Our Choice for Decarbonizing: Double Diamond, or Sheer Cliff

November 12, 2021

The jarring graph above is a great visual representation of the increasingly steeper slope of action needed to stabilize carbon emissions. Each year of delay means that future emission cuts must be an increasingly steeper slope, as Zeke Hausfather recently described on twitter.

Zeke Hausfather on Twitter:

If emissions had peaked back in 2000 we would be skiing down a bunny slope toward 1.5C. Today we face a double black diamond, and in a few years it will be a cliff. 

We are almost certainly going to overshoot 1.5C and need large-scale permanent carbon removal to get back down.

Scenarios commonly used to limit warming to 1.5C include a lot of late century negative emissions – sucking a quarter to a half of current emissions out of the atmosphere each year by 2100 – in order to make near-term reductions more plausible:

There is, of course, no guarantee that negative emissions of that scale will pan out, but any chance of ultimately limiting warming to 1.5C likely requires both speeding up emissions reductions significantly and building a robust carbon removal industry later in the century. 

Thankfully, the pathways to 2C with limited net-negative emissions are a lot less daunting, but every year global emissions continue to rise or stay flat it too becomes much more difficult to achieve:

It is worth mentioning that reducing global emissions 20 years ago would have been much harder than today. China was still industrializing rapidly through expanded coal use, clean energy was expensive, and political will was lacking. 

Its much easier to mitigate today, but at the same time the emissions that have accumulated in the atmosphere over the past 20 years make it much more difficult to meet our ambitious climate mitigation targets. 

Finally, its worth emphasizing that climate change is fundamentally a matter of degrees rather than thresholds. It not like 1.4C is fine but at 1.6C there be dragons; similarly, things do not suddenly spiral out of control at 2.1C. Its important to mitigate as much as we can. 

Below, an illustration of why delay does damage. Not only is mitigation more difficult as we procrastinate, but in the meantime, emissions continue to accumulate at a high rate, meaning a delayed response inevitably results in more heat trapping gases in the atmosphere, even as we bring emissions to (hopefully) zero.


2 Responses to “Our Choice for Decarbonizing: Double Diamond, or Sheer Cliff”

  1. jimbills Says:

    “Central planning” is a dirty term in our capitalistic society, but every corporation itself has central planning as a cornerstone of their success. It’s not just a cornerstone of warfare, it’s the foundation. Without it, there are multiple failures of communication, inefficient use of resources, conflict between groups, and a failure to meet broader goals.

    A largely believed idea is that the invisible hand of the market will produce the needed drop in carbon emissions. It might, and probably will, result in some level of drop, but it will also produce an enormous amount of waste in time and resources. We need central planning between disparate groups – working out common goals, prioritizing, and smoothing communications – and we simply don’t have that. But, that is the framework that a conference like COP26 could in theory provide.

    If I were a central planner and looking at the above charts on this post, I’d simply remove all the highly unlikely scenarios (the enormous drops on the right of each chart) as impossible to implement. The ones on the left would be more realistic if coordinated precisely, efficiently, and effectively.

    Looking at those charts, it might be a realistic view to take the time frames worked out in the left of each chart and extrapolate what we’re really looking at in a best case scenario – what is a realistic level of warning IF we Incorporated central planning, action, and coordination immediately? Then, if we didn’t have that planning, and just left it to the market, what would the curve look like? Then we’d have a fairly probable view of what we’re facing.

    The COP26 delegates are currently fighting to keep the 1.5 degree goal in the final draft. That’s all well and good. But, it’s so wildly unprobable that it’s really a waste of time. They’re focusing on the symbols, and that is politically preferable and popular, and just what a politician would do, without spending much time at all on concrete steps, and this by itself makes 1.5 impossible. There isn’t any more time.

    • jimbills Says:


      My only comment on COP26’s results is going to be here. They were nowhere close to the goals set for the conference. They couldn’t even agree to the $100 billion development fund, which was a major goal of this conference.

      There were more promises. Even these don’t limit warming to 2 degrees. But so far, not a single country is meeting the pledges from Paris:

      A promise, many times, is just a way to say “I will do” instead of “I am doing”. There are a handful of countries actively implementing plans, and that’s great, but very few, especially the major emitters, have real plans and actions in place now. The U.S., for instance, can promise anything, but fail to pass real climate legislation when a Democrat is in power, and then elect a Republican the next cycle.

      The COP26 delegates are holding onto 1.5 with an iron grip, but the math just isn’t there. We’ve passed the time where “I will do” means anything towards that goal. We’re pretending we’re acting, when we’re really just kicking the can down the road. It’s false hope – and I might be alone in thinking it, but false hope, especially one without real action, is deception. It’s lying, and it only enforces the thing that we’re trying to prevent.

      I believe history will judge COP26 very harshly. Right now, we’re pretending it went okay and it wasn’t a failure, which leads to the quote from the recently posted video:

      “Being honest would mean admitting that we’re failing, and we can’t do that, coz then we’d have to stop failing.”

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