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Climate action or carbon debt?

posted Mar 22, 2018, 9:38 AM by Paul Price   [ updated Mar 22, 2018, 9:42 AM ]

How quickly are different regions and nations committing to responsibility for substantial negative emissions? Or, to tacit mitigation failure?

The Paris Agreement commits the signatory Parties (essentially all sovereign nations of the world) to aligning their actions with,

“[h]olding the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change”    Article 2, Paris Agreement

Thanks to the strong climate science showing a direct, linear relation between cumulative total human-caused emissions of carbon dioxide (CO2) and resultant long-term global warming, a global carbon budget (GCB) range can be estimated for any given probability of limiting to any given threshold of warming. Using a 66% probability of avoiding 2ºC, the IPCC give a post-2011 GCB range of 750 to 1400 GtCO2 (where Gt means gigatonnes or billions of tonnes). Adjusting this for emissions up to the end of 2015, Rogelj et al. (2016) suggest a remaining post-2015 (i.e., post-Paris Agreement) budget of 590 to 1240 GtCO2, with a mid-point of 915 GtCO2. Of course, a “lay”/common-sense interpretation of “well below 2ºC” (surely at least better than 66% probability of staying below, say, 1.75ºC?) or any “efforts” at all to respect the lower limit of 1.5ºC (surely at least 50% probability?) would yield significantly smaller ranges for the GCB.

A somewhat simplistic, but still informative starting point to compare the current emissions of regions and nations is on the basis of per capita CO2 emissions relative to per capita CO2 quotas, where quota means some allocated share of the remaining global carbon budget.  Simply, dividing the Rogelj et al. range by the 2015 global population of 7.4 billion people, gives a globally averaged range of remaining post-2015 per capita quota of 80 to 169 tCO2, with a mid-point of 124 tCO2.  

Although this is an ‘equal per capita’ GCB division, derived from regional or national population share in 2015, it’s important to be very clear that this sharing formula is not “on the basis of equity” (Article 4, Paris Agreement) because it ignores very significant differences in: historic responsibility (based on past emissions), technical and economic capacity to undertake mitigation measures, vulnerability to climate impacts, and the wider objectives of the sustainable development goals (SDGs). Taking such equity considerations adequately into account would greatly diminish the quotas assigned to the wealthy, developed nations (indeed, would arguably put at least some of these nations already in a situation of quota deficit or global “CO2 debt”). Nonetheless, this equal per capita cumulative emissions (EPCCE) basis might provide us with at least an initial “rough and ready” baseline to compare the “good faith” commitments with the actual efforts of regions and nations to deliver on the temperature goals of the Paris Agreement.

For this blogpost analysis, let’s look at how quickly the EPCCE quotas would be exhausted (from 2015), assuming that every region or nation simply ‘flatlined’ their existing CO2 emission rate at 2016 levels. Globally, for territorial fossil fuel and cement emissions, this ranges from very high emitters such as the USA with 16.5 tCO2 per capita per year and high emitters such as Ireland with 8.5 tCO2 per capita per year, to very low emitters such as Bangladesh with only 0.5 tCO2 per capita per year. Let’s assume that current global land use emissions, about 5 GtCO2 per year (nett, allowing for land use carbon sinks) are also allocated per capita, adding about 0.7 tCO2 per capita per year to each nation’s per capita CO2 emissions. (This is, of course,  another very simplistic assumption – that, for example, more than doubles the emissions assigned to Bangladesh but only adds 4% to the USA per capita figure.)

For the midpoint global carbon budget of Rogelj et al., the chart below therefore shows the resulting (straight line) annual depletion of EPCCE for selected regions and nations: starting all with an equal EPCCE and, thereafter, for each region or nation, just subtracting the 2016 value of estimated total CO2 emissions for each subsequent year, giving the remaining per capita quota for each yer..

For reference, the curved, dashed black “global decarbonisation” line shows how global EPCCE would decline under a constant year-on-year fractional emission reduction rate (exponential emission rate decline), chosen in such as way as to extend the remaining global carbon budget for the maximum time i.e., the “softest possible landing trajectory” for global decarbonisation (albeit, already very difficult to achieve at this point…). As of 2015, from current global emissions of about 41 GtCO2, this would require annual emission rate reductions of 4.5% per year. The pink area below zero indicates carbon debt and dotted lines for the nations or regions indicates negative quotas, where the available EPCCE would have been exhausted, implying those nations would, from that point on, be accumulating a growing responsibility for implementing (or paying someone else to implement) so-called “negative emissions” or “carbon dioxide removal”. For Ireland, this would become the case before 2030 in this analysis.

Even using assumptions heavily biased in favour of developed nations/members of the OECD and/or EU28  (i.e., the weakest conceivable interpretation of the Paris temperature goals, and of the Paris commitments to reflect “common but differentiated responsibilities and respective capabilities, in the light of different national circumstances”), this chart graphically shows how developed nations, or even a rapidly developing nation like China, are all very quickly exhausting their Paris Agreement ‘CO2 credit’. Without urgent action they are heading toward deep (likely irrecoverable) CO2 debt relative to the Paris target. Aligning their actions with “well below 2ºC” without such tacit reliance on speculative future “negative emissions” requires radical mitigation measures to reduce from currently high, whole economy CO2 emissions (at an annual reduction rate, sustained indefinitely, of at least the global requirement of 4.5%/yr). In addition, if serious about Paris-level ambition, then precautionary commitment to careful (limited) anthropogenic enhancement of  CO2 removals from the atmosphere will very likely be necessary.

Meanwhile, low emitting, less developed nations like Bangladesh, are only using up their carbon quotas very slowly – despite often being the most exposed to the climate change impacts resulting from the fossil fueled development and consumption elsewhere.

Unfortunately, to date, emission projections and Paris mitigation pledges (Nationally Determined Contributions) are in fact mostly in the range of merely ‘flatlining’ near-term emissions rates, so the chart is a very concerning reflection of the current situation in global (developed world) climate policy.

Indeed, for Ireland, the EPA’s projections to 2035 indicate that annual CO2 emission rates will actually continue, not merely to “flatline” but to increase even “with additional measures” – in other words an even worse outlook for very early, rapid, and deep entry into carbon debt than the chart shows. We might call this “carbon bankruptcy”, except, of course, that the climate system is not a bank, and has no mechanism to offer “debt restructuring”. Rather, there will be only harsh, perhaps unbearable, consequences, though these will likely impact “innocent bystanders” in poorer and more vulnerable nations first. As the chart makes very clear, ‘flatlining’ (or, much worse, increasing) CO2 emissions is not an option for any nation if the aim is to restrict warming in any way equitably. Nations with high emissions will need to cut much faster and deeper to leave any ‘CO2  emission space’ for countries with lesser responsibility and capacity.

Rich nations are committing to achieving large "negative emissions", or are they "choosing failure"?

Looking at this chart we can ask: Is a tacit commitment being made by those going into carbon debt to achieving large negative emissions (removals of CO2 from the atmosphere)?  Or, are they simply “choosing to fail” – to quietly renege, in practice, on the requirements of the Paris Agreement?  In the absence of sufficient mitigation, It might easily be assumed to be the latter, unless sufficient investment to support real achievement of balancing negative emissions. This would sadly vindicate the blunt assessment of eminent climate scientist James Hansen, that the Paris Agreement is a mere “precatory” instrument – wishful thinking, dressed up in diplomatic and legal language.

Flatlining Ireland’s current emissions and aligning climate action with Paris would imply a commitment to total emissions of about 1540 MtCO2 just up to 2050 – and much more beyond. As Ireland’s post-2015, remaining national quota is only about 600 MtCO2 (on the generous 2015 EPCCE basis), flatlining implies achieving carbon dioxide removal of close to 940 MtCO2 by 2050. This is an enormous and likely unfeasible quantity to store, the equivalent of over 20 years of current emissions. It would necessitate the urgent development now, and use within a decade, of carbon capture from bioenergy (BECCS) and direct air capture (DACCS), then piping and injection to storage deep underground.  As a guide, the almost-exhausted Kinsale Gas Field is thought to have a capacity for “easy” (low-pressure) CO2 storage of only about 100 Mt.

Compared to the costs of CO2 storage and the risk that negative emission technology will not deliver at scale, aiming to deliver actual whole-economy, gross emission reductions now and in the near-term, at rates hitherto thought ‘unfeasible’, combined with some commitment to modest achievement or enhancement of negative emissions may well prove more ‘cost effective’ (see previous post). Even if these measures are expensive or reduce aggregate economic activities they will likely be the cheapest course, if indeed we are serious about aligning climate mitigation efforts with the Paris Agreement. The overwhelming consensus of mitigation literature makes clear that any and all delay in peaking and very rapidly decarbonising rapidly increases the costs (and human impacts) of meeting the temperature targets.

As agreed in Paris, for all developed nations, early and deep climate action is critical to mitigation success. Our chart above clearly illustrates this difficult reality and the urgency of coordinated action now required to observe the Paris temperature limits. Are choosing to fail? Or, are we collectively ready to discuss this reality frankly and honestly?


Rogelj, J., Schaeffer, M., Friedlingstein, P., Gillett, N.P., van Vuuren, D.P., Riahi, K., Allen, M., Knutti, R., (2016). Differences between carbon budget estimates unravelled. Nature Clim. Change 6, 245–252.