The Washington Post

Extreme weather 2011: warmest La Nina year on record, around 10th warmest overall

NOAA global temperature anomalies since 1950, colored coded according to whether La Nina. El Nino or neutral conditions prevailed (NOAA)

Considering all years in records dating back to 1880, 2011 was about the 10th warmest year the two agencies reported today.

Both agencies calculated 2011’s global average temperature to be 0.92 F above average. This placed 2011 as 9th warmest overall in NASA’s record compared to a tie for 11th warmest in NOAA’s.

The unusually warm years keep mounting. NOAA said all 11 years of the 21st century rank among the 13 warmest. And NASA noted 9 of the top 10 warmest years in its record have occurred since 2000, the lone exception being 1998 (tied with 2010 as the warmest year).

Global average surface temperatures compared to averaged since 1880 (in degrees C) (NASA)

“Higher temperatures today are largely sustained by increased atmospheric concentrations of greenhouse gases, especially carbon dioxide,” NASA wrote in a press release.

Although La Nina depressed the global average temperature in 2011 to the second coolest in the 21st century to date, it still matched the second warmest year of the 20th century NOAA said.

NASA said today La Nina “is peaking” but stopped short of saying whether a return of El Nino, associated with warm ocean temperatures in the equatorial Pacific, is imminent.

“It’s always dangerous to make predictions about El Niño, but it’s safe to say we’ll see one in the next three years,” said James E. Hansen, director of NASA’s Global Institute for Space Studies. “It won’t take a very strong El Niño to push temperatures above 2010.”

As soon as El Nino returns, Hansen predicts record-breaking global warmth.

La Nina pattern elevated U.S. extreme weather in 2011

While global temperatures modestly cooled off, an amped-up polar jet stream - characteristic of La Ninas - charged an unending wave of weather extremes in the U.S. NOAA, which had previously documented 12 billion dollar weather disasters in 2011, added two more to the list today:

* Tropical Storm Lee (early September) - which caused record flooding across the Northeast states, especially Pennsylvania and New York.

* A Rockies and Midwest severe weather outbreak (July 10-14) which included tornadoes, hail and high winds.

Location of 2011 billion dollar weather disasters (NOAA)

While NOAA announced 2011 set a record for most billion dollar disasters since 1980, at least one researcher says the record is questionable due to NOAA’s incomplete economic analysis of weather extremes early in the record.

Weather stations recording wettest, driest, warmest and coolest years on record in 2011 (NOAA)

As we previously reported, the record wet (near and north of the jet stream) and record dry conditions (south of the jet stream) were in amazingly close proximity, especially during the spring. The strong contrast between the neighboring moist and dry airmasses generated high levels of atmospheric instability, leading to a record-breaking tornado season. 1150 tornadoes were confirmed in the spring, NOAA said. And the 551 tornado-fatalties were the most on record since 1950.

Top weather events of 2011

NOAA convened a list of the top 10 U.S. and global weather events of 201l, shown below.

Top 10 extreme weather events in the U.S. and NOAA as determined by NOAA
Jason is the Washington Post’s weather editor and Capital Weather Gang's chief meteorologist. He earned a master's degree in atmospheric science, and spent 10 years as a climate change science analyst for the U.S. government. He holds the Digital Seal of Approval from the National Weather Association.


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