US: Global warming is upon us and with it will come major changes that cannot easily be reversed. Sea level rise, damage to existing food webs and radical changes to weather patterns are the inevitable consequence.
The American Association for the Advancement of Science (AAAS) annual science meeting under way in Washington DC yesterday heard a particularly bleak assessment of the realities of climate change. A collection of speakers stressed over and again that the climate change being seen today is a result of human activity and not natural variability or solar effects.
Climate models from the UK and US as well as actual measurements were used to conduct a detailed look at climate change, said Prof Tim Barnett of Scripps Institution of Oceanography in California.
Natural variability was examined as a cause and "the answer was clearly No", he said. Volcanic activity and an increase in solar energy output were also studied but again, the answer was "not a chance", Prof Barnett said.
"The debate about whether there is or is not global warming is over. There is no doubt," he told the AAAS meeting.
For many years the reality was hidden as scientists watched for rising atmospheric temperatures as a sign. All the while the oceans were masking atmospheric temperature change by mopping up 90 per cent of the heat energy delivered by global warming.
"The real action is in the oceans. The temperature is not the key here, it is the energy that has gone into the seas," Prof Barnett stated.
That energy figure has actually been calculated. The oceans have picked up an estimated 1022 joules, he said. This was equivalent to all the electricity needed to power the state of California for the next 200,000 years, he said.
These changes were causing disruption to the existing water cycle in which moisture is taken from the sea surface and deposited as rain, according to Prof Sharon Smith of the University of Miami.
This, plus the loss of a water source from glaciers and snow melt in the mountains, would leave the western US without water within 20 years.
Vast amounts of fresh water were flowing into the north Atlantic due to ice melt, which could alter existing ocean currents, the so-called "Ocean Conveyor Belt", she said.
There was also evidence of instability at the edges of the Greenland ice sheet.
If it melted, the ice held enough water to raise sea level by a colossal 7 metres.
New figures showed the Arctic has lost 20,000 cubic kilometres of ice over the 30 years from 1965 to 1995, she said. The annual loss is now estimated to be about 5,000 cubic metres. "The ice in the Arctic is diminishing fast."
Prof Ruth Curry of Woods Hole Oceanographic Institution described impacts of climate change on the Arctic food web.
Algae growing in the ice represented an enormous biomass that would be lost if the ice went. "Once the ice is gone it will not come back."