New heat records for the month of September have been recorded around the world, putting 2014 on course to become one of the hottest years on record.
The hot September follows the record-equalling or record-breaking months of April, May, June and August. The April-September period was clearly the warmest for those six months, NASA reported, beating a record set 16 years ago during an extreme El Nino event.
"We shouldn't be beating the all-time records without an intense El Nino," said Andy Pitman, director of the ARC Centre of Excellence for Climate System Science at the University of NSW. "What the hell's going to happen when we do get [one]?"
According to NASA's Goddard Institute of Space Studies, combined land and ocean surface temperatures last month were 0.77 degrees above the long-term average, eclipsing the previous record warmth for September set in 2005.
Regions of Antarctica were again among the most unusually warm on the planet, with anomalies approaching 10 degrees.
A large swathe of inland Western Australia also set record maximum temperatures for the month, while nationwide maximums were the fifth highest in data going back to 1910, according to the Bureau of Meteorology.
Climatologists say greenhouse gas emissions mostly from human activity are pushing up background temperatures and increasing the likelihood that new heat records will be set.
Globally, year-to-date temperatures are currently the third-warmest and could rank higher as near-El Nino conditions persist in the Pacific. During El Nino years, the Pacific becomes less of a heat sink, instead lifting global temperatures.
"The warm months experienced globally in 2014 have been driven by sea-surface temperatures, which are currently the second warmest on record for the year-to-date," the bureau told Fairfax Media, citing figures to the end of August from the US National Climate Data Centre.
"These conditions are expected to at least persist for the remainder of the year," the bureau said.
Among Australian heat records to fall this year, the Kimberley town of Bidyadanga earlier this month set a new mark. Its 45.2-degree reading on October 6 was an early-season record for temperatures above 45 degrees, beating the previous high set 15 days later in the year in 2002, the bureau said.
Japan's Meteorological Agency has also recorded September as the hottest in its records going back to 1891.
Last month's anomaly was 0.34 degrees compared with its 1981-2010 average - smashing the previous variance of 0.26 degrees set just last year. The next warmest Septembers were 2012, at 0.25 degrees, and 2005 and 2009, with an anomaly of 0.22 degrees.
