It’s official: 2023 was the hottest year on record. NASA confirmed it last week in this report and the EU’s Copernicus Climate Change Service reported the same thing here. Atmospheric concentrations of CO₂ are the highest they’ve been in at least 800,000 years. Not surprisingly, the Global Carbon Project reported worldwide carbon emissions from fossil fuels also reached record highs in 2023.

Yet also in 2023, the International Energy Agency (IEA) predicted that global carbon emissions from fossil fuels will peak before the end of this decade. And Ember, an energy think tank, reported that half the countries of the world have already passed a peak in one important sector: electricity generation from fossil fuels. In fact, emissions from power generation in 107 countries have fallen by 20% in the last decade.

Can both these things be true at the same time? If so, what does it mean to reach “peak” carbon emissions? And when emissions peak, does that mean global temperatures will peak too?  

To clear this up, I’ve put together an infographic to show the relationship between annual CO₂ emissions, the total concentration of CO₂ in the atmosphere, and changing global temperatures over the period from 1850 to 2100. We need to get control of all the other greenhouse gasses too, but CO₂ is the most important one.

You can download a PDF version including clickable links here:

So what happens after temperatures peak? 

It’s risky to make predictions that far into the future but one thing is clear: we’ll have to sustain net zero emissions indefinitely. There’s no going back to burning fossil fuels.

Once we do hit net zero, Earth’s climate system will gradually cycle CO₂ out of the atmosphere, but that will take centuries.

So all the impacts of warming – extreme weather events, forest fires, floods, drought, etc. – will continue. The poorest regions and poorest people of the world will continue to be hit hardest.

If we want to reduce global temperatures faster, we have two options: negative emissions and geoengineering.

Negative emissions means pulling CO₂ out of the atmosphere. The simplest way of doing this is planting trees, but I doubt that would be enough. We’d also need new technologies like direct air carbon capture.

Geoengineering is all about actively managing the Earth’s climate system. One example is solar radiation management where we’d inject aerosol particles or droplets of sea water into the stratosphere to reflect more sunlight back into space. These methods get a little science fiction-y and we need to do way more research before attempting any of them.

Our immediate challenge is to keep peak emissions, peak CO₂ concentration and peak warming as low as possible. We do that by reaching these peaks as soon as possible.

Thanks for reading.

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Related Links

See How 2023 Shattered Records to Become the Hottest Year
Raymond Zhong and Keith Collins. The New York Times. Jan. 9, 2024.

Global carbon emissions from fossil fuels reached record high in 2023
University of Exeter and Stanford Doerr School of Sustainability. Dec. 5, 2023.

Global CO2 emissions from fossil fuels to hit record high in 2023 -report
Kate Abnett. Reuters. Dec. 4, 2023.

What happens after net zero? The impacts will play out for decades, with poorest countries still feeling the heat
Liam Cassidy, Andrew King, Josephine Brown and Tito Ziehn. The Conversation. Dec. 4, 2023.

What Happens After the World Reaches Net-Zero Emissions?
Sana Pashankar and Eric Roston. Bloomberg. Nov. 14, 2023.

The Zero Emissions Commitment and climate stabilization
Palazzo Corner S, Siegert M, Ceppi P, Fox-Kemper B, Frölicher TL, Gallego-Sala A, Haigh J, Hegerl GC, Jones CD, Knutti R, Koven CD, MacDougall AH, Meinshausen M, Nicholls Z, Sallée JB, Sanderson BM, Séférian R, Turetsky M, Williams RG, Zaehle S and Rogelj J. The Zero Emissions Commitment and climate stabilization. Front Sci (2023) 1:1170744. doi: 10.3389/fsci.2023.1170744