Niklas Höhne

Since the adoption of the 2015 Paris Agreement, countries have put forward emission reduction pledges which altogether would keep global warming below 2°C. Policy implementation lags these pledges but has nevertheless markedly impacted the outlook. Policy implementation and the shifts in, for example, technology costs they engender have lowered end-of-century global warming prospects since 2015 by about 1°C, yet still imply exceeding 2°C and 1.5°C of global warming by a large margin.

Long-term global emissions scenarios underpin climate policy by providing quantitative benchmarks for near-term actions consistent with long-term temperature goals. However, scenario benchmarks can quickly become outdated as real-world emissions, policies, technologies and even geopolitics evolve. Here we present an updated and curated ensemble of global integrated assessment model (IAM) scenarios developed since the IPCC Sixth Assessment Report. We use a continuous “live” collection and vetting framework designed for regular updating - with planned annual releases - to derive up-to-date policy-relevant benchmarks. Of more than 1,500 collected scenarios, only a minority remains consistent with recent trends between 2015 and 2025. After assessing feasibility, plausibility, and sustainability, 162 scenarios form the basis for updated benchmarks. These indicate that pathways limiting peak warming to around 1.7 °C above pre-industrial levels represent the lowest warming outcomes currently supported in the recent literature, requiring global greenhouse gas (GHG) emissions reductions of around 60% by 2035 and 90% by 2050 relative to 2019, with net-zero CO₂ emissions reached around 2050. All Paris-consistent benchmarks require a rapid transitioning away from unabated fossil fuels, an unprecedented scale-up of renewable energy, and limited but necessary deployment of carbon dioxide removal (CDR). While limiting peak warming to 1.5 °C with low or no overshoot is no longer feasible, returning warming to 1.5 °C this century (after overshooting to about 1.7 °C) remains possible.

To identify means to improve mitigation efforts, we investigated whether the number of climate policies is associated with emission projections up to 2030 and compared policies’ prevalence across country groups. We find that larger and more comprehensive policy portfolios are conducive to emission reductions, regardless of whether absolute emissions increase or already decline. However, country groups have distinct entry points to expand climate policy. Countries with fast-increasing emissions have significantly fewer policies overall but policies are especially missing in energy-demand sectors, such as buildings and transport. Countries with stalling emissions lack climate strategies and other cross-sectoral policies. This suggests the need for better coordination of mitigation efforts across sectors. In all country groups that fail to reduce emissions, policies to reduce energy and material demand are also substantially fewer. Despite the collective increase of policies in force, countries can still expand climate policy to use the full breadth of mitigation options available.

Many years passed since the adoption of the Paris Agreement, which invites countries to determine their own contributions to climate change mitigation efforts. The Agreement does not offer a standard to measure progress but relies on a process of periodic stocktakes to inform ambition-raising cycles. To contribute to this process, we compare 2021 greenhouse gas emission projections up to 2030 against equivalent projections prepared back in 2015. Both sets of projections were prepared using the same bottom-up modelling approach that accounts for adopted policies at the time. We find that 2021 projections for the G20 as a group are almost 15% lower (approximately 6 GtCO₂eq) in 2030 than projected in 2015. Annual emissions grow 1% slower in the coming decade than projected in 2015. This slower growth mostly stems from the adoption of new policies and updated expectations on technology uptake and economic growth. However, around one-quarter of these changes are explained by the effects of the COVID-19 pandemic on short-term emissions and economic forecasts. These factors combined result in substantially lower emission projections for India, the European Union plus the UK (EU27 + UK), the Unites States, Russia, Saudi Arabia, and South Africa. We observe a remarkable change in South African projections that changed from a substantial increase to now a decline, driven in part by the planned phase-out of most of its coal-based power. Emissions in India are projected to grow slower than in 2015 and in Indonesia faster, but emissions per capita in both countries remain below 5 tCO₂eq in 2030, while those in the EU27 + UK decline faster than expected in 2015 and probably cross the 5 tCO₂eq threshold before 2030. Projected emissions per capita in Australia, Canada, Saudi Arabia, and the United States are now lower than projected in 2015 but remain above 15 tCO₂eq in 2030. Although emission projections for the G20 improved since 2015, collectively they still slightly increase until 2030 and remain insufficient to meet the Paris Agreement temperature goals. The G20 must urgently and drastically improve adopted policies and actions to limit the end-of-century warming to 1.5 °C.

By January 2022, 156 countries had submitted new or updated nationally determined contributions (NDCs) under the Paris Agreement. This study analyses the greenhouse gas (GHG) emissions and macroeconomic impacts of the new NDCs. The total impact of the updated unconditional and conditional NDCs of these countries on global emission levels by 2030 is an additional reduction of about 3.8 and 3.9 GtCO₂eq, respectively, compared to the previously submitted NDCs as of October 2020. However, this total reduction must be about three times greater to be consistent with keeping global temperature increase to well below 2 °C, and even seven times greater for 1.5 °C. Nine G20 economies have pledged stronger emission reduction targets for 2030 in their updated NDCs, leading to additional aggregated GHG emission reductions of about 3.3 GtCO₂eq, compared to those in the previous NDCs. The socio-economic impacts of the updated NDCs are limited in major economies and largely depend on the emission reduction effort included in the NDCs. However, two G20 economies have submitted new targets that will lead to an increase in emissions of about 0.3 GtCO₂eq, compared to their previous NDCs. The updated NDCs of non-G20 economies contain further net reductions. We conclude that countries should strongly increase the ambition levels of their updated NDC submissions to keep the climate goals of the Paris Agreement within reach.

This paper analyses how fiscal stimulus spending in response to the COVID-19 pandemic supports the low-carbon transition. We developed a new framework to categorise rescue and recovery spending measures according to their level of greenness and their type of expected impact on greenhouse gas emissions. This framework allows to better capture how measures’ emission impacts may unfold over time and to identify the share of fiscal spending missing robust conditions or incentives to be considered low carbon. We assess nearly 2500 measures announced by 26 emitters as of May 2021, representing around 67% of global GHG emissions excluding land use in 2019. Our findings show that the largest share (35%) of spending with potential GHG emission implications went to measures that cannot be explicitly coded as high-carbon or low-carbon but substantiate current business-as-usual practice (‘supporting the status quo’). Our assessment reveals the different magnitudes to which the emitters have missed the opportunity for a green recovery. Low-carbon spending is sizeable (22%) across countries. However, almost two-thirds will likely rather unfold its impact over time. This fiscal spending may trigger emissions reductions through enabling or catalytic causal effects over time but will not necessarily lead to direct emission reduction impacts before 2030.

The number and coverage of climate change mitigation policies have increased in the past twenty years, but important policy adoption gaps remain. To analyse sectoral climate policy in the G20 over time (2000–2019), we compiled a dataset of climate change mitigation-relevant policies and identified 50 key policy options that constitute a comprehensive sectoral climate policy package. Approximately half of these policy options are not widely adopted. Adoption is particularly low for policies that aim to: phase out coal and oil and mandate energy reductions in electricity and heat supply; reduce industrial process emissions and incentivise fuel switch in industry; design urban planning strategies for retrofits; and support the use of renewable energy for cooking and heating/cooling purposes in buildings. Policies to remove fossil fuel subsidies and support carbon dioxide removal also need substantial improvement. However, many policy adoption gaps exist as the coverage of at least one policy option could be improved in each sector. Policy adoption gaps leave at least one-tenth of the G20’s emissions completely uncovered. Filling these gaps is fundamental to realize the full mitigation potential of existing policy options and to advance the transition towards global net zero greenhouse gas emissions.

This paper analyses how fiscal stimulus spending in response to the COVID-19 pandemic supports the low-carbon transition. We developed a new framework to categorize rescue and recovery spending measures according to their level of greenness and their type of expected impact on greenhouse gas emissions. This framework allows to better capture how measures’ emission impacts may unfold over time and to identify the share of fiscal spending missing robust conditions or incentives to be considered low-carbon. We assess nearly 2,500 measures announced by 26 emitters as of May 2021, representing around 65% of global GHG emissions in 2018. Our findings show that the largest share (35%) of spending with potential GHG emission implications went to measures that supported the status quo in the respective countries when there were low-carbon alternatives. Our assessment reveals the different magnitudes to which the emitters have missed the opportunity for a green recovery. While low-carbon spending is also significative in size (22%) across countries, almost two-thirds of it can be considered enabling or catalytic in nature and will rather unfold its impact over time. This fiscal spending will trigger transformational change over time but will not necessarily lead to direct emission reduction impacts before 2030.

The 2030 Agenda with its Sustainable Development Goals (SDGs) and the Paris Agreement on climate change were adopted in 2015. Although independently defined, the two agreements are strongly interlinked. We developed a framework that scores the impacts of climate-change actions on all SDG targets based on directionality (i.e., trade-offs or co-benefits) and likelihood of occurrence (i.e., ubiquitous or context-dependent), and categorizes them by dependence on four key context dimensions—geographical, governance, time horizon and limited natural resources. Through an extensive literature review, we found that climate-change mitigation measures directly affect most SDGs and their targets, mostly through co-benefits. Improving energy efficiency, reducing energy-services demand and switching to renewables provide the most co-benefits. In contrast, carbon capture and storage and nuclear energy likely lead to multiple trade-offs. We show how understanding the relevant context dimensions facilitates policy design and policy mixes that enhance co-benefits and minimize trade-offs. Finally, by assessing the prevalence of climate-change mitigation measures in G20 countries, we found that measures with more co-benefits are more frequently adopted. Our study advances the knowledge of climate–SDG interactions, contributing to climate and sustainable development governance research, and facilitating policy design for a joint implementation of the Paris Agreement and the 2030 Agenda.