As a society, we are only now beginning to understand the emotional, physical and economic toll of recent catastrophic events such as hurricanes Harvey and Irma, says Auburn University climate scientist Hanqin Tian.
In August, the National Oceanic and Atmospheric Administration, NOAA, had forecast the likelihood that 2017 would be an above-normal hurricane season with 14 to 19 named storms and two to five major hurricanes within the Gulf of Mexico, Atlantic and Pacific oceans.
Tian says what is abnormal about this season is the formation of five named hurricanes — Harvey, Irma, Jose, Katia and now Maria — all within four weeks. Furthermore, according to NOAA, not since 2010 have we seen three hurricanes occurring in the Atlantic basin at the same time.
Tian leads Auburn’s Climate, Human and Earth System Sciences, or CHESS, strategic cluster and is director of the International Center for Climate and Global Change Research in Auburn’s School of Forestry and Wildlife Sciences.
He and fellow scientists point to a combination of factors which contribute to increased frequency of hurricanes, including sea surface temperatures being higher than normal, a weak or non-existent El Nino, weaker trade winds, more conducive wind patterns coming off Africa, a stronger west African monsoon and average or weaker-than-average vertical wind shear in that same region.
“Multiple lines of scientific evidence have shown that Earth’s ecosystems and our economic system are very vulnerable to the adverse impacts of climate change, and are already experiencing increased impacts of persistent extreme weather events such as droughts and hurricanes, heat waves and sea-level rise,” said Tian.
Auburn climatologist and physical geographer Chandana Mitra, an associate professor in the College of Sciences and Mathematics, also elaborated on the factors influencing hurricane frequency.
“Strong El Ninos and wind shear typically suppress development of Atlantic hurricanes, so the prediction for weak conditions points to more hurricane activity this year,” said Mitra. “Also, warmer sea surface temperatures tend to fuel hurricanes as they move across the ocean.”
Based on these existing conditions, the intense frequency of this year’s hurricanes can be attributed to a mixture of complex weather and climatic elements which impact the system uniquely.
There is a heated debate playing out in the media regarding the correlation between global warming and increasing hurricane activities in the North Atlantic.
One side of this debate insists the increase in hurricane activities is part of the natural weather variability, while the other side suggests there is a strong correlation between the upward trend of hurricane activity and sea surface temperature increasing, which many researchers believe is caused by increasing greenhouse gas emission.
The National Academy of Sciences, a private, nongovernmental institution established by Congress to advise the nation on issues related to science and technology, states, “Theoretical and modeling assessments consistently point toward an increase in hurricane intensity with global warming. For the North Atlantic, the annual number of the most intense hurricanes has been predicted to increase by more than 50 percent for each degree Celsius increase in surface temperatures.”
Many scientists agree a greater discussion must occur that seeks to mitigate societal impacts and economic losses that occur from aberrant weather events such as catastrophic hurricanes.
Economists with Moody Analytics estimate that our recent hurricanes, Harvey and Irma, have caused $150 billion and $200 billion in damages to Texas and Florida, respectively.
“To develop the knowledge and strategies effectively for responding to the risks of hurricanes and tropical storms as well as restoring the impacted ecosystems and economic systems, is of critical importance to adopting a coupled climate-human-earth system approach and engaging policy makers and the public,” Tian said.