The Weather Guys

Roberto Salas, left, and Lewis Sternhagen check a flooded car in Houston on May 26. This spring the Houston area has experienced five separate rain events that have been classified as “once in a hundred year” events, which have a 1 percent chance (or a 1-in-a -100 chance) of occurring in any given year. (Photo credit: Associated Press)

In 2004, the Boston Red Sox won the World Series for the first time in 86 years and their loyal fans were ecstatic. In the very next year, the Chicago White Sox won their first World Series title in 88 years.

Never in the long history of baseball had two teams that had been denied championships for so long won those long-coveted titles in successive years. This circumstance was at least partially a function of the changes in baseball brought about by free agency — a fundamental change to the rules.

This spring the Houston area has experienced five separate rain events that have been classified as “once in a hundred year” events. A 100-year event has a 1 percent chance (or 1-in-a-100 chance) of occurring in any given year.

This designation is meant to suggest that the intensity of these events is not likely to return to Houston except every 100 years or so. Thus, to have experienced five such storms in a single season is extremely unlikely and points toward an alteration in the climate (a fundamental change in the “rules”) of the region.

In a similar way, readers might recall that here in Madison in March 2012 we recorded five days with temperatures at or above 80 degrees. In the prior 100 years, only five other March days had ever topped 80 degrees, so that was also exceptionally unusual and provided evidence also suggestive of a shift in the climate toward a warmer world.

As isolated incidents, these meteorological phenomena can be expected every so often even in an unchanging climate as there is a lot of internal variability in the atmosphere.

In the seemingly recurring sequence we have experienced in the past couple of decades, however, there is little doubt that such events are among the fingerprints of a changing climate — a reality that we simply must confront in a coordinated, scientifically informed manner. A great number of dedicated scientists at UW-Madison are actively seeking better understanding of the complicated weather/climate system.

Motorists and a fire engine brave high water on East Washington Avenue between the cross streets of Blount and Livingston Streets after a strong storm dumped large amounts of rain in Madison on June 30, 2014. Storms in the warmer, moister atmosphere of the future have the potential to be more severe than otherwise similar storms today. (Photo credit: M. P. King, State Journal archives)

In an individual storm, the release of latent heat results in stronger updrafts of air (which form the precipitation) and in stronger winds associated with the storm.

One of the consequences of the gradual global warming that is currently occurring is that more water vapor finds its way into the atmosphere when the temperature rises.

As the temperature continues to warm, even more water vapor will reside in the atmosphere. Thus, storms in the warmer, moister atmosphere of the future have the potential to be more severe than otherwise similar storms today.

Though the storms themselves develop in response to their large-scale environments, their development also directly impacts those environments in ways that are not yet well understood.

Especially unknown is the way in which the more abundant moisture of a warmer atmosphere will help shape the large-scale environments of the future.

Some studies suggest that the overall number of storms may decrease but that particularly severe storms may become more frequent.

Still others suggest no increase in the number of severe storms.

One thing seems certain: As the planet continues to warm, increases in the water vapor content of the atmosphere will likely change the frequency and distribution of mid-latitude storms and our agricultural and transportation infrastructure will have to adapt to those changes.