PAOC Spotlights

Assessing changes and risks to the oceans, land and atmosphere

Wed October 23rd, 2019
Mark Dwortzan | MIT Joint Program on the Science and Policy of Global Change

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Read this at MIT Joint Program on the Science and Policy of Global Change

Thirteen researchers and affiliates of the MIT Joint Program on the Science and Policy of Global Change plan to deliver or contribute to nine oral and poster presentations at the American Geophysical Union (AGU) 2019 Fall Meeting on December 9-13 at the Moscone Center in San Francisco. The largest Earth and space science conference in the world, the AGU Fall Meeting provides a platform for new research and emerging trends in more than 25 disciplines, including global environmental change.

Joint Program studies featured in this year’s talks and posters showcase in-depth studies of Earth systems, managed resource systems, modeling tools and techniques, and policy scenarios. Topics include detecting ozone-depleting substances; evaluating changes in the oceans and global nutrient and carbon cycles; assessing the potential impact of global change on wind and solar power production; evaluating modeling uncertainties under emissions scenarios consistent with long-term goals of the Paris Agreement, and estimating the economic benefits of air quality policies.

All presenters identified below as co-authors of talks or posters are current or recent members or affiliates of the Joint Program; additional co-authors of these talks and posters, and more complete descriptions of their presentations, can be found by accessing the links provided.

Earth Systems

Since 2012 increased emissions of CFC-11 have been detected from China (Rigby et al., Nature, 2019), violating restrictions by the Montreal Protocol to save the stratospheric ozone layer. These new emissions are assumed to arise mainly from losses during production of foam. In fact, independent studies have detected that several recently produced foams from China contain CFC-11, the release of which threatens to delay the recovery of the stratospheric ozone layer by several years. A poster co-authored by Co-Director Ronald Prinn summarizes and updates the results of Rigby et al. (2019), discusses potential CFC-11 production pathways, and examines the recent behavior of CFC-12, which, while co-produced with CFC-11, has not been observed as a source of emissions increases in the stratosphere.

Understanding the future availability of nitrogen and its effect on carbon sequestration in Northern Eurasia, which plays a significant role in the Earth’s carbon cycle, is key to developing effective regional and sub-regional strategies for addressing global change (climate and land-use change) impacts. A poster co-authored by Joint Program-affiliated researchers David Kicklighter and Jerry Melillo, former Principal Research Scientist Erwan Monier and Research Scientist Andrei Sokolov explores how changes in nitrogen availability associated with permafrost degradation, atmospheric nitrogen deposition, and the abandonment of agricultural land to forest regrowth influence carbon storage in the region’s forest vegetation over the 21st century. The study provides new insight into the role of human activity on future nitrogen availability and its influence on carbon sequestration in Northern Eurasia forests, and further highlights the importance of accounting for carbon-nitrogen interactions when assessing the regional and sub-regional impacts of climate and land-use change policies.

Iron is the limiting factor for biological production over a large fraction of the surface ocean because ferric iron is rapidly scavenged or precipitated. Standing stocks of dissolved iron are maintained by association with biogenic organic ligands which, in turn, are produced by microbes. A poster co-authored by Senior Research Scientist Stephanie Dutkiewicz hypothesizes a positive feedback between iron cycling, microbial activity and ligand abundance where external iron input fuels microbial production, which creates organic ligands that can then stabilize more dissolved iron, drawing down macronutrient concentrations, and so on. This reinforcing cycle matches the availability of iron and other nutrients at the global scale, maximizing oceanic productivity and carbon storage, and driving the ocean to global-scale nutrient co-limitation.

Managed systems: renewable energy

Any global, low-carbon development target will require a large penetration of renewable energy-generation technologies, and any such landscape will place a high premium on identifying potential predictability and trends of relevant environmental conditions—which are all determined by weather and climate. A talk by Deputy Director C. Adam Schlosser will explore the potential impact of global change on wind and solar power production throughout this century. The presentation will consider multiple MIT Integrated Global System Modeling (IGSM) framework scenarios whose projections of global climate change assume Paris Agreement pledges as well as stringent 2˚C and 1.5˚C climate-warming mitigation targets. Schlosser will highlight salient patterns of risk against the current landscape of wind and solar deployments as well as projections of deployment that would meet the increased generation capacities required under aggressive, low-carbon global targets.

Modeling tools and techniques

Coupled human-Earth system models have been developed to explore the interactions and feedbacks between human systems and Earth systems, but there are major uncertainties in both systems and how they evolve over time. A talk by Research Scientist Jennifer Morris will take a probabilistic ensemble approach to representing both socioeconomic and climate uncertainty, which yields probability distributions of human and Earth system outcomes. Drawing on results of simulations using the MIT IGSM framework, this work provides insight into the range of uncertainty in human system outcomes, the contribution of human system uncertainty to uncertainty in climate outcomes, and key components and parameter assumptions within human system models.

Climate impacts of a given policy depend not only on assumptions about climate system parameters defining the response to radiative forcing, but also on assumptions about economic development in the absence of any policy. A poster co-authored by research scientists Andrei Sokolov and Jennifer Morris and Deputy Director Sergey Paltsev will estimate uncertainty in the climate impact of the Paris agreement using the MIT IGSM framework. The results show that the range of the decrease in surface air temperature due to implementation of the Paris Agreement associated with uncertainty in climate system properties is slightly narrower than the range associated with uncertainty in economic development.

There is great uncertainty about the emissions pathway the world will be on over the next century. Even for a given emissions trajectory, there are many possibilities as to how those emissions might be distributed across sectors and regions, and how energy systems, technologies and the economy might evolve. A poster co-authored by research scientists Jennifer Morris and Andrei Sokolov, Deputy Director Sergey Paltsev and Co-Director John Reilly explores those possibilities using a probabilistic ensemble approach applied to the MIT IGSM framework. Considering a range of emissions pathways, including those resulting from business-as-usual, policy continuing at 2030 commitment levels into the future, flat emissions, 2°C stabilization and 1.5°C stabilization, the IGSM simulations yield insights into how we might protect Earth’s climate between now and 2100, including the conditions under which better climate outcomes are more likely.

The state and amount of water in the soil is a critical determinant in many complex processes of the water, carbon and energy cycles in the Earth system. Model-simulated soil moisture has been widely employed to understand these processes attributed to its large spatial and long temporal coverage at any desirable location and time. However, challenges remain for validating and improving these models to faithfully represent soil moisture, particularly on the large scale. A poster co-authored by Principal Research Scientist Xiang Gao and Deputy Director C. Adam Schlosser shows that the percentage of expected soil moisture variance explained by uncertainty in four parameters and their interactions varies considerably by seasons and sites. Nevertheless, across all the sites and seasons, the majority of the variance is described by uncertainty in porosity and shape-parameter (excluding their interaction effects). The results from this study could spur further research leading to improved modeling of soil moisture on a global scale.

Policy Scenarios

In 2018, the US Environmental Protection Agency (EPA) proposed changes to the Mercury and Air Toxics Standards that would make the rule vulnerable to legal challenge and rollbacks. The EPA revised its estimate of the monetized benefits of the rule to 4-6 million, in contrast to its previous estimates of tens of billions. At debate is how benefits (including co-benefits, and unquantified benefits) are weighed against costs and what counts as a benefit of policy. A poster co-authored by former research assistant Amanda Giang and faculty affiliate Noelle Selin summarizes recent research on the benefits of mercury policy, providing insight into widely differing estimates. The co-authors argue that the EPA’s revised estimates do not reflect scientific developments since the MATS rule was first proposed in 2011, and offer perspectives on how up-to-date research in environmental, health and social sciences could be better reflected in regulatory cost-benefit practices.

Story Image: AGU Fall Meeting Poster Hall (Source: AGU)