Cape Town - Don’t pack away your sunshade and swimming costume just yet: scientists at America’s space agency Nasa say 2012 was the ninth warmest since 1880, and that this continues the long-term trend of rising global temperatures.

The two hottest years on record are 2010 and 2005, but for the US, last year was its warmest year on record by far.

Nasa’s Goddard Institute for Space Studies (Giss) in New York, which monitors global surface temperatures on a continual basis, this week released an updated analysis comparing temperatures around the globe last year to the average global temperature from the mid-20th century.

According to a media release about the new analysis, the average global temperature in 2012 was about 14.6°C, which is 0.6°C warmer than the mid-20th century baseline and about 0.8°C warmer than 1880.

The Nasa scientists emphasised that weather patterns would always cause fluctuations in average temperatures from year to year, and that each successive year would not necessarily be warmer than the previous one. However, the continued increase in greenhouse gas emission levels in the Earth’s atmosphere would cause a long-term rise in global temperatures, and on the current course of increased emissions, they expected each successive decade to be warmer than the previous one.

“One more year of numbers isn’t in itself significant,” explained Giss climatologist Gavin Schmidt. “What matters is this decade is warmer than the last decade, and that decade was warmer than the decade before.

“The planet is warming. The reason it’s warming is because we’re pumping increasing amounts of carbon dioxide into the atmosphere.”

Carbon dioxide, or CO2 – one of the so-called greenhouse gases emitted during the burning of fossil fuels that trap heat within Earth’s atmosphere and largely control the planet’s climate – has been rising steadily: from about 285 parts per million (ppm) in 1880, the first year of the Giss temperature record, to 315 ppm in 1960 to today’s 390 ppm-plus.

Giss director James E Hansen commented: “The climate dice are now loaded. Some seasons still will be cooler than the long-term average, but the perceptive person should notice that the frequency of unusually warm extremes is increasing. It’s the extremes that have the most impact on people and other life on the planet.” - - Cape Argus