HOW many times have you heard it said, the science is settled, we will have catastrophic global warming unless we change our ways and reduce our greenhouse gas emissions?
While the “science might be settled” it does not seem to be well understood.
At least there has been a dramatic rise in key greenhouse gases in the past last two years, in particular methane, but temperatures have not gone up.
In fact, global temperatures are falling. That’s right – falling.
While Australian farmers have been told they should make a transition from cows to kangaroos to reduce their greenhouse gas emission, in particular emissions of methane, it is increasingly unclear that such a dramatic action, even if it was undertaken, would have any effect on global methane levels.
The amount of methane in Earth’s atmosphere shot up in 2007, bringing to an end a period of about a decade in which atmospheric levels of the potent greenhouse gas were essentially stable.
At least that’s according to a team of scientists led by Matthew Rigby and Ronald Prinn at the esteemed Massachusetts Institute of Technology (MIT) with their findings about to be published in the journal Geophysical Research Letters.
Methane in the atmosphere comes from a variety of sources including cattle, rice paddies, the coal industry.
It is destroyed by reaction with the hydroxyl free radical (OH), often referred to as the atmosphere’s “cleanser.”
A surprising feature of the recent surge in atmospheric methane levels is that it occurred almost simultaneously at all measurement locations across the world.
The scientists say a rise in northern hemispheric emissions may be due to the warm conditions observed in Siberia throughout 2007, potentially leading to increased bacterial emissions from wetland areas. However, a potential cause for the increase in the southern hemisphere is less clear.
It was thought an explanation for the rise may lie, at least in part, with a drop in the concentrations of the methane-destroying OH.
Theoretical studies, however, indicated that if this had happened, the required global methane emissions rise would have been smaller and more strongly biased to the Northern Hemisphere, so this can’t really explain the simultaneous rise in methane levels that have occurred all around the world either.
Indeed while the science of climate change is according to some “settled”, there really is a lot we don’t understand.
Not even our Federal Climate Change Minister, Penny Wong, can guarantee that a dramatic change in how Australian farmers go about their business would have any effect on global temperatures.
First published in The Land, on November 13, 2008.