The year 2012 is now at the ninth place among the 10 warmest years since 1850, when world meteorologists started keeping records, according to a statement released from The World Meteorological Organization. Surprisingly, early last year saw a drop in temperature due to the cooling effect of a La Niña episode.

Last year, the average sea-surface temperature between January and December 2012 was 0.45°C (±0.11°C) above the average of 14.0°C during 1961 to 1990. Also, North America witnessed the fourth smallest winter last year, a sharp contrast from the earlier years which had recorded the highest-ever snowfall.

A recent report from a federal agency had also shown that sea-surface temperature along the Northeast coast last year had hit record-breaking levels.

WMO added that 2001-2012 were among the 13 warmest years since record-keeping began.

"Although the rate of warming varies from year to year due to natural variability caused by the El Niño cycle, volcanic eruptions and other phenomena, the sustained warming of the lower atmosphere is a worrisome sign. The continued upward trend in atmospheric concentrations of greenhouse gases and the consequent increased radiative forcing of the Earth's atmosphere confirm that the warming will continue," said WMO Secretary-General Michel Jarraud in a news release.

Although a rise in temperature was seen in many parts of the world, some regions such as Alaska, parts of northern and eastern Australia, and central Asia recorded a dip in temperatures. Likewise, some regions were drier than usual, such as central United States, northern Mexico, northeastern Brazil, central Russia, and south-central Australia, and some received higher-than-average rainfall such as northern Europe, western Africa, north-central Argentina, western Alaska, and most of northern China.

The Arctic sea ice extent recorded its lowest ever last year. A recent study had shown that in the next 50 years, vegetation growth will reach record levels in the Arctic region due to global warming. The loss of ice in the Arctic will result in winters in middle latitudes getting colder.

"The record loss of Arctic sea ice in August-September - 18% less than the previous record low of 2007 of 4.17 million km2 - was also a disturbing sign of climate change," said Jarraud. "The year 2012 saw many other extremes as well, such as droughts and tropical cyclones. Natural climate variability has always resulted in such extremes, but the physical characteristics of extreme weather and climate events are being increasingly shaped by climate change."

The entire statement released by the World Meteorological Organization can be read here.