阅读理解 Recently, we have already shown that climate change has led to a dramatic increase in storm surge risk in New York City, making devastating events like Hurricane Sandy more likely.
What can we say about the role of climate change in the unprecedented disaster that is unfolding in Houston with Hurricane Harvey? There are certain climate change-related factors that we can, with great confidence, say worsened the flooding.
Sea Level rise attributable to climate change-some of which is due to coastal subsidence(下沉) caused by human disturbance such as oil drilling-is more than half a foot(15cm) over the past few decades. That means the storm surge was half a foot higher than it would have been just decades ago, meaning far more flooding and destruction.
In addition to that, sea surface temperatures in the region have risen about 0.5C(close to 1F) over the past few decades from roughly 30C(86F) to 30.5C(87F), which contributed to the very warm sea surface temperatures(30.5-31C, or 87-88F). There is a simple thermodynamic(热力学的) relationship known as the Clausius-Clapeyron equation that tells us there is a roughly 3% increase in average atmospheric moisture content for each 0.5C of warming. Sea surface temperatures in the area where Harvey intensified were 0.5-1C warmer than current-day average temperatures, which translates to 1-1.5C warmer than “average” temperatures a few decades ago. That means 3-5% more moisture(水分) in the atmosphere. That large amount of moisture creates the potential for much greater rainfalls and greater flooding. The combination of coastal flooding and heavy rainfall is responsible for the devastating flooding that Houston is experiencing.
Not only are the surface waters of the Gulf of Mexico unusually warm right now, but there is a deep layer of warm water that Harvey was able to feed upon when it intensified at near record pace as it neared the coast. Human-caused warming is penetrating down into the ocean. It's creating deeper layers of warm water in the Gulf and elsewhere. Harvey was almost certainly more intense than it would have been in the absence of human-caused warming, which means stronger winds, more wind damage and a larger storm surge.
Finally, the more tenuous but potentially relevant climate factors: part of what has made Harvey such a devastating(毁灭性的) storm is the way it has stalled near the coast. It continues to strike Houston and surrounding regions with a seemingly endless flood, which will likely top out at nearly 4ft(1.22m) of rainfall over a days-long period before it is done. The stalling is due to very weak prevailing winds, which are failing to steer the storm off to sea, allowing it to spin around and wobble back and forth. This pattern, in turn, is associated with a greatly expanded subtropical high pressure system over much of the US at the moment, with the jet stream pushed well to the north. This pattern of subtropical expansion is predicted in model simulations of human-caused climate change. More tenuous(微弱的), but possibly relevant still, is the fact that very persistent, nearly “stationary” summer weather patterns of this sort, where weather anomalies(both high-pressure dry hot regions and low-pressure stormy/rainy regions) stay locked in place for many days at a time, appears to be favoured by human-caused climate change.
In conclusion, while we cannot say climate change “caused” Hurricane Harvey, what we can say is that it exacerbated several characteristics of the storm in a way that greatly increased the risk of damage and loss of life. Climate change worsened the impact of Hurricane Harvey.
