There is no doubt that the climate agreement struck in Paris created a mood of optimism about tackling global climate change, with most countries signing up after years of political procrastination. However, after a turbulent 2016, the mood has been tempered by concerns that the consensus is at risk.

At the same time, the need for deep and rapid reductions in greenhouse gas emissions has never been clearer. In 2016 global greenhouse gas concentrations remained over 400 ppm for the first time, up from 316 ppm in 1958. It was the warmest year on record, the rate of ocean warming is now estimated to be more rapid than previously thought, and arctic ice continues its rapid retreat.

The climate science is clear - we have a finite carbon budget and global greenhouse gas emissions must be zero before the end of the century, and much earlier if we want to load the probability in our favour of limiting warming to below an average 2°C. 

If the world is to have a chance of meeting this target, countries need to move to zero carbon energy systems now. Here’s why.

Why the energy sector?

The energy sector is the largest source of global greenhouse gas emissions, producing about two-thirds of all the greenhouse gases that are emitted worldwide.  So, how the energy sector develops is key to avoiding the mode negative of the effects of global climate change.

As discussed in our paper published in Nature Energy, any effort to reduce emissions will mean significant changes in the energy system. 

But how significant?

To answer this question we can first look at the Paris Agreement.

All together, 143 countries have ratified the Paris Agreement, including the United States, China, and members of the European Union. At the heart of this agreement is a specific aim:

“…to strengthen the global response to the threat of climate change by keeping a global temperature rise this century well below 2 degrees Celsius above pre-industrial levels and to pursue efforts to limit the temperature increase even further to 1.5 degrees Celsius.”

To achieve this goal, the world needs to work together to meet a finite carbon budget. This budget is often described as a “bathtub” that we are trying to prevent from overflowing, where greenhouse gas emissions are represented by the water flowing into the bathtub. Today, two-thirds of the water flowing into the bathtub comes from the energy sector.

Credit: US EPA

If we want to prevent the bathtub from overflowing, every country has to do its part to reduce the flow of water into the tub. That is, each country needs to rapidly decrease their own greenhouse gas emissions.

But how much is each country responsible for?

There are a number of different ways to define each country’s “responsibility” for reducing their greenhouse gas emissions. In our research, we focus on two key arguments:

  1. equity’ (i.e. population rules) – in this case, each country gets a portion of the global “carbon budget” based on how many people live in their country. In turn, countries with bigger populations are allowed to emit more carbon emissions (and vice versa).
  2. inertia’ (i.e. do relatively the same as what you’re already doing) – here, each country is allowed to emit greenhouse gases according what they are doing today. For example, the United Kingdom (UK) currently produces around 1.5% of global greenhouse gas emissions. So, in the future, the UK would be able to emit ~1.5% of future emissions.

The wording of the Paris Agreement suggests that more economically developed countries need to do more to tackle climate change, given their level of development and economic resources. This would suggest the need to move towards an ‘equity’ approach. 

In our research, we looked at what this approach would mean for one developed country – the United Kingdom. But the answers should hold true for any developed economy.

How fast would one developed country (the United Kingdom) need to move to a zero carbon energy future?

According to our research, countries need to move toward zero carbon energy now if we want to achieve the agreements put together under the Paris Agreement.

This is because technologies used in the energy system generally have long shelf-life. For example, your car will likely be on the road ~12 years and the power plant that keeps the lights on will last for 30, 40 or more years before it is retired. This means that the power plants that are built today could still be operating in 2065 or beyond.

In our research, we used computer models of the energy system to see what would need to be done to get for the UK to achieve its Paris Agreement commitments.  According to our analysis, the UK energy system needs to be carbon-free by:

  • 2045 – if we want to achieve the Paris Agreement’s call a “well below 2°C” future, as shown by the thick, black line in this graph
  • 2070 – if we want to avoid the worst effects of climate change, this is the very latest point for the UK to achieve a zero carbon energy system
Figure 1. Net CO2 emissions from the UK energy system under the 2 °C (66% probability) carbon budget range of 590-1240 GtCO2, based on ‘Equity’ and ‘Inertia’ allocations (used with permission of the authors

This means that the United Kingdom needs to move to a zero carbon energy system now if it wants to truly stand behind its Paris Agreement commitments. This is why, soon after Paris, the UK Government committed to putting a net zero target into law (though no actions have been formally made to follow through on this…).

While these findings are specific to the United Kingdom, the answers almost certainly hold true for other rich countries. This is why some are already moving ahead with “zero emission” policies. For example, Sweden is planning to be carbon-neutral by 2045 with their own net-zero emission strategy.

But more countries need to move to zero carbon energy – and quickly – if we want to have a chance at meeting global targets.

One can reach the full research paper by Pye, S., Li, F. G., Price, J., & Fais, B. (2017). Achieving net-zero emissions through the reframing of UK national targets in the post-Paris Agreement era. Nature Energy2, 17024 here.