More than 300 scientists from around the world, including several Canadians, hope to blunt some growing skepticism about climate change with a new report that says global warming is a fact and the Earth is hotter than ever.
"The conclusion is unmistakable - yes, the planet is warming," said Derek Arndt, a co-editor of the report, called State of the Climate, which was published by the U.S. National Oceanic and Atmospheric Administration, or NOAA.
"The facts speak for themselves, and speak simultaneously," said Mr. Arndt, who runs the Climate Monitoring Branch at NOAA. "And, they all point toward the same conclusion - the globe is warming."
The report - co-edited by researchers in the United States, Canada, Britain and Australia - pulled together data from 10 climate indicators measured by 160 research groups in 48 countries. The scientists compared the figures decade by decade as far back as possible, more than 100 years in some cases. They concluded 2000 to 2009 was the warmest decade ever, and the Earth has been growing warmer for 50 years. Each of the past three decades - 1980s, 1990s and 2000s - was the hottest on record, the researchers said.
This year is shaping up to be even warmer. For the first six months of 2010, the combined global land and ocean temperature was the warmest on record, according to the NOAA.
The study is the most extensive ever done by the agency and it comes after controversy erupted last year when leaked e-mails purported to show that scientists at a world-leading climate institute in Britain had fudged research. Three investigations have concluded that the researchers at the University of East Anglia's Climatic Research Unit did not tamper with data or interfere with the peer review process to exaggerate the threat of global warming.
Mr. Arndt said the NOAA report is meant to be a kind of medical check-up for the planet in which measurements are taken and the results documented. He said it will be up to others to draw conclusions about why climate change is occurring and what should be done about it. "This is basically a broad and comprehensive telling of what's going on with the climate system," he said.
Nonetheless, he said he was personally taken aback by how all 10 indicators clearly showed the Earth is heating up. "Seeing them standing next to each other, kind of nakedly, and pointing to the same conclusion, it very much jumped off the page at me... Absolutely, yes, we live in a warming planet."
Of the 10 measurements, the report said seven are rising - air temperature over land, sea-surface temperature, air temperature over oceans, sea level, ocean heat, humidity and the temperature of the troposphere, which is the atmosphere closest to the Earth's surface. Three indicators are declining - Arctic sea ice, glaciers and spring snow cover in the Northern Hemisphere. All of which point to a warming trend.
The past decade was 0.6 degrees Celsius warmer than the 1960s, and 0.2 degrees warmer than the 1990s, the report found. While that may seem small, Mr. Arndt said, the planet has already been changed. "Glaciers and sea ice are melting, heavy rainfall is intensifying and heat waves are more common. And, as the new report tells us, there is now evidence more than 90 per cent of warming over the past 50 years has gone into our ocean."
The researchers also found the retreat of mountain glaciers, an important signal of climate change, continued for the 19th consecutive year in 2009. The cumulative loss of the past 30 years is "equivalent to slicing 13 metres off the top of the average glacier," the study said. The majority of glaciers in every region surveyed receded last year. For example, of the 88 glaciers examined in Switzerland, 81 had retreated, two advanced and five were stable last year. Of the 93 glaciers in Austria, 85 receded, seven didn't move and one advanced.
As for Canada, the report noted the mean temperature for 2009 was 0.8 C above normal, tying 1988 as the 14th warmest year since nationwide records began in 1948. The warmest year was 1998, which was 2.5 C above normal. For the decade as a whole, "it is clear that the 2000s was the warmest decade out of the six that are available for this national study, with an average temperature of 1.1C above normal."