Multiple Disaster Problem

A hurricane causes flooding, power outages, and widespread wind damage. An earthquake leads to an electrical fire that spreads through a neighborhood blocked off by quake damage. A tsunami causes a chemical spill. All of these are examples of multiple disasters striking at once. Within a 10-year period beginning in 2001, there were three catastrophic instances of simultaneous multiple disasters. The terrorist attacks in the United States on September 11, 2001, involved attacks on multiple sites, as well as numerous interrelated problems at those sites. Hurricane Katrina in 2005 resulted in the failure of New Orleans's levee system, such that flooding was caused by two distinct sources, and structural damage and transportation around the city became that much more complicated. In 2011, the Tohoku earthquake and tsunami in Japan led to multiple nuclear meltdowns and releases of radioactive material at the Fukushima Daiichi nuclear power plant over a series of days. The problem of multiple disasters such as these has become of increasing interest in the field of emergency management, enough so that in 2012, the Philippines held a nationwide simultaneous earthquake and fire drill to increase preparedness for the country's most likely multiple disaster scenario.

The problem of multiple disasters occurring in close proximity is one often caused or exacerbated by unusual trends in weather. The 21st century has seen uncommon weather patterns unlike any in modern meteorological history, including numerous historical records broken, in some cases repeatedly. The patterns have not been of a single type: A given region might experience both drought and floods in consecutive years, both historically mild winters and historically snowy ones, or cold, rainy summers and hot, dry summers. The effects of these unusual weather patterns are not yet fully understood and involve much more than simply the weather on a given day: The mild winter in the Northern Hemisphere in 2011–12 (after the extremely cold winters in 2009–10 and 2010–11), for instance, led to a premature spring blooming for some plants, which then lost their blossoms to frost or freeze. The commercial pie cherry crop for 2012 was decimated as a result. Two years earlier, citrus crops in the United States had similarly been decimated by an unusually cold autumn and icy rain that crushed fragile fruit. The mild winter of 2011–12 also led to lowered river and lake levels the following spring, because they were not fed by spring thaw. This, in turn, affected the life cycles of numerous wildlife: Migrating birds didn't migrate as far south, which depleted populations of their prey species in northern climes and ballooned populations of their prey species in southern ones; mosquito populations increased in many parts of the country and were discovered to carry the West Nile virus in the Midwest and New England.

One of the proximate causes for these weather patterns was the change in the position of the jet stream, the air current driving the Northern Hemisphere weather system. In the past, changes in the jet stream have been responsible for extreme El Niño (warming in the Pacific Ocean) and La Niña (cooling in the Pacific Ocean) events, and contributed to the extreme drought of the Dust Bowl in the 1930s, though the most direct cause of the latter drought was the human-made alteration of the prairies. Since 2007, the jet stream's path across the United Kingdom has been at an unusually low latitude—10 degrees further south than usual, at 50 degrees north latitude near the English Channel, instead of 60 degrees north on the other side of the British Isles. This has occurred in spite of the observed trend in previous decades of a steady if slow northward climb of the jet stream.

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