climate change science

The two sides of climate change action

One of the more positive items of climate news this year was the finding that global CO2 emissions haven’t risen substantially for three years. We’ve hit a plateau. It would be great to see them falling, but halting their inexorable rise is a start. Here’s the International Energy Agency’s chart:

The sooner CO2 emissions peak, the better our chances of halting dangerous climate change. Leave it much later, and we’ll need much more radical negative emissions technologies to make up the shortfall. We’ll only know in hindsight, but if 2014/2015 marks a peak, it may turn out to be just in time.

Before we get too excited though, last week the World Meteorological Organisation released their annual bulletin. It shows that concentrations of carbon dioxide in the atmosphere have surged to a record high. They now stand at 403.3 parts per million. Emissions may be leveling off, but the CO2 content of the atmosphere is still streaking ever further away from the 350ppm that we need to aim for. Why the discrepancy?

As the WMO says, “emissions represent what goes into the atmosphere. Concentrations represent what remains in the atmosphere after the complex system of interactions between the atmosphere, biosphere, cryosphere and the oceans.”

The second graph shows an ongoing rise because even if emissions are leveling off somewhat, the final concentrations in the atmosphere depend on the earth’s capacity to absorb CO2. There were a number of significant droughts in 2016, and the reduced vegetation meant that less CO2 was soaked up. That was expected: last year was an El Niño year, and records show that CO2 concentrations tend to rise more steeply when El Niño is strong.

The contrast between these two measurements highlights the two sides of climate change action. The first side is cutting emissions – reducing the quantity of gases we put into the sky. That’s where renewable energy comes in, the transition away from fossil fuels in transport, better insulated homes, avoiding flying, and reducing the amount of meat we eat.

The other side of climate change action is protecting and enhancing the earth’s capacity to process CO2. The most important action is preventing deforestation, but really the challenge is to re-forest land wherever we can. Soil stewardship matters in this context too. Any time trees are cleared for agriculture, or land is paved over for development, we chip away at the earth’s CO2-processing capacity.

Reducing emissions is half the equation, and it looks like we might be able to see early signs of progress. If we can protect and expand the planet’s carbon sinks, we’ll see that CO2 concentrations graph peak too, and then we’ll really be getting somewhere.


  1. Great concise summary! I’m eager for the 2017 emissions numbers… if they begin to dip back down, the world might perhaps really begin to believe change is possible.

  2. A falling human population would help enormously. If everybody had one less child than they might otherwise have, the population would soon start to drop, them emissions AND deforestation etc would decrease.

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