Why no stabilization of CO2 levels in the atmosphere when emissions have fallen?

Imagine my surprise when I coincidently came across a blog post in which this surprising question was answered: Why has a drop in global CO2 emissions not caused CO2 levels in the atmosphere to stabilize? Some of their readers apparently asked why there has been no stabilization in the measured levels of carbon dioxide in the atmosphere when reported emissions of CO2 have fallen. In the post explained that it was very simple: the sinks for CO2 currently offset only about 50 percent of the emissions and additionally these sinks will slowly lose their efficiency as they start to saturate.

That is remarkable answer to a remarkable question. I wasn’t aware that global emissions dropped. The article was only written yesterday, so I was curious what new information they found. I didn’t find any new information after all, but the post linked to a IEA article which was referred to as “recent stabilization in global emissions”.

So is it a drop or a stabilization? Confusing was also the emissions graphs that were present in two places in the post. Yet at a closer look it didn’t exactly serve their case. It mentioned that there was a 2.2% increase of emissions between 1990 and 2014 and a 0.6% increase between 2013 and 2014 (which was the last year in their figure).

global emissions 1990 2014 Global Carbon Project

So what is it? A drop, a stabilization or a (modest) increase? Time to have a look at the data. Going to the source they linked to, I realized rather quickly that there is a much, much, much simpler answer than the mumbo jumbo answer about the sinks.

The link went to an IEA article dated March 16. It is titled: Decoupling of global emissions and economic growth confirmed.

The article was not about “global emissions”, but about “global energy-related emissions”. Although this may be a big chunk of global anthropogenic emissions, how much does the CO2 level in the atmosphere depend on energy-related emissions? There are also non energy-related anthropogenic emissions and even natural emissions that can possibly influence atmospheric levels.

The article explained that global energy-related emission stayed flat in the last two years, while the global economy grew 3%, therefor coming to the conclusion that emissions decoupled from economic growth for the last two years.

Global energy-related emissons 1975 2015 IEA

Apparently, IEA attributed this to improvements to the energy efficiency (which I can dig) and the growth of renewables (which I doubt have much effect). More down in the article they attributed it more specifically to the efforts of two major emitters: China (less coal use, plus share of hydro and wind) and USA (switch from coal to natural gas), but offsetted by most other Asian economy and increasing emissions in Europe (hey, don’t they also have an increasing share of renewables?). The share of wind power in China is I think much overrated: it is about 3% of the electricity production and about 1% of primary energy production, so whatever the addition of wind power capacity was in 2014 and 2015, its impact would be marginal at best.

The end of the graph seemed indeed rather flat, but there was also a possibility to download the source data which seemed to be rather interesting. These are the emission values of last years:

Year Emissions
(gigaton)
2011 31.29
2012 31.49
2013 32.07
2014 32.13
2015 32.14

32.14 gigaton in 2015 is more than 32.13 in 2014 and that is more than 32.07 in 2013. That is a (small) increase in my world, one could call it a stall compared to previous years, but certainly not a “drop”. Not sure where that question from “readers” came from. It was not to be found in previous posts.

Finally, the question has a much simpler answer: the “drop” in “global emissions” has no influence on the CO2 level in the atmosphere for the simple reason that there was no drop in global emissions in the first place. If putting as much, or even a bit more, CO2 in the atmosphere than previous year(s) and assuming one thinks that anthropogenic emissions are driving the atmospheric level of CO2, then why would one expect the level in the atmosphere to stabilize?

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4 thoughts on “Why no stabilization of CO2 levels in the atmosphere when emissions have fallen?

  1. poitsplace

    If you look at the things the sinks involve…you’ll notice they can’t saturate for any reasonable projection of CO2 levels. Plants will continue to grow faster even if we pushed the CO2 levels to 2000ppm. Essentially all of the oceans are at rough equilibrium with CO2 levels far lower than today’s and so they cannot become saturated for centuries, if not millennium. Out-gassing can’t be a problem if CO2 proxies are to be believed because the last interglacial was warmer yet had CO2 levels lower than today…so even if we reached those levels, the oceans would still be sucking down CO2 like crazy.

    If anything, sinks will become MORE efficient over the rest of the century, assuming CO2 levels rise.

    Reply
    1. trustyetverify Post author

      Didn’t look at the sink issue, but in this case I think it is not necessary. There is a much simpler explanation for why the CO2 level in the atmosphere didn’t stabilize, especially when they would start from the assumption that our emissions drive CO2 level in the atmosphere.

      Reply
  2. manicbeancounter

    Perhaps the reason for the failure to show a link in the short term is that human emissions only add to the much larger natural CO2 emissions and absorptions of CO2. Looking at the longer term data the quantity of CO2 emissions from fossil fuels to increase CO2 levels has been roughly consistent at about 15 billion tonnes. I would have expected it to be increasing. In 2015 CO2 levels increased by 3.05ppm – the highest increase since the start of the series in 1959 and probably for many thousands of years. The previous record increase was in 1998. Like 2015, it was also the year of a strong El Nino with record average temperatures. The erratic changes in CO2 increases at from 1987 to 1993 are also consistent with sharp swings in average temperature, but it is unclear which is the leading factor. It is an interesting comparison to make and there are no clear, simple, answers.

    Reply
    1. trustyetverify Post author

      That is certainly a possibility. They only focused on energy-related emissions, probably in the assumption that this is what drives the CO2 level in the atmosphere. They didn’t mention anything about the trend or the quantity of other sources.

      The graph showing the relation between energy-related emissions per 1 ppm increase CO2 level is very interesting. Thanks.

      Reply

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