Due to finish last Friday, this year’s UN climate conference limped through the night to dawn on Saturday morning. With all of this year’s proceedings closed, OCS reviews what progress was made towards meaningful action on climate change over the past fortnight.
Rupert Stuart-Smith, Oxford Climate Society President 2017/18
The Paris Agreement (Article 2) seeks to restrict climate change to ‘well below 2°C above pre-industrial levels’, with the ethically imperative goal of ‘pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels’. An important question, discussed in greater detail in my previous article, is whether the more ambitious of these two goals was merely aspirational, or if this is indeed an achievable target.
By some measures, global temperature rise is already knocking on the door of 1.5 degrees. Some studies have argued that we could have emitted enough carbon dioxide into the atmosphere to reach that level of warming as soon as 2021. But these numbers rely on different assumptions than were made when the goals of the Paris Agreement were devised in 2015, at which time delegates were advised that global temperatures had risen by ‘only’ 0.85 degrees. With this in mind, the 1.5 degree goal in the Paris Agreement should be seen as a very real possibility, with recent studies indicating that net-zero greenhouse gas emissions must be achieved by 2045 (figure 1) or 2055 (partly dependent on our ability to reduce emissions of non-CO2 greenhouse gases). In other words, achieving the 1.5-degree goal will be extremely difficult and require rapid decarbonisation of every part of every economy in the world, but it is possible.
Figure 1: Future emission trajectories under business as usual (baseline), the Nationally Determined Contributions to the Paris Agreement (NDC), uniform pricing on all greenhouse gas emissions to deliver a 50% probability of staying within the 2°C target (default 3.4), as with default 3.4 but with a probability of at least 66% of staying below 2°C of warming (default 2.6), as with default 2.6 but minimising the use of bioenergy with carbon capture and storage as a means of carbon dioxide removal from the atmosphere (No BECCS 2.6), and delivering a 50-66% probability of remaining below the 1.5°C target (van Vuuren et al. 2017)
If we can understand the 1.5-degree target as being achievable and set with the intention of it being fulfilled, rather than a meaningless phrase added to placate many of the world’s countries at greatest risk from the impacts of climate change, who may otherwise have walked out of the discussions at Paris, the implications are huge. No longer will the biggest emitting countries and companies be able to drive global temperatures up beyond safe levels and then be able to claim that by the time we understood the science of climate change and came to a global consensus on its prevention, it was too late to do anything about it. We know it will be tough, and that we must be fully determined in our ambition to achieve rapid decarbonisation, but the knowledge that this trajectory is possible will greatly strengthen future claims of responsibility for causing climate change.
With this in mind, any future, not prevented impacts of climate change, including forced movement of people due to sea level rise, economic losses from extreme weather attributed to climate change, loss of life, and non-economic losses should be subject to ‘loss and damage’ claims. Those failing to play their part in preventing further climate change now, and pushing warming beyond global targets are responsible for its impacts. The fact they now know they can do something about it will simply add to their responsibility, should they fail to act now. And if they don’t, they should be liable to compensate those affected by conscious decisions to contribute to the devastation resulting from climate change – stories of which can be heard from delegates throughout COP23.
Despite the apparent logic of this, much of the developed world (perhaps unsurprisingly, given their large historical emissions and responsibility for climate change) remain unmovably opposed to developing mechanisms through the UN climate process to facilitate loss and damage claims. The latest attempts to block this process has been led at COP23 by the US, EU, Canada and Australia, whose contention that financing should be excluded from negotiations on loss and damage is apparently grounded in the fact that not every natural disaster can be attributed to climate change. The absurdity of this argument is underlined by recent and rapid advances in the science of attributing (probabilistically) extreme weather events to climate change. Since we can now model to what extent climate change influenced a particular event, we can determine with ever growing certainty how responsible for climate-related losses are those who contributed most to climate change.
If we can formalise a regime for loss and damage, and render the biggest emitters liable for the impacts of their actions, this would be a small but significant step towards addressing the vast injustices of climate change. For the developed world to continue to ignore their moral duty on this matter is simply unacceptable.
This article follows Oxford Climate Society’s side event at this year’s UN Climate Conference, on 12 November 2017, and is in part inspired by the talks given by the speakers, Professor Myles Allen and Kya Raina Lal.
Rupert Stuart-Smith, Oxford Climate Society President 2017/18
Since the fairly disastrous 2009 UN climate conference in Copenhagen (COP15), the slogan of many of the countries most vulnerable to the impacts of climate change has been “1.5 to stay alive”. Six years later, the Paris Agreement (and all its signatories) implicitly acknowledged the inadequacy of the 2°C goal agreed in 2009, and recognised that limiting climate change to 1.5°C above pre-industrial levels ‘would significantly reduce the risks and impacts of climate change’. Yet with the global policymaking focus of the past few years firmly centred on limiting climate change to 2°C, relatively few efforts have been made to understand the future emissions permissible if we are to stay within 1.5°C.
In fact, the answer to the question of our ‘carbon budget’ for 1.5°C is perhaps more dependent on what story you want to tell than the predictive abilities of climate modellers. Depending on what baseline of ‘pre-industrial’ temperatures is used, it is possible to come up with very different (but equally scientifically accurate) estimates of the extent of past manmade climate change.
Millar et al. (2017) use a baseline of average global temperatures from 1861-1880 (equivalent to that used by the Intergovernmental Panel on Climate Change), and calculate that global temperatures have risen 0.93°C from the baseline to the present decade (when the influence of short-term variability from El Niño is excluded). Based on their projections, only a further 200 Gigatonnes of carbon can be added to the atmosphere between now and 2055, and by that point we must have reduced our net carbon emissions (the balance of release into the atmosphere and removal from it) to zero, if we are to have a reasonable chance of limiting climate change to 1.5°C. To put this into context, current annual net CO2 emissions are approximately 10.4 GtC, leaving less than 20 years of emissions at current rates to exceed the 1.5°C carbon budget identified by this paper.
Figure 1: Idealised mitigation trajectory for limiting climate change to 1.5°C. Dashed line shows a peaking of global emissions in 2020, followed by linear decline to net zero in 2055. Thin solid orange line is the climate response to the emissions scenario in 66% of CMIP5 models, showing a warming of under 1.5°C. Thick solid line shows the 50th percentile of the climate response to this scenario. Source: https://www.carbonbrief.org/guest-post-why-the-one-point-five-warming-limit-is-not-yet-a-geophysical-impossibility.
Based on Millar et al., to stay within the 1.5°C budget, unwavering commitment to rapid global decarbonisation is required, and emission reductions of 4-6% per year will be needed in the 2030s and 2040s. This rate of CO2 emission reductions is historically unprecedented and requires worldwide replacement of existing capital. This will include a revolution in our energy systems through the development and massive deployment of renewables, and an as-yet undemonstrated scale of Carbon Capture and Storage (CCS) and CO2 Removal (CDR), for instance through Bioenergy with CCS (BECCS). The rate at which this transition can happen is limited due to the lifespans of existing infrastructure and the inertia of our economic system, and Millar et al. advocate for immediate and ambitious emission reductions to have any chance of keeping up with the precipitous fall in emissions demanded by their 1.5°C scenarios.
At the same time, the key message of Millar et al. is that the 1.5°C temperature goal is not impossibly ambitious, even though current national pledges require dramatic strengthening. With current national commitments falling far short of global ambition on climate change mitigation, technologically and economically feasible scenarios such as those this paper propose can provide a strong framing for the global stocktake process to increase national level climate commitments.
Alternative estimates of the future emissions compatible with limiting climate change to 1.5°C, using different measures of global temperature and baseline periods (such as 1750, since when global temperatures have risen more than they have since the mid-nineteenth century), indicate far smaller emission budgets. Under some estimates, cumulative emissions committing us to 1.5°C will be reached as soon as 2021.
The question is: is the bigger the panic the better? Does presenting climate change mitigation in line with the 1.5°C goal as being an unsurmountable challenge propel individuals, companies and world leaders into action? Or rather, in line with Miller et al., are we more likely to be able to inspire the behavioural, economic and policy revolutions required if science explains that we have a chance to avoid the vast human suffering brought about by inadequate climate change mitigation and warming of over 1.5°C, but only if we act now?
Join Professor Myles Allen, a co-author of the Millar et al. paper, the Oxford Climate Society, Oxford Martin School and Environmental Change Institute in a discussion on the findings of the paper and these questions on Sunday at COP23, in an event chaired by Kya Raina Lal.
Full details: https://www.oxfordmartin.ox.ac.uk/event/2514
OCS Media Team
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