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Showing posts from November, 2007

The mother of all floods

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It was around 18,000 years ago that the climate pendulum swung in favour of warmer times. The Earth continued to orbit the Sun as it had done through the ice age but summers in the northern hemisphere started to see a little more warmth. At first, it was just a glimmer; a little extra warmth here and there. Over the next few thousand years, however, the heat from the Sun continued to rise inexorably over the high latitudes of the northern hemisphere. The effect was striking. Temperatures rose 4° to 7 °C and many of the ice sheets in the north began to melt.
In North America, the Laurentide Ice Sheet persisted longer than most, although by 9,000 years ago it was a shadow of its former self. As the ice shrank back to the Hudson Bay, some of the water ponded up inland over what is now central north Canada, building a vast lake known as Lake Agassiz. It was only a matter of time before the ice barrier gave way.
Sometime between 8,700 and 8,200 years ago the dam finally broke. It was a catac…

Not much of a silver lining

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It’s been a mixed news week for greenhouse gases. After last month’s ‘revelation’ that levels were dangerously high, there is a glimmer of hope that it’s not too late to act. But crucially, a new piece of work shows the window of time for dealing with the problem is becoming increasingly small.
On an Australian Broadcasting Corporation program called Lateline it was suggested that greenhouse gases were now beyond the level considered likely to cause dangerous climate change. Although the amount of greenhouse gases in the atmosphere is dangerously high, this is just part of the story when it comes to warming our planet. Other factors also play a role in controlling the temperature of our atmosphere and some of these help to cool things down - a phenomenon known as ‘Global Dimming‘. One example is sulphur dioxide given off during volcanic eruptions; this can react with moisture in the air to form a fine mist of sulphuric acid droplets. These aerosols have an impact on the world’s climate…