Broken windows and caved-in walls. Downed power lines and trees. The severe storm that hit Houston and the Gulf Coast on Thursday left the destructive footprint of a hurricane, but without any tropical blow-in.
Severe thunderstorm swarms cause extensive damage across the United States each year, not only with rain and flooding, but also with hail, tornadoes, and walls of wind. Here's what you need to know about such storms and how they might change in a warming climate.
Global warming creates conditions that make severe storms more likely.
As the planet warms, severe storms of all kinds are likely to produce even more rainfall. The reason: As the air warms, it holds more moisture, effectively increasing the ability of storms to transport precipitation.
Because air can hold more water, it also means there is more water vapor in the sky, which can condense into liquid and form clouds. The heat energy released into the atmosphere by this condensation causes thunderstorms. In other words, more condensation means stronger storms.
Warmer temperatures can also increase atmospheric instability, increasing the energy needed to quickly lift moist air skyward during storms.
Scientists are still trying to understand how this happens.
Just because we have the ingredients for a powerful storm doesn't mean it will always happen. Many other factors determine when a storm occurs, whether it occurs, and how destructive it will be. That means it's not easy to determine how global warming will affect the overall trend of storms.
“Theoretically, we have a good understanding of what's going on,” said Andreas F. Prine, a climate scientist at the National Center for Atmospheric Research in Boulder, Colorado. I have a few more questions. ”
For example, there is no clear evidence that tornadoes have become more frequent or more intense in recent decades. But they seem to be happening in more concentrated bursts.
Thunderstorms can also produce strong winds that spread in a straight line rather than in a meandering pattern. In a study published last year, Dr. Plein estimated that such straight-line wind gusts now occur over a much larger area of the central United States than they did in the early 1980s.
Damage from thunderstorms is already causing major losses for home insurance companies.
Hurricanes and wildfires aren't the only things disrupting the U.S. homeowners insurance market. As a New York Times investigation documented this week, severe storms are causing insurance companies to lose money on homeowner coverage.
These losses are impacting insurers in states such as Iowa, Arkansas and Ohio, far from the coastal areas hardest hit by hurricanes.
Already, Dr. Prine said, the cumulative losses from heavy thunderstorms are not much smaller than those caused by hurricanes. “It's much closer than you usually think.”