Acceleration Stopped. CO₂ Didn’t.
Our future has not been averted
This last week, the International Energy Agency, IEA, announced that “Defying expectations, CO2 emissions flatlined in 2019.” Global coal emissions are down, total emissions in developed countries are down, emissions in less developed nations grew a little less than expected, and CO₂ emissions in 2019 were the same as in 2018, not larger. We seem, for one year at least, to have contained the ongoing acceleration of how much CO₂ we keep dumping into the air.
Many of the usual suspects immediately jumped in. Anthony Watts wrote “Bad news for climate alarmists.” Twitter erupted with people proclaiming the end of the CO₂ scam. A message emerged from climate denier chatter, that this means that somehow we no longer need to fear a high CO₂ future.
There is undeniable good news here. Our efforts at shifting dependence from the dirtiest fossil fuels are starting to show some results, at least in the developed nations. The worst scenarios for our future seem to be pretty definitively avoided. But the deniers are wrong. Bad future scenarios for CO₂ are still very much on the table. We are far from containing the problem.
Predicting future CO₂ and warming
Predicting how much the planet will warm in the future is a problem with two parts. One is pure science — if we add a certain amount of CO₂ and other greenhouse gasses, how much will the planet warm, how fast, and in what ways will the climate change because of it. The climate models are our best tools for working to answer those questions.
The other part of the problem is political and economic, a question of human behavior. How much of various greenhouse gasses are we going to emit in the future? There is no scientific calculation of future human decisions.
To avoid the inherently unscientific practice of trying to guess at future human behavior, climate scientists for the last several years have been working with standardized future emissions pathways, the so-called Representative Concentration Pathways. These were developed for the IPCC 5th Assessment report in 2014, to contain a broad range of possible future greenhouse emissions. Essentially, these are “what if” pathways for how much we’re going to emit in the future, so that we can use the models to see what happens for each.
The worst of those pathways, RCP8.5, was commonly called the “business as usual” pathway. When it was developed starting in 2011, it assumed that all of the things driving the year to year increase in CO₂ emissions would continue unchanged. It has become clear over the last couple of years that this worst-case ‘business as usual” scenario was not happening, that we have controlled some of the growth in CO₂. This has happened primarily because of a large scale shift in the energy economy from coal to natural gas. Last week’s announcement drives a definitive nail in the coffin of this worst-case “business as usual” scenario.
The best-case of the pathways, RCP2.6, assumed that the world would aggressively confront the problem and that greenhouse gas emissions would start dramatically decreasing by 2020. That also has definitively not happened.
With the worst and the best of the 4 future pathway scenarios now ruled out, we’re left with something approximately like the two middle scenarios. Depending on where we fall in those future emissions scenarios, we’re looking at a current best-estimate of another 1⁰- 3⁰C warming by the end of the century. Newer estimates of the rate of warming in those scenarios are making it possible that warming will be higher than that. It’ll be interesting to see what the IPCC consensus estimates will be, based on the accumulated science over the last 5 years, when the IPCC 6th Assessment Report comes out late this year.
The bad news is, emissions continue as fast as ever. We didn’t emit more CO₂ in 2019, but we emitted just as much. CO₂ keeps inexorably increasing nearly 2.5 PPM every year, year after year, with no hint that it’s going to do anything except keep going up.
One year of flatline means another year of growth
The year I was born, in 1957, CO₂ was at about 315 PPM. Last year, 62 years later, we had increased that by100 PPM. At the current rate of increase, by the end of this coming decade in 2030, we’ll be somewhere between 435 and 440 PPM. A one year flatline in growth has done nothing to reduce the ongoing rate of accumulation.
On February 10 at the Mauna Loa CO₂ Instrument, we briefly reached 416 PPM of CO₂ in the atmosphere for the first time.
The news announced this week by the IEA says that at least this year wasn’t worse than last year. It was only just as bad, and that’s still bad. Don’t let the distracting chatter from those trying to pretend there’s no problem hide that inexorable fact.
IEA press release can be found here: https://www.iea.org/news/defying-expectations-of-a-rise-global-carbon-dioxide-emissions-flatlined-in-2019
Wikipedia has a very good article on the RCPs, here: https://en.wikipedia.org/wiki/Representative_Concentration_Pathway
Climate Scientist Zeke Hausfather’s article on the demise of RCP 8.5 here: https://co2coalition.org/2020/01/30/emissions-the-business-as-usual-story-is-misleading/
