the same time raises questions about their possible linkages to the predicted increase in intensity and frequency of extreme events, for example, as stipulated in the IPCC Fourth Assessment Report published in 2007. The Report stated that “…the type, frequency and intensity of extreme events are expected to change as Earth’s climate changes, and these changes could occur even with relatively small mean climate changes. Changes in some types of extreme events have already been observed, for example, increases in the frequency and intensity of heat waves and heavy precipitation events” (Summary for Policy Makers, WG I, FAQ 10.1, p. 122).

Similar questions were also frequently asked following the summer heatwave in Europe in 2003, which was the hottest in continental Europe since at least 1540. In a number of studies, particularly “Human contribution to the European heatwave of 2003” (Nature, 2004) Stott, Stone and Allen stated that “it is very likely (confidence level >90%) that human influence has at least doubled the risk of a heatwave” such as that which occurred in 2003. As Beniston and Diaz report in their paper published in Global and Planetary Change in 2004: “although a single extreme event, however intense, is by no means proof of global warming, the lessons that can be learned from the recent heat wave could be used to help shape future policy response. […] Society will face considerable challenges in trying to cope with heat waves of similar or even greater magnitude to 2003 that are projected to become more common in the latter decades of the 21st century.”

A series of recent publications indicate that main patterns of atmospheric variability exhibit noticeable changes and are predicted to be different in a warmer climate.... "

See Current Extreme Weather Events for the WMO's full statement.