Subnational and non-governmental actors are expected to provide important contributions to broader climate actions. A consistent and accurate quantification of their GHG emissions is an important prerequisite for the success of such efforts. However, emissions embodied in domestic and international supply chains, that can undermine the effectiveness of climate agreements, add challenges to the quantification of emissions originating from the consumption of goods and services produced elsewhere. This study examines emission transfers between the states that have joined the U.S. Climate Alliance (USCA) and others. The results show that states pledging to curb emissions consistent with the Paris Agreement were responsible for approximately 40% of total U.S. territorial GHG emissions. However, when accounting for transferred emissions through international and interstate supply chains of the products they consume, the share of Alliance states increased to 52.4% of the national total GHG emissions. The consumption-based emissions for some Alliance states, such as Massachusetts and New York, could be more than 1.5 times higher than their production-based emissions. 

Ambition of Cities, Regions and Companies 

• As of March 2023, 3,008 cities and 175 subnational states and regions made quantifiable emission pledges covering 26.5% of the total global population. Three-quarters of these subnational governments come from the EU. In Australia, the United Kingdom and Japan, more than 99 percent of the national population is covered by city and regional climate targets. In some countries, cities and regions took the lead in setting net-zero targets before their respective national governments, demonstrating their ability to catalyze more ambitious climate actions.

• Encouragingly, the number of cities and regions with quantifiable emission reduction targets has increased in 2023 compared to 2022, although some of this growth is due to enhanced data collection methods. North American countries, including Canada, the United States, and Mexico, have all seen notable increases in cities and regions recording targets.

• A growing number of cities and regions have pledged net-zero and carbon neutrality. 572 cities and regions are aiming for 100 percent emission reductions, carbon neutrality or net-zero, with one-third aimed at before 2050 and the majority for 2050 or later.

Tracking the progress of climate mitigation for global cities 

• Following a brief slump post the COVID-19 pandemic, subnational climate action is beginning to rebound. As of March 2023, more than 3,000 cities and 175 subnational states and regions, accounting for 26.5% of the global total population, have pledged to reduce their greenhouse gas emissions . This number represents an increase in the number of cities and regions pledging quantifiable emission reduction targets, compared to 2022. 

• While more cities and regions are reporting needed data to evaluate progress towards their own declared mitigation targets, the overall picture of implementation remains weak, with less than 40% of total subnational governments on track. 

• To correct course toward achieving their emission reduction targets with an average remaining time of 17 years, cities and regions need an average annual reduction of nearly 3%. The median reduction is, however, only 1.6% per year. They will need to double efforts to stay on track. 

• To align their targets with 1.5°C-climate scenarios, cities and regions would need to increase the overall ambition of current efforts by 2.5 times. On-track targets are achieving a median annual emission reduction of 3.6% per year, falling short of the required 4% per year needed for 1.5°C goals. Less than one-fifth of cities and regions meet this threshold.  

Greenhouse gas (GHG) emissions in the U.S. peaked and declined in the first decade of the 21st century, largely attributed to the increased use of natural gas and renewable energy replacing coal. However, if and to what extent household consumption also played a role in this trend is still debated. Finding demand-side options is necessary to hedge against the risks of technology solutions failing to materialize. To fill this gap, this study analyzes the change in GHG emissions driven by U.S. household consumption, explores the drivers of this change and the contribution of different income groups. To this end, this study combined the U.S. consumer expenditure survey with an environmentally-extended multi-regional input-output framework to analyze changes in GHG emissions induced by household consumption between 2001 and 2015. This study further analyzed how much population, consumption volume and consumption patterns drove emission changes by quintile income groups. The results show that changes in household consumption contributed approximately one-third of the national emission decline. The decline in GHG emissions from U.S. households was mainly associated with a decrease in the consumption of carbon-intensive products, including gasoline, electricity, and animal-based food products. The top quintile income households were the main contributors to the emission increase before the peak, while the third and fourth income quintiles became emission mitigation leaders after 2010. Carbon inequality increased during the 2001–2006 period, mainly driven by increased wealth and consumption of high-income households, and was relatively stable after the peak. Emissions from certain consumption categories of the top quintile group are significantly higher than the bottom four quintiles with increasing trends, especially leisure-related services and goods, which require more attention in future policymaking for emission reduction.

Phasing out coal-fired power plants is one of the most urgent steps needed to achieve the 1.5- or 2-degree target in the Paris Agreement. Many developed and developing countries have announced their plans to phase out coal from their electricity sectors. Managing the social and economic impacts of this energy transition is key to achieving political and social acceptability and pursuing environmental and social development hand in hand. As one of the leading countries committed to decarbonization in Latin America, Chile has launched a plan to phase out coal by 2050. To analyze the impacts of phasing out coal in Chile on jobs and value added, we combined an Input-Output analysis with ad-hoc labor surveys. We analyzed four contrasting electricity production scenarios that the Chilean government used to frame the policy debate: the current Long-Term Energy Plan (a baseline), and three scenarios that phase out coal-based generation by 2030 or 2050. Our findings show that coal phase-out will contribute to net job creation on the national level, adding 23–26 thousand jobs by 2030. In addition, value-added in the power generation sector will also grow by 1.7 billion dollars above today's levels as a result of the coal phase-out. These overall positive numbers mask a gross job destruction of 4.4 thousand jobs in coal power plants, concentrated in a few communities. In the most affected community, 7.1% of the population works in a coal power plant. Negative impacts in coal-reliant communities require special attention to ensure a just transition towards a clean power generation system. The results of this study highlight the need for strategic policy development that supports a smooth transition to a low-carbon economy, taking into account the associated national and local impacts. Our study also contributes to the literature about the evaluation framework of coal phase-out projects around the world, improving the understanding of their associated impacts beyond the case study country.

Although certain emission standards have been implemented to reduce the air pollution from the steel industry, heavy metal pollution associated with steel production in China has not been well addressed yet. Arsenic is a metalloid element, commonly present in various compounds in many minerals. When it presents in steelworks, it not only affects the quality of steel products, but also causes environmental consequences such as soil degradation, water contamination, air pollution and associated biodiversity loss and public health risks. At present, most of the studies on arsenic were limited to its removal in a certain process, while there has not been a thorough analysis of the flow path of arsenic in steelworks that can facilitate a more efficient removal from its lifecycle. To achieve this, we established a model to depict arsenic flows in steelworks for the first time using adapted substance flow analysis, and further analyzed arsenic flows in the steelworks using a case study in China. Finally, input-output analysis was applied to study the arsenic flow network and explore the reduction potential of arsenic-containing wastes in steelworks. The results show that: 1) the arsenic in the steelworks comes from inputs of iron ore concentrate (55.31 %), coal (12.71 %) and steel scrap (18.67 %), while the outputs were hot rolled coil (65.93 %) and slag (33.03 %). 2) The input, circulation, and final product content of arsenic are 96.120, 32.510, and 66.946 g/t-CS, respectively, and the recycling rate of arsenic was 48.28 %, in the steelworks. 3) The total arsenic discharge from the steelworks is 34.826 g/t-CS. 97.33 % of arsenic is discharged in the form of solid waste. 4) The reduction potential of arsenic in wastes is 14.31 % in the steelworks by adopting low-arsenic raw materials and removing arsenic from processes.

Crude oil pipelines are critical infrastructures for the energy system, but accidents can cause oil spills that pose significant public health and environmental threats to nearby communities. To better guide local environmental agencies in developing varied levels of oil spill emergency plans and to aid health departments in targeted health monitoring, we develop a novel indicator named Annual per capita oil spill exposure (APCOE). This indicator quantifies individualized exposure to oil spills resulting from pipeline accidents over a period of 55 years, at the state level in the United States. The APCOE integrates spill volumes, geographic areas, and populations to assess human exposure to oil spills. Results reveal that the Gulf Coast region has faced disproportionately high crude oil spill exposures compared to the East Coast. Within states, Wyoming, Oklahoma, and Texas maintained the highest APCOE levels from 1968 to 2022. Increased per capita income is associated with reduced APCOE. We also identify high-spill accidents, constituting the top 10% of total accidents, which are responsible for nearly 80% of the spill volumes. Monte Carlo sampling simulations suggest a 50% reduction in these high-spill accidents could decrease nationwide oil spills by 1.6 million barrels, resulting in a nearly 37% reduction in APCOE. Our research has strong policy implications for enhancing pipeline safety regulations and directing preparedness resources to states facing elevated spill exposure risks. 

Global warming increases health risks from heat exposure. Historical evidence suggests disproportionate impacts of heat exposure in different regions across socioeconomic groups in the US. However, little is known about the scale of potential disparities and which populations stand to be most vulnerable under different future climate scenarios. Here, we assess county-level heat exposure, measured by Heat Index (HI) from now to 2100, in the contiguous US using an ensemble of Integrated Assessment Models results that present five future warming and socioeconomic development pathways. Our results reveal stark spatial and sociodemographic disparities in present and future heat stress, mainly for people of color and those aged 65 and older. The large proportion of high-risk populations residing in the Southern US makes this region particularly vulnerable to increases in HI, future climate warming will further enlarge disparities between presently-disadvantaged sociodemographic groups. Our findings underscore the need for considering sociodemographic factors when developing climate adaptation plans and prioritizing policy responses for vulnerable communities.