How Should We Think About Extreme Weather Events?

The rough weather of 2010 teaches us that climate change is risky business.

Recently, I posted a blog discussing the possible link between global climate change and two related extreme weather events: the heat wave in Russia and historic flooding in Pakistan. Although there is no method to definitively attribute any single event to climate change, based on documented trends in extreme weather events and research showing that specific types of meteorological phenomena are more common in a greenhouse-warmed world, I said:

“It is reasonable to conclude that, in aggregate, the documented increase in extreme events is partially a climate response to global warming, and that global warming has increased the risk of extreme events like those in Russia and Pakistan. On the other hand, there is no scientific basis for arguing that these events have nothing to do with global warming.”

That’s as far as the science permits me to go with this question. We simply cannot know whether any particular weather event was “caused” by climate change. In recent weeks, however, the media have done their all-too-common “he said-she said” routine of finding one source who says the extreme weather of 2010 is because of climate change and another who says it’s not. This is a meaningless argument that distracts us from what we should be thinking about, which is what these events can teach us about our vulnerabilities to climate change.

Climate Risks: Lessons from 2010’s Extreme Weather


Update: Dr. Jay Gulledge is featured on National Journal's Energy & Environment Expert Blogs. Click here to read Dr. Gulledge's take on Climate Risks Here and Now

Last fall I posted a blog about the unusual number and severity of extreme weather events that have been striking around the globe for the past several years. That entry focused on the alternating severe drought and heavy flooding in Atlanta in 2007-2009 as an example of the roller coaster ride that climate change is likely to be. As every dutiful scientist does, I stopped short of blaming those individual weather events on global warming, but I am also careful to point out that it is scientifically unsound to claim that the confluence of extreme weather events in recent years is not associated with global warming; I’ll return to this question later.

Tempestuous 2010

The weather of 2010 continues the chaos of recent years. In the past six months, the American Red Cross says it “has responded to nearly 30 larger disasters in 21 [U.S.] states and territories. Floods, tornadoes and severe weather have destroyed homes and uprooted lives …” Severe flooding struck New England in March, Nashville in May, and Arkansas and Oklahoma in June.

Weather vs. climate, and what a difference a few degrees can make

There seems to be some confusion out there about weather vs. climate.  For example, a Virginia Republican Party video urged citizens to call their Congressmen and tell them how much global warming they got during the big snowstorm a couple of weeks ago. But that doesn’t really make any sense.  In simple terms, weather determines whether you need to take an umbrella with you today; climate determines whether you need to own an umbrella.  Weather determines whether you need your down coat today; climate determines whether you need to own a down coat.  Weather determines whether you turn on your air conditioning unit today; climate determines whether you own an air conditioner.  Weather determines whether the plants in your garden have a good day; climate determines what plants will likely thrive in your local environment. 

Climate is the long-term average of weather.  Weather changes all the time; climates are generally fairly stable, allowing us to make long-term decisions based on the notion that the future climate will be like the past.  One unusual weather event does not mean the climate is changing. But many unusual weather events could mean the climate is changing. And climate change will mean that on average, the weather we will have in the future will be different from what we had in the past.   That could even mean that record-breaking snowfall events happen more and more often in Virginia and Washington, D.C.

Update #2: It’s so cold! What happened to global warming?

Science Q&A

In the past few weeks I’ve posted twice (here and here) on reasons why global warming could be increasing the frequency of heavy snow events in certain parts of the United States (and likely in other similarly situated places around the world).

In a recent post on his WunderBlog (Weather Underground Blog), Dr. Jeff Masters gives his take on this issue. Dr. Masters is co-founder and Director of Meteorology of Weather Underground, a weather service that provides real-time weather information via the Internet. Unlike me, he’s a real weather expert and I highly recommend his blog.

Update: It’s so cold! What happened to global warming?

Science Q&A

The cold weather continues across much of the Unites States, Europe, and central Asia as the Arctic Oscillation remains in a strong “negative” state, forcing cold Arctic air down to the mid-latitudes. A couple of weeks ago I explained why more frequent heavy snowfall events could be a consequence of global warming for mid-latitude areas near large bodies of water, like Washington, D.C., and Syracuse, New York (see figure).

The average amount of annual snowfall has been increasing in Syracuse, New York, for most of the past century. (SOURCE: Increasing Great Lake–Effect Snowfall during the Twentieth Century: A Regional Response to Global Warming? Journal of Climate vol. 16, pp. 3535-3342, Figure 1)

On January 31, I noticed a forecast for lake-effect snowfall around the Great Lakes on Weather.com:  “Lake-effect snows are also possible near the central and western Great Lakes today and tonight.”