An inconvenient fact: The frequency of violent tornadoes like the ones in the Midwest has been declining, not increasing

Great post from economist Mark Perry

Following a series of tornadoes in 2011, including an especially violent one (category EF5) that hit Joplin, Missouri and killed 158 people, many climate alarmists quickly drew a connection between the string of tornadoes and global warming climate change (or to their keep their options open, some in the green movement now prefer the term “violent weather“). For example, see this Washington Post op-ed by Bill McKibben (founder of the global climate campaign 350.org and a distinguished scholar at Middlebury College) from May 23, 2011 (“A link between climate change and Joplin tornadoes? Never!“) that generated more than 1,000 comments. Earlier this year, after tornadoes killed more than 20 people in Oklahoma, climate alarmists were again quick to blame global warming climate change violent weather, see articles here at The Huffington Post and here at Fox News, which quoted Senator Barbara Boxer from the floor of the Senate connecting the Oklahoma tornado to climate change:

This is climate change. We were warned about extreme weather, not just hot weather but extreme weather. … When I had my hearings … scientists all agreed that what we’d start to see was extreme weather.  … It’s going to get hot. But you’re also going to see snow in the summer in some places. You’re going have terrible storms. You’re going to have tornadoes.

Now the climate alarmists, like former United Nations adviser and economist Jeffrey Sachs (now director of the Earth Institute at Columbia University) are at it again, linking the recent tornadoes and thunderstorms in the Midwest to global warming. Via The Daily Caller:

Former United Nations adviser and economist Jeffrey Sachs sent out tweets Sunday night that the severe storms that hit Illinois on Sunday were the result of human-induced global warming, for example:

Tweet 1. Weather tragedy in Illinois. Research shows human-induced warming is likely to lead to more severe thunderstorms.

Tweet 2. Today’s tornadoes in Illinois were very uncommon in number and severity for the month of November. Not unprecedented, but very uncommon.

Tweet 3. Climate liars like Rupert Murdoch and Koch Brothers have more and more blood on their hands as climate disasters claim lives across world.

MP: As I reported earlier this year, there’s just one small, very inconvenient problem with making a connection between global warming climate change and an increasing frequency of violent, deadly tornadoes – it’s a link that doesn’t actually exist. Here are some inconvenient weather facts based on publicly-available data from the National Oceanic and Atmospheric Administration’s (NOAA) National Climatic Data Center.

The top chart above displays the annual number of “strong to violent tornadoes” (F3 to F5 on the Fujita Scale) in the US from 1954 to 2012, with these highlights:

1. Between 1954 (earliest year available) and 2012, there has been a downward trend in the frequency of strong to violent tornadoes in the US, and that declining trend is statistically significant at the 1% level (see red line in chart, based on a linear regression model). On average, there has been a decline of 0.44 violent tornadoes every year since 1954, or a decline of 4.4 violent tornadoes every decade since the 1950s.

2. Although there was a significant number (84) of violent tornadoes in 2011 (which generated responses like Bill McKibben’s op-ed in the Washington Post that linked tornadoes like the one that hit Joplin, Missouri to climate change), there were actually more violent tornadoes in the years 1957 (99), 1965 (98), 1973 (86) and 1974 (131).

3. In the first half of the sample period from 1954 to 1983, there were ten years when there were more than 60 violent tornadoes, and the average was 55.4 tornadoes annually during that 30-year period. In contrast, during the second half of the sample from 1984 to 2012, during a period when global warming was supposed to be increasing, there were only two years when there were more than 60 violent tornadoes (1999 and 2011), and the annual average was only 37.2 during that 30-year period.

4. The bottom chart above displays the ten deadliest tornadoes in US history, according to the NOAA (measured by number of weather-related deaths), and only one (the Missouri tornado in 2011) has occurred in the last 50 years; the other nine deadliest tornadoes in the US took place between 1840 and 1953. And the five deadliest tornadoes in US history that combined killed almost 1,500 people, all took place in 1936 or before.

Bottom Line: The statistical evidence on violent tornadoes, although frequently ignored by the media, politicians, and others claiming a link between violent weather and climate change, clearly shows that the frequency of violent tornadoes like the recent ones in the Midwest, has actually been declining over time, and not increasing. Further, of the ten most deadly tornadoes in US history, nine took place in 1953 or before, and only one has occurred in the last sixty years. But climate alarmists always prefer “green hysteria” over evidence, hard facts and data, and we can expect more Sachs-like tweets and McKibben-like op-eds in the days to come, with false claims linking the Midwest tornadoes to global warming and climate change.