Every country is now pledging to tackle CO2 emissions. It's still not enough.

This December, negotiators from around the world will meet in Paris to haggle over a new international treaty on climate change. And in the run-up to those talks, every single country is putting forward pledges to take at least some steps to address their greenhouse gas emissions. That includes Europe, the United States, even China and India.

Even if every nation met its climate pledge, we'd still be on course for 2.6°C of warming by 2100

So what does it all add up to? A new report from the International Energy Agency (IEA) analyzes all the different climate pledges put forward thus far. On the one hand, they're rather ambitious. If countries actually followed through on what they've pledged — a big "if" — it would mark a huge advance for clean energy. Global coal consumption could peak within a decade, while renewables (including solar, wind, hydro, and especially biomass) would become the world's biggest energy source by 2030 or so.

The bad news? Current pledges aren't yet enough to avoid significant global warming. Even if every nation followed through on its existing climate promises, the world would still be on course for at least 2.6°C of warming (4.7°F) by the end of the century and 3.5°C of warming (6.3°F) by the end of next century.

In other words, if the world wants to stay below 2°C of global warming — which has long been considered the danger zone for climate change — these pledges are only a first step. Countries will have to do a whole lot more than they're currently promising. And the IEA has a few ideas for what "do a whole lot more" might entail.

Countries are currently pledging to rein in CO2 emissions...

As part of the climate talks, every country is making its own voluntary pledge to take action. Some of the pledges are fairly sweeping. So, for instance, the United States has pledged to cut its greenhouse gas emissions 26 to 28 percent below 2005 levels by 2025. China has vowed to get 20 percent of its energy from clean sources by 2030.

These individual promises are called Intended Nationally Determined Contributions, or INDCs. A few other examples that have been submitted so far:

(International Energy Agency)

To be sure, it's an open question whether all these countries will actually follow through on their INDCs. They are, after all, voluntary and non-binding. The Obama administration, for example, is currently enacting a flurry of EPA rules to nudge down America's emissions from power plants, cars, heavy trucks, and other sources. But a successive Republican president could dismantle those policies. Similarly, fast-growing countries like Mexico or China could struggle to meet their goals. Still, this is what's being promised so far.

Current pledges aren't yet enough to avoid significant warming

Now let's assume every country does follow through on its promises. In this scenario, the world's energy-related CO2 emissions would keep growing for the next few decades, albeit at a much slower pace than they have historically:

(International Energy Agency)

And, according to the IEA's calculations, the world would bust through its "carbon budget" by 2040 — that is, the amount of carbon dioxide that we can load into the atmosphere before we put the Earth on course for a likely 2°C or more of warming. At that point, the world would have officially failed to meet its climate goals.

Here's how the IEA expects the world's energy mix to evolve under this scenario:

(International Energy Agency)

By 2030, the IEA projects, the world will be using a lot more energy than it does today, thanks to fast-growing countries like China, India, and various African nations. But — again, assuming every nation followed through on its climate pledge — global coal use would grow more slowly than in the past and peak around 2025.

The world would also be using significantly more renewable energy by 2030 under this scenario. Most of that, the IEA projects would be in the form of "bioenergy" — burning biomass for electricity or using biofuels in vehicles. (That's not entirely good news, since there are longstanding questions around just how sustainable it is to use trees or crops for fuel.) Other renewables like wind and solar would be a small but fast-growing slice of the mix.

So this is the future that governments are currently promising. Gradually clamp down on coal consumption. Use much more renewable energy, particularly biomass. But ultimately emissions keep rising, and we blow through our carbon budget to stay below 2°C by 2040 or so.

So what if we wanted to go further than that?

How the world could cut emissions even more sharply

The IEA report argues that if the world wants to keep below 2°C of warming, countries will have to take even more drastic action in the near future — with global emissions peaking around 2020 or so, rather than continuing to rise until 2040.

The report identifies five quick and straightforward measures that countries could adopt to do this — all using current technology:

1. Increase energy efficiency in the industry, buildings, and transport sectors. 
2. Progressively reduce the use of the least efficient coal-fired power plants and banning their construction.
3. Increase investment in renewable energy technologies in the power sector from $270 billion in 2014 to $400 billion in 2030.
4. Gradually phase out fossil fuel subsidies to end-users by 2030.
5. Reduce methane emissions in oil and gas production.

Think of these five steps as an emergency crash course in reducing emissions. They're not all easy (phasing out fossil fuel subsidies in countries like Iran or Egypt can be a painful process). But they're all technically feasible and cost-effective steps nations could take in the next five years to curtail emissions dramatically without impinging on economic growth.

In addition, the IEA recommends that countries take the 2°C target far more seriously that they're currently doing and pursue policies that get us closer to that goal. That includes more aggressive support for things like wind, solar, energy storage, electric vehicles, and carbon capture and storage technology for coal and gas plants.

The IEA calls this the "450 Scenario" (because it aims to limit CO2 concentrations in the atmosphere to 450 parts per million — we're at 400 now). Here's how it compares to the INDC Scenario that countries are currently striving for. Emissions drop much more sharply in the decades ahead:

(International Energy Agency)

What's more, the IEA argues that any climate treaty negotiated in Paris this December should have a review process whereby every five years, countries officially take stock of their actions and adjust their pledges as necessary.

Would this more aggressive plan be enough to keep global warming below 2°C? Possibly not. As we've discussed plenty of times before, staying below the 2°C target would require staggering reductions in carbon intensity emissions around the world, unprecedented scaling of clean energy, and possibly new technological breakthroughs. We'd also likely need to find some way to pull CO2 out of the atmosphere by the end of the century — a still nascent and uncertain technology.

So even a more ambitious program for cutting emissions could well fall short and leave us on pace for significant climate change. We shouldn't have any illusions about that. But, the IEA report points out, the course we're currently on is almost certain to bust through the 2°C limit.

Further reading

For a more optimistic view of the ongoing UN climate talks, read this interview with David Victor. The basic point is that even though all these pledges are largely voluntary, the hope is that they can build momentum for further action over time.

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