The most striking aspect of the Committee on Climate Change report on the impact on air travel on global warming is the uncertainty of forecasting.
Its underlying premise is that the number of passengers using UK airports could increase by 200%* by 2050. That alone raises many questions? Is the market for low cost flights becoming saturated? How will the demographic of an ageing population and the looming pensions crisis affect demand? Do we have the infrastructure for a massive rise in incoming tourism?
Then there's the issue of how much alternative means of communication could alleviate carbon emissions from flying. They include the impact of video-conferencing on business travel which, says the report, could reduce it by anything from a few percentage points to almost one third.
The potential development of alternative fuels for aircraft is also shrouded in unknowns. How much land will be available for the production of biofuels. How practical will it prove to produce biofuels that would not require agricultural land for growth – such as those base on algae, or grown with water from low-carbon desalination? This “must be considered speculative today”, admits the committee.
In addition there is the impact of other emissions besides CO2 (the committee was not tasked with looking at there – only with gases covered by the Kyoto agreement) such as mono-nitrogen oxides. The report says they are almost certain to result in some additional warming. But in sharp contrast with some of the anti-flying lobby it notes there remains “considerable scientific uncertainty over their precise magnitude.”
These then, form part of the shifting sands on which the committee concludes that demand growth of around 60% would be compatible with meeting the Government's aims of keeping CO2 emissions in 2050 no higher than in 2005.
That could leave room for a new runway at Heathrow, whose impact will in any case be mitigated, if only by about 1,5%, by the reduction in emission from aircraft forced, by congestion, to stack.
It might mean, eventually, an increase in fares as demand is constrained. But suppose technology allows more significant increases in aircraft engine efficiency than the committee predicts – or biofuels represent consumption greater than the committees'aaumtion of 10%. And suppose demand doesn't increase by anywhere near as much as 200% by 2050. Then the impact on travelling habits might not be as severe as some have feared.
*Unconstrained - with no inhibiting penalty for carbon emissions.