Alexander’s paper begins by stating, “The purported link between extreme weather and global warming has captured the public imagination and attention of the mainstream media far more than any of the other claims made by the narrative of human-caused climate change.”
This is surprising because data and analyses from the Intergovernmental Panel on Climate Change (IPCC)—the U.N. body that climate alarmists in academic, political, and media circles continually cite as the authoritative source of information on climate change—confirm that “if there is any trend at all in extreme weather, it’s downward rather than upward. Our most extreme weather, be it heat wave, drought, flood, hurricane or tornado, occurred many years ago, long before the carbon dioxide level in the atmosphere began to climb at its present rate,” wrote Alexander.
“Recent atmospheric heat waves in western Europe,” wrote Alexander, “pale in comparison with the soaring temperatures of the 1930s, a period when three of the seven continents and 32 of the 50 US states set all-time high temperature records, which still stand today.”
Nor has IPCC discerned or identified any long-term trend in drought patterns, either in the United States or globally. And even though rainfall has modestly increased in recent years, there is no evidence floods are becoming more frequent or severe. Alexander notes that many recent flood events can be traced almost entirely to land-use changes, including channelization, deforestation, destruction of wetlands, and the building of dams.
“Climate at a Glance: Floods” confirms Alexander’s assessment, citing data showing there has been no evidence of increasing flooding frequency or severity in the United States or elsewhere over the past century and a half. Indeed, IPCC writes that it has “low confidence” in any climate change impact regarding the frequency or severity of floods, going so far as to state it has “low confidence” in even the “sign” of any changes. In other words, it is just as likely that climate change is making floods less frequent and less severe.
On top of that, a 2017 study on the climate impact of flooding for the United States and Europe, published in the Journal of Hydrology, found, “The number of significant trends was about the number expected due to chance alone,” and “Changes in the frequency of major floods are dominated by multidecadal variability.”
Alexander notes hurricanes and tropical cyclones actually show a decreasing trend around the globe, with the frequency of land-falling hurricanes of any strength (Categories 1 through 5) remaining unchanged for at least 50 years. While the frequency of major North Atlantic hurricanes, which are the most studied, has increased during the past 20 years, the current heightened activity level is comparable to the 1950s and 1960s—a period when the earth was cooling, not warming.
“Climate at a Glance: Hurricanes” confirms Alexander’s hurricane conclusions, citing the IPCC and the National Oceanic and Atmospheric Administration (NOAA) which report there has been no increase in number or severity of hurricanes as the planet has modestly warmed. The United States recently went through its longest period in recorded history without a major hurricane strike, experiencing its fewest total hurricanes in any eight-year period. And IPCC’s 2018 Interim Report observes there is “only low confidence for the attribution of any detectable changes in tropical cyclone activity to anthropogenic influences.”
“Likewise, there is no trend in the frequency of tornadoes in the United States since at least as far back as 1954. The frequency of strong (EF3 or greater) tornadoes has even diminished over that interval. The average number of strong tornadoes annually from 1986 to 2017 was 40 percent less than from 1954 to 1985,” Alexander wrote, concerning the absence of changes in tornado trends during the recent period of modest warming.
Simultaneously, the IPCC reports with “high confidence” that precipitation has increased over mid-latitude land areas of the Northern Hemisphere (including the United States) during the past 70 years, while the IPCC has “low confidence” about any negative trends globally.
Extreme weather events do occur, but they are the result of “natural patterns in the climate system, not global warming,” wrote Alexander. In particular, he cites the periodic, although irregular shifts in the Atlantic Multidecadal Oscillation, which governs many extremes such as intense hurricanes in the North Atlantic basin and major floods in eastern North America and western Europe.
Further, El Niño and La Niña cycles in the Pacific Ocean often cause catastrophic flooding in the western Americas, as well as severe droughts in Australia. In Europe, recent heat waves have been driven by changes in the jet stream that block normal weather patterns.
In short, the oft-repeated assertions that weather is getting more extreme is patently false. Drought, flooding, hurricane, and tornado numbers are well within their normal historic range of severity and frequency. Looking at the data, there is absolutely no basis for alarm.