JP

The economics of climate change involves a vast array of uncertainties, complicating both the analysis and development of climate policy. This study presents the results of the first comprehensive study of uncertainty in climate change using multiple integrated assessment models. The study looks at model and parametric uncertainties for population, total factor productivity, and climate sensitivity. It estimates the pdfs of key output variables, including CO2 concentrations, temperature, damages, and the social cost of carbon (SCC). One key finding is that parametric uncertainty is more important than uncertainty in model structure. Our resulting pdfs also provide insights on tail events.

Expanding the use of wind energy for electricity generation forms an integral part of China’s efforts to address degraded air quality and climate change. However, the integration of wind energy into China’s coal-heavy electricity system presents significant challenges owing to wind’s variability and the grid’s system-wide inflexibilities. Here we develop a model to predict how much wind energy can be generated and integrated into China’s electricity mix, and estimate a potential production of 2.6 petawatt-hours (PWh) per year in 2030. Although this represents 26% of total projected electricity demand, it is only 10% of the total estimated physical potential of wind resources in the country. Increasing the operational flexibility of China’s coal fleet would allow wind to deliver nearly three-quarters of China’s target of producing 20% of primary energy from non-fossil sources by 2030.

China, the world’s largest energy consumer and greenhouse gas emitter, has made deploying wind-generated electricity a cornerstone of long-term plans to mitigate climate change, air pollution and other energy-related environmental impacts. Following rapid expansion in recent years, especially in remote, less populous areas, wind has faced significant challenges integrating into the coal-heavy power grid owing to its fundamental operational differences compared to conventional energy sources. We present the first assessment of China’s wind energy potential and its regional distribution that incorporates an operational model of the grid and undertakes systematic exploration of key uncertainties.

Recent policy in China targets an increase in the contribution of natural gas to the nation’s energy supply. Historically, China’s natural gas prices have been highly regulated with a goal to protect consumers. The old pricing regime failed to provide enough incentives for natural gas suppliers, which often resulted in natural gas shortages. A new gas pricing reform was tested in Guangdong and Guangxi provinces in 2011 and was introduced nationwide in 2013. The reform is aimed at creating a more market based pricing mechanism. We show that substantial progress toward better predictability and transparency of prices has been made. China’s prices are now more connected with international fuel oil and liquid petroleum gas prices. The government’s approach for temporary two tier pricing when some volumes are still traded at old prices reduced potential opposition during the new regime implementation. Some limitations created by the natural gas pricing remain: it created biased incentives for producers and favors large natural gas suppliers. The pricing reform at its current stage falls short of establishing a complete market mechanism driven by an interaction of supply and demand of natural gas in China.

This thesis frames design in infrastructure public-private partnerships (P3s) as an exercise in negotiated collaboration. I investigate whether the collaborative design process in P3s can systematically deliver the benefits of innovation in design. The focus is on two aspects of the design process: project co-design, and collaboration mechanism. I find that both aspects enable innovation by driving project actors to learn about the design space and develop a shared understanding of the design problem. Learning through shared understanding not only improves quantifiable payoffs (Objective Value) but also enhances the actors’ psycho-social outcomes (Subjective Value).

Co-design is a process in which project actors simultaneously design technical and contractual features of a project. I developed a tradespace model to visualize and explore value trade-offs from co-design, using a desalination P3 as a project case. Co-design is a fundamental improvement over the traditional sequential design process because it reveals the zone of negotiated agreement, a frontier set of designs available to project actors, that can help them meet their own objectives while balancing value trade-offs. The combination of flexible modular designs and risk sharing revenue guarantee mechanisms emerged as a frontier design choice in the co-design analysis.

Communication and common knowledge are two different collaboration mechanisms that affect the design choices of project actors. A controlled design experiment with 112 experienced designers tested the relative effects of these two mechanisms. The role-playing designers negotiated design decisions for a desalination P3 using the co-design tradespace model. Only the communication mechanism systematically shifted outcomes. To increase the reliability of meeting uncertain water demand, the firm traded away an expected net present value profit share of 24% (p<0.001) on average, subject to the parameter assumptions. The water authority increased contractual payments by an expected net present value share of 6.6% (p<0.001) on average. Final designs in the exercise were on average 97.5% reliable in meeting uncertain water demand. Communication dominated common knowledge as a collaboration mechanism because it enabled participants to learn about the effects of modularity and revenue guarantees on counter-party outcomes and use these design features to negotiate value trade-offs.

Objective Value represents the technical (reliability) and economic (profits, payments) payoffs to project participants. Subjective Value on the other hand captures social psychological outcomes such as the degree of trust and rapport between collaborators and perceived fairness and legitimacy of the process, which are important for the partnering relationship. Participants in the 3 collaboration experiment overwhelmingly reported high Subjective Value scores, which are positively correlated with both their improved understanding of the project’s design objectives (r = 0.37, ρ = 0.41, p<0.001) and their ability to communicate with collaborators to agree on design choices (r = 0.36, ρ = 0.36, p = 0.001).

This work directly addresses the literature on infrastructure public-private partnerships and shows how negotiated collaboration can create objective as well as psychosocial benefits for a stronger partnering relationship. The co-design approach speaks to the literature on systems design to emphasize how a systems view can help designers balance trade-offs. The experimental study is a methodological contribution to both the design and negotiations literature, applying the Subjective Value framework in an integrated design setting.

We collected mercury observations as part of the Nitrogen, Oxidants, Mercury, and Aerosol Distributions, Sources, and Sinks (NOMADSS) aircraft campaign over the southeastern US between 1 June and 15 July 2013. We use the GEOS-Chem chemical transport model to interpret these observations and place new constraints on bromine radical initiated mercury oxidation chemistry in the free troposphere. We find that the model reproduces the observed mean concentration of total atmospheric mercury (THg) (observations: 1.49 ± 0.16"¯ng m−3, model: 1.51 ± 0.08"¯ng m−3), as well as the vertical profile of THg. The majority (65"¯%) of observations of oxidized mercury (Hg(II)) were below the instrument's detection limit (detection limit per flight: 58–228"¯pg m−3), consistent with model-calculated Hg(II) concentrations of 0–196"¯pg m−3. However, for observations above the detection limit we find that modeled Hg(II) concentrations are a factor of 3 too low (observations: 212 ± 112"¯pg m−3, model: 67 ± 44"¯pg m−3). The highest Hg(II) concentrations, 300–680"¯pg m−3, were observed in dry (RH"¯ < "¯35"¯%) and clean air masses during two flights over Texas at 5–7"¯km altitude and off the North Carolina coast at 1–3"¯km. The GEOS-Chem model, back trajectories and observed chemical tracers for these air masses indicate subsidence and transport from the upper and middle troposphere of the subtropical anticyclones, where fast oxidation of elemental mercury (Hg(0)) to Hg(II) and lack of Hg(II) removal lead to efficient accumulation of Hg(II). We hypothesize that the most likely explanation for the model bias is a systematic underestimate of the Hg(0) + Br reaction rate. We find that sensitivity simulations with tripled bromine radical concentrations or a faster oxidation rate constant for Hg(0) + Br, result in 1.5–2 times higher modeled Hg(II) concentrations and improved agreement with the observations. The modeled tropospheric lifetime of Hg(0) against oxidation to Hg(II) decreases from 5"¯months in the base simulation to 2.8–1.2"¯months in our sensitivity simulations. In order to maintain the modeled global burden of THg, we need to increase the in-cloud reduction of Hg(II), thus leading to faster chemical cycling between Hg(0) and Hg(II). Observations and model results for the NOMADSS campaign suggest that the subtropical anticyclones are significant global sources of Hg(II).

Mexico’s climate policy sets ambitious national greenhouse gas (GHG) emission reduction targets—30% versus a business-as-usual baseline by 2020, 50% versus 2000 by 2050. However, these goals are at odds with recent energy and emission trends in the country. Both energy use and GHG emissions in Mexico have grown substantially over the last two decades. We investigate how Mexico might reverse current trends and reach its mitigation targets by exploring results from energy system and economic models involved in the CLIMACAP-LAMP project. To meet Mexico’s emission reduction targets, all modeling groups agree that decarbonization of electricity is needed, along with changes in the transport sector, either to more efficient vehicles or a combination of more efficient vehicles and lower carbon fuels. These measures reduce GHG emissions as well as emissions of other air pollutants. The models find different energy supply pathways, with some solutions based on renewable energy and others relying on biomass or fossil fuels with carbon capture and storage. The economy-wide costs of deep mitigation could range from 2% to 4% of GDP in 2030, and from 7% to 15% of GDP in 2050. Our results suggest that Mexico has some flexibility in designing deep mitigation strategies, and that technological options could allow Mexico to achieve its emission reduction targets, albeit at a cost to the country.

© 2016 Elsevier

We present a spatially and temporally resolved global atmospheric polychlorinated biphenyl (PCB) model, driven by meteorological data, that is skilled at simulating mean atmospheric PCB concentrations and seasonal cycles in the Northern Hemisphere midlatitudes and mean Arctic concentrations. However, the model does not capture the observed Arctic summer maximum in atmospheric PCBs. We use the model to estimate global budgets for seven PCB congeners, and we demonstrate that congeners that deposit more readily show lower potential for long-range transport, consistent with a recently described "differential removal hypothesis" regarding the hemispheric transport of PCBs. Using sensitivity simulations to assess processes within, outside, or transport to the Arctic, we examine the influence of climate- and emissions-driven processes on Arctic concentrations and their effect on improving the simulated Arctic seasonal cycle. We find evidence that processes occurring outside the Arctic have a greater influence on Arctic atmospheric PCB levels than processes that occur within the Arctic. Our simulations suggest that re-emissions from sea ice melting or from the Arctic Ocean during summer would have to be unrealistically high in order to capture observed temporal trends of PCBs in the Arctic atmosphere. We conclude that midlatitude processes are likely to have a greater effect on the Arctic under global change scenarios than re-emissions within the Arctic.

The sustainability of future water resources is of paramount importance and is affected by many factors, including population, wealth and climate. Inherent in current methods to estimate these factors in the future is the uncertainty of their prediction. In this study, we integrate a large ensemble of scenarios—internally consistent across economics, emissions, climate, and population—to develop a risk portfolio of water stress over a large portion of Asia that includes China, India, and Mainland Southeast Asia in a future with unconstrained emissions. We isolate the effects of socioeconomic growth from the effects of climate change in order to identify the primary drivers of stress on water resources. We find that water needs related to socioeconomic changes, which are currently small, are likely to increase considerably in the future, often overshadowing the effect of climate change on levels of water stress. As a result, there is a high risk of severe water stress in densely populated watersheds by 2050, compared to recent history. There is strong evidence to suggest that, in the absence of autonomous adaptation or societal response, a much larger portion of the region’s population will live in water-stressed regions in the near future. Tools and studies such as these can effectively investigate large-scale system sensitivities and can be useful in engaging and informing decision makers.

© 2016 the authors

Globally, 15.5 million km2 of land are currently identified as protected areas, which provide society with many ecosystem services including climate-change mitigation. Combining a global database of protected areas, a reconstruction of global land-use history, and a global biogeochemistry model, we estimate that protected areas currently sequester 0.5 Pg C annually, which is about one fifth of the carbon sequestered by all land ecosystems annually. Using an integrated earth systems model to generate climate and land-use scenarios for the twenty-first century, we project that rapid climate change, similar to high-end projections in IPCC’s Fifth Assessment Report, would cause the annual carbon sequestration rate in protected areas to drop to about 0.3 Pg C by 2100. For the scenario with both rapid climate change and extensive land-use change driven by population and economic pressures, 5.6 million km2 of protected areas would be converted to other uses, and carbon sequestration in the remaining protected areas would drop to near zero by 2100.

This paper develops and applies methods to quantify and monetize projected impacts on terrestrial ecosystem carbon storage and areas burned by wildfires in the contiguous United States under scenarios with and without global greenhouse gas mitigation. The MC1 dynamic global vegetation model is used to develop physical impact projections using three climate models that project a range of future conditions. We also investigate the sensitivity of future climates to different initial conditions of the climate model. Our analysis reveals that mitigation, where global radiative forcing is stabilized at 3.7 W/m2 in 2100, would consistently reduce areas burned from 2001 to 2100 by tens of millions of hectares. Monetized, these impacts are equivalent to potentially avoiding billions of dollars (discounted) in wildfire response costs. Impacts to terrestrial ecosystem carbon storage are less uniform, but changes are on the order of billions of tons over this time period. The equivalent social value of these changes in carbon storage ranges from hundreds of billions to trillions of dollars (discounted). The magnitude of these results highlights their importance when evaluating climate policy options. However, our results also show national outcomes are driven by a few regions and results are not uniform across regions, time periods, or models. Differences in the results based on the modeling approach and across initializing conditions also raise important questions about how variability in projected climates is accounted for, especially when considering impacts where extreme or threshold conditions are important.

© 2015 the authors

Pages

Subscribe to JP