Tipping Point Already Reached, Ten Years Early?

It was paramount we stay below 450ppm Now it looks like we're already there
Global Greenhouse Gas Emissions May Already be Beyond 'Worst-Case' Scenarios

Just yesterday, a worrying statistic was disclosed in Australia. During an interview on the Australian Broadcasting Corporation’s Lateline program, Professor Tim Flannery (author of The Weather Makers) revealed that the Intergovernmental Panel of Climate Change (better known as the IPCC) has found the amount of greenhouse gases in the atmosphere to be a lot higher than originally thought.

In contrast to the common gases like nitrogen and oxygen that are measured in terms of percentages, most greenhouse gases are in relatively low abundance. You might have read that the amount of carbon dioxide in today’s air is around 380 parts per million – or ppm – and rising. The ppm simply means the proportion of a gas relative to the total amount of other gases in dry air. Because the amount of moisture in the air is so variable across our planet – just imagine the difference between the Sahara Desert and Highlands of Scotland – the water content is not included in the calculation for the purposes of comparison. So 380 ppm is the same as writing there are 380 molecules of carbon dioxide for every million molecules of dry air. But of course there are other greenhouse gases. The heating equivalent of these gases (for instance, methane from flatulent livestock and nitrous oxide – laughing gas – from soils and oceans) can be combined to give a value equivalent to carbon: the so-called carbon dioxide equivalent. Until recently, the levels were thought to be about 430 ppm.

How high can the carbon dioxide equivalent get before we’re in trouble? Arguably we’re already in trouble but if we want to avoid setting off a series of changes that will be impossible to stop, we need to keep world temperatures from rising above 2°C. This might not sound much but hides a range of regional climate extremes that would result in devastating impacts on our planet’s flora and fauna. How this translates through to greenhouse gas levels is still being debated. Essentially it’s all expressed as probabilities of risk. A recent paper (PDF) suggests that the odds are only in our favour of keeping below 2°C – with an estimated risk of 28 percent – if the equivalent level is kept to 400 ppm; a value of 550 ppm has a 68 to 99 percent chance of breaching 2°C.

This is where the latest results are truly worrying: the atmospheric levels look like they’ve reached 455 ppm equivalent. For the first time it's probable we'll hit 2°C; there’s now more than a 50 percent chance the world will get dangerously warm. The odds are now out of our favour. And if this wasn’t enough, a value of 455 ppm equivalent wasn’t expected for another decade; we’ve got even less time to get our house in order. It all adds extra urgency to the United Nations negotiations in Bali later this year.

Aspirational targets for greenhouse gas levels have to be dropped. Binding targets have to be set, and fast. The time for procrastination is over; the time for action is now.

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  • Posted on Oct. 10, 2007. Listed in:

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