Concentrations of carbon dioxide are rising faster we thought:
The concentration of carbon dioxide in the atmosphere has reached a record high, according to the latest figures, renewing fears that climate change could begin to slide out of control.
Scientists at the Mauna Loa observatory in Hawaii say that CO2 levels in the atmosphere now stand at 387 parts per million (ppm), up almost 40% since the industrial revolution and the highest for at least the last 650,000 years.
The figures, published by the US National Oceanic and Atmospheric Administration on its website, also confirm that carbon dioxide, the chief greenhouse gas, is accumulating in the atmosphere faster than expected. The annual mean growth rate for 2007 was 2.14ppm – the fourth year in the last six to see an annual rise greater than 2ppm. From 1970 to 2000, the concentration rose by about 1.5ppm each year, but since 2000 the annual rise has leapt to an average 2.1ppm.
Scientists say the shift could indicate that the Earth is losing its natural ability to soak up billions of tonnes of CO2 each year. Climate models assume that about half our future emissions will be reabsorbed by forests and oceans, but the new figures confirm this may be too optimistic. If more of our carbon pollution stays in the atmosphere, it means emissions will have to be cut by more than is currently projected to prevent dangerous levels of global warming.
Roger Revelle, one of the scientists who first detected rising carbon emissions in the 1950s and concluded it would lead to rising temperatures (using data collected at the same Mauna Loa observatory) remarked that “human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future.”
Well, here we go. This vast carbon cycling system, upon which we all intimately depend, may be losing resilience, making it harder to “fix” with changes in human behavior. But like many experiments, the results of this one can’t be anticipated except in general terms. We know it’s getting warmer, but we don’t know exactly how the oceans, plant life, and atmosphere will dynamically interact as carbon dioxide concentrations continue to rise, and as deforestation and industrial activities expand – or, if our current projections are off, if our policy fixes will come close to making a difference.