numbers, not adjectives — D. J. C. MacKay

How good is the Paris Agreement?

by Carl Edward Rasmussen, 2024-05-25, 5 minute read

Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change;

The question is not whether the PA has had any benefit at all, which would of course be difficult to answer, because we can't know the hypothetical baseline where it hadn't come into force. Instead, the question is whether the agreement will likely live up to its goal to limit temperature rise by +1.5°C or +2.0°C.

When the PA came into force in November 2016, the atmospheric concentration of CO₂ was 404 ppm (parts per million) and the growth rate was 2.5 ppm/y (parts per million per year). Unless emissions change massively and immediately, we will reach +1.5°C warming at about 450 ppm CO₂ in around 2035. Unfortunately, since the PA came into force over 7 years ago, the growth rate of CO₂ has remained at 2.5 ppm/y, the highest rate seen in modern times. There is no indication that the growth rate is diminishing. And remember, the growth rate has to be zero, for the climate to stop warming. Therefore, it is clear that while the goals of the agreement may be appropriate, the mechanisms are completely inadequate.

What's wrong with the agreement?

Let's analyse why the mechanisms of PA have been completely inadequate so far. Is the PA essentially sound, just needing a little more time to deliver, or does it have fundamental structural deficiencies meaning that it is practically guaranteed to fail? This will be really important to understand, because it will determine whether we should push on with the agreement, or whether we may have to implement alternative mechanisms to achieve the PA's goals.

The nature of the climate challenge is that of sharing a global common resource. Because of the well understood greenhouse effect, limiting a rise in temperature requires limiting the atmospheric concentration of greenhouse gases. Since natural processes removing the airborne fraction of CO₂ are very slow (on the order of hundreds of years), only a fixed amount of CO₂ can be emitted, while staying within the temperature limit. This amount of CO₂ is a finite global resource, which we must share.

Fortunately, a lot is known about when cooperation over shared resources work. The necessary ingredients for cooperation are: responsibility, commitments, transparency and a framework of trust. How does the PA fare on these?

• responsibility: The agreement prescribes committing collectively to the 1.5°C or 2.0°C limits. Thus, no party in particular will be at fault if, or when, the commitments are broken. An effective agreement in contrast, would require specific, measurable commitments from the parties, with a clear assignment of responsibility. In its current form, the agreement invites to universal abdication of responsibility.


• commitments: According to the agreement, countries are encouraged to submit non-binding, increasingly ambitious Nationally Determined Contributions (NDCs) at regular intervals. But these are only weak incentives:
  • there is nothing, above perhaps peer pressure, pushing countries to raise their ambitions. Since weaning from fossil fuels is difficult, countries have unsurprisingly resisted
  • countries are free to water down their future NDCs or simply not implement them
  • there is no requirement of NDC immediacy. Some politicians boast impressive pledges for the far future, say 2050, when they'll no longer be active; it's not going to be their problem
  • NDCs are not legally binding, which may encourage some countries to submit pledges which they have no intention of complying with (but it will necessarily take decades before we will know how widespread this problem is).
  There is no effective pressure to ensure ambitious NDCs and no mechanisms of enforcement, so any commitments are largely vacuous in practice.


• transparency: The PA targets the global average temperature. But the global average temperature is a proxy for what we really care about, which is the living conditions on the planet. Living conditions are of course difficult to quantify, so we need proxies. But is global average temperature a good proxy? Not on its own, for several reasons:
  • global average temperature is not directly attributable to our actions. To be effective, an agreement must (also) target greenhouse gas emissions which are causing heating, are directly measurable and whose emissions are attributable
  • global average temperature is subject to significant natural statistical fluctuations. This means that it will take time after the smooth time averaged temperature has exceeded the 1.5°C or 2.0°C limits before we will know it with confidence
  • because of inertia in the climate system, temperature takes time to respond to our actions. If we hypothetically stopped releasing greenhouse gases today, average global temperatures would still keep increasing for a while due to what has been called global warming in the pipeline.
  For these reasons the PA choice of temperature proxy undermines transparency.


• trust: The long time horizons of the NDCs and the lack of commitments make it impossible for countries to verify the integrity of their partners, and mistrust ensues, poisoning cooperation. Therefore the PA forsters mistrust.

Constructive alternative

It is important that we acknowledge the fundamental deficiencies of the PA. Carrying on and hoping that the problem will go away by iteself is simply delusional. We need new effective mechanisms which deal with the problems outlined above. The Equitable Atmosphere Climate Cooperative provides such mechanisms.

back