The world’s most important number

July 1, 2009

350 or three hundered and fifty or CCCL. 350 BC was the year when Aristotle argued that the earth was spherical. A significant moment in human history no doubt, but not the reason why 350 is the most important number in the world. That title goes to the proportion of CO2 in the atmosphere that scientists are increasingly stating as the safe upper limit; 350 ppm (parts per million). Consider this; prior to the Industrial Revolution the proportion of CO2 in the earth’s atmosphere was believed to be 275 ppm. It was 275 ppm when old Aristotle was arguing the world was not flat in 350 B.C and during all of human history. And 275 ppm is a good number as we need some CO2 in the atmosphere to keep the earth warm enough for survival.

But things began to change in the past 200 years that mark our love affair with fossil fuels. No disrespect to fossil fuels. Madame Coal, Oil and Gas were ideal mistresses. They were easy to find, extract, transport, use and unlike their human counterparts brought no guilt. All this has changed in recent decades. Now fossil fuels are harder to find and extract as larger reserves are found in inaccessible places like under the sea and in politically unstable countries.They are now saddled with a guilt trip as well. In the 1980s we knew enough about the molecular structure of CO2 and its ability to trap heat. Scientists were beginning to realise that all the millions of tonnes CO2 being released into the atmosphere every year was bound to  have consequences. By 1995, the correlation between CO2 and temperature rise was established beyond a doubt. 15 years of climate change skepticism, vested interest lobbying and quest for double digit growth later, we are now at 387 ppm of CO2. And already we are experiencing the effects of climate change.

The decade of 1998-2007 was the warmest on record. Drought, floods, retreat of glaciers, melting of polar ice caps, coastal erosion and spread of diseases & pests are affecting us NOW at 387 ppm of CO2. It is obvious that we should be aiming for something below 350 ppm to have any chance of adapting to a changing climate. The Draft Negotiation Text for a post-2012 climate agreement does list 350 ppm as a commitment. Accordingly this translated to developed countries reducing CO2 emissions by more than 85% of 1990 levels by 2050. However, 350 ppm is only 1 of 4 options listed in the Draft for countries to negotiate on in December at Copenhagen.  The 450 ppm option is not good enough (particularly for small island countries) as we are already struggling to cope at 387 ppm. The  2 degrees celsius limit option presumes we can control the earth’s temperature like an oven (what we have control of is the amount of CO2 we emit).  The global 2 tonnes CO2 per capita could mean that the poor everywhere could be subsidising the big emitters. Thus, the only effective and equitable target is 350 ppm. Get real, get 350.


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