Monday, May 19, 2014

Severe Weather in the United States

There was a very interesting article in the May 6th issues of Eos, Transactions, American Geophysical Union. The article, Severe Weather in United States Under a Changing Climate, takes a thorough look at the way various aspects of severe weather have changed since the 1950s and the message is pretty definitive. There is a nice graphic (figure 1 in the article) that shows the frequency of different kinds of severe weather in each decade since the 1950s. It takes a little bit of reading because there is so much information in the figure, but certain things really stand out right away. Below is a summery of some of the information in this paper.

Damages due to billion dollar events
The NOAA/NCDC Billion Dollar Weather website lists 151 weather/climate disasters resulting in at least $1 billion in damages that have occurred since 1980. The damages for these events have all been adjusted to reflect constant dollar values (2013 dollars). The total amount of damages exceeds $1 trillion. That comes out to about $3000 for every person in the U.S., or roughly $100 per year on average. The total for 2011 was for about $200 for every person ($60 billion total) and $360 per person in 2012 ($110 billion total). These costs are only as a result of the billion dollar-plus events and include such events as major heat waves, severe storms, tornadoes, droughts, floods, hurricanes and wildfire. The list does not include expenses such as increased expenses for utilities, food and increased insurance that are the result of daily climate change conditions.

Temperature extremes
The article states the average temperature has increased by 1.5 degrees F since 1895 with most of the warming occurring since 1970, "culminating with the warmest year on record in the United States in 2012." They found there has been a significant increase in the number of record high temperatures the last two decades. There has been a significant drop in the number of record low temperatures over the same period. Heat waves have become more frequent across the U.S.

Precipitation extremes
Over the last three decades the heaviest rainfall events in rainy areas have become more frequent and the amount of rain in heavy rain storms has been significantly above average. Other areas have seen significant decreases. The total number of extreme snowstorms has been substantially higher the last three decades.

Floods and droughts
There has been no nation-wide trend detected for droughts, but regional trends have been detected. In particular, the on-going drought in the western U.S. has resulted in the driest the region has been in 800 years. Floods have followed the same pattern. We don't know enough yet to detect a nationwide trend, but regional trends have been detected. In other words, it appears the regions that tend towards the dry end are getting drier and regions that tend toward the wet end are getting wetter.

Hurricanes and severe storms
There has been an increase in the intensity, frequency, and duration of category 4 and 5 (the strongest) storms in the Atlantic. The number of category 3, 4 and 5 storms in the North Atlantic since the year 2000 is the greatest since the 1950s. This increase in activity is linked to higher sea surface temperatures. The number of strong tornadoes and East Coast winter storms have not been seen to have changed over the last 60 years.

As we all know, weather forecasting is complicated and difficult. So, too, is the climate. But, what we see is a very clear picture that severe weather in the U.S. is becoming ever more severe. We may not have all of the details worked out just yet, but there can be no doubt that the weather is changing in response to a changing climate. And, once again, we see the end user is the one that gets stuck paying the bills. Everyone always passes increased costs on to their customers. The people at the end have no customers to pass it on, so they get stuck.

So, when you decide to deny climate change and resist efforts to do something about it, be sure to pull out you checkbook and make out a check to the rich and powerful.

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