Harvey, Irma And Global Warming: The Facts From Experts Whose Opinions Matter More Than Mine Or Yours

After hurricanes Harvey and Irma, it was hard to miss the multitude of headlines demanding that we pay attention to global warming now. Those who refuse to see this connection are science deniers at best and possibly criminals at worst (some are suggesting politicians who deny or minimize global warming should be arrested). 

But there were other voices as well, voices cautioning that the correlation was not so clear. The more I read, the more I realized how many 'weasel words' permeated the coverage (might, could, likely, probably, many speculate, etc). Even worse, headlines and even conclusions within articles often did not align accurately with the actual facts in the article. 

I figured it was time for some research. I looked for national and international agencies, think tanks, meteorologists and climatologists. I did not try to avoid anything or confirm a particular bias. As far as I know, what I have to offer represents the mainstream or consensus scientific view. I know "consensus" is a dirty word in some circles, but if it's good enough to give force to the global warming argument, it should be good enough to give weight to this topic as well.

These quotes will address the number of hurricanes, their strength and duration as compared with existing data over the history of hurricane activity, and whether or not we should be drawing a connection between the power of the recent hurricanes and global warming. 

I think you will see that while there is minor disagreement, the general consensus is solid: global warming does not get credit for Harvey and Irma (except for perhaps a couple extra inches of rain). These are not climate change deniers saying this. Everyone I read affirms that the globe is warming, and that if trends continue we should eventually see significant impact, even if it might be a while. 

(It's worth noting I have only a few links to comments after 2015, since the study of the storms go on for quite some time after the hurricane seasons are over.) 

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• The National Oceanic and Atmospheric Administration, Hurricane Research Division, has a Chronological List of All Hurricanes which Affected the Continental United States from 1851-2015, sorted by decade. If you check out their stats, you will see that we had more hurricanes in the past, many quite powerful, and that’s a record compiled without the recording devices we have today. It is certain we missed many hurricanes and misunderstood the strength.

• Check out NOAA’s history of hurricanes (tropical storms) in the Atlantic Basin. Be sure to read the details, because they note how the stats jump as record keeping becomes better.  

• A 2015 article in Climate Change Dispatch, “An Inconvenient Truth: Cyclones, Hurricanes, Wildfires Aren’t Getting Worse,” notes: “The 5-year running sum for tropical cyclones globally hit a 45-year low [in 2015]… In ’the pentad [five years] since 2006, Northern Hemisphere and global tropical cyclone ACE has decreased dramatically to the lowest levels since the late 1970s’ and ‘the frequency of tropical cyclones has reached a historical low.’"

• According to the Journal of Climate, the number of smallest tropical storms have increased recently, but not the number of midlevel or large storms. Here is Wikipedia’s list from all over the world; unfortunately, as you will see, the data is limited. You can see for yourself the number of hurricanes, as well as their intensity.

• “Global Tropical Cyclone Landfalls, 1970-2014, an article by the often cited Roger Pielke Jr. in The Climate Fix, reports:  “The Intergovernmental Panel on Climate Change says there’s “no significant observed trends in global tropical cyclone frequency over the past century… No robust trends in annual numbers of tropical storms, hurricanes and major hurricanes counts have been identified over the past 100 years in the North Atlantic basin.” [note: this was in 2014]

• Atmos, the University Corporation for Atmospheric Research, is "a nonprofit consortium of more than 100 North American member colleges and universities focused on research and training in the atmospheric and related Earth system sciences. UCAR manages the National Center for Atmospheric Research with sponsorship by the National Science Foundation." In an article entitled “Hurricanes, Typhoons, Cyclones," they state: “On average there are about 70 to 110 named tropical cyclones per year across the world, including about 40 to 60 that reach hurricane strength. This range has held remarkably steady within the last 40 years. Within each basin, the numbers often vary more dramatically than the global average…After dipping to 30-year lows in the early 2010s, global ACE values have begun rising again.  Of all the hurricanes that build over the North Atlantic and Gulf of Mexico each year, only a small fraction make it to the U.S. coastline at hurricane strength. As of early 2013, the nation had not seen a major landfall (Category 3 or stronger) since 1995. However, the total number of hurricanes swirling across the North Atlantic remains unusually high. “ 

• When Harvey made landfall as a Cat 4, it had been 4,324days since a major hurricane landfall.  

• According to“Historical Global Tropical Cyclone Landfalls”: "While there is continued uncertainty surrounding future changes in climate… current projections of TC frequency or intensity change may not yield an anthropogenic signal in economic loss data for many decades or even centuries… Thus, our quantitative analysis of global hurricane landfalls is consistent with previous research focused on normalized losses associated with hurricanes that have found no trends once data are properly adjusted for societal factors.”

• A governmental agency, Geophysical Fluid Dynamics Laboratory, while affirming that they expect to see an impact in the future, concludes: “It is premature to conclude that human activities–and particularly greenhouse gas emissions that cause global warming–have already had a detectable impact on Atlantic hurricane or global tropical cyclone activity.”  

• In an article about Hurricane Harvey, The Atlantic reports: “Thomas Knutson, a research meteorologist at the NOAA fluid-dynamics laboratory in Princeton, New Jersey, told me that a “trade-off” signal still isn’t strong enough to see in the hurricane data. “We haven’t really detected clear changes in the data in the same way we can detect changes in global mean temperature,” he says. “I just think [30 years] is a rather short record to be inferring [human-caused climate] effects, because you can also have natural modes of variability over a period of several decades.”  

• “If we just look at frequency, there’s really no theory that says we should see fewer or more storms,” says James Elsner, a climate scientist and geographer at Florida State University. “But if we look at intensity separately, there is theory that says they should get stronger—especially the strongest ones. And we do see some evidence for that in the data.” Last year, Elsner and his colleague, Nam-Young Kang, published a review of how climate change has affected tropical hurricanes over the last 30 years in Nature Climate Change. It found a slight trend in the data toward more powerful, less frequent storms. As the tropical cyclones that have formed have gotten more intense, fewer have spun into existence. “If you look at frequency and intensity together, it appears that it’s really the efficiency of intensity that matches the global-warming signal the best. The strongest get stronger, but at the expense of the number of storms.” 

• Wunderground has a handy picture to go with their discussion of hurricane history. They also note, “ There is no evidence of a systematic increasing or decreasing trend in ACE for the years 1970-2012.” They have another page that provides stats for a number of different ways of looking at hurricane activity. It definitely shows increasing numbers more recently, but not in every category, and I assume it does not take into consideration the tropical storms that we know we missed when our instruments were not so proficient.

• It's no secret that increased cyclone activity correlates with increased sea temperatures. The NOAA notes: “Natural variability apparently plays a significant role in hurricane frequency and intensity, and currently appears to play a bigger role than greenhouse warming…. the Atlantic Multidecadal Oscillation, or AMO… is a pattern of sea surface temperature changes between warm and cold phases in the North Atlantic Ocean. The pattern tends to vary on multidecadal time scales, but the limited length of the Atlantic sea surface temperature record prevents scientists from making more definitive statements about the precise nature of the AMO.”

• Some have  emphasized the role of a natural 20-40 year cycle in ocean temperature (the AMO, for example). Others think the effect is minimal. Christopher Landsea, quoted in an NOAA article, says: "The late nineteenth century was a very busy period… Then from the 1900s until about 1925, it was very quiet. The late 20s to the 60s were very busy. The 1970s to the mid-90s were quiet again, and then from the late 90s onward, it's been generally very busy."

• "What I think we can say is that the fact that we do have climate change, our atmosphere is warmer, it contains more moisture, it means that when we do have a hurricane, a tropical cyclone like this, then when an event does occur, then you know climate change does very likely increase the associated rainfall. But climate change per se does not cause tropical cyclones," said Clare Nullis Kapp of the World Meteorological Organization. 

• In an article about a research team's paper published in Nature Geoscience in 2010: "Landsea and Kossin worked with Thomas Knutson, a research meteorologist at NOAA's Geophysical Fluid Dynamics Laboratory, and seven other researchers. Citing roughly 50 sources, most of them published in the previous five years, the authors concluded that it was uncertain whether the recent increase in tropical cyclone activity exceeds what could be expected from natural variability. That's not to say, however, that tropical cyclones have not changed due to human influences, nor that any changes in future tropical cyclones will not be attributable to our warming climate." 

• On a final note, while the flooding in Houston was terrible, it’s not unprecedented. Houston has been flooding since it was built. Yes, the cost of damage is increasing, but that is mainly because the population and infrastructure have increased. Check out this link to read about the history of flooding in Houston. 

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I'm not that interested in debating climate change. I'm interested in truth, and I am frustrated and a little angry about what happened during and after the recent hurricanes: the click bait headlines, the fear-mongering, the shrill decrying of anyone who dares question the hurricane/global warming correlation, the ridiculous assertion that people who question anything about the global warming narrative are either stupid, evil, criminal, or a combination of all three. 

Stop. 

Have you heard the story about the boy who cried wolf/global warming? Eventually, nobody believed him when the danger was clear and present. This distortion of reality for the sake of an argument will end up simply raising the level of skepticism when there is a real argument to be made. 

Let truth carry its own weight. If you need to lie so people take your claim seriously, maybe you should be building your argument with another claim.