Carbon dioxide not th only gas threat to climate


Over the last 17 years there has been a growing focus on the threat posed by the emission of carbon based gases to the climate. Whilst much of the concern is merited, it has by and large ignored methane. With concern starting to grow about the potential impact of large scale methane releases, it is time to re-evaluate the threat that this gas poses.

Before one tackles the problem methane poses, we need to be aware of its composition. To be clear, methane itself is a carbon based gas (1 atom of carbon with 4 atoms of hydrogen attached).  Compare this to carbon dioxide (one carbon atom with 2 oxygen atoms attached), Methane has numerous sources, both natural and artificial. Livestock contribute significantly to the problem across the world, especially in India where slaughter of cows is banned in all but two states and the low income of farmers mean they cannot afford fodder that reduces belching.

In a New Zealand context, carbon dioxide is not our largest greenhouse gas contributor to the international greenhouse equation. The primary gas New Zealand contributes is methane, This is why agriculture was the key focus of New Zealand efforts to address climate change under the Helen Clark-led Labour Government – and perhaps why farmers got significant sympathy from National when in opposition. Politics aside though, despite both parties seeming to think that largely symbolic agreements in front of the media are action, and the lack of policy initiatives at home to back them up, there has been a general acceptance that climate change is a credible issue, despite questions about the science.

However there is a major threat that is largely unnoticed by everyone, including the environmental lobby, which poses a much bigger threat than carbon dioxide will if it is realized. This is the melting of the permafrost in the Arctic, which traps huge volumes of methane. One estimate of the carbon trapped in the permafrost is as high as 1,700 gigatons ( 1gt is a billion metric tons), compared with 730gt in the Earth’s atmosphere, and 650gt trapped in vegetation. If the world is to achieve the goal of no more than 2°C global warming, it cannot have more than an estimated 1,000gt of carbon in the atmosphere).

As the permafrost melts, the biological plant and animal matter that has been stored safely under its icy wrap resumes the biological process of bacterial decay. This will cause carbon and methane discharge to start. Methane has a shorter life time as a gas in the atmosphere, but it is many times more potent because it has a short term warming effect. The Global Warming Potential index is a measure of a gas’ potential impact on the climate, with carbon having a reading of GWP 1, as it is the base line indicator against which the others are measured. Methane over 20 years has a reading of GWP 34 and over 100 years a reading of GWP 72. The release of methane may happen in several ways. Scientists researching the gas have noticed random deep holes in the ground in northern Siberia, and have wondered if these were caused by pockets of methane being released explosively. Although there is no suggestion that the permafrost will suddenly completely disappear, if caused by methane no longer being trapped, these holes will become more common the future.

But most terrifying of all, is once melted, there is no way to refreeze the permafrost – no way to retrap in the icy enthralls of Siberia and the Arctic all of that methane and carbon dioxide. For possibly the first time, climate change is reaching a tipping from where there is no return.

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