The International Energy Agency is right to highlight the fact that energy-related CO2 emissions have flatlined for the last two years. That has to be very good news. It means that the global energy revolution that is underway–and it is a revolution in the way we produce electrical power and in the way we use energy–is having a tangible and verifiable impact on global emissions of CO2. The media has been noisily proclaiming that CO2 emissions are no longer hogtied to economic growth. And like a freight train that has managed to uncouple an obnoxious freight car, economic growth can now proceed unhindered by increases in CO2 emissions that always seemed in the past to be firmly attached to its coattails.
Yet this is only half the story: the graphic below from NOAA shows measurements of atmospheric CO2 at the observatory in Hawaii right up to February this year. Any increase in CO2 concentrations shown here comes from all the sources of CO2 everywhere on the planet–not just from primary energy production.
It doesn’t look anything has flatlined here. In fact, the latest figure released by NOAA show that the level of CO2 in the atmosphere increased by 3.05 ppm in 2015. That’s the largest annual increase in CO2 concentration ever recorded. Nothing on this graph suggests that the year on year increases in ppm levels 0f atmospheric CO2 are slowing down.
Atmospheric concentrations of CO2 respond quickly to changes in global emissions. The atmosphere is a well-stirred pot, and CO2 emissions are spread out over wide areas of the globe. So if CO2 concentrations are increasing in the atmosphere it means CO2 emissions from terrestrial sources are also increasing. Period. So what explains this divergence?
CO2 emissions come from several sources. The Global Climate Budget (GCB) programme has a database on its (easily accessible) website that provides a clue. Emissions of carbon are reported as coming from two sources: fossil fuel and cement production (added together), and from land use changes. Fossil fuel and cement emissions is the big one: in 2014 it was nine times larger that emssions from land use changes (36 GtCO2/yr for fossil fuel and cement, compared with 4 GtCO2/yr for land use changes). And it’s true that fossil fuel+cement emissions have been levelling off since about 2012 as renewable energy sources replace fossil fuels. But emissions from land use changes have not levelled off. They have been increasing for the last five years: almost certainly due to the clearing of forests for agriculture and intensive monocultures like palm oil plantations. When you add the two together, the flatline disappears–at least through 2014, the last year shown in the GCB database.
But there’s another angle. In 2015 emissions from land use change took a major hit. Forest fires. Lots of them. The worst fires were in Indonesia. So extensive they were visible from space, they spewed tons of CO2 into the atmosphere. The best estimate is that roughly a billion tonnes of CO2 was produced by the fires in the Indonesian forests. That would produce an increment in atmospheric CO2 of about 0.13 ppm.
But the forest fires in Indonesia were not the only ones burning in 2015. There were widespread forest fires in the US–most violently in California but also further north in Oregon and Washington State. Bushfires in Australia added more CO2 to the mix. A rough estimate is that about 1.5 Gt of CO2 was expelled into the atmosphere by all these fires. That translates to an increase of about 0.18 ppm CO2 in the atmosphere.
So this explains why CO2 atmospheric concentrations have continued to increase even though energy related emissions have levelled out. 2015 was the worst year for forest fires since the MODIS satellite started tracking these events in 2000.