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50 years on: The Keeling Curve legacy
Helen Briggs, BBC
It is a scientific icon, which belongs, some claim, alongside E=mc2 and the double helix.
Its name – the Keeling Curve – may be scarcely known outside scientific circles, but the jagged upward slope showing rising carbon dioxide (CO2) levels in the atmosphere has become one of the most famous graphs in science, and a potent symbol of our times.
It was 50 years ago that a young American scientist, Charles David Keeling, began tracking CO2 in the Earth’s atmosphere at two of the world’s last wildernesses – the South Pole and the summit of the Mauna Loa volcano in Hawaii.
His very precise measurements produced a remarkable data set, which first sounded alarm bells over the build-up of the gas in the atmosphere, and eventually led to the tracking of greenhouse gases worldwide.
The curve set the scene for the debate over climate change, and policies, sometimes controversial, that address the human contribution to the greenhouse effect.
(2 December 2007)
With cracks and holes in the Greenland ice sheet, we may well have to ‘geo-engineer’ the climate
Thomas Homer-Dixon, Globe and Mail
… Two issues particularly exercise climate scientists: positive feedbacks and ice-sheet dynamics.
A positive feedback is a causal cycle – essentially a vicious circle – in which warming causes a series of changes that reinforces warming. One feedback of special importance to Canada is the ice-albedo feedback in the Arctic. The sea ice floating on the Arctic Ocean is white, so it reflects a large proportion of the sun’s radiation back into space. As this ice melts from global warming, it leaves behind open water that absorbs about 80 per cent more of the sun’s radiation. This ocean water becomes warmer. Then, after the summer passes and fall comes, the water releases its heat back into the atmosphere, which impedes refreezing. So winter generates thinner ice, which melts more easily the next summer.
This feedback is one of the reasons why the planet is warming, and will continue to do so, much more rapidly in its northern reaches.
…The ice-albedo feedback is an example of one of two main kinds of positive feedback: the kind that operates more or less directly on energy flows and temperature. Feedbacks of this kind are reasonably well built into current climate models. But there’s another kind that operates on the carbon cycle.
In these cases, warming produces a change in the amount of carbon in the atmosphere. Carbon cycle feedbacks are not so well understood, but it’s becoming increasingly clear that they could literally be deal-breakers for humanity. We may be quite close to creating circumstances in which the biosphere releases huge quantities of carbon into the atmosphere.
At that point, warming could become its own cause; it would no longer really matter what we do to mitigate our emissions of carbon dioxide. The global ecosystem would take over.
…In light of these two trends, climate scientists are now beginning to discuss a topic that only two years ago many fervently hoped they’d never have to discuss: geoengineering, or the intentional human modification of the planet’s climate to arrest or slow global warming. Geoengineering would involve, for example, putting sulphate aerosols into the atmosphere or putting mirrors into space to try to block a fraction of incoming solar radiation.
Today the topic is at the margins of the public-policy dialogue about climate change, but I expect it will be at the centre of public discussion within five years. In 10 years, we will see demands from some segments of the public and many opinion leaders that we carry out geoengineering. And we’ll probably start doing it within 20 years, likely when it becomes apparent that the Greenland ice sheet is starting to collapse.
(1 December 2007)
Earth’s tropics belt expands
Seth Borenstein, Associated Press
Earth’s tropical belt seems to have expanded a couple hundred miles over the past quarter century, which could mean more arid weather for some already dry subtropical regions, new climate research shows.
Geographically, the tropical region is a wide swath around Earth’s middle stretching from the Tropic of Cancer, just south of Miami, to the Tropic of Capricorn, which cuts Australia almost in half. It’s about one-quarter of the globe and generally thought of as hot, steamy and damp, but it also has areas of brutal desert.
… The newest study, published Sunday in the new scientific journal Nature Geoscience, shows that by using the weather definition, the tropics are expanding toward Earth’s poles more than predicted. And that means more dry weather is moving to the edges of the tropics in places like the U.S. Southwest.
(2 December 2007)
Call for action to save Himalayan glaciers
Kyoko Hasegawa, AFP
As industrial powers debate global warming, some of the greatest concern lies in the remote Himalayas where melting glaciers pose catastrophic risks, experts say.
The retreat of the ice causes so-called glacial lakes in the Himalayas, which are a key source of water to densely populated South Asia — a region that already suffers deadly floods on an annual basis.
“We don’t have much time to avert the risks of the bursting of a glacial lake,” Ken Noguchi, a Japanese alpinist who has visited the Himalayas dozens of times, told a first-of-a-kind Asian “water summit” in Beppu, Japan.
(3 December 2007)
Durham may face water crisis first
Matt Dees, News Observer (North Carolina)
With central North Carolina suffering through the worst drought on record and a projected dry winter ahead, the Triangle is as close as it has ever been to severe restrictions limiting water use to hygiene and extinguishing fires.
Durham, with just 59 days left in its main water supply, could be on the front lines of this worst-case scenario.
Up to now, the prospect has been too far-fetched to entertain in detail, which is why there are few specifics in Durham ordinances about what would happen if the drought doesn’t let up. Raleigh also lacks a set plan for an end-times-type drought.
Durham would ban industrial water use — a potentially devastating economic blow. It would hit water-driven businesses such as car washes and laundries directly but also could force businesses to cut shifts or even lay off workers.
Residential water would be rationed, but it’s unknown how that would be implemented.
(30 November 2007)
