Global temperatures continued to climb last month, with combined land and sea-surface temperatures setting fresh records amid prospects of more to come as El Nino conditions form in the Pacific, the US National Oceanic and Atmospheric Administration said.
Temperatures last month were 0.85 degrees above the 20th century average of 12.7 decrees, eclipsing the previous high in 2010 by 0.05 degrees, NOAA said. The figures complement similar readings from Japan.
Seven of the past 11 months have tied or set new record monthly temperatures, with March's departure from long-term averages behind only February 1998 and January 2007 in the 136 years of figures, the US agency said.
The first three months of 2015 also came in as the hottest on record, with global temperatures edging out the 2002 record by 0.05 degrees. Areas singled out for note include the waters off eastern Australia, which the Bureau of Meteorology this week noted were the warmest on record for March.
So far this year, Australia's mean temperatures are ranked the third-warmest according to Bureau of Meteorology records going back to 1910.
Monthly carbon dioxide levels first time topped 400 parts per million on a seasonally adjusted basis in March for the first time on record, according to the US space agency NASA.
The rise in greenhouse gases, mostly related to human activity since the start of the industrial revolution in the mid-18th century, means more heat from the sun is being trapped in the Earth's biosphere, scientists says.
"All across the world, there is mounting evidence of the warming of the Earth due to rising greenhouse gas levels in the atmosphere," Bob Ward, policy and communications director at the Grantham Research Institute on Climate Change and the Environment at London School of Economics and Political Science, said. "This should focus the minds of policy-makers and governments across the world as they negotiate an international agreement on climate change for the United Nations summit in Paris at the end of this year."
El Nino watch
Natural climate variability overlays the background warming with some weather patterns, such as El Ninos giving global temperatures an extra kick.
The Bureau of Meteorology this week raised its forecast for an El Nino event this year to at least a 70 per cent chance.
"El Nino conditions tend to enhance global temperatures, with stronger events having generally larger impacts," NOAA said in its Friday release.
El Nino years see the Pacific Ocean absorb less heat from the atmosphere, with the effect on global temperatures often more evident in the following year. Such an outcome may see 2014's ranking as the hottest year on record broken both this year and next, climatologists say.
Climate change, meanwhile, is having contrasting impacts on the poles.
The average Arctic sea ice extent for March was 7.2 per cent, or 1.1 million square km below the 1981–2010 average, NOAA said. It was the smallest March extent since records began in 1979, according to analysis by the National Snow and Ice Data Centre based on data from NOAA and NASA.
Antarctic sea ice, though, is on the increase as glaciers melt on the continent and regional wind speeds accelerate. Sea ice during March was 24.3 per cent, or 1.08 million square km above the 1981–2010 average. It was the second largest March Antarctic sea ice extent behind 2008, NOAA said.
