2013 unusually warm year worldwide

WASHINGTON, D.C.: Last year was among a handful of the warmest on record since 1880, according to United States (US) government figures out Tuesday that provide more evidence that the planet is heating up.

Human-caused pollution and the burning of fossil fuels such as oil and coal have driven up greenhouse gas levels, leading to this long-term rise in temperatures, said the US space agency National Aeronautics and Space Administration (NASA).