2015 - the planet's hottest year

US government scientists are widely expected to announce Wednesday that 2015 was the planet's hottest year in modern times, amid mounting concerns over the pace of climate change worldwide.

Last year's global average temperature over land and sea surfaces is scheduled to be revealed at 11:00 am (1600 GMT), in a conference call between the National Oceanic and Atmospheric Administration (NOAA), the US space agency Nasa and reporters.

Scientists who track climate expect 2015 will beat 2014 for the warmest since the 1800s, particularly since NOAA announced in December that global heat records were broken in nine months of the year, including the last seven in a row.

The "first 11 months of 2015 were the warmest such period on record across the world's land and ocean surfaces," NOAA said in that report, the same kind it delivers each month, tallying the world's extreme weather events and temperature averages.

Jake Crouch, climate scientist at NOAA's National Centers for Environmental Information, added: "At this point we're virtually certain that 2015 will be the warmest year on record."

Another group, Berkeley Earth -- a US non-profit organization that says it was founded by people who saw some merit in the claims of climate change skeptics -- has already released its findings.

"2015 was unambiguously the hottest year on record," it said in a statement last week.

"For the first time in recorded history, the Earth's temperature is clearly more than 1.0 C (1.8 F) above the 1850-1900 average."

The group was previously more cautious than NOAA in anointing 2014 the hottest year on record. Berkeley Earth said its scientists determined that 2014 ended in a statistical tie with 2005 and 2010.

This time, though, record highs in much of South America and the Middle East, and parts of the United States, Europe and Asia leave very little wiggle room.

"Now, however, it is clear that 2015 is the hottest year on record by a significant margin," said executive director Elizabeth Muller.

Specifically, 2015 exceeded the previous record-holder 2014 by 0.14 degrees Celsius, according to the global surface temperature average on land and sea for the year, it said.

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