After having increased by 42 per cent since the Industrial Revolution, global concentrations of carbon dioxide are now exceeding the 400 parts per million threshold. In other words, for every million molecules in the troposphere, a paltry four hundred are CO2. Global concentrations of methane, meanwhile, are now around 1,834 parts per billion. Among every billion molecules, just 1,800 are CH4. Even at such tiny proportions, however, they are trapping part of Earth’s infrared radiation and are already altering the planetary energy balance.
While carbon dioxide emissions have been growing at a slightly slower pace, the amount of methane in the troposphere appears to be increasing at a faster and faster rate. A paper published in Environmental Research Letters revealed that methane emissions, long thought to be stagnant, have soared in the last two decades. In 2014 alone their growth rate doubled.
Methane is a much more potent greenhouse gas than carbon dioxide. And if the latter is only partially produced by human activities, the former is decidedly more dependent on them, in particular when it comes to food production. Rice paddies emit methane when they’re flooded and, more dramatically, the 1.6 billion heads of cattle currently roaming the world profusely emit methane at both ends. Furthermore, methane has been leaking from oil and gas wells for more than a century. If we add that human-induced warming is thawing Siberian permafrost where natural methane has been trapped for millennia, the picture is clear… and worrying.
“We now have 7.4 billion mouths to feed, and better living standards have spread animal protein consumption in much of the developing world”
We now have 7.4 billion mouths to feed, and better living standards have spread animal protein consumption in much of the developing world (something the World Health Organization recommends curbing). The expected 1.6 billion more tablemates by mid-century doesn’t suggest our food and energy needs are likely to decline.
With the Paris Agreement, world governments targeted a maximum warming of 2°C. Until now though, all the attention has been drawn to carbon dioxide emissions from fossil fuel combustion. If we are to reach that vital climatic goal, it is time for us to swiftly check on methane emissions from oil fields and cattle as well.
This was published in the February 2017 edition of Geographical magazine.