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Future greenhouse gas emissions

Future greenhouse gas emissions scenarios

In this section

What trajectory is the world currently on?

What does the future of our carbon dioxide and greenhouse gas emissions look like. In the visualization we show a range of potential future scenarios of global greenhouse gas emissions (measured in gigatonnes of carbon dioxide equivalents), based on data from Climate Action Tracker.1 Here, five scenarios are shown:

  • No climate policies: projected future emissions if no climate policies were implemented; this would result in an estimated 4.1 to 4.8°C warming by 2100 (relative to pre-industrial temperatures);
  • Current climate policies: projected warming of 2.8 to 3.2°C by 2100 based on current implemented climate policies;
  • National pledges: if all countries achieve their current targets/pledges set within the Paris climate agreement, it’s estimated average warming by 2100 will be 2.5 to 2.8°C. This will go well beyond the overall target of the Paris Agreement to keep warming “well below 2°C”.
  • 2°C consistent: there are a range of emissions pathways that would be compatible with limiting average warming to 2°C by 2100. This would require a significant increase in ambition of the current pledges within the Paris Agreement.
  • 1.5°C consistent: there are a range of emissions pathways that would be compatible with limiting average warming to 1.5°C by 2100. However, all would require a very urgent and rapid reduction in global greenhouse gas emissions.
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What would be needed to stay below 1.5°C?

What would it take to limit global average temperature rise to 1.5°C?

Robbie Andrew, senior researcher at the Center for International Climate Research (CICERO), mapped out the global emissions reduction scenarios necessary to limit global average warming to 1.5°C. Robbie Andrew’s description of this work, visualizations and open-access data is available here.

These ‘mitigation curves’ are based on the carbon budget outlined in the IPCC’s Special Report on 1.5°C and the methodology for converting a cumulative carbon budget into annual quotas from Michael Raupach, publish in Nature Climate Change.2,3 These mitigation curves are based on the assumption of zero negative emissions (actively removing CO2 from the atmosphere).

The visualization here shows the range of mitigation curves necessary to have a >66% chance of limiting warming to 1.5°C. We first see global emissions to date – sourced from the Global Carbon Project – shown in black. Then, shown are the range of mitigation curves which would be necessary if mitigation (here meaning a near-immediate peak in global emissions then reduction) started in any given year. For example, the curve ‘Start in 2005’ shows the necessary emissions curve if mitigation had started in 2005.

What becomes clear is that the later the peak in emissions, the steeper the curve: the longer we wait, the more rapid emissions reductions need to be.

If emissions had peaked around 2000, for example, global emissions would have had to fall at an average of around 3% per year. As of 2019, we can only emit around 340Gt CO2 before we exceed the 1.5°C budget – this is equal to around 8 years of current emissions.4,5 If we peaked emissions today, we would have to reduce emissions by around 15% each year through to 2040 to limiting warming to 1.5°C without negative emissions technologies.

What would be needed to stay below 2°C?

In the section above we looked at the emissions reductions necessary to limit warming to 1.5°C. How does this change when we extend the carbon budget to one which limits warming to 2°C?

Robbie Andrew, senior researcher at the Center for International Climate Research (CICERO) also mapped out the mitigation curves for a 2°C target.6

In the visualization we see the various emissions scenarios to achieve 2°C depending on the year that global emissions peak.

We see that the same principle applies as for 1.5°C: the later we wait to peak global emissions, the more drastic reductions will need to be.

In the section above we looked at the emissions reductions necessary to limit warming to 1.5°C. How does this change when we extend the carbon budget to one which limits warming to 2°C?

Robbie Andrew, senior researcher at the Center for International Climate Research (CICERO) also mapped out the mitigation curves for a 2°C target.7

In the visualization we see the various emissions scenarios to achieve 2°C depending on the year that global emissions peak.

We see that the same principle applies as for 1.5°C: the later we wait to peak global emissions, the more drastic reductions will need to be.

As explained by Zeke Hausfather in the Carbon Brief, if we’d started global mitigation in 2000, the required rate of reduction would have been around 1 to 2% per year. If we peaked emissions in 2019 it would require reductions of 4 to 5% every year to limit warming to 2°C without negative emissions technologies.