People are unaccountably convinced that there is an upward trend in severe weather events due to global warming. But there is no upward trend in the data on either the frequency or severity of those events. Forget, for the moment, the ongoing debate about the true extent of climate warming. In fact, I’ll stipulate that warming has occurred over the past 40 years, though most of it was confined to the jump roughly coincident with two El Ninos in the 1990s; there’s been little if any discernible trend since. But what about the trend in severe weather? I’ve heard people insist that it is true, but a few strong hurricanes do not constitute a trend.
The two charts at the top of this post were created by hurricane expert Ryan N. Maue. I took them from an article by David Middleton., but visit Maue’s web site on tropical cyclone activity for more. The last month plotted is September 2018, so the charts do not account for Hurricane Michael and the 2018 totals are for a partial year. The first nine months of each year typically accounts for about 3/4 of annual tropical cyclones, so 2018 will be a fairly strong year. Nevertheless, the charts refute the contention that there has been an upward trend in tropical cyclone activity. In fact, in the lower chart, the years following the 1990s increase in global temperatures is shown to have been a time a lower cyclone energy. Roy Spencer weighs in on the negative trend in major landfalling hurricanes in the U.S. and Florida stretching over many decades.
Warren Meyer blames ‘”media selection bias” for the mistaken impression of dangerous trends that do not exist. That is, the news media are very likely to report extreme events, as they should, but they are very unlikely to report a paucity of extreme events, no matter how lengthy or unusual the dearth:
“Does anyone doubt that if we were having a record-heavy tornado season, this would be leading every newscast? [But] if a record-heavy year is newsworthy, shouldn’t a record-light year be newsworthy as well? Apparently not.”
It so happens that 2018, thus far, has seen very close to a record low number of tornadoes in the U.S.
Meyer also highlights the frequent use of misleading statistics on the real value of damage from natural disasters. That aggregate value has almost certainly grown over the years, but it had nothing to do with the number or severity of natural disasters. Meyer explains:
“Think about places where there are large natural disasters in the US — two places that come to mind are California fires and coastal hurricanes. Do you really think that the total property value in California or on the US coastline has grown only at inflation? You not only have real estate price increases, but you have the value of new construction. The combination of these two is WAY over the 2-3% inflation rate.”
Recent experiences are always the most vivid in our minds. The same is true of broad impressions drawn from reports on the most recent natural disasters. The drama and tragedy of these events should never be minimized, and the fact that there is no upward trend in cyclone activity is no consolation to victims of those disasters. Still, the media can’t seem to resist the narrative that the threat of such events is increasing, even if it can’t be proven. Indeed, even if it’s not remotely correct. Reporters are human and generally not good at science, and they are not immune to the tendency to exaggerate the significance of events upon which they report. A dangerous, prospective trend is at once scary, exciting, and possibly career-enhancing. As for the public, sheer repetition is enough to convince most people that such a threat is undeniable… that everybody knows it… that the trend is already underway. The fact is that the upward trend in hurricane activity (and other kinds of severe weather) is speculative, not real.