This graph is the Ace Index – a measure of both the strength and number of tropical cyclones (aka hurricanes and typhoons). The graph clearly shows that the number/strength of tropical cylones is essentially flat since 1970. If anything the ACE index is down ever so slightly since the mid 1990s.
Every so often (and more often after a year with significant hurricane activity in the U.S. like 2005 (Katrina, Rita, Wilma) or 2017 (Harvey, Irma, Maria) I see a tweet or I get an email stating that hurricanes are much more numerous and/or much more intense than in decades past. Some make ridiculous claims. I’ve seen memes that say that “there are five times more hurricanes than 1970 (or pick a year). Another said that hurricanes are 700% stronger than in the past. Ke.ep in mind that while 2017 was a big year for hurricanes hitting the U.S., it was the quietest year ever in the Southern Hemisphere and global, the ACE Index wasn’t too far from average.
I thought I’d write about this tonight, because I saw this quote from Dr. Chris Landsea, the National Hurricane Center Science and Operations Officer. “There’s periods where it’s busy and quiet and busy and quiet, but no trend,” said Landsea, “There’s no statistical change over a 130-year period. Since 1970, the number of hurricanes globally is flat. I haven’t seen anything that suggests that the hurricane intensity is going to change dramatically. It looks like a pretty tiny change to how strong hurricanes will be. It’s not zero, but it’s in the noise level. It’s very small.” This is from an interview with NBC News.