When words emit a powerful odour

Methane is a greenhouse gas which, once release into the atmosphere can contribute to global warming.

But, interestingly, it was not until a month ago scientists realised living plants emit methane and these emissions could account for up to 30 percent of the world's annual global methane emissions.

Climate models, which have predicted future rises in global temperature, are based on atmospheric levels of greenhouse gases.  So I was rather surprised to find that such a significant source of an important greenhouse gas had only just been discovered.

When this finding was published in science journal Nature, I was expecting a flurry of activity as policy officers considered the implications for the Kyoto agreement on greenhouse emissions ("Save the planet -- cut down a tree", The Land, January 26, pg 22).

I was certainly not expecting the scientists who published the original findings, to put out a media release stating that their findings had been misinterpreted and that for all intents and purposes methane from trees could not be considered a source of greenhouse gases or a source of global warming.

Why?  Because according to these scientists, emissions of methane from plants are natural, and while the physical processes that influence global climate don't distinguish between human and natural sources of methane, the United Nations does.

Indeed, the United Nation's Framework Convention on Climate Change has defined "climate change" as only change from human activity.

I have always considered it rather strange the United Nations would redefine something as natural as the climate's changing characteristics to only include human impact.

Of course the earth's climate has always changed, but we don't know exactly how much is now -- due to the burning of coal and oil -- and how much is from natural variation.

In Lewis Carroll's classic Through the Looking Glass Humpty Dumpty says "When I use a word it means just what I choose it to mean -- neither more nor less", and so it seems, does the United Nations.

While scientists and bureaucrats play with the meaning of words, graziers in western Queensland and NSW are struggling to make sense of the last round of restrictions on broad-scale tree clearing, which were driven, at least in part, by the Federal Government's global warming concerns and our Kyoto targets.

Even though trees emit methane, they remain a net sink for greenhouses gases because they store so much carbon.

Mick Keogh from the Australian Farm Institute has calculated that the bans on clearing woody regrowth would be worth $600 million to landholders as carbon credits.

But farmers can't access this money because agriculture is not part of any national carbon trading scheme -- and even if it was, woody regrowth probably wouldn't count for anything ... because it re-grows naturally.

ADVERTISEMENT