The latest round of United Nations climate talks in Poland in December 2019 sought to get the world on track to meet the Paris Agreement’s long-term goal of keeping global warming well below two degrees Celsius (2ºC). Toward that end, negotiators from the Agreement’s nearly 200 signatory nations were asked to report on their country or region’s progress toward fulfilling its Paris pledge, or Nationally Determined Contributions (NDC). But just how accurate were those progress reports? That depends on the integrity of the underlying greenhouse gas emissions data that each country used to assess its performance toward meeting the emissions reduction targets spelled out in its NDC. The measurement, reporting and verification (MRV) of a country’s overall emissions and emissions reductions involves culling and validating emissions data from multiple sources, including firms—industrial, nonprofit and government entities—in different economic sectors. Building reliable firm-based systems for emissions MRV is no easy task, especially in developing countries where misreporting of environmental data can be significant, but a new MIT-led study in Nature Climate Change identifies challenges and opportunities to achieve that goal.

Co-authored by researchers at MIT, Tsinghua University and Wuhan University, the study focuses on China, the world’s largest carbon dioxide (CO₂) emitter. China’s climate-change mitigation strategy centers on a national emissions trading system (ETS) whose success depends upon accurate emissions reporting at the firm level. Using data obtained from two of China’s pilot regional ETS programs, one in Beijing, a highly developed major city, the other in Hubei, a less developed province, the researchers compared firms’ self-reported CO₂ emissions numbers with those verified by independent third parties. The average discrepancy in these numbers decreased significantly in Beijing, going from 17 percent in 2012 to 4 percent in 2014 and 2015 for approximately 400 firms. In Hubei, which launched its system one year later, the number of discrepancies started lower and showed a statistically-insignificant decrease (from 6% in 2014 to 5% in 2015).

The study emphasized that building effective MRV systems at firms in China and other developing countries takes time, resources and attention to detail. Among its recommendations to increase reporting accuracy and prevent manipulation or collusion is to provide external funding from governments or multilateral entities, at least in early years, to pay the independent verifiers. If firms pay for verification, government back-checks are essential to ensure reporting integrity. The study also maintains that strong law enforcement will be necessary to punish any detected incidents of collusion between verifiers and firms.

Mercury is a global pollutant released into the biosphere by varied human activities including coal combustion, mining, artisanal gold mining, cement production, and chemical production. Once released to air, land and water, the addition of carbon atoms to mercury by bacteria results in the production of methylmercury, the toxic form that bioaccumulates in aquatic and terrestrial food chains resulting in elevated exposure to humans and wildlife. Global recognition of the mercury contamination problem has resulted in the Minamata Convention on Mercury, which came into force in 2017. The treaty aims to protect human health and the environment from human-generated releases of mercury curtailing its movement and transformations in the biosphere. Coincident with the treaty's coming into force, the 13th International Conference of Mercury as a Global Pollutant (ICMGP-13) was held in Providence, Rhode Island USA. At ICMGP-13, cutting edge research was summarized and presented to address questions relating to global and regional sources and cycling of mercury, how that mercury is methylated, the effects of mercury exposure on humans and wildlife, and the science needed for successful implementation of the Minamata Convention. Human activities have the potential to enhance mercury methylation by remobilizing previously released mercury, and increasing methylation efficiency. This synthesis concluded that many of the most important factors influencing the fate and effects of mercury and its more toxic form, methylmercury, stem from environmental changes that are much broader in scope than mercury releases alone. Alterations of mercury cycling, methylmercury bioavailability and trophic transfer due to climate and land use changes remain critical uncertainties in effective implementation of the Minamata Convention. In the face of these uncertainties, important policy and management actions are needed over the short-term to support the control of mercury releases to land, water and air. These include adequate monitoring and communication on risk from exposure to various forms of inorganic mercury as well as methylmercury from fish and rice consumption. Successful management of global and local mercury pollution will require integration of mercury research and policy in a changing world.