Monthly ratio of daily high temperature records vs low ones set in the U.S. for June 2010 through July 23, 2011, data from NOAA.
One way to tell if a nationwide heat wave is truly record-breaking is, well, to look at the total number of records that it breaks. Even better is to compare the high records with the low records, since we have very good historical data and analysis on that — and it covers the whole nation.
Steve Scolnik at Capital Climate analyzed the data from NOAA’s National Climatic Data Center (NCDC) and found, “U.S. Summer Heat Records Continue Overwhelming Cold Records By Over 8:1.” These large ratios for the summer and the first 23 days of July are a big deal compared to, for instance, the average over the last decade of about 2-to-1 (see “Mother Nature is Just Getting Warmed Up” and below).
But the conservative media can’t even bring themselves to admit that, as Media Matters documents:
On his radio show yesterday, Rush Limbaugh declared that “almost no temperature records were broken” during the recent heat wave and that media outlets who reported on “record-breaking” heat were telling “a bunch of lies” to “advance a political agenda of liberalism.”
Limbaugh’s remarks echo a Newsbusters post in which Noel Sheppard claims that “almost no temperature records were actually broken.” He came to this conclusion by ignoring most of the temperature records. Nevertheless, Sheppard’s claim was picked up not only by Limbaugh but also Fox Nation:
Citing the NOAA database, Sheppard claims “There were only 34 new all-time daily temperature records set during last week’s ‘record-breaking heat.’ This is out of over 6000 records previously set for each day since such things have been reported.”
Actually, it’s not out of over 6000 records “set for each day,” but out of over 6000 records set for all-time at each location. Sheppard is confusing all-time and daily records.
See, NOAA keeps track of records for different time scales: The daily record compares the temperature on July 24, for instance, to the temperature on every previous July 24; the monthly record compares the temperature on July 24 to the temperature of any day in July of any year; and the all-time record compares the temperature on July 24 to the temperature of any day in any year. On top of that, NOAA provides these records for both the highest maximum temperature and the highest minimum (nighttime) temperature.
Sheppard is reporting the all-time records, describing them as though they are daily records, and ignoring everything else.
Here’s the data (from NOAA) on the number of U.S. records broken or tied in the month of July so far:
- All-Time Highest Maximum Temperature: 70
- All-Time Highest Minimum Temperature: 175
- Monthly Highest Maximum Temperature: 125
- Monthly Highest Minimum Temperature: 330
- Daily Highest Maximum Temperature: 2,125
- Daily Highest Minimum Temperature: 4,787
Downplaying the heat wave, Limbaugh claimed “It does this every year.” Is that true?
Not according to Christopher Vaccaro, a spokesman for the National Weather Service who told the New York Times that “this is different”:
“One could say, ‘Oh, it’s summer, its late July, it’s hot,’ ” said Christopher Vaccaro, a spokesman for the National Weather Service. “But this is different.”
According to Mr. Vaccaro, this heat wave is exceptional not only for its strength, but also for its breadth and duration.
Meteorologist Jason Samenow wrote that “It’s the humidity the sets this heat wave apart – not just in D.C., but over large parts of the country and for a long duration.” Samenow added:
To conclude: where it’s been dry, the day time heat has been unusual; elsewhere, the night time heat and humidity has been unusual. It will take more time and analysis to objectively rank where this heat wave stacks up in the record books, but it’s clear that it’s far from the ordinary.
Jeff Masters, Director of Meteorology for the Weather Underground, writes that “July 2011 is on pace to be one of the five hottest months in U.S. history, but may have a tough time surpassing the hottest month of all time, July 1936.” Masters added that in contrast to the 1930s heat waves, the humidity during the most recent heat wave was high:
The heat index–how hot the air feels when factoring in both the temperature and the humidity–has been exceptionally high during this week’s heat wave, due to the presence of very high amounts of water vapor in the atmosphere. That has made this heat wave a very dangerous one, since the body is much less able to cool itself when the humidity is high….
During the 1930s, there was a high frequency of heat waves due to high daytime temperatures resulting in large part from an extended multi-year period of intense drought. By contrast, in the past 3 to 4 decades, there has been an increasing trend in high-humidity heat waves, which are characterized by the persistence of extremely high nighttime temperatures.
Masters further stated that global warming makes heat waves like this one more likely to occur. Indeed, we’ve noted that scientists expect heat waves to become “more intense, more frequent and longer-lasting” as a result of human-induced climate change.
Which brings us to the question of why conservative media figures feel the need to downplay last week’s scorching heat. Apparently, a distaste for policies designed to address climate change has led some to reject the scientific consensus that humans are changing the climate, which has, in turn, led them to deny the validity of the evidence supporting human-induced climate change and denounce climate-related information as “propaganda.”
And now Limbaugh has dug himself into such a hole that he feels he can’t even acknowledge an unusually intense heat wave and has to attack the heat index as a figure “manufactured by the government.” It’s clear that to Limbaugh, weather and climate data aren’t information to consider, but a “weapon” to use in political battles.
The many businesses and public entities that provide services affected by changing weather patterns don’t have that luxury.
Let’s return to the ratio of daily record highs to lows, from the 2009 National Center for Atmospheric Research study of the past six decades (see “Record high temperatures far outpace record lows across U.S.“):
This graphic shows the ratio of record daily highs to record daily lows observed at about 1,800 weather stations in the 48 contiguous United States from January 1950 through September 2009. Each bar shows the proportion of record highs (red) to record lows (blue) for each decade. The 1960s and 1970s saw slightly more record daily lows than highs, but in the last 30 years record highs have increasingly predominated, with the ratio now about two-to-one for the 48 states as a whole.
NCAR explained their 2009 findings in a news release:
Spurred by a warming climate, daily record high temperatures occurred twice as often as record lows over the last decade across the continental United States, new research shows. The ratio of record highs to lows is likely to increase dramatically in coming decades if emissions of greenhouse gases continue to climb.
“Climate change is making itself felt in terms of day-to-day weather in the United States,” says Gerald Meehl, the lead author and a senior scientist at the National Center for Atmospheric Research (NCAR). “The ways these records are being broken show how our climate is already shifting.”
The scientific paper itself is here (subs. req’d). And NCAR posted a video of lead author Meehl discussing his findings here. The study looked into the future and found that “if nations continue to increase their emissions of greenhouse gases in a ‘business as usual’ scenario, the U.S. ratio of daily record high to record low temperatures would increase to about 20-to-1 by mid-century and 50-to-1 by 2100.”
So the 8-to-1 ratio for this summer is indicative of a monster heat wave. There’s no denying that.