Hot weather records falling left and right

By Andrew Freedman

* Heat strikes back: Full Forecast | Classic D.C. snow photo *



Temperature anomalies (degrees Celsius) for January to June 2010. Red dots indicate warmer-than-average conditions, and blue dots indicate areas that were colder than average. Credit: NCDC/NESDIS/NOAA.

As she did for winter 2010, this summer Mother Nature has truly outdone herself, this time by brewing up a miserable combination of heat and humidity that has enveloped not only the northeastern U.S., but much of the Northern Hemisphere as well. As Ian Livingston reported on Saturday, July was the warmest single calendar month of all time in Washington (tied with July 1993). The warmest day in the city was July 7th, when the temperature soared to 102 degrees Fahrenheit at Reagan National Airport. The day before, the temperature rose to a sweltering 105 F at Baltimore-Washington International Airport.

In total, Washingtonians sweated through 21 July days during which temperatures exceeded 90 degrees. Baltimore set a new record for the average daily high temperature, which was 92.5 degrees, beating July 1988's 91.9 degrees.

New York City and Philadelphia experienced their second-warmest months since records began in the late 1800s. New York recorded an average monthly temperature of 81.3 degrees, which was 4.8 degrees above the July average. The warmest July on record there occurred in 1999, when the average temperature was 81.4 degrees.

Worldwide, this year already stands second to 2007 for the largest number of all-time high-temperature records set in one year, including the searing 128.3 (!!!) degrees recorded in MohenjuDaro, Pakistan, on May 26. If the World Meteorological Organization verifies this reading, it will go down as the hottest temperature ever recorded in Asia.

As detailed by Jeff Masters of Weather Underground, all-time high-temperature records have fallen from Finland to Russia to Sudan. Moscow in particular has been suffering through an unprecedented heat wave, which has featured the city's first-ever 100-degree plus reading, and poor air quality due to smoke from nearby wildfires.



Flames travel along a parched forest floor near a suburb of the town of Voronezh some 500 km (294 miles) south of Moscow, Sunday, Aug. 1, 2010. (AP Photo/Mikhail Metzel)

Although long-term global climate change doesn't directly cause a particular heat wave, the pronounced warming trend in global average temperatures during the past century has increased the odds of more frequent and severe heat waves. For example, scientists have partially attributed the deadly 2003 European heat wave, which killed tens of thousands, to manmade climate change.

Despite cooler-than-average conditions in parts of the Southern Hemisphere, thus far 2010 ranks as the warmest year on record on a global basis, with the warmest March, April, May and June ever recorded. Furthermore, high-temperature records have occurred twice as often as low-temperature records in the U.S. during the past 10 years, according to a study published last year.

As Masters noted, "Of the 229 countries with extreme coldest temperature records, 14 of these records have occurred in the past ten years (6% of all countries). There have been five times as many (74) extreme hottest temperature records in the past ten years (33% of all countries)" as extreme coldest temperature records.

Part of the warmth this year has been due to the influence of an El Nino event in the Pacific Ocean, which featured warmer-than-normal water in the equatorial tropical Pacific. However, the El Nino has transitioned to its opposite phase -- La Nina -- that is characterized by cooler-than-average waters. La Nina conditions can cool global temperatures, and may keep 2010 from becoming the warmest year on record.

Influence on public opinion?

Much has been made of the recent decline in public concern about global warming, and support for policies to combat climate change. It will be interesting to see if the hot summer will affect the public opinion polls, albeit for reasons that are far from scientifically accurate.

As detailed in a New York Times article on Sunday, daily weather conditions do influence people's thoughts on long-term climate change, despite the tenuous links between the weather on a particular day and long-term climate trends. For example, this past winter, when Washington was buried in snow and Europe suffered through an unusually cold winter, many polls showed a decline in concern about global warming.

The Times article said that psychologists have found "a high correlation between a participant's stance on global warming and how he perceived the outdoor temperature on the day he was asked about it."

For people at either extreme - that is, those alarmed by or dismissive of climate change - the local weather isn't going to have much influence, although they may use it conveniently to drive home a point.

But for those in the mushy middle - about a third of the overall population - the local weather, rightly or wrongly, influences their thoughts on the topic, often subconsciously.

The views expressed here are the author's alone and do not represent any position of the Washington Post, its news staff or the Capital Weather Gang.