A mental model for managing CO2 emissions
For regular readers, this may seem like a repeat of recent themes, but there is a point which will become clearer as the new Shell scenarios are released later this week.
Over recent years, the focus for managing rising CO2 emissions has been a combination of targets, energy mix mandates, efficiency drives and various attempts at carbon pricing. The climate lexicon is full of phrases such as;
- “We need to reduce global emissions by 50% by 2050 (relative to 1990 / 2000 / 2005 . . .)”
- “We will reduce the CO2 intensity of the economy by 30%.
- “By 2020, renewable energy will make up 20% of the energy supply”
- “We must first improve energy efficiency, that can have a significant impact on emissions”
- The “Green Economy”
- “We must stimulate clean energy investment”
- “We need more clean energy for development”
The question is, are these the right types of policies for solving the CO2 problem? There is no doubt that such approaches have gained traction and wide support from policy makers, but in many instances they are the result of a desire to solve a broad range of topical issues, ranging from energy security and energy access to jobs and economic growth. There is apparently then an underlying assumption that because each of these has a link with reducing emissions or low emissions that this must also be a solution to the real elephant in the room, the rising levels of CO2 in the atmosphere. This may not be the case.
All of the above approaches appear to rest on the assumption that responding to climate change depends on managing the rate of emissions from the global economy, sometimes on an absolute basis but often on a relative basis, e.g. relative to GDP. But this doesn’t correspond with how the atmosphere sees our emissions of CO2. Rather, the rising level of CO2 in the atmosphere is ultimately a stock problem, meaning that what really matters is the total cumulative amount of CO2 that is released over time from fossil sources and land use change. Additional CO2 is accumulating in the ocean / atmosphere system at a much faster rate than it is being removed. The difference is several orders of magnitude when compared with its return to geological storage through processes such as weathering and ocean sedimentation, which is why in the context of managing the problem we can treat it as a stock issue or liken it to the rising level of water in a bathtub (where even a dripping tap will eventually result in overflow). By contrast, many other emissions to atmosphere don’t accumulate, they disperse, break down or drop out very rapidly.
Over the last 250 years since the beginning of the industrial era, some 570 billion tonnes of fossil and land-fixed carbon (over 2 trillion tonnes of CO2) has been released, which in turn has led to a shift in the global heat balance and a likely 1°C of warming before the ocean / earth / atmosphere system reaches a new equilibrium state. An accumulation of a trillion tonnes of carbon equates to the 2°C temperature goal, but as a median within a broad distribution of outcomes, both higher and lower (Allen et. al., Warming caused by cumulative carbon emissions towards the trillionth tonne, Nature Vol 458, 30 April 2009). As long as the total fossil / fixed carbon released remains less than this amount over, say, a 500 year period, the climate problem is contained, at least to some extent.
Thinking about climate change as a stock problem then changes the nature of the solution and the approach. Although emissions in 2020 or 2050 may be useful markers of progress, they do not necessarily guarantee success as they are measures of flow, not stock. For example, meeting a 2050 global goal of reducing emissions by 50% relative to 1990 would be a remarkable achievement, but of only modest value if emissions then stayed at this level and the stock accumulated well beyond the trillion tonne level, albeit at a later date than might have otherwise been the case.
Current global proven reserves of hydrocarbons (BP Statistical Review of World Energy) will release some 0.9 trillion tonnes of carbon when used, irrespective of how efficiently we might use them, how many wind turbines are built in the interim or even how many green jobs are created in the process. In combination with cement production and continued land use change, this will then take the cumulative carbon towards two trillion tonnes, with the likelihood of a temperature increase of well over 2°C.
Not using these reserves and leaving them in the ground permanently (i.e. forever) so as not to contribute to the ocean / atmosphere stock will only happen if we develop alternative energy sources that out compete them, without subsidy or support, 24/7 365 days a year. Another way forward is to recognize that many economies around the world will choose to continue using the resources that they have, and therefore the focus should be on the development and deployment of carbon capture and storage (CCS), which returns the carbon back to the “geosphere” instead of allowing it to accumulate in the biosphere.
CCS has the potential to address CO2 emissions on a scale equal to its production and at a cost that appears more than manageable by society. Most importantly, it fits the “stock model” thinking, which means that this particular solution matches the nature of the problem itself, rather than being a derivative of it. But as I have noted in previous posts, CCS is struggling politically to gain the necessary funding and momentum. There are no large scale CCS power generation plants operating in the world today, but only a tiny handful of industrial emission CCS facilities, with most under construction. New thinking and impetus will need to emerge to ensure that CCS becomes central to climate policy development, rather than it having to compete with the long list of other objectives that seem to prevail.
The issue of accumulating CO2 in the atmosphere is a relatively simple one, which can’t be addressed by energy efficiency standards, renewable directives or similar such measures. They may impact on the short term consumption of fossil fuels in one region for a limited period of time, but they offer no guarantee of permanent reductions nor do they deliver a guarantee of a lower cumulative stock of CO2 over time – in other words, the fossil fuel that they displace locally simply gets shifted geographically and / or temporally (used later) such that the same accumulation of CO2 results. The CO2 issue is only addressed by two approaches – either leaving the fossil fuel in the ground forever or using the fossil fuel and returning the CO2 to the ground via CCS.