Climate change skeptics like to point out that if the weatherman can’t predict the weather with much accuracy, how can scientists be sure that global warming is actually happening?
The answer is that putting together a weather forecast involves many often conflicting short-term variables.
Analyzing climate trends over the long term is much easier, because it deals with long-term global averages, according to University of Manitoba climate scientist Dave Barber, who has seen the effects of a warming climate on board an icebreaker decked out with $40 million worth of high-tech monitoring devices in the high Arctic.
“If I asked all of you guys in the room here, ‘What’s the temperature going to be next year on March 15?’ There’d be lots of variability in the answers,” said Barber, in a presentation at Assiniboine Community College’s annual Innovation Forum in Brandon.
“But if I asked you what the temperature next March would be as an average over the whole month, the variability would come down and it would be closer to the average, because it doesn’t change very much over the years.”
Of course, humans can adapt to 4 difference on any given day in Manitoba by putting a hat on or taking it off.
But judging from ice core samples collected from polar glaciers that go back hundreds of thousands of years, a drop of 4 in the global average climate would put Manitoba back in the Ice Age, a time when the Wisconsin ice sheet covered a good portion of the continent, he said.
Those same ice core samples show a direct correlation between carbon dioxide levels and global average temperatures.
Current CO2 levels stand at 390 parts per million. Compared to the last glacial maximum, about 18,000 years ago when the Wisconsin ice sheet covered the province, that level was about 180 ppm.
“Historically, over the last 400,000 years according to the instrumental record, it has never gone over 300 ppm. It’s always been below that. So, the natural cycle of CO2 in the atmosphere follows along between 300 and 180 ppm. Now it’s at 390 ppm and it’s on its way upward.”
That means if greenhouse gas emissions from the global fossil fuel-based economy continue in line with the trend that began in 1960 and double to over 600 ppm by 2050, a 4 rise in the global average temperature is virtually a done deal.
Climate change and rising and falling CO2 levels have always been a part of life on Earth. What’s unprecedented, is the rate of change due to human activity over the past five decades, he said.
Due to a phenomenon called “polar amplification,” which is related to ocean currents and trade winds, the effects of rising CO2 become most visible at the North and South poles. That’s why climate scientists are concentrating their efforts on studying the effects of melting in the Arctic.
Back in the 1980s, when Barber began his career as a climate scientist, he was a skeptic, too.
Then in the 1990s, when he began looking at the Arctic data, he figured it might be icefree in the summer by 2100. In 1998, he pulled his estimate down to 2050. Now he thinks there’s a good chance of an icefree Arctic summer by 2013.
“The last time we had no ice in the Arctic over the summer was over a million years ago. Why should we care? The Arctic is a sentinel and it’s telling us what’s happening to the planet because of our overreliance on fossil fuels.”
Media reports that trumpet the perilous effects of global warming miss the point, he added, which is that public policy and new technology could be used to adapt to future changes and reduce emissions.
“If you crash an asteroid into the planet and wipe out 99 per cent of the species, that’s a catastrophe. Humaninduced climate change is nothing compared to that. It’s only important to humans, and especially you guys who are farmers because you would like to have a predictable hydrological cycle, with a predictable amount of moisture at predictable times,” he said.
“But the first thing that general circulation models are telling us is that we’re going to see increasing unpredictability: colder colds, warmer warms, drier dry spells, and wetter wets with lots of spatial variability and patterns all over the place. That’s a big concern for people’s livelihoods.” [email protected]