I MAKE no apologies for talking about the thorny issue of climate change yet again. There’s a good reason why: after a decade or more of unwillingness to listen to criticism of the IPCC story on climate change, this week a mainstream paper was published in Nature Geoscience that to all intents and purposes shows many of the criticisms to be justified.
Even the most objective-sounding paper is open to different interpretations, and this one is no exception, despite its apparently unambiguous title: Emissions budgets and pathways are consistent with limiting warming to 1.5°C. The message from the authors is seemingly a clear one. If we try hard, global warming can be limited and managed.
To quote from the paper’s summary: “Hence, limiting warming to 1.5°C is not yet a geophysical impossibility, but is likely to require delivery on strengthened pledges for 2030 followed by challengingly deep and rapid mitigation. Strengthening near-term emissions reductions would hedge against a high climate response or subsequent reduction rates proving economically, technically or politically unfeasible.” This straightforward message is taken up by the BBC under the headline Paris climate aim is ‘still achievable’.
The authors’ research was a reassessment of the projections from climate models, the output of which has so often in the past been used to argue that the world was, in effect, already past the point of no return. The iconic figure of a 2°C rise in average temperatures had been taken as the limit above which the net impacts of climate change would become seriously negative. At the end of the 20th Century, stories of what life might be like on an Earth that had warmed by 4, 6 or 8 degrees were commonplace.
The surprising thing about the current study, therefore, is that not only is the 2° temperature rise seen as a practical reality, but that the more stretching 1.5° target arising from the Paris agreement is also deemed possible. The underlying message is that the computer models have indeed overestimated the extent of warming and that all is not lost. The BBC nevertheless report a conflicting view from another recent paper: Importance of the pre-industrial baseline for likelihood of exceeding Paris goals.
Co-authored by Michael Mann, this paper argues that, as the target temperature is measured against a baseline of pre-industrial conditions, taking an earlier reference point makes the goal more difficult to achieve. This is hardly surprising, given that the last few centuries have seen the planet emerge from the so-called Little Ice Age.
Since cooler conditions have historically been less favourable for farming and hence for society overall, it seems a little perverse to consider this to have been an ideal climate to which we should aspire. Nevertheless, Professor Mann is quoted by the BBC as saying "There is some debate about [the] precise amount of committed warming if we cease emitting carbon immediately. We're probably very close to 1.5C."
However, there are alternative views. The Times, for example, put the story on the front page under the headline We were wrong – worst of effects of climate change can be avoided, say experts. The focus of this story is that the present climate models systematically overstate the amount of warming arising from a rise in carbon dioxide levels. In this report, co-author Professor Michael Grubb explains this.
Having said at the Paris summit “All the evidence from the past 15 years leads me to conclude that actually delivering 1.5C is simply incompatible with democracy”, he told the Times “When the facts change, I change my mind, as [John Maynard] Keynes said. It’s still likely to be very difficult to achieve these kind of changes quickly enough but we are in a better place than I thought.”
The comments about facts and evidence are interesting. The ‘facts’ referred to in Paris were the output from the computer models now deemed to be biased. The ‘evidence’ of today is that these models have projected higher temperatures than observed for the century so far. Until the models can produce a reasonable hindcast of the pattern of average temperatures over the past 50 years without incorporating unexplained or unjustified fudge factors, we can hardly place much credence on the forecasts for the next half century. Even then, we have to bear in mind that modelling is not reality, but at least it might then represent our best current understanding and be some guide to the future.
Whatever the different interpretations of this important paper, it is hard to escape the conclusion that the understanding of climate change espoused by the mainstream of scientists and the IPCC is looking more and more like that of sceptics whose views have so often been dismissed and who have regularly been tagged ‘deniers’. This, surely, should be good news, and an illustration of shifts in the paradigm based on an increasing body of evidence. In an ideal world, it means that the common ground can be occupied by many more scientists and policymakers, working together both to improve our understanding of the complexities of climate and to formulate effective and economic ways to deal with any challenges.
Would that this were so, but in practice there is still a clear line separating many critics from the mainstream view: the nature of governments’ response to the situation. The clear message from the latest Nature Geoscience paper is that policymakers need to continue to increase their efforts, but that these will be rewarded by the outcome. Meanwhile, there are others who continue to argue that the consensus remedy – a drastic reduction of carbon dioxide emissions – cannot be achieved with the current tools at our disposal.
No matter how low the price of wind-generated electricity, no matter how sophisticated electric cars become, no matter how quickly we convert domestic heating to electricity, the costs of a secure energy supply given the current state of technology will be very significantly higher than at present. It need not be like this if the best minds on both sides of the ideological divide can work together to develop better solutions.
Martin Livermore writes for the Scientific Alliance, which advocates the use of rational scientific knowledge in the development of public policy. To subscribe to his regular newsletter please use this link.