Charts du Jour, 13 March 2015: Two Cheers for Emissions Slowdown

The International Energy Agency (IEA) announced today that CO2 emissions in 2014 were flat year on year at 32.3 billion tonnes. This is undoubtedly good news–particularly if it marks the start of a trend.

The chart below is from an article from the FT here (free registration for access). Note, the three previous occasions when emissions flatlined or fell were all associated with recessions or economic crises (click for larger image).

Global GDP and Emissions jpeg

The IEA also points out that global GDP growth in 2014 was around 3%, so the better emission performance was the result of lower GDP-to-energy intensity and reduced energy-to-carbon emissions intensity (the so called Kaya Identify, which maps GDP to emissions, can be found in my post here).

In January, I wrote a couple of posts suggesting that China’s economic model would eventually hit a brick wall so capping emission growth (here) and that the Intergovernmental Panel on Climate Change (IPCC)‘s most emission heavy pathway (Representative Concentration Pathway 8.5) looks unrealistic (here). Note that RCP 8.5 would have us emitting 88 billion tonnes of CO2 by 2060, more than double what we are seeing now. The good news is that if we see further evidence of a flat-lining in emissions, then the second most pessimistic pathway (RCP 6) that the IPCC models would also look unlikely.

So why only two cheers. First, one swallow doesn’t make a summer. I would need to see an emissions plateau (or better still a dip) over more than one year. Data collection for many countries, including China, is difficult (or bloody awful). The precise-looking 32.3 billion tonnes of CO2 in reality will come with a large confidence interval, which we don’t get to see.

In a perfect world, we could cross check yearly emissions with actual atmospheric measurements, remembering that one part per million of CO2 is equivalent to 7.7 billion tonnes of CO2. So if we knew the carbon fraction (how much CO2 stays in the atmosphere and is not absorbed by ocean and land sinks), we could translate a yearly rise in CO2 concentrations into CO2 emissions. In reality, the carbon fraction moves around. In particular, the land (biosphere) sink is volatile as it is impacted by such events as forest fires and strong vegetation growth spurts when arid or semi-arid areas receive unseasonal rain (click for larger image).

Change in CO2 jpeg

Nonetheless, I quibble with these caveats; in truth, this is good news to start the weekend on.

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