WMO: “Unprecedented sequence of extreme weather events … matches IPCC projections of more frequent and more intense extreme weather events due to global warming.”
Both NASA and the World Meteorological Organization both have excellent posts I’m going to excerpt at length. The first, from NASA’s Goddard Institute for Space Studies website, is titled
The July 2010 global map of surface temperature anomalies (Figure 1), relative to the average July in the 1951-1980 period of climatology, provides a useful picture of current climate. It was more than 5°C (about 10°F) warmer than climatology in the eastern European region including Moscow. There was an area in eastern Asia that was similarly unusually hot. The eastern part of the United States was unusually warm, although not to the degree of the hot spots in Eurasia.
There were also substantial areas cooler than climatology, including a region in central Asia and the southern part of South America. The emerging La Ni±a is now moderately strong, as evidenced by the region cooler than climatology along the equator in the eastern and central Pacific Ocean.
The global average July 2010 temperature was 0.55°C warmer than climatology in the GISS analysis, which puts 2010 in practically a three way tie for third warmest July. July 1998 was the warmest in the GISS analysis, at 0.68°C.
The 12-month running mean of global temperature (Figure 2 [posted at the top]) achieved a record high level during the past few months. Because the current La Ni±a will continue at least several months, and likely strengthen somewhat, the 12-month running mean temperature is expected to decline during the second half of 2010.
Will calendar year 2010 be the warmest in the period of instrumental data? Figure 3 shows that through the first seven months 2010 is warmer than prior warm years. The difference of +0.08°C compared with 2005, the prior warmest year, is large enough that 2010 is likely, but not certain, to be the warmest year in the GISS record. However, because of the cooling effect of La Ni±a in the remainder of the year, there is a strong possibility that the 2005 and 2010 global temperatures will be sufficiently close that they will be practically indistinguishable.
Climate anomalies in the Northern Hemisphere summer of 2010, including the heat in Eastern Europe and unusually heavy rainfall and floods in several regions, have received much attention. Are these climate anomalies an example of what we can expect global warming to look like? Maps of temperature anomalies, such as Figure 1, are useful for helping people understand the role of global warming in extreme events.
The location of extreme events in any particular month depends on specific weather patterns, which are unpredictable except on short time scales. The weather patterns next summer will be different than this year. It could be a cooler than average summer in Moscow in 2011.
But note in Figure 1, and similar maps for other months, that the area warmer than climatology already (with global warming of 0.55°C relative to 1951-1980) is noticeably larger than the area cooler than climatology. Also the magnitude of warm anomalies now usually exceeds the magnitude of cool anomalies.
What we can say is that global warming has an effect on the probability and intensity of extreme events. This is true for precipitation as well as temperature, because the amount of water vapor that the air carries is a strong function of temperature. So the frequency of extremely heavy rain and floods increases as global warming increases. But at times and places of drought, global warming can increase the extremity of temperature and associated events such as forest fires.
The paper describing the GISS analysis of global temperature has been revised in response to reviewer suggestions and submitted to Reviews of Geophysics. The biggest change in the paper is inclusion of an additional analysis is which global temperature change is based only on stations located in “pitch dark” regions, i.e., regions with satellite-observed brightness below the satellite’s detection limit (1 Î¼W/m2/sr/Î¼m). Our standard analysis uses stations with satellite-observed brightness below 32 Î¼W/m2/sr/Î¼m. This more strict brightness limitation has no significant effect on analyzed global temperature change, providing additional confirmation that any urban effect on the GISS analysis of global temperature change is small.
The second, from the World Meteorological Organization, is titled:
Several regions of the world are currently coping with severe weather-related events: flash floods and widespread flooding in large parts of Asia and parts of Central Europe while other regions are also affected: by heatwave and drought in Russian Federation, mudslides in China and severe droughts in sub-Saharan Africa. While a longer time range is required to establish whether an individual event is attributable to climate change, the sequence of current events matches IPCC projections of more frequent and more intense extreme weather events due to global warming. The Monsoon activity in Pakistan and other countries in South-East Asia is aggravated by the la Ni±a phenomenon, now well established in the Pacific Ocean….
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 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. Several reports state that climate phenomena such as El Ni±o and La Ni±a will be noticeably different from those observed in the past. This poses an urgent question for climate science: whether the frequency and longevity of the blocking episodes are going to change. Research on extreme climate events is one of the focuses of the World Climate Research Programme.
Kudos for NASA and WMO for spelling this out.