BONE-DRY: Much of the US experienced intense drought last year.

Melanie Gosling

Environment Writer

THE planet is getting hotter, and the temperature records are there to show it.

Scientists from Nasa and from the US National Oceanic and Atmospheric Administration (Noaa) have released figures that show there is undoubtedly a warming trend in the global climate – and most of the warm years have been this century. The cause is people pumping greenhouse gases into the air.

Last year was the ninth-warmest year since temperature records began in 1880. And 2012 marked the 36th consecutive year, since 1976, that the annual global temperature had been above the long-term average.

Nasa’s Goddard Institute for Space Studies in New York, which monitors global surface temperatures, said in a statement released last week that there were always fluctuations in temperatures from one year to another, but what they were measuring was a continuing warming trend.

All 12 years to date in the 21st century rank among the 14 warmest since records began. Only one year in the 20th century – 1998 – was warmer than 2012.

Gavin Schmidt, a climatologist from the institute, said in the release: “One more year of numbers isn’t itself significant. What matters is this decade was 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 are pumping increasing amounts of carbon dioxide into the atmosphere.”

Carbon dioxide occurs naturally in the atmosphere, traps heat and is largely responsible for controlling the Earth’s temperature.

Without this “greenhouse” effect there would be no life.

However, with an economy based on fossil fuels, we have been pumping increasing levels of carbon into the air since the Industrial Revolution, with the result that more heat is being trapped.

The carbon dioxide level in 1880, the first year in the Goddard Institute’s temperature record, was 285 parts to a million. By 1960, the atmospheric carbon dioxide concentration, measure by Noaa’s Mauna Loa Observatory, was around 315ppm. Today it is 390ppm.

The global annual temperature has increased at an average rate of .06°C a decade since 1880 and at an average rate of .6°C since 1970.

In the northern hemisphere the warmest year on record, combining land and ocean temperatures, was 2010.

In the southern hemisphere it was 1998. Globally it was 2010. While the world had relatively warm temperatures in 2012, it was the warmest year on record in the US.

James Hansen, director of Nasa’s Goddard Institute, said in the release that the US experience last year was an example of a new trend of seasonal extremes in temperatures that were warmer than the hottest seasonal temperatures of the 20th century.

Much of the US experienced intense drought last year.

“The climate dice are now loaded,” Hansen said.

“Some seasons still will be cooler than the long-term average, but the frequency of unusually warm extremes is increasing.

“It is the extremes that have the most impact on people and other life on the planet.”

Nasa’s Goddard Institute temperature analysis is compiled from weather data from more than 1 000 meteorological stations around the world, from satellite observations of sea surface temperatures and research stations in the Antarctic.

The warming trends from the institute’s analysis show close agreement with those of Noaa’s National Climate Data Centre in the US and with the Met Office Hadley Centre in the UK.