Block’s Indicator of Sustainable Growth

by Ray Block

Two scientific papers in Nature (edition of April 29 2009) believe there is a more practical way of looking at the impact of greenhouse gases on climate change than the constant stressing of reducing carbon to a required level by 2020 and 2050.

The papers say that the key factor of assessing carbon build up in the atmosphere is a product of the total amount of carbon dioxide released over several hundred years, with a finite size to what the atmosphere can absorb, without a dangerous rise in temperature.

Dangerous is seen as a temperature exceeding two degrees Celsius.

Naomi Antony, editor of Nature in a summary of the papers prepared for the Science and Development Network (www.scidev.net) says a team at Oxford University (UK) led by Myles Allen found that a total of half a trillion tonnes (500 billion tonnes) of  anthropogenic carbon (carbon produced by human activities) has been emitted into the atmosphere between the beginnings of industrialisation in 1750 and now- that is at time of article preparation in 2008.

Allen in a press briefing (April 27 2009) said : “It took 250 years to burn the first half trillion tonnes. On current predictions, we’ll burn the next half trillion in less than 40 years.”  The Allen study used a combined climate and carbon cycle model to produce simulations spanning a range of climate futures consistent with the changes already observed.

The second study led by Malte Meinshausen at the Potsdam Institute for Climate Impact Research in Germany prepared a computer model to demonstrate that to avoid two degrees Celsius by 2100, cumulative carbon emissions must not exceed 0.9 trillion tonnes.

The researchers found that only about a third of economically recoverable oil, gas and coal reserves can be burned, if global warming of two degrees Celsius is to be avoided by 2100. This is an amount of fossil fuel that would be burned by 2029, if carbon consumption remains at current levels. Meinshausen says: “We have already emitted a third of a trillion tonnes in just the past nine years.”

A co-author of the Allen report, David Frame, who is also one of the researchers at Oxford, said that the findings “treat these emissions……as an exhaustible resource. For economists, this way of looking at the problem will be a huge simplification,” Frame says.

“Basically, if you burn a tonne of carbon today, then you can’t burn it tomorrow…. You’ve got a finite stock. It’s like a tank that’s emptying far too fast for comfort.”