Summary: ​An interdisciplinary analysis of human interactions with mercury through history that sheds light on efforts to promote and achieve sustainability.

In Mercury Stories, Henrik Selin and Noelle Eckley Selin examine sustainability through analyzing human interactions with mercury over thousands of years. They explore how people have made beneficial use of this volatile element, how they have been harmed by its toxic properties, and how they have tried to protect themselves and the environment from its damaging effects. Taking a systems approach, they develop and apply an analytical framework that can inform other efforts to evaluate and promote sustainability.

After introducing the framework, which uses the lens of a human-technical environmental system and a matrix-based approach to analyze mercury use and exposure, the authors examine five topical mercury systems that each illustrate important issues in mercury science and governance: global cycling of mercury through the atmosphere, land, oceans, and societies; mercury's dangers to human health, including from occupational, medical, and dietary exposure; mercury emissions to the atmosphere from industrial sources; mercury in commercial products and production processes; and mercury use in artisanal and small-scale gold mining. Finally, looking across the five mercury systems, they distill insights for sustainability analysis more broadly, and draw lessons for researchers, decision-makers, and concerned citizens.

Abstract: The Kingdom of Saudi Arabia (KSA) is a water-scarce region with a dry, desert climate, yet flood-producing precipitation events and heat extremes lead to loss of life and damages to local infrastructure, property and economy. Due to its distinctive natural and man-made spatial features (e.g., coastal features, wadis, agricultural areas) studying changes in the mean climate and extreme events requires higher-resolution climate projections than those available from the current generation of Earth System Models.

Here, a high-resolution convection-permitting regional climate model is used to downscale the middle of the 21st century (2041–2050) climate projections of the Community Earth System Model (CESM) under representative concentration pathway (RCP) 8.5 and for a historical time period (2008–2017) focusing on two months (August and November) within KSA’s dry-hot and wet seasons, where extreme events have historically been observed more frequently. Downscaling of climate reanalysis is also performed for the historical time period (2008–2017) to evaluate the downscaling methodology.

An increase in the intensity and frequency of precipitation events is found in August by mid-century, particularly along the mountainous western coast of KSA, suggesting potential for water harvesting. Conversely, the northern flank of the Empty Quarter experiences a noticeable reduction in mean and extreme precipitation rates during the wet season. Increasing August heat index is found to particularly make regional habitability difficult in Jeddah by mid-century.

Abstract: Nitrous oxide (N₂O), like carbon dioxide, is a long-lived greenhouse gas that accumulates in the atmosphere. Over the past 150 years, increasing atmospheric N₂O concentrations have contributed to stratospheric ozone depletion¹ and climate change², with the current rate of increase estimated at 2 per cent per decade. Existing national inventories do not provide a full picture of N₂O emissions, owing to their omission of natural sources and limitations in methodology for attributing anthropogenic sources.

Here we present a global N₂O inventory that incorporates both natural and anthropogenic sources and accounts for the interaction between nitrogen additions and the biochemical processes that control N₂O emissions. We use bottom-up (inventory, statistical extrapolation of flux measurements, process-based land and ocean modelling) and top-down (atmospheric inversion) approaches to provide a comprehensive quantification of global N₂O sources and sinks resulting from 21 natural and human sectors between 1980 and 2016.

Global N₂O emissions were 17.0 (minimum–maximum estimates: 12.2–23.5) teragrams of nitrogen per year (bottom-up) and 16.9 (15.9–17.7) teragrams of nitrogen per year (top-down) between 2007 and 2016. Global human-induced emissions, which are dominated by nitrogen additions to croplands, increased by 30% over the past four decades to 7.3 (4.2–11.4) teragrams of nitrogen per year. This increase was mainly responsible for the growth in the atmospheric burden.

Our findings point to growing N₂O emissions in emerging economies—particularly Brazil, China and India. Analysis of process-based model estimates reveals an emerging N₂O–climate feedback resulting from interactions between nitrogen additions and climate change. The recent growth in N₂O emissions exceeds some of the highest projected emission scenarios, underscoring the urgency to mitigate N₂O emissions.