Congratulations to Edgar Hertwich, Glen Peters and the NTNU team for presenting the 'Carbon Footprint of Nations' as a politically relevant way of accounting for greenhouse gas emissions, based on a sound methodology.

The publication and website comes at an important time – the decisive climate policy negotiations in Copenhagen are only half a year away – and it will be a useful input to this process. For both, producers and consumers, as individuals, companies and nations are responsible for emissions and both have a joint responsibility to address the problem with determination. The burden of this responsibility must be shared, only then can a meaningful and comprehensive deal to cut global emissions be achieved. The exact nature of this sharing is yet to be determined in negotiations but it is certainly useful to provide the viewpoint of both, production-based and consumption-based emission inventories.

The work is also important from a methodological point of view. Whilst it is, of course, not the first publication to present findings from an environmentally extended multi-region input-output (EE-MRIO) model (numerous other researchers and the authors themselves have driven forward this field of research), it clearly emphasises the applicability and usefulness of this method. The consistent combination of existing, mostly standardised, environmental and economic accounts and the unambiguous allocation of impacts to consumption categories are the strengths of EE-MRIO. It is also an acknowledgement that international trade is the key element in separating production from consumption in a globalised world and that the complex trade relationships need to be addressed in a methodological sound manner. Clearly, much more needs to be done to make the method robust enough for political target setting. An upcoming report from the recent European EIPOT project makes suggestions on methods, data and institutions to develop EE-MRIO in that direction (www.eipot.eu).

Looking at greenhouse gas emissions from a consumption perspective is politically significant and addresses arguably the most important environmental challenge faced to date. But it cannot provide the full picture of relevant impacts and it will be necessary to monitor other indicators alongside the carbon footprint, such as the ecological footprint, water footprint and results from more specialised ecological impact models, informing about biodiversity, ecosystem health and other categories.

I wish the 'Carbon Footprint of Nations' website plenty of attention and hope it helps in conveying the message of consumption-based accounting.