Fasten Your Seatbelt – Weather Whiplash is the New Normal
May 9, 2013
If you get struck from behind in an auto accident, a common mechanism of injury would be “whiplash”, as your head snapped back and forth violently. Standard safety measures to protect auto drivers and passengers against whiplash effects: seatbelts and headrests.
“Whiplash” is the word more and more meteorologists are using to describe the violent swings in extreme weather that we have been seeing in the northern hemisphere, especially since the rapid and unforeseen decay of arctic ice cover that began in 2007.
Does anyone make a headrest big enough for, say, Iowa?
Weather Whiplash–a term originally coined by science writer Andrew Freedman of climatecentral.org to describe extreme shifts between cold and hot weather–is also a excellent phrase we can use to describe some of the rapid transitions between extreme drought and floods seen in recent years. I brought up a remarkable example in mid-April, when a 200-mile stretch of the Mississippi River north of St. Louis reached damaging major flood levels less than four months after near-record low water levels restricted barge traffic, forcing the Army Corp to blast out rocks from the river bottom to enable navigation.
As the climate warms, the new normal in coming decades is going to be more and more extreme “Weather Whiplash” drought-flood cycles like we have seen in the Midwest and in Georgia this year. A warmer atmosphere is capable of bringing heavier downpours, since warmer air can hold more water vapor. But you still need a low pressure system to come along and wring that moisture out of the air to get rain. When natural fluctuations in jet stream patterns take storms away from a region, creating a drought, the extra water vapor in the air won’t do you any good. There will be no mechanism to lift the moisture, condense it, and generate drought-busting rains. The drought that ensues will be more intense, since temperatures will be hotter and the soil will dry out more.
This year’s “Weather Whiplash” in Georgia is the second time in the past decade the state has gone from exceptional drought to flood. In September 2007, Atlanta, Georgia was in the midst of a 1-in-100 year drought, and was just weeks away from running out of water. Yet just two years later, the drought had been busted, and a phenomenal 1-in-500 year flood ripped through the city, killing ten and causing $500 million in damage.
According to a 2011 study by a Duke University-led team of climate scientists, “Changes to the North Atlantic Subtropical High and Its Role in the Intensification of Summer Rainfall Variability in the Southeastern United States”, the frequency of abnormally wet or dry summer weather in the southeastern United States has more than doubled in recent decades, due to an intensification of the Bermuda High. The scientists found that the Bermuda High, which is centered several hundred miles to the east of the Southeast U.S., has grown more intense during summer and has expanded westwards over the past 30 years. Since high pressure systems are areas of sinking air that discourage precipitation, this has made abnormally dry summers more common over the Southeast U.S. However, in summers when the Bermuda High happens to shift to the east, so that high pressure is not over the Southeast U.S., the stronger winds blowing clockwise around the Bermuda High bring an increased flow of very moist subtropical air from the south to the Southeast U.S., increasing the incidence of abnormally wet summers.
Thus, the intensification of the Bermuda High has made extreme droughts and extreme floods more likely over the Southeast U.S. Using climate models, the scientists determined that human-caused global warming was likely the main cause of the significant intensification in the Bermuda High. Thus “Weather Whiplash” between drought and flood will probably become increasingly common in the coming decades over the Southeast U.S.
Some changes, however, have been harder to unearth but recent exciting findings are shining some illumination. Among the most exciting areas of research is the connection between loss of arctic sea ice and extreme weather in the Northern Hemisphere. The arctic, which has been warming at an alarming rate has seen an approximately 75% decrease in the summer sea ice volume. Consequently arctic waters, which had been covered by ice, are now absorbing tremendous amounts of solar energy during the summer and releasing it to the atmosphere during the autumn and early winter.
This change in the arctic energy balance has begun to have an effect on the weather patterns, particularly on the jet stream. This rapidly flowing stream of high-altitude air separates the cold dry arctic air from warmer moist air closer to the equator. When that jet stream dips southward, watch out! Cold air and potential downpours or snow storms may be coming your way. Recently, the jet stream has been more likely to be found in an undulating, slowly moving state.
And since climate change is global, the whiplash isn’t only happening in North America.
“In the U.S. of course, it is going from floods in 2011 (Missouri through Ohio River Valley to New England, flooding Mississippi and Missouri) to widespread drought in 2012 and back to floods in 2013,” said climate researcher Kevin Trenberth of the National Center for Atmospheric Research. “But it’s much worse in Australia: a nine-year drought then floods mid-2010 to mid-2011 and then back to drought and record heat in Jan(uary) this year.”
Nor can the pattern be expected to get any better, say climate scientists.
“Society and its infrastructure were designed for the climate of the past, not for the rapidly changing climate of the present or the future,” reads the Climate Nexus report, quoting from the 2013 National Climate Assessment. “Climate change, once considered an issue for a distance future, has moved firmly into the present. Impacts related to climate change are already evident in many sectors and are expected to become increasingly challenging across the nation throughout this century and beyond.”
The sinkhole that opened up on a Chicago street happened when a water main built in another time, for another weather regime, could not withstand climate juiced flooding this spring.