Last month was the warmest November on record, according to a report released this week from the National Climatic Data Center (NCDC).
"It's the first time we've seen a big spike like this in the global surface temperature in several years," said Deke Arndt, chief of the climate-monitoring branch of the NCDC, which is part of the U.S. National Oceanic and Atmospheric Administration.
November's worldwide average was 1.40°F (0.78°C) higher than the 20th-century global average temperature of 55.2°F (12.9°C). It was the sixth warmest of any month since record-keeping began in 1880, marking the 345th consecutive month—more than 28 years—that temperatures were above the 20th century's average. (See "Rising Temperatures May Cause More Katrinas.")
"This surprised us a little bit when we saw the numbers come in," Arndt said. While 2010 was the hottest year on record, global temperatures have tapered off since then. (See "Does 'Global Warming Pause' Debate Miss Big Picture?")
There weren't any large-scale patterns that would have hinted at such an upswing. Unlike in 2010, there was no El Niño event this year, which would have had a slight warming effect.
Previously, the hottest November was in 2004, which was 1.37°F (0.75°C) warmer than the average. The new record may not seem much warmer, Arndt said, but the leap is significant considering the fact that the numbers are averaged across the entire world.
Although such a spike in itself doesn't prove or validate anything about climate change, it's consistent with the overall global trend of rising temperatures, he said. "It's a single piece of evidence that tends to support what we've seen over the last 30 years, that the average surface temperature of the planet is getting warmer." (See also "New Study Predicts Year Your City's Climate Will Change.")
Hot, Hot, Hot
The month was so warm despite the fact that the U.S. was 0.27°F (0.15°C) cooler than average. Other parts of North America, northern Australia, Greenland, and the waters south of South America were also slightly cooler.
But the rest of the world more than made up for it. For example, Russia experienced the hottest November since the country started keeping records in 1891. Parts of the Ural Mountains in Siberia and the arctic islands in the Kara Sea experienced temperatures that were 14°F (8°C) higher than the average.
The first 11 months of 2013 are tied with 2002 as the fourth warmest such period, putting this year on pace to be one of the hottest ever recorded. (See also "2012: Hottest Year on Record for Continental U.S.")
The report also noted that in November, the sea-ice cover in Antarctica spanned 6.63 million square miles (17.1 million square kilometers), 5.3 percent more than the average between 1981 and 2010 and breaking the 2010 record by 90,000 square miles (233,000 square kilometers).
Recent months have seen record or near-record sea-ice extent in Antarctica, puzzling scientists, Arndt said. In terms of ocean currents and atmospheric patterns, Antarctica is somewhat isolated from the rest of the world, which may help to explain this anomaly.
Still, Arndt said, the recent upsurge in Antarctic ice is much less than all the ice that has been lost so far in the Arctic.
In November, Arctic sea-ice continued its downward trend, dwindling by 6.8 percent below the 1981-2010 average of 4.24 million square miles (10.8 million square kilometers). November was also the month with the sixth-lowest extent of Arctic sea ice in 35 years of record-keeping.