By Robert Henson
In 2004 the brother-and-brother team of Maxwell and Jules Boykoff wrote a widely publicized paper
for the journal Global Environmental Change called "Balance as bias: global warming and the US prestige press." Through a content analysis of more than 600 stories published in four influential U.S. newspapers, the Boykoffs deftly showed how coverage of climate change that appears even-handed ("some scientists say it's real; others say it's not") can greatly distort the degree of consensus that really exists. The Boykoffs concluded that "adherence to the norm of balanced reporting leads to informationally biased coverage of global warming."
There's a similar phenomenon that often crops up in weathercasts and even in small talk. Often when temperatures run well above average in one part of the nation, they're below average somewhere else. This is a natural outgrowth of the characteristic scale of blocking patterns, but it also makes a sort of intuitive sense: what goes up must come down, and if it's warm here, it must be cool there, to "balance things out."
Jason Samenow's ForecastToday:
Mostly cloudy and humid with a 50% chance of showers and thunderstorms, particularly during the afternoon and evening. Highs in the mid 80s.Tonight:
A 30% chance of showers and thunderstorms. Lows 69-74.Monday:
Mostly cloudy with a 40% chance of showers and thunderstorms. Highs in the upper 80s.
This summer offers a striking example of the perils of this notion of meteorological balance. In one corner, we have the brutal heat wave that's been centered on the northern Plains and Rockies most of the summer, with Montana at its epicenter. As of Friday, July 27, Missoula has seen nine days at or above 100°F (their previous record was six, in the peak Dust Bowl year of 1936). They hit a new all-time high of 107°F on July 6 and scored an all-time warmest low last Tuesday, July 24, with 71°F. Even more impressive, Bozeman, MT, has matched or topped its former all-time record high of 103°F no less than five times this month! (Their new all-time max is 106°F.)
In the other corner, further south, Texas and Oklahoma have enjoyed an oddly mild summer by their usual broiling standards. The Dallas-Fort Worth station has topped 96°F only twice all summer, and they've yet to break the century mark - very unusual. The story is similar in Oklahoma City, where only one day all summer has made it above 93°F (July 15, which managed to hit 96°F). By comparison, Oklahoma City's average high for this time of year is around 94°F.
However, these two areas of anomalies don't quite balance each other out. The southern-plains mildness is related to an amazingly persistent wet pattern that held through much of June into July. According to the Oklahoma Climatological Survey
, the town of Minco, not far from Oklahoma City, has logged 44 inches of precipitation in 2007 - far more than its usual yearly total - with most of it falling in the last three months. Because of the clouds and moisture, overnight lows have held close to average, and there's been an unusually uniform temperature regime from day to day. The upshot: June as a whole ran only 0.4°F below average in both Oklahoma City and DFW, and July is running between 1°F and 2°F below average in both cities. Contrast that to places like Missoula, where June averaged 2.7°F above average and the July anomaly is close to an astounding 11°F.
As a whole, we're experiencing yet another hotter-than-usual summer in the United States, a fact borne out by NOAA's June analysis
(23rd warmest on record for the lower 48 states) and by one of my favorite Web sites: the "operational global circulation and anomalies
" page from NOAA's Physical Sciences Division. By scrolling down to Surface Temperatures and scrolling across, you can display worldwide temperature anomalies for a whole variety of recent periods, ranging from a single day
to an entire year
. Notice how most of the cold anomalies evident on almost any single day disappear when you stretch to a longer time period, such as 30 days, and especially for a full year. Even when day-to-day weather appears to "balance out" from coast to coast, it's clear that the scales are tipping in one direction over the longer term - and it's not toward cooling.Meteorologist Robert Henson is a writer and editor at the University Corporation for Atmospheric Research, which operates the National Center for Atmospheric Research. He is the author of "The Rough Guide to Weather" (second edition, 2007) and "The Rough Guide to Climate Change" (2006). Henson is filling in for Andrew Freedman this week and next week.