“A journey of a thousand miles begins with a single step” Laozi, 6th century BC

“If everyone does a little, we’ll achieve only a little” David Mackay, 2009

At the beginning of October 2016, a landmark agreement has been reached.  Or should that be airmark?  The international aviation industry has agreed, in Montreal, to limit future growth in the industry’s CO2 emissions.  Specifically, it has agreed to engage in offsetting measures, such as tree-planting, that will cancel out any further growth in its CO2 emissions from the year 2020 onwards.

For instance, suppose the global emissions from aviation are 1.0 billion tonnes CO2 per annum in 2020.  If in a future year this annual emission rate increases to 1.1 billion tonnes CO2, the industry has agreed to engage in tree-planting (and other measures) that will absorb the increase of 0.1 billion tonnes above the 2020 level.

This sounds helpful, but there are a few serious issues.  Firstly, how will it be possible to distinguish between measures taken by the industry that lead to additional offsetting from measures that would have happened anyway?  More generally, how do we attribute emissions reduction fairly to an industry with a powerful vested interest to exaggerate its environmental credentials?  Secondly, what about radiative forcing – there is general agreement amongst scientists that emissions at 30,000 feet are 2-3 times as potent in terms of their warming effect as emissions at ground level – this suggests the offsetting should be 2-3 times as great if tCO2e (tonnes of CO2 equivalent) rather than tCO2 (tonnes of CO2) are used as the basis.  Thirdly, most climate scientists would argue that emissions need to be significantly reduced below the likely 2020 level if we are to avoid catastrophic climate change.

Fourthly, there is a problem with the rate of capture: let’s say the trees last for 20 years, and over that 20-year period absorb as much CO2 as is emitted by the aviation industry in 1 year.  Meanwhile, the industry is presumably emitting CO2 at the same rate (or higher) during years 2-20 inclusive.  In this example, the rate of planting is only able to keep up with 5% of the (growth in) CO2 emissions.

So, the target is mismeasured but in any event not ambitious enough, and the offsetting measures are hard to attribute but in any event almost certainly inadequate.   At least this marks a beginning – the first time that there has been an international aviation agreeement to reduce CO2 emissions.  Supporters will argue that we have to start somewhere in an international agreement of this kind; detractors will point out that this is all still aspirational only, and even if the proposal is enacted we need to take much larger steps if we are to avoid catastrophic climate change.