Last month tied for the warmest September in the global modern record, scientists at the US government's National Oceanic and Atmospheric Administration reported on Monday.
This September tied with the same month in 2005 for the record. The land-and-sea global average temperature was 60.21 F (15.67 C), or 1.21 F (.67 C) above the 20th century average.
In addition to being hottest since 1880, the month was the 36th consecutive September and 331st consecutive month with a global temperature above the 20th century average.
The last time September temperatures were below that average was 1976, and the last time any month was below that average was February 1985, NOAA scientists said in a statement.
September's globally averaged temperature on land was third-warmest for that month. The average combined global land and ocean surface temperature so far this year was the eighth-warmest first nine months of a year on record.
Central Russia, Japan, western Australia, northern Argentina, Paraguay, western Canada and southern Greenland had higher-than-average temperatures in September, while eastern Russia, western Alaska, southern Africa, much of China and parts of the upper Midwest and southeast United States were notably below average.
"The irony of this is that we (in the United States) finally did get a little relief from breaking and threatening heat records for months," said Deke Arndt, chief of climate monitoring at NOAA's National Climatic Data Center. "The thing is, the United States takes up about 2 per cent of the globe."
Arndt noted that September in the continental United States was still the 23rd warmest on record, out of 118 years in the US record. "It's nothing to sneeze at," he said by telephone. "It's very close to the front of the line."
Arctic ice cover shrank to its lowest extent ever last month, far eclipsing a record set in 2007, while Antarctic sea ice had its all-time high ice extend on Sept. 26.
Arndt cautioned against equating these two polar records.
"The magnitude of the records in each (Arctic and Antarctic) are vastly different," he said. "The Arctic is plumbing new depths, completely leaving the rest of the record behind ... there kind of aren't enough superlatives to describe what has gone on there over the last five or six years."
To put 2012's Arctic sea ice record in context, compare it to the previous record set five years ago, when US ice experts called the drop in ice cover around the North Pole "astounding" and a sign of the accelerating impact of human-caused global warming.
This year, that "astounding" low level of sea ice in the Arctic was equaled or surpassed every day in September, and on some days in August and October as well, Arndt said.
So if the record-large amount of sea ice in the Antarctic is "king of the hill," Arndt said, "the Arctic record is just building an entirely different hill and an entirely different neighborhood. The change is bigger, the change is more rapid, it is establishing a new characteristic there."
Conditions in the Arctic are important, since the Arctic is sometimes called "Earth's air conditioner" for its ability to influence weather around the globe.
Temperatures were near average over Antarctica in the southern winter. Scientists at the US National Snow and ice Data Center reckon the increase in Antarctic sea ice was due to stronger circumpolar winds, which whip around the southern continent and blow the sea ice outward, increasing its extent.
More information is available at http://www.ncdc.noaa.gov/sotc/global/2012/9 .