Environmental Audit CommitteeWritten evidence submitted by Dr Ulrich Loening, former Director of the Centre for Human Ecology, University of Edinburgh

I write at the suggestion of Aubrey Meyer, Global Commons Institute to give my reaction to key climate-feedbacks in the UKMO’s UK-Climate-Act.

My justification for being nvolved in this is that I was for many years close to several research groups on resource modelling, (these include the Balaton Group who make a feature of not publicising their deliberations but helping participants in their understanding, and the Edinburgh EU funded resource accounting programme) including climate scientists who were authors or co-authors of IPC reports. I am not in any way a climate scientist; I did consult some Edinburgh climate modellers.

I have examined the submission that Aubrey Meyer has made to your Committee, and understood the issues but not the detail.

As I understand it, the Climate Act is based on modelling information of projected global temperature rises that omit some possibly key feedbacks from the models; and that the Met Office has more recently explained that this is indeed the case. There is therefore a discrepancy between the terms in the Act and the realities of scientific understanding.

The terms negative feedback and positive feedback tend to be used with equal abandon. It is important first to stress that these are not just opposites but effectively very different phenomena. Negative feedback exerts self-control and is therefore limiting and becomes predictable; positive feedback is self-propagating and is therefore likely to grow out of control without limit and become unpredictable.

The MO’s omission of positive feedbacks from the modelling that is used to estimate emission budgets is therefore very serious.

My first reactions were that this omission was poor science, with the consequence that the conclusion would be misleading.

However, there are real problems: firstly because of the uncertainties about the scale of positive feedbacks, like the melting of permafrost, they are too difficult to model properly. Indeed one might justifiably argue that large positive feedbacks cannot be modelled because of their very nature; more research would improve the situation but not solve it sufficiently to allow coupling into the climate models.

Secondly, the resulting errors in the modelling could have serious political and implementation consequences. It is for this reason that IPCC has repeatedly under-estimated the likely effects of rising greenhouse gas concentrations, (as can be seen from the lengthy discussions about detailed wording).

These two problems and others like them are, as the MO explained, why the more long term and difficult positive feedbacks were omitted.

However, this situation cannot be left to stand. Budget emission scenarios must be realistic; otherwise the consequences can become worse. At the very least positive feedbacks must be coupled into the models sufficiently to give a budget which avoids the onset of the largest potential positive feedbacks; once they start in earnest, it is too late to stop them.

My understanding is that the Climate Act would require updating to accommodate the coupling. The question then becomes how to deal politically with this frightening “inconvenient truth”. To continue as at present knowing that full coupling would entail a stricter carbon budget, would expand the position into a wider context. The solution is of course up to your Committee, but I can suggest that a reasonable guess about what to budget can be made, such that warming remains limited to below what would set positive feedbacks in train. In other words, the position can be avoided by being honest about it, and presenting the best plausible carbon budget.

The scenarios proposed by Aubrey and the Global Commons Institute to remain within these limits, seem realistic and achievable. The essential fairness in the C&C process would one would think and hope, enable all nations to join in. I have over many years supported the GCI initiatives, and still hope that this would allow the UK to set the tone and agenda.

10 July 2013

Prepared 3rd October 2013