Under the landmark Paris Agreement aiming at tackling climate change, countries agreed to hold the increase in global average temperature to well below 2 degrees C (3.6 degrees F), pursue efforts to limit the increase to 1.5 degrees C (2.7 degrees F), and achieve net-zero emissions in the second half of this century. Their current national commitments represent a substantial improvement over the trajectory the world was on before the Paris Agreement was struck. Nonetheless, warming is on track to reach 2.7 degrees C to 3.7 degrees C (4.9 degrees F to 6.7 degrees F) under current pledges over the course of the century, which is lower than business as usual but still sets the world on course for dangerous sea level rise, drought and other effects.

Fortunately, several features in the Paris Agreement can help strengthen national commitments over time. In 2018, a “facilitative dialogue” will take stock of collective progress towards the Paris Agreement goals and inform the preparation of future national climate plans. Countries that have joined the Agreement, known as Parties, will communicate or update their national commitments by 2020, and strengthen them every five years thereafter. Additionally, Parties are invited to communicate their “mid-century long-term low GHG emissions development strategies,” or “long-term strategies” by 2020.

While the Paris text does not provide further guidance on these long-term strategies, if done right, they can help strengthen countries’ ambition and bring their plans in line with what’s needed to hit the 1.5-2 degrees C goal.

Why Do We Need Long-term Strategies?

Many countries’ current climate plans only go until 2030, so there’s a risk that they may achieve them in a manner that actually makes the long-term goals more difficult to accomplish. This is because it takes a relatively long time for infrastructure like power plants, buildings and vehicle fleets to reach the end of its lifespan and be replaced. To the extent that climate change mitigation targets are met by making incremental improvements in the emissions intensity of fossil-fueled infrastructure, the remaining emissions associated with this infrastructure may be locked in for decades unless the infrastructure can be retired early or its emissions captured. For example, replacing a coal-fired power plant with a gas-fired power plant reduces emissions, but may lock in future emissions for the lifespan of that new gas-fired plant. Replacing such technologies with emissions-neutral alternatives before the end of their useful lifespan would be expensive, but waiting until the end of their lifespan could put the Paris goals at risk.

It is therefore imperative that countries think long-term, considering how they’ll meet their current commitments as well as more ambitious plans in the future. Long-term strategies provide an opportunity for countries to think through what the Paris goals mean for their own long-term emissions trajectories, and in turn, what this implies for the best ways to implement their mitigation targets. Countries that act on the Agreement’s invitation to develop such strategies can:

Making Countries’ Long-term Strategies Consistent with Paris Agreement Goals

Long-term strategies should be guided by the goals to limit warming to 1.5-2 degrees C and reach net-zero emissions in the second half of the century. Because countries’ economies and stages of development vary widely, there is no one-size-fits-all approach to reaching net-zero emissions. There are, however, hard physical limits to the emissions the atmosphere can support while limiting global temperature increase to the agreed goals. Three important questions countries should consider are:

  • When to phase out net-GHG emissions. To have a likely chance of limiting warming to 1.5 degrees C, carbon dioxide emissions must reach net zero by 2045-2050, and total greenhouse gas (GHG) emissions by 2060-2080. (For a likely chance of limiting warming to 2 degrees C, the same milestones must be met 15 to 20 years later.) This does not suggest that every country must reach net zero at the same time, but it does imply that every unit emitted anywhere after these milestone dates must be offset by negative emissions elsewhere. But some technologies proposed for achieving the required level of negative emissions, such as bioenergy with carbon capture and storage, have yet to be proven at scale and carry potential risks.

  • How to avoid reliance on an unrealistic decarbonization rate. Governments must ensure that the annual rate of emissions decline is feasible, and avoid relying on overly steep reductions in later years, which would be costly and may not be technologically and socially realistic.

  • How to limit cumulative emissions. Temperature increase is directly related to the total amount of emissions in the atmosphere over time. While national commitments tend to focus on a single target year, setting more regular milestones along the pathway to net-zero emissions can help ensure that long-term strategies consider the need to limit cumulative emissions.

Next Steps

The Paris decision invited countries to submit their long-term strategies by 2020. Some are getting a head start – Canada, Mexico, the United States and Germany have committed to developing their strategies by the end of this year. The key is ensuring these plans serve as a bridge between today’s national commitments and the goals of the Paris Agreement.