Editorial Board

Do Emissions Cause Tornadoes? Climate Service Would Know

Last weekend, more than 100 tornadoes tore across the Plains states, smashing homes, tossing cars and killing six people.

This might have counted as a rousing start to the spring tornado season, except for the dozen or more twisters that struck Dallas and Fort Worth earlier this month and the 223 that hit the U.S. in March -- almost three times the average for that month since 1990. Tornadoes have been blamed for 63 deaths this year in the Midwest and South.

Already 2012 is looking as if it could keep up with last year’s lethal record of 550 tornado-related deaths nationwide -- more than in the previous 10 years combined.

What’s up? Might this destructive weather have something to do with global warming?

Wouldn’t we like to know. And who better to tell us than the National Oceanic and Atmospheric Administration, the federal agency that monitors the atmosphere, predicts the weather and collects and analyzes climate data?

The agency has for years wanted to create a National Climate Service that would track and assess climate change, figuring out whether it is to blame for specific extreme weather events such as tornadoes, floods, droughts, heat waves and hurricanes. In this and other ways, it would help people -- farmers, insurance companies, policy makers -- plan for changes in the growing season, coastal erosion, water supply, human health and so on.

Climate Plan Killed

In November, however, Republican members of the House of Representatives killed that plan, even though it would have required no new funding at all. The agency already collects and analyzes climate data, and publishes outlooks for events such as floods, wildfires and droughts, but the information is spread across various offices and is therefore not centrally coordinated.

The House members worry that a dedicated office might reinforce a reality they don’t recognize: that greenhouse-gas emissions are changing Earth’s climate.

But the need to focus directly on how climate change affects all our lives is growing and, along with it, fortunately, scientists’ ability to discern what’s happening. In the past, when asked whether a flood or drought or a rash of hurricanes could be attributed to climate change, they would merely note that such extreme weather is what we might expect warming to cause.

Lately, though, scientists have been able to work out more specific odds. For example, after careful study of the European heat wave of 2003, researchers at the U.K. Met Office (the British weather service) and the University of Oxford were able to conclude with confidence that human influence on climate had more than doubled the probability of such extreme temperatures that year.

Scientists would like to be able to assess attribution in this way more quickly. At the University of Cape Town, in South Africa, researchers are at work on a pilot project that basically compares models of today’s actual climate with models of a pretend world that might have been had humans not interfered. In these, atmospheric concentrations of greenhouse gases are set as low as they were in 1900, and ocean temperatures are cooled by the amount they seem to have warmed because of increased greenhouse gases in the air.

Looking at the U.S. in this way, the researchers can say with confidence that human-induced climate change has at least doubled the chance the month we’re in now will be unusually warm. And their best estimate -- in other words, a prediction they can make with less than full confidence -- is that the chance of a warm April is about eight times higher than it would have been without the level of greenhouse gases now in the air.

Scientific Challenges Ahead

Calculating the probability of hot and cold temperatures is easier than determining the influence of climate change on rainfall, let alone on tornadoes and hurricanes, but all of this will become possible in time.

Most scientists no longer doubt that greenhouse gases have made the planet warmer, and that it stands to become warmer still. But we don’t know how much hotter it will get or how quickly the seas will rise. And we’d like to know exactly how floods, droughts and other side effects of climate change will play out in specific regions.

It’s also important to learn, of course, which bits of seemingly strange weather are not connected to emissions.

In 2011 alone, the U.S. experienced 14 extreme weather events -- from the Groundhog Day blizzard to the summer drought and wildfires in Texas, from Hurricane Irene in late August to the big October snowstorm in the Northeast. Each one did more than $1 billion worth of damage.

At least some state policy makers are paying attention. California, New York and Washington are now requiring large insurance companies to disclose how they intend to assess the risks posed by climate change and encourage policyholders to prepare for them.

These insurers, and many others, should be able to get the best possible information about what to expect from NOAA. Congress must allow the agency to make a direct effort to assess how a changing climate will change our lives.

    To contact the senior editor responsible for Bloomberg View’s editorials: David Shipley at davidshipley@bloomberg.net .

    Before it's here, it's on the Bloomberg Terminal.