In the 15th edition of its annual “emissions gap” report, the UNEP calls for “no more hot air” as countries approach the February 2025 deadline to submit their next nationally determined contributions (NDCs) setting mitigation targets for 2035.
These NDCs “must deliver a quantum leap in ambition in tandem with accelerated mitigation action in this decade”, the report says.
The report charts the “gap” between where emissions are headed under current policies and commitments over the coming decade, compared to what is needed to meet the Paris goal of limiting global warming to “well below” 2°C and pursuing efforts to stay under 1.5°C.
It highlights that greenhouse gas emissions reached record levels in 2023, up 1.3 per cent from 2022, and rising notably faster than the average over the past decade.
The report warns that both progress and ambition have “plateaued” in recent years, with relatively little of substance occurring since the pledges made at COP26 in 2021. And many countries are not even on track to meet their existing NDCs, with current policy projections from G20 nations exceeding NDC commitments by a collective 1bn tonnes of greenhouse gas emissions (in carbon dioxide equivalent, CO2e) in 2030.
Current policies put the world on track for 2.9°C of warming by 2100, the report finds – though this could be reduced to 2.4-2.5°C, if all existing NDCs are met (with a 50 per cent chance).
But unless global emissions in 2030 are brought below the levels implied by current NDCs, a pathway to 1.5°C with no or limited overshoot becomes “impossible”, the report says, and “strongly” increases the challenge of limiting warming to 2°C.
While the magnitude of the challenge is “indisputable”, there are “abundant opportunities for accelerating mitigation”, the report says. It finds that global emissions could be cut by 54 per cent by 2030 and 72 per cent by 2035 at a cost of less than US$200 per tonne of CO2.
This indicates that the gap between commitments and current policies is a result of a lack of policy support rather than more fundamental barriers to decarbonisation.
Global greenhouse gas emissions at record levels
The UNEP report finds that human emissions of greenhouse gases – CO2, methane, nitrous oxide and fluorinated gases (F-gases) – reached a record 57.1bn tonnes of CO2 equivalent (GtCO2e) in 2023.
The chart below shows how fossil CO2 (black) is by far the largest contributor to annual emissions and the main driver of the increase in recent decades, with methane (grey) playing the second largest role.
Global annual emissions of greenhouse gases (in GtCO2e using 100-year global warming potentials). Source: UNEP (2024) Figure 2.1.
Global emissions grew 1.3 per cent (0.7 GtCO2e) in 2023, compared with 2022 levels – a rate notably faster than that over the prior decade (2010-19, at 0.8 GtCO2e per year).
(As the report notes, these numbers do not include many of the climate-related impacts on greenhouse gas emissions that are not a result of direct human interventions – such as the catastrophic Canadian wildfires in 2023. The ability of the biosphere to absorb a portion of human emissions is broadly expected to weaken under scenarios where the world does not rapidly reduce emissions.)
These emissions were driven by energy use, industrial process emissions and land-use change across a variety of sectors.
As the chart below shows, electricity generation was the largest driver of greenhouse gas emissions globally in 2023, responsible for approximately 26 per cent of the total. Other major contributors were transportation (15 per cent), industry (11 per cent), fossil-fuel production (10 per cent) and industrial processes (9 per cent).
Allocation of global greenhouse gas emissions by sector in 2023. Source: UNEP (2024) Figure 2.2
The report finds that global aviation had the largest relative increase in emissions, increasing 19.5 per cent between 2022 and 2023 as the sector recovered from Covid-era lows. Fossil-fuel production emissions, road transportation and industrial process emissions also increased notably from 2022.
The authors note that the fossil share of generation is starting to decrease in the power sector as solar and wind expand rapidly, with capacity additions increasing by 50 per cent in 2023. Global investment in renewable power, grids and storage is now considerably higher than global investment in oil, gas and coal.
Despite rapid growth in clean energy, power-sector emissions have yet to peak, with new clean additions globally not quite keeping up with the rate of demand growth. However, the report notes that both power-sector emissions and overall global greenhouse emissions are expected to peak in the next few years, even if they did not in 2023.
An even wider emissions gap
The primary focus of this edition of the report is tracking the gap between where the world is heading today – both under current policies and near-term commitments – and what would be needed to meet Paris Agreement goals of limit warming to well-below 2°C.
However, since the 2023 report, there have not been any notable changes in country pledges or policies – and global emissions continued to grow.
This means that the emissions gap is wider than it was last year and the world is further off track from its climate goals.
The report explores a number of different future emissions scenarios including: those under policies in place today; emissions if Paris Agreement NDCs are met; emissions if both NDCs and national-level net-zero pledges are met; and emissions required under scenarios that limit warming to below 2°C and to 1.5°C with no or limited overshoot by 2100.
While these NDCs – alongside other policies enacted by countries – have helped move the world away from some of the darkest climate futures that seemed plausible a decade ago, the gap continues to grow between where the world is today and a path to meeting the Paris Agreement.
The report finds an emissions gap in 2030 of around 14GtCO2e between where the world is headed if countries achieve their “unconditional” NDCs (that is, those not conditioned on “climate finance” or other external assistance) – shown by the mid-blue line – and an emissions pathway that limits warming to below 2°C (defined in the report as a >66 per cent chance of avoiding 2°C warming) – shown by as the pale red line.
The gap is even larger – around 22GtCO2e – between unconditional NDCs and a scenario consistent with limiting warming to 1.5°C by the end of the century (red line). If conditional NDCs are fully implemented in addition to unconditional ones (light blue line), this emissions gap would shrink by around 3GtCO2e in 2030 for both the 2°C and 1.5°C scenarios.
Median emission scenarios adapted from Figure 4.1 in the 2024 UNEP Emission Gap Report. The dotted grey line shows a scenario with no new climate policies after 2010, while dark blue shows existing policies already implemented by governments, and mid and light blue lines show additional conditional and unconditional NDCs, respectively. The pale red line shows emissions consistent with a below 2°C trajectory, and red line shows emissions consistent with a 1.5°C trajectory. Chart by Carbon Brief.
If NDCs are not strengthened by 2035, this gap would grow to 18GtCO2e for keeping warming below 2°C and 29GtCO2e for 1.5°C, the report finds. In the absence of a ratcheting up of commitments in recent years, limiting warming to 1.5°C with no or low overshoot is now much more difficult to achieve. Further delays could similarly imperil the 2°C target.
In addition, many countries are “not even on track to deliver on their current NDCs” today, the report says. Major countries, including Australia, Brazil, Canada, Indonesia, Japan, South Korea, the UK and the US, are all off track to meet their targets under existing policies. (Several of those that are on track had set weak targets, it adds.)
Countries are expected to update their NDCs by February 2025 and these should include mitigation targets up to the end of 2035 (compared to the 2030 date for the initial round of Paris NDCs).
However, the ability of post-2030 commitments to put the world on track to limit warming to below 2°C is highly dependent on action pre-2030. As the report shows, strong climate action starting in 2024 would require a 4 per cent reduction per year on average, while doing so in 2030 would increase this to 8 per cent per year.
An upward revision of current policy warming
The UNEP report author team has been one of the main groups assessing the range of warming impacts the world could expect under current policies. However, their estimate has continued to increase over the past three reports – from 2.5°C in 2022 to 2.7C in 2023 and 2.9°C in 2024. This reflects both continued increases in global greenhouse gas emissions and methodology updates by UNEP.
The figure below compares these estimates between the 2022 (dark blue) 2023 (mid blue blue) and 2024 (light blue) versions of the UNEP report. Compared to the 2023 report, current policy warming outcomes increased notably, unconditional NDC outcomes were unchanged, conditional NDC warming increased slightly, and net-zero pledge warming decreased slightly.
Global average surface warming projections in 2100 relative to pre-industrial levels from the 2022, 2023 and 2024 UNEP Emissions Gap reports. Bars show the central (50th percentile) estimate, while 90th percentile uncertainties are shown by the grey bars on top. Chart by Carbon Brief.
The report finds that a continuation of current policies would result in a 100 per cent chance of exceeding 1.5°C, a 97 per cent chance of exceeding 2°C and a 37 per cent chance of exceeding 3C by 2100. (And the world will continue to warm after 2100 as long as CO2 emissions remain above (net) zero.)
Under NDCs, the odds of exceeding 1.5°C remains at 100 per cent, while there is a 94 per cent chance of exceeding 2°C by 2100 under unconditional NDCs and a 79 per cent chance under conditional NDCs.
If all country net-zero pledges are implemented (which, the report notes, few, if any, countries are on track to achieve today), these likelihoods are reduced to a 77 per cent chance of exceeding 1.5°C, a 20 per cent chance of exceeding 2°C and a near-zero chance of exceeding 3C.
The figure below compares the latest UNEP estimates (mid blue bars) to others in the literature – the emissions scenarios featured in the Intergovernmental Panel on Climate Change’s (IPCC) sixth assessment report (dark blue), estimates published by Climate Action Tracker (light blue), and the IEA’s 2024 World Energy Outlook (grey).
Global average surface warming projections in 2100 relative to pre-industrial levels from the IPCC sixth assessment report (dark blue bars), UNEP report (mid blue), Climate Action Tracker (light blue), and IEA 2024 World Energy Outlook (grey). Bars show the central (50th percentile) estimate, while uncertainty ranges are shown by the upper and lower lines. Chart by Carbon Brief.
Current policy outcomes are broadly in-line with the IPCC’s middle-of-the-road SSP2-4.5 scenario, though a notable gap has developed in recent years between UNEP and IEA estimates. While the three were nearly identical in 2021, the UNEP’s current policy warming estimate has increased while the IEA’s has decreased.
The UNEP provides a high-end warming estimate for its scenarios that is notably higher than that of other groups. This is because its approach includes both future emissions uncertainties associated with each scenario, plus the range of possible climate system responses from climate sensitivity and carbon cycle feedbacks. While the latter can be expressed probabilistically, the likelihood of future emissions outcomes under these scenarios are more difficult to assess.
High potential for deep emissions cuts
While countries are far from being n track to meet Paris Agreement goals today, the new report explores what it would entail – and cost – to close the emissions gap.
They find that, across all sectors of the economy, global emissions could be reduced by 31GtCO2e by 2030 (54 per cent below current policy levels) for a cost of less than US$200 per tonne of CO2. In 2035 this increases to 41GtCO2e (a 72 per cent reduction from current policy levels), reflecting expected continued cost declines of mitigation technologies.
The figure below, taken from the report, shows the assessed mitigation potential for US$200 per tonne of CO2 or below for each different sector of the economy.
Annual mitigation potential estimates (GtCO2e/year) for each sector in 2030 and 2035 for under US$200/tCO2e. Source: UNEP (2024) Figure 6.1
The energy sector has the largest potential for low-cost decarbonisation at 12GtCO2e/yr in 2030 and 15GtCO2e/yr in 2035, largely driven by the replacement of fossil fuel electricity production with clean energy sources.
Agriculture, forestry and other land uses (AFOLU sector) have the second largest potential for decarbonisation, with forestry making up the largest component of this.
While substantial increases in investments and finance are required to accelerate mitigation across all of these sectors, the report shows that deep decarbonisation is achievable in the next decade at a reasonable cost.
Ultimately, the report highlights that the growing emissions gap reflects a lack of political will by countries to address emissions, rather than any fundamental constraint on the world’s ability to rapidly mitigate.
This story was published with permission from Carbon Brief.
