It Was a Toasty, Stormy October

U.S. temperature departures from average during October 2010. Credit: NOAA/NCDC.

Today’s business pages are packed (as always, it seems) with some of the periodic economic reports that give snapshots of the economy, giving an idea of where things stand and where they may be headed — last week’s unemployment numbers, the September trade deficit, the October oil-price increase and more.

The government’s economic agencies aren’t the only ones who put out reports like this, however. Each month, the National Climatic Data Center, part of the National Oceanic and Atmospheric Administration (NOAA), issues its State of the Climate report, and the numbers for October have just come in. The document is packed with enough maps and data to satisfy the wonkiest climate junkie, but for the rest of us, a few highlights stand out:

  • The average temperature in the U.S. for October was 56.9°F (13.8°C), which is 2.1°F (1.2°C) above the 1901-2000 average, the eleventh warmest on record in the United States. Warmer-than-average conditions prevailed throughout the western U.S. and into the Midwest. Of the nine climate regions, none had below normal temperatures and only two, both along the Eastern Seaboard, experienced a monthly average temperature that was close to average.
  • No state had below normal average temperatures, while more than half were above-average. Wyoming had its fourth warmest October and Montana its seventh.

That’s for the lower 48 states of the U.S.; for the world as a whole, the numbers are a month behind, since the data takes longer to process and quality control. You can peruse the whole global section of the report at leisure, but here’s the bottom line:

The combined global land and ocean surface temperature for September 2010 was 0.90°F (0.50°C) above the 20th century average of 59.0°F (15.0°C), and tied with 1998 as the eighth warmest on record. September 2005 is still ranked as the warmest September on record.

What makes all of this — and especially the U.S. temperatures — so significant is that we’re now under the influence of the cool Pacific ocean and atmospheric cycle known as La Niña. La Niña, which appears every five to seven years on average, tends to lower global temperatures by about a tenth of a degree C from what they would otherwise have been. Here’s how meteorologist Dan Satterfield puts it on his blog for the American Geophysical Union:

In spite of this, 2010 may end up being the warmest year globally on record. With the La Niña in full bore, we still set 8 record highs for every record low in October…. We are almost certainly witnessing something that has not been seen in all of history. Human interference with the planet’s climate. While there are month to month and even decade to decade fluctuations in the global temperature, there is nothing left to explain the  long term rise. Everything except rising greenhouse gases from fossil fuels have been ruled out…

Satellite image showing the massive storm over the Midwest on October 26, 2010. Credit: NASA Earth Observatory.

But wait! There’s more! Climate change involves more than just warmer temperatures; it also leads to extreme weather events, and the NCDC report has some data on those as well. One of them is the “megastormthat battered the Midwest a few weeks ago, bringing rain, snow, high winds and no fewer than 78 tornadoes to the region, along with an atmospheric pressure reading that bottomed out at 28.24 inches of mercury — a record low for a continental storm, and equivalent to a major hurricane. (While scientists cannot say that this particular storm was related to climate change, there is evidence that the odds of certain extreme weather events are increasing). As the National Weather Service put it:

The bottom line is that the storm that struck the Upper Mississippi River Valley on October 26-27, 2010 was a very intense and rare storm, something that is not seen in this part of the country very often. While the minimum sea level pressure may not necessarily be the lowest on record, the storm was undoubtedly one of the most intense on record in the continental United States