Record-Breaking Weather? What Else Is New?

Between Dec. 27 and Jan. 11, a record 17 inches of rain fell in Los Angeles. Now the storms have started up again; the city needs only about 5 more inches before June 30 to make this the rainiest year since 1883-84.

In Boston, 43 inches of snow fell during the month of January, the most reported there for a single calendar month. Louisville, Ky., and Pittsburgh recorded their wettest year in 2004, and, of course, Florida was struck by an unprecedented four hurricanes during August and September. On Dec. 30, the United Arab Emirates recorded its first-ever snowfall.

Such facts might lead one to believe that the weather is becoming increasingly extreme, perhaps a result of global warming. Last year, after all, was the second-warmest ever measured on the planet.

But even though global warming is now an indisputable scientific fact, the link between it and extreme weather remains tenuous. The fact is that extreme weather records are broken every single day somewhere in the world. They always have been and always will be.

In fact, while Southern California was having record rains, other parts of the nation and the world have been experiencing a relatively normal winter.

And even where records are being broken, there’s no indication of a long-term problem. Before Florida’s disastrous hurricane season last year, for instance, the state had gone for one of its longest periods without being hit by a major tropical storm (Opal in 1996 was the last). In fact, by the time Hurricane Charley roared ashore in August, the United States had enjoyed its longest stretch (five years) without a major hurricane (a “Category 3” storm, with winds over 110 mph) since 1900-1906 -- in other words, the longest period free of major hurricanes in nearly a century.

People have extraordinarily short attention spans when it comes to weather events, and the media encourage this by reporting anything slightly out of the ordinary as extraordinary. As a contributor to Weather, the bulletin of Britain’s Royal Meteorological Society, puts it, “The occurrence of a record breaker is not of itself an indication of any change in causative mechanisms.”

All these points aside, there may be some aspects of the weather that are becoming more extreme. One of those is heat itself.

This, of course, should be expected if the average temperatures are rising. As meteorologist Bob Henson, a writer for the National Center for Atmospheric Research, said, “If you push the baseline up without changing the standard deviation, you’re bound to raise the ceiling of record.”

A good example of this would be the heat wave that struck Western Europe in August 2003, when temperatures averaged well above normal for weeks on end, and in turn the hottest days reached unprecedented levels, killing thousands in France. All-time national record-high temperatures were broken in Britain (101.3 F), Belgium (104 F), Germany (105.5 F) and Switzerland(106.7 F).

That same summer, much of the Rocky Mountains and interior Southwest reported their hottest month ever (July). Last summer was Alaska’s hottest, although for the Lower 48 it was an exceptionally cool one.

There has also been a shift -- and this too could be related to global warming -- toward rainstorms of shorter duration but greater intensity. As the atmosphere warms, there’s more water evaporating from the oceans and more fuel for rain and snow. The U.S. gets about 10% more rain than it did a century ago.

But is a “Day After Tomorrow” scenario of extreme weather imminent? Absolutely not.

In fact, if one were to examine the historical record, the 1930s was America’s decade of extreme weather. February 1936 was the single coldest month from Montana to the Great Plains, while July 1936 was its hottest. In North Dakota, the temperature ranged from minus-60 F in February to 121 F in July that year. The temperature soared to 106 F in Manhattan’s Central Park.

Thirty-six of the 100 all-time record state high and low temperatures were established in the 1930s (over a period dating back to the 1880s). The most powerful hurricane to strike a U.S. shoreline devastated the Florida Keys in 1935. The worst hurricane hit New England in 1938. In January 1937, the worst flood to affect the Ohio River inundated Louisville and all points along the river from Pennsylvania to Illinois. Temperatures fell to minus-66 F and minus-63 F in Wyoming and Montana in 1933.

The greatest natural disaster in American history, the Dust Bowl, beset the nation from 1933 to 1938, and yet a freak rainfall of 24 inches in six hours flooded parts of eastern Colorado in 1935, even as a giant dust storm raged just to the east.

Another decade of extreme weather is bound to occur again, and scientists will continue their quest to determine how extremes might change as our climate warms up. In any case, we can learn much from the weather extremes that nature has always dealt us.