The International Energy Agency (IEA) was asked by the COP26 Presidency in 2021 to give an indication of what achieving the 1.5 °C goal would mean for the energy sector. Responding to this request, the Net Zero Emissions by 2050 Scenario (NZE Scenario) was developed. It represents a global pathway towards the goal of limiting global warming to 1.5 °C, but not the only possible one. The IEA has always been clear that there are various paths to reach this objective and that each country will have its own route. Since 2021, the IEA has updated its NZE Scenario each year, in line with changes in real world investment, technology developments and greenhouse gas (GHG) emissions.

Three inter-related trends have marked the last several years:

• Energy sector emissions have continued to set record highs.

• Progress in deploying low-emissions technologies and increasing energy efficiency has been very rapid in some cases but is uneven across sectors and countries.

• The context in which governments and energy companies are operating remains complex and challenging, marked by features such as increasing geopolitical fragmentation, high government debt burdens, and rising levels of concern about energy security and affordability after the global energy crisis.

With these in mind, we have revisited several aspects of the design of the NZE Scenario in 2025, while maintaining the end point of net zero energy-related CO₂ emissions by 2050, in order to provide an up-to-date analysis of the current state of efforts to meet the Paris Agreement target of 1.5 °C and additional efforts needed to achieve it in the current context.

Consequently, while the NZE Scenario still achieves the COP28 energy goals of doubling the pace of annual efficiency improvements and tripling the installed capacity of renewables, it sees a slightly less rapid transition, with higher emissions in the near term than in previous WEO editions. Warming exceeds 1.5 °C degrees for several decades, and returning to below 1.5 °C by 2100 is only possible with the deployment in the second half of this century of carbon dioxide removal technologies that are currently unproven at large scale. This updated NZE Scenario nevertheless remains a highly ambitious and challenging pathway. Critically, it remains below the upper limit enshrined in the Paris Agreement of holding warming to well below 2 °C above pre-industrial levels throughout the 21st Century.

The Intergovernmental Panel on Climate Change (IPCC) Working Group III Sixth Assessment Report on Mitigation of Climate Change , released in April 2022, assessed a large number of scenarios that led to at least a 50% chance of limiting the temperature rise to 1.5 °C in 2100. As outlined in the World Energy Outlook 2025, in contrast with previous editions, the NZE Scenario is no longer a limited-overshoot scenario, as warming peaks at over 1.6 °C and remains above 1.5 °C for several decades before falling back below 1.5 °C by 2100. Nevertheless, as the figure illustrates, the updated NZE Scenario trajectory still lies well within the envelope of these IPCC scenarios, including both limited and high overshoots categories.

The IEA began exploring scenarios to limit CO₂ emissions in 2006, with the Energy Technology Perspectives (ETP) Accelerated Technology (ACT) Scenarios that sought to curb emissions growth by bringing emissions back down to 2005 levels by 2050. This analysis continued with the ETP BLUE Map Scenario in 2008, which targeted a 50% reduction in CO₂ emissions by 2050, and later evolved into the 2 °C Scenario (2DS).

Several special reports designed to feed into United Nations Framework Convention on Climate Change (UNFCCC) Conference of the Parties (COP) negotiations have examined the energy implications of climate scenarios in depth. These include:

• The World Energy Outlook 2008, which assessed two scenarios in which the atmospheric concentration of emissions stabilised at 550 parts per million (ppm) and 450 ppm respectively, to inform the design of a post-Kyoto climate framework at COP15 in Copenhagen in 2009.

• Redrawing the Energy-Climate Map, a World Energy Outlook special report published in 2013, that fed into COP19 in Warsaw, setting out key measures for the energy sector to stay within the 2.0 °C target and make further reductions.

• The World Energy Outlook 2015 Special Report on Energy and Climate Change, which contributed to preparations for COP21 in Paris with a detailed assessment of how national climate pledges impact the energy sector.

• The Net Zero Roadmap 2021 and its 2023 update played a key role in formulating the COP28 target to triple renewable energy capacity and double energy efficiency improvements by 2030.