Climate dreaming 209 spite of the half-hearted mitigation now, the amount of BECCS consequently required in the future to reduce the ‘over-shoot’ in emissions and keep the temperature low enough does not require more land or water than is compatible with future food security. Such a risk transfer from present to future is not justified.15 But we have so far assumed that if the gamble did in fact ‘turn out well’, no damage would have been done by the shortfall in mitigation in the present. The prospect of BECCS later would have ‘bought us time’ so that humanity could get away with mitigating less now. But, could it? 5 A PROMISE THAT CANNOT BE FULFILLED: COULD ANY NET ‘BUY TIME’, EVEN IF IT WOULD WORK? What we have seen so far suggests that the positive case in favour of reliance on BECCS in particular is quite weak, resting more on wish than on evidence. Moreover, two arguments in the negative case consist of the danger of failure and the injustice of gambling that this technology will rescue later people from the results of excessive avoidable emissions now. Reliance on BECCS that compromises the ambitiousness of mitigation now and in the immediate future has two kinds of severe moral costs: potential damage and actual injustice in taking the gamble. That negative case against relying on negative emissions will next turn out to contain another strong argument, the third. And this third consideration is not specific to BECCS alone, but is applicable to all NETs.16 The beguiling allure of all NETs rests on the fantasy that they ‘buy the world more time when it comes to reducing our overall greenhouse-gas emissions’.17 These (not yet proven) technologies will provide, it is hoped, an ‘insurance policy’ against any untoward consequences from our current relaxed approach to mitigation. They are thought, or at least hoped, as Peters observed to journalist Harvey, to provide ‘getout-of-jail cards’ valid in the future in case our choice of half-hearted mitigation now seems to have locked the planet into too high a temperature level. I want to explore now a powerful reason why such wishful thinking is both deeply illusory and unjust, not simply for BECCS but for all NETs – and indeed for any form of geo-engineering that motivates less ambitious mitigation now. The fundamental reason against reliance on ‘un-doing’ an ‘over-shoot’ from insufficient mitigation with any NET is that some effects of high cumulative emissions – even some supposedly ‘temporary’ effects – simply cannot be undone: these effects are irreversible by humans, even in the cases in which they are not literally permanent but may gradually be cancelled out by planetary dynamics over a time-scale of centuries that is far too protracted to be beneficial to any humans except perhaps those in far, far distant generations. The irreversible consequences of excessive cumulative emissions can be clustered loosely into relatively longer and relatively shorter effects, although the distinction between these two is obviously only in degree, and the distinction makes no discernible difference to any humans for centuries. 15. The concept of risk transfer was insightfully applied to warfare in M Shaw, The New Western Way of War (Polity Press, Cambridge 2005). 16. I am grateful to Joshua Wells for underlining the importance of distinguishing general objections to all NETs from objections specifically to BECCS. 17. Harvey (n 3). © 2017 The Author Journal compilation © 2017 Edward Elgar Publishing Ltd