The world must burn less diesel and wood, Nobel peace prize-winner Al Gore said yesterday, as the soot produced is accelerating the melting of ice in polar and mountainous regions.
Gore, backed by government ministers and scientists, said that the soot, also known as "black carbon", from engines, forest fires and partially burned fuel was collecting in the Arctic where it was creating a haze of pollution that absorbs sunlight and warms the air. It was also being deposited on snow, darkening its surface and reducing the snow's ability to reflect sunlight back into space.
"The principal [climate change] problem is carbon dioxide, but a new understanding is emerging of soot," said Gore. "Black carbon is settling in the Himalayas. The air pollution levels in the upper Himalayas are now similar to those in Los Angeles."
The impact of the soot is as significant as it is surprising — it was not mentioned as a warming factor in the UN's major 2007 report on climate change. A study this month indicated that soot from industry, cars, farming and wood fuel burning has been responsible for half the total temperature increases in the Arctic between 1890 to 2007. Temperatures there are rising twice as fast as anywhere else on the planet, making it the region worst affected by climate change.
Gore warned that all the world's icy regions were experiencing rapid and dangerous global warming. "The cryosphere – the frozen water part of the Earth – is disappearing. Global warming is causing the permafrost to thaw. It contains more carbon than anywhere else and the risk is that it releases methane. That has the potential to double the global warming potential in the atmosphere," he said.
Norwegian foreign minister Jonas Store said action on black carbon was even more urgent than that on CO2: "Even if we turn the rising curve of greenhouse gas emissions in the coming years, the reduction will not occur quickly enough to preserve the polar and alpine environments. We must address short lived climate pollutants such as black carbon."
Glaciologists working in Latin America, Nepal, China and Greenland all reported at the meeting in Tromso that glaciers were losing ice more rapidly and becoming less thick as a result of global warming.
Dorthe Jensen, from the Niels Bohr Institute in Denmark, said: "In the last five years we have seen many ice streams double in speed. Their floating snouts have moved back 30km. We never imagined the ice discharge would change so much."
Glaciers in the Himalayas and on the Tibetan plateau, from which 40% of the world derives its fresh water, are retreating fast, said Yao Tandong, a researcher with the Chinese academy of sciences. "This is causing severe social problems as lakes get bigger and people are forced to move. Himalayan glaciers are mostly retreating at an accelerating rate."
The meeting also heard, in a new report from the international Arctic Monitoring and Assessment Programme (Amap), that climate change was now affecting every aspect of life in the Arctic. Norwegian, Canadian, Russian, US and other polar scientists reported that, in the last four years, air temperatures have increased, sea ice has declined sharply, surface waters in the Arctic ocean have warmed and permafrost is in some areas rapidly thawing, releasing methane.
The report's main findings are:
Permafrost is warming fast and at its margins thawing. Plants are growing more vigorously and densely. In northern Alaska, temperatures have been rising since the 1970s. In Russia, the tree line has advanced up hills and mountains at 10 metres a year. Nearly all glaciers are decreasing in mass, resulting in rising sea levels as the water drains to the ocean.
Summer sea ice
The most striking change in the Arctic in recent years has been the reduction in summer sea ice in 2007. This was 23% less than the previous record low of 5.6m sq kilometres in 2005, and 39% below the 1979-2000 average. New satellite data suggests the ice is much thinner than it used to be. For the first time in existing records, both the north-west and north-east passages were ice-free in summer 2008. However, the 2008 winter ice extent was near the year long-term average.
The Greenland ice sheet has continued to melt in the past four years with summer temperatures consistently above the long-term average since the mid 1990s. In 2007, the area experiencing melt was 60% greater than in 1998. Melting lasted 20 days longer than usual at sea level and 53 days longer at 2-3,000m heights.
In 2007, some ice-free areas were as much as 5C warmer than the long-term average. Arctic waters appear to have warmed as a result of the influx of warmer waters from the Pacific and Atlantic. The loss of reflective, white sea ice also means that more solar radiation is absorbed by the dark water, heating surface layers further.