Is Extreme Weather Increasing?

January 10, 2012 0 Comments

We have heard through the last few years about how the weather is supposedly getting more “wild” or extreme, primarily due to anthropogenic global warming (AGW) and there is some data that seems to back this up. Insured losses have been increasing in recent years and last year was the worst. 2011 was the costliest year of natural disasters on record, totaling 380 billion across the world!

One thing to remember, and something many commentators have pointed out, is that this is a record for INSURED losses. This plays a part in trying to assess any increase in extreme weather. Just because insured losses hit a record, does not necessarily mean that there were more devastating weather events. If could be that the worst weather of the year just happened to hit highly populated “expensive” areas of the world. The previous record year was 2005 when category 5 hurricanes Katrina and Rita hit the gulf coast of the U.S. including the major population center of New Orleans. There have been other years with category 5 hurricanes that were unremarkable for insured losses because the hurricanes did not strike populated areas. So in order to know for sure that extreme weather is increasing, we will need to consider objective data besides insured losses. Climatologists have been busy tabulating the number of flood events, amounts of rainfall, number of heat waves, the number of record temperature events, and many other things. So far, the one trend that has been confirmed is that the frequency of heavy rain events is increasing in many parts of the world. At this page you can find some data about severe weather (including heavy rain) and whether or not it is increasing.

Many other trends in extreme weather have not been robustly confirmed. There has been much debate about whether hurricanes have increased in number and/or intensity in recent decades. Many people expect this should be (or will be) the case because the temperature of the oceans has gone up a little and the heat content of the ocean is one of the key drivers of hurricanes. Reality has not kept up with these expectations. Hurricanes are complex weather phenomena and the temperature of the ocean is only one factor. Wind shear is quite important as well. A recent study by Christopher Landsea has found no substantial direct link between hurricanes and AGW and suggests that effects will be negligible through 2100. Once Landsea factored in population growth along the coast of the U.S. and better monitoring techniques, the apparent increase in insured losses and number/intensity of hurricanes was not substantial.

Which brings us back to the record year of insured losses in 2011. It would not have been a record year for insured losses of natural disasters except for one event and you can probably guess what it was – the Japan earthquake and tsunami.  The earthquake and tsunami resulted in an estimated 210 billion in insured losses. Taking out that one event and we end up with only 170 billion in losses. It was still a bad year for “bad” weather and natural disasters, but 170 billion is 50 billion less than the previous record of 220 billion in 2005. Since earthquakes and tsunamis are not directly weather related, this should be kept in mind when using insured losses as a metric of whether extreme weather is increasing.

When discussing extreme weather and AGW, the vast majority of the content is negative. The basic premise is that AGW is going to theoretically destroy the environment. Once in a while though, something positive makes it into the discussion. In the past, the few positive aspects of the theoretical future warming hinge upon more areas around the poles becoming more habitable. The frozen north of Canada (and Siberia) might become a productive growing area.

Another potential positive (I think it is a good thing anyway), is that theoretical AGW might stall the onset of the next ice age. According to some geologists we are already overdo for an ice age. According to this latest research, an new ice age should begin within the next 1,500 years but the co-authors claim AGW will delay or prevent it. This is a good thing because if the planet became 5 degrees colder instead of 5 degrees warmer, we would have much bigger problems, in my opinion. Colder temps would mean an expansion of frozen tundra and the ice caps and likely lead to much less rainfall due to colder ocean temps and more water being locked up as ice at the poles. The would be much less space for agriculture. Much suffering would ensue. I am not saying hooray for AGW, but I am saying that delaying the next ice age is a good thing. If it a new ice age was upon us, we would probably be compelled to spend a lot of resources figuring out ways to warm up the planet.

Have a good Tuesday! Meteorologist Justin Loew.

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