We’re going to hear a lot more in coming months about INDCs, Intended Nationally Determined Contributions, says CDKN's Executive Chairman Simon Maxwell. INDCs are the country pledges that will form the basis of negotiation in the run-up to the UNFCCC's twenty-first Conference of the Parties (COP21) in Paris in 2015.

The scene has been set for INDCs by the publication of the various parts of the IPCC Fifth Assessment Report, including the Synthesis Report, which came out at the beginning of November, and also by UNEP’s Emissions Gap Report, also published in November.

The key thing to know from the Emissions Gap Report is that there is a finite budget for greenhouse gases if we want a likely chance of keeping warming to 2oC – and that we are well on the way to exhausting it. It is important to distinguish between long-lived CO2 and shorter-lived other gases, like methane. In round numbers, the remaining budget for CO2 is about 1000 Gigatonnes (Gt). Emissions are of the order of 35-40 Gt a year, and rising. That gives us 25 years at current rates. The Emissions Gap Report uses integrated assessment models to estimate least-cost pathways for the future, and those suggest that the world has to reach zero CO2 emissions by about 2065. That’s not ‘close to zero’ or ‘on the way to zero’. That is zero CO2, full stop.

After that, the only option is to remove CO2 permanently from the atmosphere, by such means as planting trees to increase biomass, or carbon capture and storage.

For non- CO2, the picture is similar, but the timescale is slightly more generous because the gases remain in the atmosphere for a shorter period. Even so, the zero emission point arrives before 2100.

Now, it would theoretically be possible to leave everything until the last minute, spend the budget, and then stop. However, that is not realistic – or desirable. As the Emissions Gap Report points out, delay will bring much higher costs and risks later on.

Instead, the Emissions Gap Report estimates optimal pathways to zero, again using integrated assessment models. I know that IAMs are dependent on many assumptions, and that they are controversial, but the general principle of staged decline is plausible. Here, the Report looks at all greenhouse gases, in gigatonnes of CO2 equivalent. Current emissions are about 54Gt and rising. The required figures are: for 2025, 47Gt; for 2030, 42 Gt; and for 2050, 22 Gt. Even then, some CO2 removal may be necessary.

These are big reductions, and current pledges by countries fall way short. The Emissions Gap Report estimates the gap between the numbers above and likely actual emissions based on current pledges. The results are sobering. To take 2030 as an example, the best estimate is that total greenhouse gas emissions based on current pledges will be up to 59 Gt. The maximum emission level for that year is 42GT. So, the gap is up to 17 Gt. That means further reductions of over a quarter are needed.

It is also worth noting that pledges need to be met for these numbers to hold. The Emissions Gap Report concludes that some countries or groups of countries are on track to meet their pledges, and others are not. And it also points out that some countries meeting their pledges are doing so because the pledge itself was unambitious. Anyway, Brazil, China, the EU 28, India and Russia are on the positive side of the ledger, while Australia, Canada, Mexico and the United States are not: they ‘are likely to require further action and/or offsets in order to meet their pledges’.

The size of the gap puts the current debate in context. There has been a broad welcome, for example, for the EU’s recent Framework for Climate and Energy, and for the joint US-China announcement on emission reductions. These are undoubtedly important in political terms, and will help impart momentum to the negotiations in 2015. On the whole, however, these do not change the existing picture significantly. The EU commitment will contribute less than 0.5 Gt to the global reduction required.  The China commitment that emissions will peak in 2030 does not yet mark a major reduction. The US reduction represents a small acceleration in reduction over the existing target. There is a useful analysis of the US-China agreement by Taryn Fransen and colleagues at WRI. Google the agreement, and you will find a clear consensus that much more needs to be done.

This brings us to the INDCs, the country pledges expected in the first half of 2015. The core issue is mitigation, and the core policy question is this: how will a maximum emission quantity of 42Gt in 2030 and 22Gt in 2050 be divvied up among the parties expected to sign a new climate agreement in Paris in 2015? That is a philosophical question, of course, and a highly political one.

First, the contributions of most countries will be symbolic but largely marginal to the question of whether global targets are reached. That is because current and likely future emissions are highly concentrated. The World Resources Institute has an excellent compendium of emissions data, known as CAIT. This shows that in 2011, 15 countries or country groups (counting the EU 28 as one) accounted for 75% of all greenhouse gas emissions, including from forestry and land use. The other 160 odd countries in the database accounted for less than 25% between them. China was the largest emitter, accounting for 22% of the total, the US was second (13%), the EU third (9%), India fourth (5%).

Second, aggregate emissions data say nothing about per capita contributions, which remain much higher in developed countries than developing ones. The Emissions Gap Report  shows total greenhouse gas emissions from OECD countries in North America still to be above 20 megatonnes (MT) of CO2 e/capita, whereas those for most regions of the world cluster around 5 MT CO2 e/capita.

Third, neither aggregate nor per capita emissions provide an automatic template for future allocations. The issue of historic responsibility and common but differentiated responsibilities will certainly play a part in the 2015 negotiations. See, for example, a recent report on the global carbon budget by Global Carbon Project, examining different ways of calculating shares. The report concludes that some compromise will have to be found between future allocations based on the share of current emissions and allocations based on pure equity: they call this the ‘blended’ outcome.

The fact remains that the gap between where we are headed and where we need to be is large. There should be no ambiguity when INDCs come to be added up. Only one set of numbers matters: not intensity of carbon use, not per capita emissions, not rates of decline, but one simple estimate of future national CO2 and other greenhouse gas emissions.

Image: air pollution, courtesy World Bank photo collection.