As hurricane preparedness week comes to an end and the 2013 Atlantic hurricane season gets officially under way, NOAA and other forecasters are expecting a very active season with up to 20 named storms and three to six major hurricanes. If it plays out that way, it would put this year as the second most active season since 2005, and well above the current active period average that started in 1995 – when the number of named storms jumped significantly over the 25 or so years before.
The variation makes sense, since hurricane numbers rise and fall every few decades with the naturally cycling Atlantic Multi-Decadal Oscillation, or AMO. But it’s not clear why the average is significantly higher now than it was during the last upswing, which ended in 1970 or thereabouts. It’s even less clear why we saw so many major hurricanes making landfall between 1950 and 1970, but none since 2005. There’s no evidence that it has to do with climate change.
The graphic below charts our understanding of various types of extreme weather, based on how good our understanding is of what causes them (Y-axis) and how reliable our observations have been (X-axis). We clearly know more about both aspects of hurricanes than we do of tornadoes, but less than we know about heavy precipitation, heat waves and other weather extremes.
The current level of understanding makes it hard to say for certain how climate change will influence Atlantic hurricanes in the future. We do know that warmer sea-surface temperatures are likely to make them stronger (though they could be fewer in number); that rising sea level will make storm surges more damaging; that hurricane driven rains will probably become even more torrential; and that rapid population growth along the Atlantic and Gulf coasts will put more people and property in harm’s way.