The Paris Agreement: are we raising climate ambition fast enough?

Neil Grant, Research Postgraduate on the Science and Solutions for a Changing Planet Doctoral Training Partnership, blogs on his latest research. The paper, published in Joule, explores whether the world is on track to address the climate crisis, and what needs to happen to increase the ambition of global climate action.

The UN Climate Change Conference (COP26) was a key moment to address the climate crisis. The conference, held in Glasgow in November 2021, was the first opportunity since the signing of the Paris Agreement at COP21 in 2015 for countries to set out more ambitious pledges to tackle climate change. In the run-up to, and during the conference, many nations announced new pledges, including the UK, the USA and India. But are these new pledges enough?

Did COP26 do enough to keep 1.5°C alive?

The UK government framed COP26 as the ‘last, best chance’ to keep 1.5°C alive. This is broadly taken to mean limiting the global average temperature rise to below 1.5°C, with at least a one-in-two chance. So did the conference in Glasgow do enough? The most important answer is clear – no. The latest assessment suggests that current pledges to reduce emissions would lead to warming of 2.4°C by 2100 – far above the Paris Agreement’s 1.5°C goal.

This is a bleak outlook. But at the same time, there are signs that change is possible. Predictions of future warming are lower now than they used to be, although large uncertainties around the exact level still remain. This is partly because climate policy is slowly getting stronger. As renewables are deployed and their costs continue to fall, the world is beginning to accelerate climate action. Not fast enough. Not even close. But still, a start.

In fact, this idea of escalating ambition is built into the design of the Paris Agreement. The agreement didn’t require that every nation immediately provide 1.5°C-compatible plans. Instead, it allowed countries to choose their own level of ambition when signing on. This came with a caveat – that these pledges had to be updated every five years, with each pledge more ambitious than the last. This is the so called ‘ratcheting mechanism’ of the Paris Agreement. The hope was that, over time, ratcheting would align government ambition with the 1.5°C target.

So another important question is: did COP26 ratchet ambition enough? While the COP26 pledges are not enough, how much better are they than those made in Paris? We’re off track, but can we get back on track fast enough to achieve the ambitious temperature targets set by the Paris Agreement, before our rapidly dwindling carbon budget runs out?

My research calculates the strength of the Paris Agreement’s ratcheting mechanism and explores what this means for tackling climate change. The initial results give hope for limiting warming to 2°C but show that action must accelerate significantly to keep 1.5°C alive.

The impact of COP26 on emissions

To calculate the strength of the ratcheting mechanism, you need two points in time, so you can measure how climate policy ambition has changed between them.

The figure below shows how future emissions, based on countries’ climate pledges, have changed between Paris (in blue) and Glasgow (in orange). In the Paris Agreement, climate pledges were going to result in around 54 billion tonnes of carbon dioxide by 2030 – a growth rate of around 0.4% per year from 2015 to 2030. The pledges made in Glasgow at least put emissions on a downwards trend. Emissions would fall around 1% per year from 2021 to 2030 if fully implemented (which is a big if).

This suggests that climate action over the six years between Paris and Glasgow has reduced the rate of emissions growth by 1.4%. This is the first estimate of how strong the Paris Agreement’s ratcheting mechanism is.

Is the ratchet strong enough to keep 1.5°C alive?

Current climate pledges are (a) too weak to deliver the Paris Agreement goals and (b) stronger than they used to be. What happens if they keep getting stronger at the same pace? Will this be enough to keep 1.5°C alive?

I modelled how future greenhouse gas emissions would change if world leaders keep ratcheting ambition with the same strength as occurred between Paris and Glasgow. I also modelled what happens if the ratchet is strengthened by two to four-fold.

I found three main things:

• Continuing to ratchet climate ambition could likely limit warming to below 2°C, and potentially achieve 1.5°C by 2100. This is good news! Ratcheting can help deliver ambitious temperature targets
• Under current ratcheting, we would overshoot the 1.5°C target by about 0.2°C. As a result, we would need massive deployment of technologies to suck carbon dioxide out of the air, which could be risky. Also, given exceeding 1.5°C even temporarily can have “irreversible” impacts, it would be safer to avoid overshoot entirely.
• To have a 50% chance of doing this, the ratchet would need strengthening four-fold. That means the increase in ambition seen in each ratcheting cycle would need to be four times larger than what we saw between Paris and Glasgow.

If you want to get technical, the figure below shows the results. Panel A shows future greenhouse gas emissions under different ratchet strengths, while panels B to E show the underlying gases. Panel F shows the implications of this for global temperatures, while Panel G shows the probability of limiting warming to 1.5 or 2°C.

Actions speak louder than words

The need for increasing ratcheting is even clearer if we look not at what world leaders are saying, but what they are doing. So far, we’ve assumed that leaders will actually deliver on what they pledge. The jury is still out on whether this is the case. Sadly, current policies are insufficient to achieve climate targets in many countries. If we take this ‘implementation gap’ into account, the results are incredibly worrying. Current ratcheting of actions, rather than words, would only limit warming to 1.9°C – and there would be a 33% chance of exceeding 2°C. This represents a very dangerous level of warming. 1.5°C would be out of sight, unless the ratchet was strengthened eight-fold. Translating ambition into action remains a crucial barrier.

What’s next for world leaders?

Current pledges remain critically misaligned with 1.5°C. The world is relying on the ratcheting mechanism to deliver a safe future. These results give hope that the ratchet could put ambitious temperature targets within reach by 2100. However, the ratchet needs to be strengthened considerably, and delivered on, to keep 1.5°C alive.

So, what’s my message to world leaders?

1. Countries need to keep increasing the ambition of their climate pledges –every government must do more.
2. Governments must raise their ambition and deliver more in the next ratchet cycle, which ends in 2025. To have a 50% change of limiting global temperature rises to 1.5°C, the ratchet must be strengthened at least four-fold.
3. Targets and ambition are meaningless unless they are achieved. As well as increasing the ambition of climate pledges, governments need to introduce policy to achieve them.