The World Meteorological Organization (WMO) has in a preliminary report has concluded that last year the global mean temperature was 14.3 °C which makes 2008 “the tenth warmest year on a record that dates back to 1850.”

“The ten warmest years on record have occurred since 1997. Global temperatures for 2000-2008 now stand almost 0.2 °C warmer than the average for the decade 1990–1999.”

Climate scientists at the Met Office Hadley Centre and the Climatic Research Unit (CRU) at University of East Anglia says that the global mean temperature for 2008 “is slightly down on earlier years” due to La Nina, an ocean-atmosphere phenomenon that has a cooling effect on the earth.

“Climate scientists at the Met Office Hadley Centre and the Climatic Research Unit (CRU) at University of East Anglia maintain the global climate record for the WMO. They say this figure is slightly down on earlier years this century partly because of the La Niña that developed in the Pacific Ocean during 2007.

La Niña events typically coincide with cooler global temperatures, and 2008 is slightly cooler than the norm under current climate conditions. Professor Phil Jones at the CRU said: “The most important component of year-to-year variability in global average temperatures is the phase and amplitude of equatorial sea-surface temperatures in the Pacific that lead to La Niña and El Niño events”.”

I wrote about La Nina and the cooling effect it had for global temperatures during the first half of 2008 in September last year. Back then John Kennedy, climate monitoring and research scientist at the Met Office’s Hadley Centre, expected that 2008 would be the 10th warmest year since 1850.

“2008 will still be significantly above the long-term average,” and that “there’s been a strong upward trend in the last few decades, and that’s the thing to focus on,” Kennedy said back then. And it seems he was correct.

The new report concludes that “human influence, particularly emission of greenhouse gases, has greatly increased the chance of having such warm years”.

“Dr Peter Stott of the Met Office says our actions are making the difference: “Human influence, particularly emission of greenhouse gases, has greatly increased the chance of having such warm years. Comparing observations with the expected response to man-made and natural drivers of climate change it is shown that global temperature is now over 0.7 °C warmer than if humans were not altering the climate.”

Calculating the changing risk attributable to human influence is part of an ongoing collaboration between the Met Office Hadley Centre and the University of Oxford. Commenting on the dramatically increased odds of such warm years because of human induced climate change, Dr Myles Allen from Oxford University said: “Globally this year would have been considered warm, even as recently as the 1970s or 1980s, but a scorcher for our Victorian ancestors.”

Beneath the underlying warming, temperature continues to fluctuate from year to year as a result of natural variations. Stott added: “As a result of climate change, what would once have been an exceptionally unusual year has now become quite normal. Without human influence on climate change we would be more than 50 times less likely of seeing a year as warm as 2008.”"

So there you have it. The science, yet again, says that the planet continues to warm up and that human activities are to be blamed.

Newly released data from the UK Met Office shows that during the first half of 2008 the global temperatures was more than 0.1 Celcius cooler than any other year after 2000. The reason for this is La Nina, an ocean-atmosphere phenomenon that has a cooling effect on the earth.

But this doesn’t mean the deniers are correct about anything else. Scientists still expects that 2008 will be the 10th warmest year since 1850. And the UK Met Office says that the global temperatures will continue to rise again when La Nina eases away.

“The big thing that’s been happening this year is La Nina, which has lowered global temperatures somewhat,” said John Kennedy, climate monitoring and research scientist at the Met Office’s Hadley Centre.

“La Nina has faded in the last couple of months and now we have neutral conditions in the Pacific,” he told BBC News.

Dr Kennedy also said that “2008 will still be significantly above the long-term average,” and that “there’s been a strong upward trend in the last few decades, and that’s the thing to focus on.”

Even during the temporarily cooling effect from La Nina we see evidence that the rapid man-made warming continues. Images from National Aeronautics and Space Administration satellites show continued breakup of 2 of Greenland’s largest glaciers. According to Canadian authorities the Northwest Passage is navigable. Recently scientists warned that the Arctic could become ice-free during the summers as early as 2013. And just yesterday a huge chunk of ice shelf nearly the size of Manhattan broke away in Canada’s northern Arctic.