Questions Remain About Climate Change-Hurricane Linkage

Recent increases in extreme weather events have prompted scientists to consider whether any of these can be directly attributed to long-term changes in climate. In an editorial last week, NASA Goddard Institute for Space Studies Director James Hansen wrote that recent events such as last year’s drought in Texas and Oklahoma could only be attributed to climate change. “There is virtually no explanation other than climate change,” he states.

According to a scientist with the National Hurricane Center, the same cannot yet be said for hurricanes. Based on an analysis of long-term records and current observation methods, Christopher Landsea, science and operations officer at the National Oceanic and Atmospheric Administration’s (NOAA) National Hurricane Center, concludes that advancements in monitoring capabilities suggest the perception that we are seeing a dramatic increase in hurricanes.  

During a recent online presentation hosted by NOAA, Landsea walked participants through his thinking when approaching the following question: How is global warming really affecting hurricanes? He clarified that this had nothing to do with doubting the effects of climate change in other phenomena or the destructive force of hurricanes. It was prompted instead by recurring references to hurricanes as proof of the dangers of a changing climate. He states that while “it is likely…that manmade global warming has indeed caused hurricanes to be stronger today,” the extent of this impact cannot be measured with existing data and technologies. His results highlight the need for sustained, long-term observations and for further research into the varying impacts of climate change. 

Landsea noted tropical storm and hurricane damages in terms of direct losses to consider whether hurricane destruction has increased. At first glance, this figure has increased dramatically since records began in the 1900s and now averages $19 billion a year. Yet he offers the following caveat: societal factors, not just climate change, are at play. In addition to the impact of an increasing population, research suggests that adults now have twice as much wealth (property and possessions) as their parents, and four times the amount as their grandparents. In other words, when a hurricane makes landfall now, more people with more personal wealth are affected, leading to increased damages. This much is clear when “normalizing” damage figures  — estimating the damage of a past hurricane were it to make landfall today. For example, damages from the category 4 Great Miami Hurricane of 1926 would normalize to $126 billion today, nearly twice what Katrina produced in 2005.

Taking a different perspective, Landsea addressed the issue of how many tropical storms and hurricanes have occurred as recorded in the Atlantic basin hurricane database (HURDAT). He cautioned that HURDAT “is a byproduct of operations” and that as such it reflects what is known about hurricanes and what can be measured at a time. Landsea argues that advances in observing and monitoring technologies account for the perceived increases in number of hurricanes.  He says that improved technologies now allow us to “see” more hurricanes than ever before, even short-lived storms that exist for 36 hours or less. Prior to the advent of polar-orbiting and geostationary satellites, such as those operated by NOAA, these weak, short-lived storms were not consistently identified, much less named. 

During his presentation, Landsea emphasized the role of advanced monitoring technologies, such as satellites, in providing an unprecedented look at hurricanes.

Landsea adds that these issues should be considered when studying the long-term record. When one includes large hurricanes that may have been missed in the past and removes “shorties” from recent records that would not have been counted before, “the [upward] trend is gone.” He suggests that what we are experiencing now is a “swing” and that we may be in the midst of a very busy period similar to those seen previously. The question is when we will go back to a “quiet period” and that “is anyone’s guess.”

Instead of predicting dramatic changes in the future, such as those expected for other phenomena like drought or extreme temperatures, modeling work suggests modest hurricane impacts: by the late 21st century, there could be a 3% wind increase and fewer tropical storms and hurricanes.

Climate change science is about advancing understanding of the degree and rate of changes imposed by long-term changes in climate conditions. Landsea’s analysis reminds us that, as observation capabilities improve, the impact of these technologies and the environmental changes that these may identify must be considered in context and over the long term.

To view Landsea’s presentation and learn more about how he is analyzing the hurricane record, visit: http://www.aoml.noaa.gov/hrd/Landsea/gw_hurricanes/index.html