Kramer and Haigh, in their opinion piece on low-carbon energy (Kramer, G.J. & Haigh, M. (2009) Nature 462, 568-569), indicate CO2 capture and storage (CCS) as an important mitigation technology, and indicate a role for governments to support the technology. I would however also like to appeal to the CCS expert community to play an important role: the role of independent CCS critics. Many supposedly independent CCS experts are currently actively promoting CCS. Although such advocacy may be typical of technological experts, it is problematic for CCS for three reasons.

Firstly, CCS is in desperate need of critical scrutiny. The technology has significant shortcomings, which can only be exposed and addressed by experts who know the ins and outs of the technology. Those experts, however, are increasingly advocates of the technology, and in many cases blind to drawbacks and selective listeners, dismissive of criticism. If CCS' weaknesses are not recognised, improvement may be hampered.

Secondly, CCS has sufficiently powerful supporters; it does not need independent academics to engage in advocacy. For the fossil-fuel industry that has to act in a carbon-constrained world CCS is a matter of survival. The industry has no choice: it has to stage an effective lobby for CCS, and it is resourceful enough. Valuable time of independent experts is best spent on research on the shortcomings of CCS, not on promotional activity.

Thirdly, the lay public, in order to make an informed assessment of CCS, needs reliable information on risks and benefits. Social science indicates that non-experts are more likely to trust independent experts than private sector or government representatives. If the public perceives the CCS expert community as CCS advocates who are largely oblivious to or out of touch with their concerns, severe public resistance and mistrust could emerge. This is already obvious in recently stalled CCS projects in the United States, Germany and the Netherlands.

Where have we seen this technological advocacy among experts before? Nuclear energy was once a promising technology, but the lack of an independent and critical expert community helped fuel controversy. The CCS community seems on track to make the same mistake. Peer pressure within the expert community to not be viewed as a CCS-sceptic is contributing to this development.

It is in the best interest of improving CCS technology and hence of mitigating climate change that an expert community is developed that leaves ample room for critical feedback and expresses the limitations of CCS, that leaves advocacy to industry, and that engages in an open and respectful debate on the technology with the general public. Only then will CCS be in a position to make a difference for climate change.