2008 to be 10th hottest year: warming trend up, or stalling?
But does that confirm a long-term trend of global warming, stoked by human emissions of greenhouse gases, or show that it has stalled? The warmest year on record is now a while ago, in 1998.
Jones, head of the Climate Research Unit at the University of East Anglia, has no doubt that the underlying trend is still up — 1998 was an unusual year when global temperatures were boosted by an El Nino weather event in the Pacific Ocean. And this year, the opposite La Nina effect is cooling the planet.
(Among signs of a cooler 2008, some high Alpine ski resorts in Switzerland have opened early…)
And Jones says that the world’s thermometers may also be underestimating temperature rises because the Arctic — visibly warming since summer ice shrank in 2007 to the smallest since satellite measurements began in the 1970s — is pretty much excluded. That’s because there’s a lack of records from 1961-90, the benchmark years for judging current global warming, because ships didn’t go there.
But Joseph D’Aleo, a meteorologist who leads ICECAP (International Climate and Environmental Change Assessment Project), wrote in a comment that “flawed science and bad siting” of thermometers often mean a bias towards warmer readings. He says that 2008 might only be in the top 20 or 30 years.
ICECAP says it is that it is worried that “the sole focus on greenhouse gases and the unwise reliance on imperfect climate models while ignoring real data may leave civilisation unprepared for a sudden climate shift that history tells us will occur again, very possibly soon”.
And many sceptics about the U.N. Climate Panel — distilling conclusions from work by 2,500 experts worldwide – are finding ammunition from the fact that temperatures are not setting records every year. The Climate Panel says it is at least 90 percent likely that human activities, led by burning fossil fuels, are the main cause of warming in the past 50 years.
D’Aleo notes that Jones’ unit forecast once that 2007 could be the warmest on record. Jones says that the La Nina was unexpected at the time and knocked it down the rankings.
Jones says that natural variations in the climate — such as El Nino, La Nina or volcanic eruptions that can dim the sun — can easily mask the faint warming trend. Each year, he says temperatures can swing about 0.2 degree Celsius from the annual average because of natural variations. Meanwhile, global warming is adding about 0.2C per decade – by that sort of reckoning, he says it’s not unusual that a year ranks 10th.
So who’s right?