Analysis: Global CO2 emissions could peak as soon as 2023, IEA data reveals

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Carbon Brief

Global carbon dioxide (CO2) emissions from energy use and industry could peak as soon as this year, according to Carbon Brief analysis of figures from the International Energy Agency (IEA).

The IEA’s latest World Energy Outlook 2023 says it now expects CO2 emissions to peak “in the mid-2020s” and an accompanying press release says this will happen “by 2025”.

Yet the IEA’s own data shows the peak in global CO2 coming as early as this year, partly due to what the outlook describes as the “legacy” of the global energy crisis triggered by Russia’s invasion of Ukraine.

Other highlights from Carbon Brief’s in-depth examination of the outlook include:

  • Global fossil fuel use peaking in 2025, two years earlier than expected last year.
  • For the first time, coal, oil and gas each peaking before 2030 under current policies.
  • Fossil fuel peaks being driven by the “unstoppable” growth of low-carbon technologies.
  • The IEA boosting its outlook for global solar capacity in 2050 by 69% since last year.
  • The IEA expecting 20% more electric vehicles on the road in 2030 than it did last year.
  • A key focus on slowing economic growth and faster low-carbon uptake in China, where fossil fuel demand is now expected to peak in 2024.

Yet climate policies remain far from sufficient to limit warming to 1.5C, the IEA warns.

The outlook reiterates the IEA’s ideas for five “pillars” to keep the path to 1.5C open at COP28, including targets to triple renewable capacity and double the rate of energy efficiency improvements by 2030.

(See Carbon Brief’s coverage of previous IEA world energy outlooks from 2022, 2021, 2020, 2019, 2018, 2017, 2016 and 2015.)

World energy outlook

The IEA’s annual World Energy Outlook (WEO) is published every autumn. It is widely regarded as one of the most influential annual contributions to the climate and energy debate.

The outlook explores a range of scenarios, representing different possible futures for the global energy system. These are developed using the IEA’s “Global Energy and Climate Model”.

The 1.5C-compatible “net-zero emissions by 2050” (NZE) scenario was introduced in 2021 and updated in September 2023.

The report notes that the path to 1.5C is made more difficult by each year of “high emissions and limited progress”, but adds that the “recent acceleration in clean energy” is keeping a path open.

Alongside the NZE is the “announced pledges scenario” (APS), in which governments are given the benefit of the doubt and assumed to meet all of their climate goals on time and in full.

Finally, the “stated policies scenario” (STEPS) represents “the prevailing direction of energy system progression, based on a detailed review of the current policy landscape”. Here, the IEA looks not at what governments are saying, but what they are actually doing.

Annex B of the report breaks down the policies and targets included in each scenario. In effect, the IEA is judging the seriousness of each target and whether it will be followed through.

For example, the provisions of the US Inflation Reduction Act are included in the STEPS. But the US target to cut emissions to 50-52% below 2005 levels by 2030 is only met under the APS.

Among various new policies included in the STEPS since last year’s outlook are Japan’s “green transformation” programme that aims to raise the share of renewables and nuclear in the country’s electricity mix, as well as ensuring all new car sales are low-emissions from 2035.

The report emphasises that “none of the scenarios…should be considered a forecast”. It says:

“The intention is not to guide the reader towards a single view of the future, but rather to promote a deeper understanding of the way that various levers produce diverse outcomes, and the implications of different courses of action for the security and sustainability of the energy system.”

Indeed, the design of the scenarios means that the STEPS is all but guaranteed to have become more ambitious by the time next year’s outlook is published – notwithstanding recent policy rollbacks in the UK – as governments around the world continue to implement their pledges.

This increase in ambition over time, as announced pledges are converted into stated policies, is clear from the historical record. (See below for charts comparing IEA outlooks over time.)

In 2021, the newly introduced NZE took centre stage in the IEA’s outlook, with the scenario mentioned 201 times per 100 pages against just 115 for the STEPS.

The STEPS returned to prominence last year and that trend continues in 2023’s outlook, which mentions the scenario 247 times per 100 pages, against just 157 mentions for the NZE.

Another notable change in the 2023 outlook is its shorter length, at 356 pages, compared with 524 last year and as many as 810 in 2019. As a result, this year’s report allows just five pages each to look specifically at coal, oil and gas, whereas the 2022 edition gave them 20-44 pages each.

Emissions peak as soon as 2023

One of the most striking findings in this year’s outlook is that global energy-related CO2 emissions could peak as soon as this year – and by 2025 at the latest.

Carbon Brief understands that the agency did not want to put a firm marker down on 2023, as the expected peak in global emissions will be affected by economic growth, weather and other factors.

However, Figure 1.15 in the report clearly shows CO2 emissions peaking this year under current policy settings in the STEPS scenario.

This curve is reproduced in the figure below, which illustrates the seismic shifts in the global trajectory for CO2 emissions since the signing of the Paris Agreement in 2015.

The thick black line shows how, for much of recent history, global CO2 emissions have marched relentlessly upwards, as growth in populations and energy use have led to higher fossil fuel use.

The pre-Paris policy baseline is shown in grey, illustrating how, on the eve of the COP21 summit where the deal was agreed, the IEA expected emissions to continue rising for decades.

Since that moment in 2015, the adoption of new climate policies and the accelerating spread of low-carbon technologies has seen the growth in global emissions slowing down.

In 2021, the IEA found government policies had advanced sufficiently to bring about a peak in global energy-related CO2 emissions (grey-blue line), with the subsequent decline deepening in the 2022 outlook (light blue).

This year’s outlook (dark blue) sees emissions peaking as soon as 2023 under current policy settings – two years earlier than expected in 2022 – and falling even more steeply after the peak.


Credit photo: Conny Polorny/Alamy Stock Photo


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