A promising act on aviation CO2 - but shall we address real numbers, or numerology?

Dimitri Simos
June 2015

In a significant and encouraging announcement, the US Environmental Protection Agency has declared its formal intention to legislate on aspects of aviation CO2 emissions. The EPA is also clearly mindful of the understandable reservations of the aviation industry with regard to legislation.

All sides to the environmental debate could act in their best interest by inviting scientific transparency into the heart of their policies. Whatever the ultimate form of any consensus legislation, the quantification of aviation CO2 emissions at its core must become technically meaningful and far more scrupulous than previous token attempts by ICAO. It is deeply worrying that one of the options under consideration is to follow in that organisation's footsteps.

ICAO has systematically evaded the issue of correct quantification. It rejected scientific modelling and objective comparisons of the direct CO2 produced by aircraft in favour of an erroneous and sanitised statistical artifice. Although ICAO promulgates this as a 'CO2 metric', this author knows no independent aeronautical engineer willing and able to defend its technical validity. ICAO failed to respond to a series of key criticisms over a period of several years.

Having no ability to appraise direct CO2 emissions or reflect operational realities, ICAO's metric will, if accepted and incorporated into a global policy, have two unavoidable consequences:

1. Legislation will be made irrelevant by the need to set low, ad hoc pass/fail levels such that the largely random nature of the metric does not, indiscriminately and unjustifiably, reject particular aircraft types. Only manipulative assertions that this or that product is 'too important to fail' will then be able to navigate this baseless black-or-white doctrine.

2. Future aircraft development will be skewed, not towards a reduction of CO2, but towards compliance with a meaningless measure, with consequences that are unknowable. Indeed, as the metric ignores the proper weight of the aircraft, it can under specific circumstances worsen emissions and will run counter to one partially valid argument that the manufacturers use, namely that there exists some natural incentive towards low fuel burn and therefore CO2.

Effective legislation for aviation CO2 must, unambiguously and distinctly, account for the true aerodynamic qualities, engine characteristics, and empty weights of aircraft, as well as the manner in which they are operated. In short, it must embrace scientific modelling and shun arbitrary 'magic numbers'.

The task is achievable and the tools for it exist. Manufacturers may assert specific claims for the above qualities, but these qualities can also be evaluated independently and objectively with sufficient accuracy. As far as assessment of direct CO2 emissions is concerned, there is simply no requirement for the industry to cooperate on anything other than a strictly voluntary basis.

There can be no excuse for legitimising the dangerous fudge that is ICAO's metric, and no obfuscation about critical numbers. It is vital that mature and flexible technical means of modelling aircraft behaviour are recognised as being key to any solution, not esoteric inconveniences. They must be assigned a formal role in a visible 'quantification core' of whatever legislation evolves. They should enter the public domain and serve accountably as global, verifiable and adjustable reference standards on which coherent decisions can be based. They should be open-sourced and made freely accessible to the public, inviting industry and peer contributions, comments and unrestricted usage. Their scientific independence should be safeguarded. Without this unequivocal transparency, future CO2 legislation will fall victim to manipulation and will fail to achieve its goals.

The modelling tools used by the EPA are acknowledged in its announcement:

(or search for endangerment finding EPA-HQ-OAR-2014-0828.)

Dimitri Simos