Less efficient natural ‘cleaning’ could tip global carbon balance


SINGAPORE — Nearly everyone is familiar with budgets. Households keep them. So do companies and national governments. But what about the carbon budget that measures the health of our climate system?

Just as accountants check financial budgets, an international team of scientists is attempting to do the same for the planet’s carbon budget. Carbon is the core of organic molecules from which all forms of life — from microorganisms to plants, trees, animals and humans — are built.

The carbon cycle is a complex series of processes in which all of the carbon atoms on Earth rotate through the land, sea and atmosphere, and are kept in a shifting balance. The ocean and land are natural sponges, or sinks, that absorb carbon in its gaseous form, carbon dioxide (CO2).

Ocean-dwelling plankton and land plants, including forests and grasslands, take in CO2 by photosynthesis. But there is a reverse process. Seawater also releases CO2 into the atmosphere, as do land plants and soils.

The natural carbon cycle has been influenced by the growing human population and its demands for resources, especially for fossil fuel energy and land. Carbon is the primary component of both fossil and biomass (wood and animal waste) fuels. Coal, oil and natural gas are called “fossil” fuels because they are made from buried remains of plants and animals that lived millions of years ago.

Carbon dioxide accounts for nearly 77 percent of the greenhouse-gas emissions from human activity blamed by many scientists for warming Earth to potentially dangerous levels. According to the 2007 report of the Intergovernmental Panel on Climate Change, nearly all of this CO2 has come from two sources, burning coal, oil and gas; and clearing forests for farming and other uses. Most of the world’s electricity is generated from fossil energy, while nearly all modern forms of land, air and sea transport are powered by oil-based fuels.

Compiling a global carbon budget is not easy. But a group of 31 oceanographers and other specialists attached to academic institutions and government-funded climate agencies in the United States, Europe, Japan, Australia and South America this month published their latest annual stock take. They found that despite the economic slowdown that started to bite in the second half of last year, the concentration of CO2 in the atmosphere rose by 1.8 parts per million in 2008, slightly below the annual average of 1.9 ppm between 2000 and 2008. This might not sound much. But 1 ppm of CO2 corresponds to over 2 billion tons of carbon and nearly 8 billion tons of CO2.

The increase brought atmospheric CO2 concentration to 385 ppm in 2008, 38 percent above the level of 280 ppm at the start of the industrial revolution in 1750, putting it at the highest point in at least 2 million years. The lead author of the Global Carbon Project study, professor Corinne Le Quere of the University of East Anglia and the British Antarctic Survey, says the only way to control climate change and keep the temperature rise to a tolerable level is through a “drastic reduction” in global CO2 emissions.

Yet the prospects for effective action when over 190 nations gather Dec. 7-18 for the U.N. climate summit in Copenhagen seems dim, with negotiations set to drag into 2010 and perhaps beyond.

At one level, an agreement should be feasible. Just three countries — China, the U.S. and India — were responsible for half of global CO2 fossil fuel emissions in 2008, while these three plus Russia, Japan and the 27 nations of the European Union accounted for 80 percent of emissions.

The leading polluters have been meeting as a group to try to decide how to apportion and pay for cuts but remain deeply divided. Finding an equitable and politically acceptable way of doing so is a test of statesmanship that appears beyond most of the key participants at a time when they are trying to accelerate economic growth, not slow it down.

The biggest rise in fossil fuel emissions in the past decade has taken place in developing countries, with close to 6 billion people, while developed countries, with less than 1 billion people, on average show steady emissions. From an historical perspective, developing countries with 80 percent of the world’s population, account for only about 20 percent of cumulative fossil fuel emissions since 1750.

Moreover, about one quarter of the recent growth in developing country emissions resulted from the increase in international trade of goods and services produced there but consumed in developed countries. If these are added to the 45 percent emissions tally of developed countries in 2008, the advanced economies remain the main source of worldwide CO2 emissions.

This kind of accounting is a recipe for international contention. Meanwhile, the global carbon balance may be on the verge of serious deficit as the amount of CO2 from human activity being spewed into the atmosphere outstrips the capacity of natural sinks to absorb it all. Global emissions from fossil fuel burning and deforestation are now about 37 billion tons of CO2 per year, 41 percent higher than in 1990.

Land and sea sinks removed an average of 57 percent (or 5.3 billion tons per year) of all CO2 from human activities between 1958 and 2008, leaving 43 percent in the atmosphere where it will stay for at least several centuries.

The research of professor Le Quere and her colleagues also indicates that the portion of CO2 remaining in the atmosphere may be rising.

Dr. Shobhakar Dhakal, an executive director of the Global Carbon Project at Japan’s National Institute for Environmental Studies, says that this has occurred over the past 50 years and suggests that natural sinks are becoming “less efficient ‘cleaners’ of human carbon pollution.”

U.S. oceanographer Richard Feely, who is also part of the Global Carbon Project, says: “We’re concerned that if the natural sinks can’t keep pace with the increased CO2 emissions, then the physical and biological impacts of global warming will accelerate over the next century.” There is disagreement among scientists about whether the capacity of Earth’s biosphere to keep the global carbon budget in balance has already been exceeded.

But even those who dispute that the tipping point has arrived say that it will certainly come without resolute steps to curb global greenhouse-gas emissions.

Michael Richardson is a visiting senior research fellow at the Institute of South East Asian Studies in Singapore.