[PAOCQ] Noelle Selin (MIT)

In October 2013, a global treaty called the Minamata Convention on Mercury was signed, aiming to protect human health and the environment from anthropogenic mercury pollution. As its tenth anniversary of this treaty has recently passed, has it been effective? In this talk, I’ll discuss how scientists and policy-makers are addressing this question. Evaluating and attributing changes in environmental concentrations of mercury is tricky: mercury cycles between the land, atmosphere, and ocean, and current levels are driven not only by contemporary emissions but also by the legacy of historical uses. While uses of mercury in products and processes are being phased out, and emissions controls are being implemented in the US and elsewhere for major sources, the most recent inventories available suggest that emissions increased globally in the 2010s. I will show new results from a combination of data analysis and modeling that suggest that these pessimistic estimates are probably wrong — contemporary anthropogenic emissions have most likely declined. At the same time, the historical legacy of past mercury emissions is still substantial, and the timescales of mercury’s environmental cycling remains uncertain. Based on improved estimates of land-atmosphere interaction, I’ll also show that deforestation could be a substantial (and as yet unregulated) source of anthropogenic mercury in the future. I’ll conclude by discussing lessons learned for evaluating the effectiveness of global environmental treaties in general.