Yes, Harvey Could Happen Here

In the last week, Tropical Storm Harvey has dropped as much as 51 inches of rain on parts of Texas, a record rainfall for the United States. At least 30 people have died, nearly 30,000 are housed in shelters, and hundreds of thousands are under evacuation orders. Why now, why Texas, and what if storms of similar magnitude strike other cities?

BU Today talked with Anthony Janetos, a College of Arts & Sciences professor of earth and environment and director of the Frederick S. Pardee Center for the Study of the Longer-Range Future. Janetos is a former director of the Joint Global Change Research Institute at the University of Maryland, where for six years he oversaw an interdisciplinary team of natural scientists, engineers, and social scientists committed to understanding the problems of global climate change and their potential solutions.

BU Today: The 50 plus inches of rain Harvey has dropped on Houston dwarfs any previous rainfall on a Texas city. Why now? How much influence did climate change have on that deluge?

Janetos: Climate change has likely influenced Hurricane Harvey in several ways. The first, and most direct, is that because of sea-level rise, there is more water for Harvey’s winds to push, thus leading to a larger storm surge than might otherwise have been the case. The second is through increased water temperatures in the Gulf of Mexico, providing more energy and more evaporated water for the storm. Waters in the gulf are always warm this time of year, which is one reason that tropical storms that pass through the gulf often increase in intensity, but the gulf is even warmer than the average for late summer, and at least part of this can be attributed to warming from climate change. Third is that there is good science that suggests that the additional energy available to tropical storms and hurricanes also can have the effect of increasing their intensity.

How much of that influence on climate change can we ascribe to human actions?

The vast majority of scientists who have studied this issue agree that most of the change that the world has seen over recent decades is attributable to human actions. While influenced by natural variability, that alone cannot account for the magnitude and rates of change that we have experienced.

What other unprecedented weather events influenced by climate change are we likely to see?

Several scientific assessments that include evaluation of the latest science of the physical climate system have concluded that extremes of both rainfall and drought will very likely increase in frequency.

If this can happen in Houston, what other cities are likely to undergo a similar fate?

The coastal cities most at risk are obviously those that are in areas experiencing rapid net sea-level rise, so especially those cities in the Gulf of Mexico and the southeastern Atlantic coast. Those cities are also subject to impacts from tropical storms with relatively high frequency compared to other parts of the Eastern seaboard. But cities farther north are also vulnerable, even if the storms that drive storm surge are not hurricanes—sea level rise and increased storm surge can make even ordinary storms much more damaging than they have been in the past.

How can cities prepare for such extreme weather events?

Cities can do a variety of things. They can improve emergency management plans. They can work with developers to ensure that there is some measure of protection against flooding, whether that is movable barriers, levees, or improved seawalls. More ambitious regional solutions may also be possible in some cases. They can take engineering actions to make it easier to control and drain floodwaters when floods do occur.

Will weather inevitably grow more severe?

Hurricane Harvey is probably a one-in-1,000 event. But we are heading into a new normal when one-in-100 events in the future have the same magnitude as today’s one-in-500 events have.

Is Boston more or less likely to be affected by such events?

It is almost inevitable that sooner or later Boston will experience an extreme event of this nature, although hopefully not as severe as Harvey. We cannot predict when such an event will occur, but we can increase our resiliency.

If such an event were to strike Boston, how prepared are we to respond?

Boston’s own studies of its vulnerability to flooding and climate change show that the city has some significant vulnerabilities. The timing of any event matters—a big storm that hits at high tide will have more consequences than a storm that comes at low tide, for obvious reasons. The city is beginning to work out the policies and actions that will be required to increase its resiliency.