Summary: Fulfilling the ultimate goal of the Paris Agreement on climate change—keeping global warming well below two degrees Celsius, if not 1.5°C—will be impossible without dramatic action from the world’s largest emitter of greenhouse gases, China. Toward that end, China began developing in 2017 an emissions trading scheme (ETS), a national carbon dioxide market designed to enable the country to meet its initial Paris pledge with the greatest efficiency and at the lowest possible cost. China’s pledge, or Nationally Determined Contribution (NDC), is to reduce its CO₂ intensity of GDP (emissions produced per unit of economic activity) by 60–65% in 2030 relative to 2005, and to peak CO₂ emissions around 2030.

When it’s rolled out, China’s carbon market will initially cover the electric power sector (which currently produces more than three billion tons of CO₂) and likely set CO₂ emissions intensity targets (e.g. grams of CO₂ per kilowatt hour) to ensure that its short-term NDC is fulfilled. But to help the world achieve the long-term 2°C and 1.5°C Paris goals, China will need to continually decrease these targets over the course of the century.

A new Joint Program-led study of China’s long-term power generation mix under the nation’s ETS projects that until 2065, renewable energy sources will likely expand to meet these targets; after that, carbon capture and storage (CCS) could be deployed to meet the more stringent targets that follow. 

Summary: Improved air quality can be a major bonus of climate mitigation policies aimed at reducing greenhouse gas emissions. By cutting air pollution levels in the country where emissions are produced, such policies can avoid significant numbers of premature deaths. But other nations downwind from the host country may also benefit. This study hows that if the world’s top emitter of greenhouse gas emissions, China, fulfills its climate pledge to peak carbon dioxide emissions in 2030, the positive effects would extend all the way to the United States, where improved air quality would result in nearly 2,000 fewer premature deaths.       

The study estimates China’s climate policy air quality and health co-benefits resulting from reduced atmospheric concentrations of ozone, as well as co-benefits from reduced ozone and particulate air pollution (PM_2.5) in three downwind and populous countries: South Korea, Japan and the U.S. As ozone and PM_2.5  give a well-rounded picture of air quality and can be transported over long distances, accounting for both pollutants enables a more accurate projection of associated health co-benefits in the country of origin and those downwind.  

Human activities have released large quantities of neutral persistent organic pollutants (POPs) that may be biomagnified in food webs and pose health risks to wildlife, particularly top predators. Here we develop a global 3‐D ocean simulation for four polychlorinated biphenyls (PCBs) spanning a range of molecular weights and volatilities to better understand effects of climate‐driven changes in ocean biogeochemistry on the lifetime and distribution of POPs. Observations are most abundant in the Arctic Ocean. There, model results reproduce spatial patterns and magnitudes of measured PCB concentrations. Sorption of PCBs to suspended particles and subsequent burial in benthic marine sediment is the dominant oceanic loss process globally. Results suggest benthic sediment burial has removed 75% of cumulative PCB releases since the onset of production in 1930. Wind speed, light penetration, and ocean circulation exert a stronger and more variable influence on volatile PCB congeners with lower particle affinity such as chlorinated biphenyl‐28 and chlorinated biphenyl‐101. In the Arctic Ocean between 1992 and 2015, modeled evasion (losses) of the more volatile PCB congeners from the surface ocean increased due to declines in sea ice and changes in ocean circulation. By contrast, net deposition increased slightly for higher molecular weight congeners with stronger partitioning to particles. Our results suggest future climate changes will have the greatest impacts on the chemical lifetimes and distributions of volatile POPs with lower molecular weights.