What’s causing the tornado tsunami
“Tornadoes are currently on a frightening upswing.” That could have been written yesterday — but was written 12 years ago, by your columnist, in the November 8, 1999 issue of The New Republic.
The onslaught of tornadoes is not some sudden, unexpected bolt out of the blue. I wrote about tornadoes a dozen years ago because 1998 and 1999 were terrible years for tornadoes. Now three of the last 12 years have been terrible for tornadoes, and the 1950-2010 trend isn’t so great either.
This spring’s tornado activity has been awful. At least 116 people died in Joplin, Missouri, on Sunday during an unusually strong and large tornado. A portion of Tuscaloosa, Alabama was destroyed by a tornado last month. Many tornadoes hit the Ozarks region in April. There were 875 confirmed tornadoes in April, triple the previous April high of 267, in 1974. So far 481 Americans have been killed by tornadoes this spring.
In recent decades, the installation of a Doppler radar warning system in tornado-prone areas has tended to reduce fatalities — sirens get people’s attention. But even 24 minutes of warning, which Joplin received on Sunday, may not be sufficient for a tornado that was a hard-to-believe half a mile across. (The touch-down part of a tornado is rarely more than 100 yards wide.) More disturbing tornado facts are here.
Weather patterns include random variation: some recent years have been mild for tornadoes. Before this spring, the worst tornado sequence in U.S. annals came in 1953, when atmospheric greenhouse gas levels were lower than today. Nevertheless, there are reasons to think tornadoes are a harbinger of climate change.
For years, pundits and politicians have claimed that strong hurricanes prove global warming. In this 2005 speech, Al Gore asserted, “The scientific community is warning us that the average hurricane will continue to get stronger because of global warming.” Gore went on to compare hurricanes to al qaeda. But not only have four of the last five Atlantic hurricane seasons been quiet, the 20th century showed no trend of rising Atlantic hurricane frequency or intensity.
Pundits and politicians attach significance to hurricanes because they are visual events — hurricane courses can be predicted, and their arrivals on shore televised. Tornadoes come and go so quickly, they are almost impossible to catch on film. But their comings and goings may be warnings of climate malfunction.
What’s causing the tornado tsunami of 2011? This spring, the jet stream has shifted south and east of its typical position. That brings the cold, dry air on the north edge of the jet stream into more contact with the warm, moist air masses on its south edge, around the Gulf of Mexico. The result is rotating thunderstorms — sometimes, as happened in the Ozarks in April, forming day after day in succession.
Surely there have been times in the past when the jet stream shifted east and south: this may or may not be related to greenhouse gases. But greenhouse gas levels in the atmosphere are rising, and weather variations are rising — not just tornadoes, but droughts and deluge rains. Chances are two plus two equals four.
It is important to bear in mind that climate change, not global warming, is the threat. They seem like the same thing but are not.
The mild warming of the past 100 years — about 1 degree Fahrenheit globally averaged — was good for crop yields, and moderated demand for energy. (Power use for warming on cold days exceeds power use for cooling on hot days). If all that happens is continued mildly rising temperatures, that might be beneficial.
Changing climate is another matter altogether. Climate change can bring more tornadoes, increase droughts in some places while increasing floods in other places — all three impacts are being observed. Long-term shifts in rainfall patterns might turn breadbasket regions into crop-failure regions. Our increasingly globalized economy is dependent on air travel and air cargo. What if storms and turbulence begin to make flying conditions unfavorable not once in a long while, but often?
Despite what the talk radio and Tea Party types say, there is strong scientific consensus that human activity has begun to alter Earth’s climate. Here is the latest statement on this matter, from the National Academy of Sciences last week.
The United States Congress — dedicated to its twin goals of doing nothing, while collecting campaign contributions — needs to act on greenhouse gases. These tornadoes are not originating from Oz.
Photo: Damaged homes and cars are seen after a devastating tornado hit Joplin, Missouri May 24, 2011. A monster tornado killed at least 116 people in Joplin, when it tore through the heart of the small Midwestern city, ripping the roof off a hospital and destroying thousands of homes and businesses. REUTERS/Eric Thayer