Connecting the dots: The Great March Heat Wave and ... climate

I had a brief conversation recently with a couple of friends, both committed, long-standing environmentalists. Both were hesitant to ascribe the extraordinary heat wave we are currently experiencing here in Vermont (and that is being felt as far west as the Dakotas) to global warming.

I told them there was no doubt in my mind about the connection.  For the record (as it were), here's why:

The temperatures have been extraordinary, far outside the realm of previous temperature ranges in our region.  Sunday's high here was 80 degrees F, breaking the old high record by 16 degrees.  Monday the temperature was 79, breaking the old record by 20 degrees.  Tuesday, 80, 13 degrees above the old record.  Wednesday 81, 10 degrees above the old record.  This is just a remarkable run of extreme temperatures. (Today, 84, 11 degrees above the old record--five straight days in which the previous high has been broken by double digits.)

The new high temperature records here and elsewhere across the U.S. dovetail with a pattern that has developed over the past four decades, in which the ratio of new highs to new lows is steadily increasing.  This pattern is detailed in two graphics, one from the blog Capital Climate and one from the University Corporation for Atmospheric Research (UCAR) that have been reproduced in two excellent articles at another blog, Climate Progress (see March Madness: This may be an unprecedented event since modern U.S. weather records began in the late 19th Century, March 22, 2012, and Record highs far outpace record lows across U.S., Feb. 11, 2010).  The articles are well worth reading and highly recommended for the detail they provide, but here is a quick summary:

Article 1, from February 2010, includes the UCAR graphic, which shows the ratio of new high records to new low records across the U.S.  If the climate were not changing, one would expect the ratio to vary around 1:1.  Instead, what is actually happening is that the ratio is increasing, and some really wild excursions are taking place.  According to the UCAR graphic, the ratios (new highs to new lows) for recent decades look like this:

1950s: 1.09 to 1
1960s: 0.77 to 1
1970s: 0.78 to 1
1980s: 1.14 to 1
1990s: 1.36 to 1
2000s: 2.04 to 1

Article 2, the "March Madness" article from today, includes the Capital Climate graphic, with the monthly ratios for 2011 and 2012: 22 to 1 for August 2011, 22 to 1 for January 2012, and 35 to 1 to date for March 2012.  That makes three extraordinary heat waves in the past eight months.




I wish I could say the news is going to get better, but I don't think it is--to me (non-scientist), it looks like we are disturbing a previously stable system and the oscillations will get larger as long as we keep increasing the main input that is the source of the disturbance--the levels of greenhouse gases in the atmosphere.

The "March Madness" article also includes a brief video from The Weather Channel, featuring Senior Meteorologist Stu Ostro.  Ostro, formerly skeptical of the findings of climate science, has become a convert in recent years as the weather has increasingly diverged from what's been normal in the past. In Ostro's words, "Something ain't right--it's not business as usual." Indeed.