Current State of Climate Change: Atmosphere, Forests, Energy, Transportation, and Policy

Following the COP21 meeting in Paris, an international consensus emerged

Kristofer
Covey
Kroon 319
9:00am
Following the COP21 meeting in Paris, an international consensus emerged: the protection and expansion of forests is necessary to limit global warming to less than 2'C. The fact that trees emit methane (CH4), however, remains underappreciated, despite the potential for these emissions to offset the climate benefits of forest CO2 sequestration. We assessed the magnitude of microbial-based CH4 production in the trunks of living trees in the eastern U.S., and estimated the extent to which CH4 emissions reduce this carbon sink. We determined CH4 concentrations in the trunks of >3,000 trees across 23 sites, finding CH4 concentrations as high as 67.4% (i.e. ~375,000-times atmospheric). Diffusion modeling suggests that the trunks of mature broadleaved trees, in particular, are a net source of CH4 to the atmosphere, a result confirmed using chamber methods to directly measure CH4 efflux through the bark of living and newly-felled trees. Using geospatial analysis and the 100-year global warming potential (GWP) for CH4 vs. CO2, we estimate that this CH4-production pathway reduces the climate mitigation value of the eastern forest by 7%, with the benefits of some forests reduced by as much as 25%. On shorter timescales (e.g. 20 yr), the GWP of CH4 is higher and so modeled effects are greater, offsetting CO2 sequestration benefits by 20% overall and for some forest stands by >65%. Our findings highlight the need to consider CH4 fluxes if the mitigation potential of forests is to be accurately determined and effectively employed to set allowable emissions targets.

Increasing public transit ridership

Michael
Cox
Kroon 319
9:00am
Increasing public transit ridership can minimize transportation-related greenhouse gas (GHG) emissions in areas with high automobile usage. However, there is limited literature comparing the life cycle impacts of transit alternatives, particularly low-cost options like bus rapid transit (BRT). New York City has identified a new transit corridor to be implemented in Staten Island, New York. The city will be constructing a bus rapid transit line or a light rail transit (LRT) line. This study uses life cycle assessment methodologies to quantify the expected GHG emissions associated with the construction and use of these transit alternatives. An assessment was performed to determine GHG emissions associated with the construction and operation of both alternatives. The use-phase was then analyzed according to the GHG emissions per passenger mile travelled, based on scenarios depicting ridership. The BRT alternative resulted in higher overall GHG emissions associated with the construction and operation of its components. Despite having higher projected ridership, the BRT system still had higher GHG emissions per passenger mile travelled. For both the BRT and LRT alternatives, the operational phase of both the BRT and LRT lines would cause the majority of lifetime GHG emissions. The results of this study can help compare the expected GHG impacts of bus rapid transit and light rail within the same transit corridor.

After President Obama's commitment to reduce carbon emission

Cristina
Madrid-Lopez
Kroon 319
9:00am
After President Obama's commitment to reduce carbon emission in the oil and gas sector by 2025 the victory of Donald Trump and OPEP's plans of curbing extraction seem to predict a new golden period for shale gas development. Despite the significant efforts that the scientific community has devoted to the impacts of shale gas production and use over the environment, the societies and the economies, we do not seem able to reach a consensus. Indeed analyses coming from different disciplines seem to reach very different conclusions about what the future of the industry should be. The systems perspective used in Industrial Ecology seems to be a good tool to frame analyses in which different narratives converge. We can analyze the trade-offs of different scenarios in the production and use of shale gas and provide valuable information of policy makers about them. In my work I do a Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism of the shale gas sector in Pennsylvania. In this presentation I describe its environmental feasibility, its social desirability and its economic viability for the current situation and for two different scenarios. First I test President Obama's commitment to cut methane emissions from the oil and gas sector to 45% below 2012 levels. Second, I test President Trump's plan to 'unleash' U.S. shale gas reserves.

Global environmental issues such as decreasing resource endowments

Benjamin
Sprecher
Kroon 319
9:00am
Global environmental issues such as decreasing resource endowments and climate change threaten to disrupt our economic systems. As such, system resilience is an integral aspect of sustainable development, to the extent that one can no longer be understood without the other. In this study, we focus on developing quantitative metrics for flexibility, a key aspect of resilience. Where resilience is understood as the capacity of a system to maintain its functionality under disruption (e.g. maintaining services during a drought), flexibility is the ability of a system to meet that criteria through reconfiguring its structure (e.g., through technology substitution). We approach system flexibility as the number of possible technology combinations when the system is disrupted. This reflects the number of substitution options a system has. Under similar disruption levels, a system with more substitution options can be considered to be more flexible and thus more resilient. We then apply linear programming to calculate possible technology configurations under increasingly stringent resource and emission constraints (e.g. water use, GHG emissions). We test this approach on two case studies pertaining to different scales: electricity generation in the 43 largest world economies, and electricity generation from 118 coal-fired plants in the Hebei Province in China. For the case of country-level electricity generation, we observed striking differences in flexibility between countries. This is mostly related to the share of renewable energies, but also due to varying production costs and other technological aspects (e.g. energy efficiency). Significant differences in flexibility were also found in the case of coal-fired plants. Overall, the results show that the developed flexibility metrics are valuable to assess the resilience of the studied systems in the face of plausible environmental constraints, for instance the Paris Agreement Intended Nationally Determined Contributions (INDCs) to GHG emission reduction and local air pollution mitigation actions.

In this study, a set of three-dimensional simulations

Shu
Tao
Kroon 319
9:00am
In this study, a set of three-dimensional simulations of stable atmospheric boundary layer was performed using Large Eddy Simulation model. By examining the results of the simulations, it is determined how large a measuring domain must be to estimate spatial covariances (fluxes) with a specified statistical significance in Large Eddy Simulation. For a given measuring domain size A there is an error between the true flux and the spatial mean flux of the given domain. This error decreases tending to zero as measuring domain size A _'. The minimum required domain for calculating eddy fluxes at 95% accuracy was discussed. The results indicated that at lower boundary layer(z/zi=0.125), the fluxes converge quickly to the true flux as A increases. As height increases, the domain required for calculating fluxes with acceptable accuracy increases because the instability of eddy fluxes grows along with increasing height. At same height, latent heat flux usually requires a larger measuring domain to obtain a 95% accuracy than sensible heat flux does. Increasing geophysical wind resulted in decreasing required domain area in lower boundary layer.

Anticipating enforcement difficulties in international climate initiatives

Zachary
Turk
Kroon 319
9:00am
Anticipating enforcement difficulties in international climate initiatives when signees fail to meet obligations, I ask whether environmental improvements abroad can originate from domestic policy. My thesis focuses on domestic incentives and resulting shifts in demand for clean versus dirty inputs to production. I develop a theoretical model of demand for production inputs that differ by polluting potential. The model predicts that policies in specific form can increase consumption of polluting inputs in heavily regulated spheres compared to unregulated ones, by extension altering the trade balance of clean versus dirty inputs. This effectively export cleanliness abroad through changes in relative prices of clean and dirty substitutes to production. Using a very large data set and advanced econometric techniques, I search for the anticipated effect in recent years in the U.S. energy sector when the required mechanisms were present. Important to targeting policies at specific climate initiative defectors, the factors defining the geographic limitation of such policies are also explored.