It’s always risky to link individual weather events to climate change – scientists tend to favor trends and aggregated data.
But as the intensity of the hurricane and tornado seasons increase year after year, the biggest storms that are 100-year or even 1,000-year events are hard for climate scientists to ignore.
So now comes Harvey and a downpour of epic proportions – 50 inches over four days, and it’s not done yet. Water in the Gulf of Mexico never got below 73 degrees this past year, and climatologists say it’s the warmer water from the Arctic to the Antarctic that is generating the more extreme fluctuations in global storms and weather.
Harvey comes five years after Hurricane Sandy, another storm of epic strength and subsequent destruction. And seven years before that, Katrina. Some skeptics of the link to climate change note that runaway coastal and lowland development is costing more lives and property each year, not because of increasing storm strength. And as for Harvey, without two blocking high pressure systems to its west and east, Houston would have been passed over by the rain within a day.
We don’t doubt that more people are putting themselves in harm’s way of nature without taking proper precautions. Federal disaster payments continue to allow rebuilding and re-insurance in floodplains without significant hardening against hurricanes. The same could be said about those who build in the middle of western pine forests without any fire hardening or on steep mountain slopes prone to mudslides.
But scientists are saying the extreme weather events caused by a warming planet will affect far more than those in obvious danger zones, and Harvey is proof. Houston, although low-lying, is not all within a 100-year floodplain as defined by the Army Corps of Engineers. Nevertheless, the city built reservoirs to account for heavy rains, but even those have been topped. If a warmer Gulf and more frequent superstorms are now the new normal, how much bigger should those reservoirs be and how much higher and stronger new roads and bridges?
Here in Flagstaff, serious flooding below the Schultz fire extended well beyond mapped floodplains. And with a warming Southwest drying out and even killing ponderosa pines and lengthening the wildfire season, city voters approved $10 million worth of thinning on the slopes above town and its reservoirs to head off similar floods.
As for the Colorado River basin, projected shortfalls of drinking water are indeed linked to population growth. But climate change that shortens the critical snowpack season is another culprit, and multiple agencies have built climate change into their river basin modeling and planned accordingly.
Those pre-emptive actions stand in contrast to President Trump and his appointees, who do not recognize climate change as a force deserving a federal response. Ironically, just this month he repealed Obama’s risk management standard to flood-proof new infrastructure projects. Engineers could use the best available climate change science; they could require that standard projects like roads and railways be built two feet above the national 100-year flood elevation standard and critical buildings like hospitals be built three feet higher; or they could require infrastructure to be built to at least the 500-year flood plain. None of those standards will now apply as Houston is rebuilt.
The bigger challenge is not just mitigating the impacts of bigger storms, wildfires or mudslides tied to climate change but also slowing and eventually reversing the warming trend itself. Even if Harvey isn’t enough to nudge the White House toward rethinking its position, voters are likely to give it a shove as the casualties and losses from future unnatural disasters mount. The tragedy playing out in Houston simply won’t be the last.