Globe has 3rd or 8th warmest October on record; year-to-date period warmest on record

October 2010 was the globe's eighth warmest October on record, according to the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center (NCDC). NASA's Goddard Institute for Space Studies rated October 2010 the third warmest October on record. Both NOAA and NASA rated the year-to-date period, January - October, as the warmest such period on record. October 2010 global ocean temperatures were the 10th warmest on record, and land temperatures were the 6th warmest on record. Global satellite-measured temperatures for the lowest 8 km of the atmosphere were the 7th or 2nd warmest on record, according to Remote Sensing Systems and the University of Alabama Huntsville (UAH), respectively. UAH rated the year-to-date period, January-October, as the 2nd warmest such period in the satellite data record, behind 1998.

For those interested, NCDC has a page of notable weather highlights from October 2010.


Figure 1. Departure of temperature from average for October 2010. Image credit: National Climatic Data Center (NCDC)

Eleventh warmest October on record for the U.S.
For the contiguous U.S., it was the 11th warmest October in the 116-year record, according to the National Climatic Data Center. The year-to-date period, January to October, was the 19th warmest such period on record. Two states had a top-ten warmest October on record--Wyoming and Montana. No states were colder than average.

U.S. precipitation
For the contiguous U.S., October 2010 was the 39th driest on record. Florida had its driest October in the 116-year record, and two other states had top-ten driest Octobers--Missouri and Texas. Nevada had its wettest October on record, and five other states had a top-ten wettest October--New York, Vermont, New Hampshire, Maine, and California.

La Niña in the "moderate" category
The equatorial Eastern Pacific Ocean is currently experiencing moderate La Niña conditions. Sea surface temperatures (SSTs) over the tropical Eastern Pacific in the area 5°N - 5°S, 120°W - 170°W, also called the "Niña 3.4 region", were 1.3°C below average during the first two weeks of November, according to NOAA. The Australian Bureau of Meteorology put this number at 1.23°C below average (as of November 14.) Moderate La Niña conditions are defined as occurring when this number is 1.0°C - 1.5°C below average. Temperatures colder than 1.5°C below average qualify as strong La Niña conditions. NOAA is maintaining its La Niña advisory, and expects La Niña conditions to last through the coming winter into spring.

Both El Niño and La Niña events have major impacts on regional and global weather patterns. La Niña typically causes warm, dry winters over the southern portion of the U.S., with cooler and wetter than average conditions over the Pacific Northwest. The Ohio and Mississippi Valleys states typically have wetter winters than usual during La Niña events. I'll have a full analysis of what La Niña might mean for the coming U.S. winter in a post next week.


Figure 2. Departure of surface temperature from average for the first half of November for the Arctic. Record low sea ice extent during this period has led to three "hot spots" with temperatures up to 12°C (22°F) above average where the sea ice loss was greatest. This unusual warmth is likely to have significant impacts on weather patterns across much of the Northern Hemisphere during the coming months. As I discussed in my post The climate is changing: the Arctic Dipole emerges last December, Francis et al. (2009) found that during 1979 - 2006, years that had unusually low summertime Arctic sea ice had a 10 - 20% reduction in the temperature difference between the Equator and North Pole. This resulted in a weaker jet stream with slower winds that lasted a full six months, through fall and winter. The weaker jet caused a weaker Aleutian Low and Icelandic Low during the winter, resulting in a more negative North Atlantic Oscillation (NAO). This pattern typically brings exceptionally cold and snowy winters to eastern North America and Europe. The winter of 2009 - 2010 saw the most negative NAO since record keeping began in 1950, which resulted in an upside-down winter in North America--unprecedented snowstorms and the coldest winter in 25 years in the U.S., and the warmest winter on record in Canada. The unusual negative NAO conditions may have been due, in part, to the unusually high Arctic sea ice loss the previous summer (3rd greatest on record.) The latest GFS forecast predicts that the NAO will go strongly negative for the remainder of November, resulting in a major cold blast for the Eastern U.S. and Western Europe. Image credit: NOAA/ESRL.

October 2010 Arctic sea ice extent 3rd lowest on record
Arctic sea ice extent in October 2010 was the third lowest in the 31-year satellite record behind 2007 and 2009, according to the National Snow and Ice Data Center. Sea ice extent as of today (November 19) is the lowest on record for this time of year, according to ice extent imagery at the University of Bremen. Ice volume in October was the lowest on record, according to University of Washington Polar Ice Center.

I'll have a new post on Monday.

Jeff Masters