How to tell if COP21 was a success

The leadership at COP21 has backed itself into a tricky corner pitting a declaration that “COP21 was a success” against the latest, best science. Leaders have a huge stake in declaring a successful outcome at this conference, but any declaration of success will likely need to suppress or disregard critical pieces of the climate puzzle. So in mid-December if/when the United Nations declares “SUCCESS! We have laid the foundations for keeping the planet below 2°C above pre-industrial levels!” don’t forget to dig into what their version of “success” means by asking these questions:

  • Success? With what probability? 66%?
  • Over what time horizon? What happens after 2100?
  • Assuming what climate feedback mechanisms? Only a subset of known mechanisms?
  • How much CO2 must be removed from the atmosphere? Probably lots, but how?
  • At what financial cost and paid by whom? How much have they contributed to-date?
  • Is 2°C a worthwhile goal? Do coastal cities and African + island nations lose out?
  • What penalties are applied to unhelpful nations? Is it legally or financially binding?

Once you receive answers to these questions and check them against your own internal senses of right vs. wrong, spin vs. science, and possibility vs. reality, you will have the tools to make your own decision about whether COP21 was a success.

And now for a little bit more detail:


Much of the research that the COP21 negotiators are working from (generally data from the IPCC: Intergovernmental Panel on Climate Change) orbits around staying below 2°C with a 66% likelihood of success. That’s often what they mean when they say “likely stay below 2°C.” But I have to ask, would you fly on an airplane or drive in a car that has a 66% chance of delivering you safely to your destination? If we seek a 90% probability of staying below 2°C, then we must stop burning all fossil fuels immediately (per David Spratt, “RECO2UNT”).

Source: David Spratt, "RECO2UNT"
Source: David Spratt, “RECO2UNT”

66 Percent Airlines COP21

Time Horizon

Negotiators will often limit predictions about the climate to 2100 as the time horizon. The climate system, however, doesn’t just stop warming when the clock ticks over. It seeks an equilibrium of energy that may not settle out for hundreds of years or more. So if you hear a climate prediction that sounds palatable, dig into whether the estimates work with an equilibrium state or not. Very often estimates just stop at 2100 with no mention that temperatures will likely rise after that year.

Feedback Mechanisms

In the pursuit of non-controversial data to support its findings, the IPCC does not take into account all known positive feedback mechanisms in the climate system (for review, a well-known feedback positive mechanism works like this: the arctic icecap melts and changes a highly reflective white ice surface into a highly absorptive dark water surface, accelerating the heating). That’s a problem in my book, and generally causes the IPCC to predict lesser climate impacts than what actually happens. (Consider this detailed assessment of feedback mechanisms by David Wasdell at the the Apollo-Gaia Project.)

CO2 Removal

All the IPCC scenarios used by the negotiators at COP21 that show us keeping warming below 2°C require some form of massive CO2 removal from the atmosphere. Any way you slice it, we’re no longer looking at a simple emissions reduction as sufficient to keep the planet below that goal. We must also actively pull CO2 from the atmosphere with technologies that have yet to be proven cost effective and/or at scale.


Decarbonizing the global economy will require a whole lot of money. The World Bank recently announced an assessment putting the number in the range of $89 trillion over the next 15 years (to stay below 2°C, and I’m not sure about the probability they use). That money will need to come from somewhere, and whoever it is has yet to put that kind of money on the table. I’m watching this front closely, possibly closest of all. The best intentions will sit on the drawing board without the financing to bring them to life.

2°C Goal

The 2°C goal is somewhat arbitrary and is often characterized as a target that will help us “avoid the worst impacts of climate change.” Renowned climate scientists James Hansen calls the 2°C target “catastrophic” and argues for a 1°C limit (we’re already experiencing this in 2015), while many others–even those within the COP21 negotiations process, particularly African and low-lying island nations– are actively trying to get the U.N. to adopt a 1.5°C target at COP21. Why those nations? Because we already have at least 1-3m of sea level rise baked into the system, and many low-lying nations disappear under those conditions. For them, this is a mortal fight. Furthermore, 2°C is a global average, but that value will vary globally depending on many factors including the proximity to oceans vs. large land masses and local weather patterns. African nations are set to bear the brunt of temperature increases for those reasons and more, and since they generally have done little to contribute to the problem, they see it as only fair that developed nations (like the United States) should bear the brunt of the atmospheric CO2 reduction burden. (I discuss the 2°C goal in great detail in the following article on Climate Change Numbers for COP21 in Paris.)

Climate Change Numbers for COP21 slide

Legally Binding

I hate to say it, but sometimes people are moved to act or not act based on the penalties applied to them. In the case of the COP21 climate negotiations, I see little evidence of anybody signing up for a legally binding agreement with any real teeth. If the word is used in a final pronouncement, check to see exactly what is legally binding. It might just be that the only legally binding thing to emerge is a provision for nations to review and revise their 2015 commitments every few years to address updates in the scientific literature.


Whatever the result at COP21 this year, it has already turned out to be a massive international focal point for collective climate action. Do the specifics matter? I think they do, but I suspect we’ll have to take whatever we can get and then cheerlead our way to even greater action the very next day. And the next. And the next. Holding ourselves accountable to the latest science, the possibilities within our collective genius, and our best moral selves.

For additional details and more of my (Mark Dixon’s) personal reflections on COP21, feel free to check out my hour-long lecture here:


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