How fast and how profoundly we act to stop climate change caused by human actions, and work to return to a safe climate, is perhaps the greatest challenge our species has ever faced, but are we facing up to what really needs to be done?
We have to come to terms with two key facts: practically speaking, there is no longer a "carbon budget" for burning fossil fuels while still achieving a two-degree Celsius (2 °C) future; and the 2 °C cap is now known to be dangerously too high.
No Carbon Budget Left - David Spratt from Breakthrough on Vimeo.
For the last two decades, climate policy-making has focused on 2 °C of global warming impacts as being manageable, and a target achievable by binding international treaties and incremental, non-disruptive, adjustments to economic incentives and regulations (1).
But former UK government advisor Professor Sir Robert Watson says the idea of a 2 °C target "is largely out of the window,” International Energy Agency chief economist Fatih Birol calls it "a nice Utopia," and international negotiations chief Christiana Figueres says we need "a miracle." This is because, in their opinions, emissions will not be reduced sufficiently to keep to the necessary "carbon budget" (2).
The carbon budget has come to public prominence in recent years, including in the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report in 2013, as being the difference between the total allowable greenhouse gas emissions for 2 °C of warming, and the amount already emitted or spent. The budget varies according to the likelihood of overshooting the target: the higher the risk, the bigger the budget. In the IPCC report, no carbon budget is given for less than a one-in-three chance of failure.
At that one-in-three risk of failure, the IPCC says the total budget is 790 GtC (gigatons, or one billion tons, of carbon), less emissions to 2011 of 515 GtC, leaving a budget of 275 GtC in 2011, or ~245 GtC in 2014 (3).
What is less well understood is that if the risk is low, there is no carbon budget left (4).
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Ian Dunlop, a former senior risk manager and oil and coal industry executive, says the management of catastrophic risk has to be very different from current processes. As serious, irreversible outcomes are likely, this demands very low probabilities of failure: management of catastrophic risk "must centre around contingency planning for high-impact and what were regarded as low-probability events, which unfortunately are now becoming more probable… Major, high-risk industrial operations, such as offshore oil exploration, provide a model, with detailed contingency planning and sequential barriers being put in place to prevent worst-case outcomes" (5).
If a risk-averse (pro-safety) approach is applied – say, of less than 10% probability of exceeding the 2 °C target – to carbon budgeting, there is simply no budget available, because it has already been used up. A study from The Centre for Australian Weather and Climate Research shows that "the combination of a 2 °C warming target with high probability of success is now unreachable" using the current suite of policy measures, because the budget has expired (6).
This is illustrated in Figure 1 where, as we move to the right (greater probability of meeting target) along the blue line which is the 2 °C carbon budget, we reach a point around 90% probability (blue circle) where the total budget intersects with what we have already emitted.
|Figure 1: Effect or risk on carbon budget, based on based on Raupach, M. R., I.N. Harman and J.G. Canadell (2011), explanatory labels added|
In addition, the carbon budget analysis makes optimistic and risky assumptions about the stability of Arctic, and of polar and other carbon stores such as permafrost. As one example, the modelling discussed in the IPCC report projects an area of summer Arctic sea-ice cover in the year 2100 higher that actually exists at the moment, yet there is a great deal more warming and sea-ice loss to come this century! In fact, many Arctic specialists think the Arctic will be sea-ice free in summer within the next decade, with consequences for global warming that the carbon budget calculations have significantly underestimated (8).
Accounting for the possible release of methane from melting permafrost and ocean sediment implies a substantially lower budget (9). This reinforces the need to take a pro-safety, risk-averse approach to the carbon budget, especially since some research suggests that Arctic permafrost may be vulnerable at less than 2 °C or warming (10).
For all these reasons – that is, prudent catastrophic risk management, accounting for food production and deforestation emissions, and for Arctic sea ice and carbon store instability – the idea of "burnable carbon" – that is, how much more coal, gas and oil we can burn and still keep under 2 °C – is a dangerous illusion, based on unrealistic, high-risk assumptions.
A second consideration is that 2 °C of warming is not a safe target. Instead, it's the boundary between dangerous and very dangerous (11), and 1 °C higher than experienced during the whole period of human civilisation (12), illustrated in Figure 2. The last time greenhouse gas levels were as high as they are today, modern humans did not exist (13), so we are conducting an experiment for which we have no direct observable evidence from our own history, and for which we do not know the full result.
Figure 2: Past and future global temperature and the safe-climate zone
It is now clear that the incremental-adjustment 2 °C strategy has run out of time, if for no other reason than the "budget" for burning more fossil fuels is now zero, yet the global economy is still deeply committed to their continuing widespread use.
We all wish the incremental-adjustment 2 °C strategy had worked, but it hasn't. It has now expired as a practical plan.
We now have a choice to make: accept much higher levels of warming of 3–5 °C that will destroy most species, most people and most of the world's ecosystems; a set of impacts some more forthright scientists say are incompatible with the maintenance of human civilisation.
Or we can conceive of a safe-climate emergency-action approach which would aim to reduce global warming back to the range of conditions experienced during the last 10,000 years, the period of human civilisation and fixed settlement. This would involve fast and large emissions reduction through radical energy demand reductions, whilst a vast scaling-up of clean energy production was organised, together with the remaking of many of our essential systems such as transport and food production, with the target being zero net emissions. In addition, there would need to be a major commitment to atmospheric carbon dioxide drawdown measures. This would need to be done at a speed and scale more akin to the "war economy," where social and economic priority is given to what is perceived to be an overwhelming existential threat.
After 30 years of climate policy and action failure, we are in deep trouble and now have to throw everything we can muster at the climate challenge. This will be demanding and disruptive, because there are no longer any non-radical, incremental paths available.
Prof. Kevin Anderson and Dr Alice Bows, writing in the journal Nature, say that "any contextual interpretation of the science demonstrates that the threshold of 2 °C is no longer viable, at least within orthodox political and economic constraints" and that "catastrophic and ongoing failure of market economics and the laissez-faire rhetoric accompanying it (unfettered choice, deregulation and so on) could provide an opportunity to think differently about climate change" (17).
Anderson says there is no longer a non-radical option, and for developed economies to play an equitable role in holding warming to 2 °C (with 66% probability), emissions compared to 1990 levels would require at least a 40% reduction by 2018, 70% reduction by 2024, and 90% by 2030. This would require "in effect a Marshall plan for energy supply." As well low-carbon supply technologies cannot deliver the necessary rate of emission reductions and they need to be complemented with rapid, deep and early reductions in energy consumption, what he calls a radical emission reduction strategy (18). All this suggests that even holding warming to a too-high 2 °C limit now requires an emergency approach.
Emergency action has proven fair and necessary for great social and economic challenges we have faced before. Call it the great disruption, the war economy, emergency mode, or what you like; the story is still the same, and it is now the only remaining viable path.