The climate change melody in my head

Toronto Star
Jun. 17, 2006
CAMERON SMITH

There's a love song from the '60s that Nat King Cole used to sing so beautifully:

The more I see you/The more I want you.

Somehow this feeling/Just grows and grows.

With every sigh I become more mad about you,

More lost without you, and so it goes.

They describe with silky elegance what I've been trying to say about feedback loops — how response keeps building on response. In Cole's version, how seeing breeds wanting, and wanting leads to more seeing ... "and so it goes."

In climate change, feedback loops pose the greatest danger, because they multiply the amount of carbon dioxide (CO{-2}) and methane entering the atmosphere. To make matters more complicated, there are compensating forces at work as well. For instance, trees breathe in CO{-2} and exhale oxygen, so as more CO{-2} becomes available, they breathe in more, grow faster and reduce CO{-2} levels.

Nevertheless, feedback loops will outpace the compensating forces. A prime example of feedback potential is the methane that can be released as permafrost melts in the Arctic — and there's twice as much methane in permafrost reservoirs as there is in all the world's natural gas reservoirs.

Then, there are the methane hydrate deposits on continental shelves in the oceans, holding methane up to 10 times the volume of natural gas reserves. This methane can be released if the oceans warm.

No one is sure where and when methane will start bubbling up, although there's a consensus it will certainly happen with ocean warming of 3 degrees Celsius. Already, the North Atlantic is warmer by slightly more than 0.7C.

There's also what's called the albedo effect, the reflectivity of ice and snow in the Arctic. With warming, ice and snow retreats northward, and heat is retained by the land instead of bouncing off. That makes everything warmer and helps speed the further retreat of ice and snow.

At the same time that all this is happening, there's the weakening of another great compensating force: the ability of phytoplankton in oceans to absorb CO{-2}{-.} They used to account for half of the CO{-2} pulled out of the air by plants. The other half was removed by land plants. NASA (the U.S. National Aeronautics and Space Administration) estimates the amount of CO{-2} removed by ocean phytoplankton has dropped by more than 6 per cent over the past 20 years.

And now I come to what has been one of the most contentious issues of all: Is there a global warming feedback loop occurring in the soil?

New research conducted in England and Wales suggests there is. Carbon is stored in soil as peat, as humus and as organic litter in the process of decomposing into humus. Soils usually contain more than twice the carbon contained in plants or the atmosphere.

Some carbon binds to clay, silicates or metals, and can remain stable for thousands of years. Some is oxidized and is released to the air as CO{-2}. Normally, there's a subtle balance between what remains stored in soil and what is released.

But the British study found the balance has been upset by "a surprisingly large release of CO{-2}." The study is reported in Nature, vol. 437, Sept. 8, 2005, pages 205-206 and 245-248.

The authors examined the carbon content of soils in 6,000 sites in England and Wales over the 25 years from 1978 to 2003. They found there had been a loss of carbon which, when translated into CO{-2} by two reviewing writers in a commentary, was equal to the entire amount by which the United Kingdom reduced emissions during the same 25-year period.

The commenting writers conclude: "These (carbon) losses completely offset the past technological achievements in reducing CO{-2} emissions, putting the United Kingdom's success in reducing greenhouse gas emissions in a different light."

The study's authors say climate change was the only factor common to increased release of CO{-2} in all areas. Mean temperatures rose 0.5C and rainfall increased. This probably led to more bacteria, or more energetic bacteria, engaged in decomposition.

However, the authors resist claiming a feedback loop is operating. They say only that evidence points this way.

In summary, then, trying to slow climate change is a terribly complicated undertaking, and it's not going to be achieved through the simplistic nostrums and the reliance on volunteer efforts that Canada's Prime Minister has been offering.