Friday, September 14, 2012

The Heat Is On

Image Credit: Climate Central.

The January-August period was the warmest first eight months of any year on record for the contiguous United States. The national temperature of 58.7°F was 4.0°F above the 20th century average, and 1.0°F above the previous record warm January-August of 2006. During the eight-month period, 33 states were record warm and an additional 12 states were top ten warm. Only Washington had statewide temperatures near average for the period.

The statewide ranks of temperatures since 1895 and the top ten warmest January-August periods in South Carolina.  Image Credit: NOAA\NCDC.

Climate Central has developed an interactive map that illustrates the record heat experienced across the country.  Not only has it been the hottest year in the U.S. since recordkeeping began in 1895, but so far more than 28,000 individual daily high-temperature records have been matched or broken.

The interactive map can be found here.  Image Credit: Climate Central.

Here is a summary of the interactive map:

  • The “Number of Records” map simply shows how many records were set in each state.
  • Since some states have a lot more measuring stations than others, the “Records/Station” map shows how many daily records were broken, on average, at each station, in order to give equal weight to states with fewer stations.
  • The “vs. Expected” map takes into account how difficult it actually is to break a record, based on what year data collection began (for example, a station that’s been recording for 100 years will have had more chances to set a very high record, which is harder to break, than a station that’s only 40 years old).
  • The “Ratio to Low” map ranks states on how much high-temperature records outnumber low-temperature records.
  • Finally, the “Overall” map represents an average of all these measures, in order to show which states broke the most records and how unusual these records are.

The “Ratio to Low” map provides a useful way of showing that record high temperatures have outnumbered record low temperatures all over the country. In an unchanging climate, the ratio of record highs to record lows is expected to be roughly 1:1 on average and in the long term. A ratio greater than 1:1 suggests a warming climate. This year, not a single state has seen more lows than highs, or even a 1:1 ratio. This follows a string of years in the last decade or so during which the record high to record low ratio over the U.S. has been persistently and significantly larger than 1 as a long term trend.

This is what you find for South Carolina:

Image Credit: Climate Central.

South Carolina comes in 39th in the overall ranking. However, it has a large ratio of record highs to record lows (almost 5:1). While this is below the national average of 13.37, it still means that every time a station reported a record low temperature, 5 other stations reported record highs.

The average summer temperature turned out to be near normal for Columbia in spite of setting an all-time record high of 109 F on the last two days of June.  It was 106 F on July 1, but the humidity was much higher and the heat index reached 119 F followed by severe thunderstorms.  It still turned out to be the hottest January-August period since the National Weather Service Forecast Office was relocated to the airport in 1948.

Image Credit: Climate Central.

The past five month have seen the top five warmest 12-month periods for the country since records began in 1895.

The warmest 12-month periods.  Image Credit: NOAA\NCDC.

Clearly 2012 is on track to be the warmest year on record.  Keep in mind that this is only for the contiguous United States and is not for the globe.  That remains to be played out, but I discussed this back in January in this post.