Freedman: Explaining an Extreme Spring

This spring's weather sounds like it was crafted from a pitch meeting between a hapless Hollywood screenwriter and a studio executive. The pitch? "It's a movie in which flooding inundates downtown middle America, tornadoes strike boy scouts, strong winds lash the nation's capital, and record heat wave has New Yorkers sweltering in early June. And no one really knows why... or do they?"

Any minute now I'm expecting Dennis Quaid to emerge from an office in Washington and walk to Cedar Rapids, Iowa to rescue his son who is trapped in a library surrounded by rising floodwaters.

Keep reading to learn if climate change is impacting severe weather trends. See Matt's forecast for local weather details through the weekend.

Unfortunately however, this is reality, which any resident of Cedar Rapids, Picher, Oklahoma, or Parkersburg, Iowa, can tell you. Different forms of extreme weather have devastated all of these communities this summer. The tornado season has stunned veteran forecasters, who are running out of red dots to put on maps to mark the locations of tornado touchdowns. And the floods are beginning to look like an early season rival to the epic floods of 1993.

Given mounting concerns about global climate change due to human activities, it's difficult not to look at such strange and damaging and wonder: "Did we do that?"

As it is with most facets of climate science, the answer is somewhat complicated. It's well-known that precipitation patterns are likely to shift as a result of climate change, and there are indications that this has already begun to occur. The mechanics of such a shift are rather basic, since a warmer atmosphere can hold more water vapor, which can in turn lead to heavier rainfall events.

However, the regional impacts of climate change are less certain, and one cannot directly attribute the flooding this year to climate change. But that doesn't mean climate change isn't involved to some extent.

For example, scientists are increasingly confident in their conclusions that statistically speaking, extreme precipitation events in many areas, including the United States, have already become more frequent. In its most recent report, the U.N. Intergovernmental Panel on Climate Change (IPCC) stated that climate change caused by increasing concentrations of greenhouse gases, such as carbon dioxide, is "very likely" to increase the frequency of "hot extremes, heat waves, and heavy precipitation events." The panel also stated that the changes in the frequency and severity of extreme events would be detrimental to both natural and human systems.

Yet that is not often the message that gets through to the public from official sources. For example, in an Associated Press story last week about the Iowa floods, Brian Pearce, a National Weather Service meteorologist, stated: "We are seeing a historic hydrological event taking place with unprecedented river levels occurring."

"We're in uncharted territory -- this is an event beyond what anybody could even imagine."

Perhaps Pearce went on to say more and just wasn't quoted as such in the story. But there could be another sentence after that which would be both consistent with the state of climate science and would help individuals put the flooding into perspective in light of what they're hearing about global warming.

That sentence might go something along the lines of: "While this flooding event cannot be attributed to global climate change, extreme precipitation events are becoming more frequent, and are expected to become more frequent and severe due to global warming." That would be in line with the science as expressed by the authoritative IPCC. It would also be consistent with the approach that other countries have taken to contextualizing extreme events within the reality of climate change. When there are extreme events in the U.K., for example, their version of the National Weather Service (known as the U.K. Met Office) often mentions climate change prominently in its public statements.

There is a need for climate scientists and the media to work together to ensure that the scientific evidence for the relationship between extreme weather and climate change is communicated accurately, fairly, and without political distortion. This is difficult to do during breaking weather events.

But if it's apparent to everyday people that there may be a connection between flooded crops and greenhouse gas emissions, or between a leveled town and global warming, then maybe it's a sign that scientists, government officials and the media should be speaking to it in a more concerted and constructive way.

There is some appetite for such an effort, although it's somewhat tainted by partisanship. The liberal-leaning Center for American Progress, for example, has complained that the media is not doing enough to link the extreme weather this season to climate change.

"Although the deadly weather has been front-page news all season, and news channels dedicate hours of coverage to "Extreme Weather," the media are strangely reluctant to discuss severe weather events in the context of climate change," declared a recent post on the organization's Web site.

However, it's not clear whether it's the media, with its well-known appetite for sensationalism, that is holding itself back from exploring a link between extreme weather and climate change. There is also resistance from government information sources as well as from many scientists who may be reluctant to be more assertive on the subject lest they get pilloried by politicians.

The bottom line is that despite the uncertainties that pervade climate science, the research is clear enough on many points to be able to paint a more complete picture for the public when extreme events occur. Will scientists and the media produce the portrait even if there are more grays than black and whites?