Regional Analysis

Modeling regional transportation demand in China and the impacts of a national carbon constraint

Climate and energy policy in China will have important and uneven impacts on the country’s regionally heterogeneous transport system. In order to simulate these impacts, transport sector detail is added to a multi-sector, static, global computable general equilibrium (CGE) model which resolves China’s provinces as distinct regions. This framework is used to perform an analysis of national-level greenhouse gas (GHG) policies. Freight, commercial passenger and household (private vehicle) transport are separately represented, with the former two categories further disaggregated into road and non-road modes. The preparation of model inputs is described, including assembly of a provincial transport data set from publicly-available statistics. Two policies are analyzed: the first represents China’s target of a 17% reduction in GHG emissions intensity of GDP during the Twelfth Five Year Plan (12FYP), and the second China’s Copenhagen target of a 40–45% reduction in the same metric during the period 2005–2020.

We find significant heterogeneity in regional transport impacts. We find that both freight and passenger transportation in some of the poorest provinces are most adversely affected, as their energy-intensive resource and industrial sectors offer many of the least-cost abatement opportunities, and the transformation of their energy systems strongly affects transport demand. At the national level, we find that road freight is the transport sector affected most by policy, likely due to its high energy intensity and limited low-cost opportunities for improving efficiency.

The type and degree of regional disparity in impacts is relevant to central and provincial government decisions which set and allocate climate, energy and transport policy targets. We describe how this research establishes a basis for regional CGE analysis of the economic, energy and environmental impacts of transport-focused policies including vehicle ownership restrictions, taxation of driving activity or fuels, and the supply of public transit.

Modeling Regional Carbon Dioxide Flux over California using the WRF-ACASA Coupled Model

Many processes and interactions in the atmosphere and the biosphere influence the rate of carbon dioxide exchange between these two systems. However, it is difficult to estimate the carbon dioxide flux over regions with diverse ecosystems and complex terrains, such as California. Traditional carbon dioxide measurements are sparse and limited to specific ecosystems. Therefore, accurately estimating carbon dioxide flux on a regional scale remains a major challenge.

In this study, we couple the Weather Research and Forecasting Model (WRF) with the Advanced Canopy-Atmosphere-Soil Algorithm (ACASA), a high complexity land surface model. Although WRF is a state-of-the-art regional atmospheric model with high spatial and temporal resolutions, the land surface schemes available in WRF lack the capability to simulate carbon dioxide. ACASA is a complex multilayer land surface model with interactive canopy physiology and full surface hydrological processes. It allows microenvironmental variables such as air and surface temperatures, wind speed, humidity, and carbon dioxide concentration to vary vertically. Carbon dioxide, sensible heat, water vapor, and momentum fluxes between the atmosphere and land surface are estimated in the ACASA model through turbulence equations with a third order closure scheme. It therefore permits counter-gradient transports that low-order turbulence closure models are unable to simulate.

A new CO₂ tracer module is introduced into the model framework to allow the atmospheric carbon dioxide concentration to vary according to terrestrial responses. In addition to the carbon dioxide simulation, the coupled WRF-ACASA model is also used to investigate the interactions of neighboring ecosystems in their response to atmospheric carbon dioxide concentration. The model simulations with and without the CO₂ tracer for WRF-ACASA are compared with surface observations from the AmeriFlux network.

Non-Nuclear, Low-Carbon, or Both? The Case of Taiwan

The Fukushima nuclear accident in Japan has renewed debates on the safety of nuclear power, possibly hurting the role of nuclear power in efforts to limit CO2 emissions. I develop a dynamic economy-wide model of Taiwan with a detailed set of technology options in the power sector to examine the implications of adopting different nuclear power policies on CO2 emissions and the economy. Absent a carbon mitigation target, limiting nuclear power has a small economic cost for Taiwan, but CO2 emissions may increase by more than 3.5% by 2035 when nuclear is replaced by fossil-based generation. With a low-carbon target of a 50% reduction from year 2000 levels by 2050, if the nuclear option and carbon sequestration are not viable, gas-fired power would provide almost 90% of electricity output due to the limited renewable resources. In particular, wind power would account for 1.6% to 4.9% of that output, depending on how it relies on other back-up capacities. With both non-nuclear and low-carbon policies, deploying carbon sequestration on fossil-based generation can significantly reduce the negative GDP impact on the economy. Lastly, lowering carbon mitigation costs further is possible with expanded nuclear capacity.

Nonlinear Effects of Coexisting Surface and Atmospheric Forcing of Anthropogenic Absorbing Aerosols: Impact on the South Asian Monsoon Onset

The direct radiative effect of absorbing aerosols consists of absorption-induced atmospheric heating together with scattering- and absorption-induced surface cooling. It is thus important to understand whether some of the reported climate impacts of anthropogenic absorbing aerosols are mainly due to the coexistence of these two opposite effects and to what extent the nonlinearity raised from such coexistence would become a critical factor. To answer these questions specifically regarding the South Asia summer monsoon with focus on aerosol-induced changes in monsoon onset, a set of century-long simulations using the Community Earth System Model, version 1.0.3 (CESM 1.0.3), of NCAR with fully coupled atmosphere and ocean components was conducted. Prescribed direct heating to the atmosphere and cooling to the surface were applied in the simulations over the Indian subcontinent, either alone or combined, during the aerosol-laden months of May and June. Over many places in the Indian subcontinent, the nonlinear effect dominates in the changes of subcloud layer moist static energy, precipitation, and monsoon onset. The surface cooling effect of aerosols appears to shift anomalous precipitative cooling away from the aerosol-forcing region and hence turn the negative feedback to aerosol-induced atmospheric heating into a positive feedback on the monsoon circulation through latent heat release over the Himalayan foothills. Moisture processes form the critical chain mediating local aerosol direct effects and onset changes in the monsoon system.

Nuclear exit, the US energy mix, and carbon dioxide emissions

If the United States were to adopt a policy to phase out nuclear generation, as has happened recently in other developed countries, what would the environmental and energy-mix implications be? Based on alternative scenarios of nuclear exit that consider the influence of potential policies to limit greenhouse gas emissions, a model of the US and global economy indicates that, under current policy, a US nuclear exit would increase carbon dioxide emissions, and likely raise electricity prices and reduce gross domestic product by relatively small amounts. Those economic impacts would be increased by additional measures to limit carbon dioxide emissions.

Passenger Transport in China Under Climate Constraints: General Equilibrium Analysis, Uncertainty, and Policy

Vehicle sales and road travel volume in China have grown rapidly in recent years, and with them energy demand, greenhouse gas emissions and local air pollution. Aviation and rail travel have also grown, while ceding a large share to private vehicles. What path will household transport demand in China take in the future? How might it interact with policies which limit greenhouse gases, and what are the implications for energy use, the environment and the economy? To contribute policy insights and a foundation for future study in this area, I undertake a new calibration of the Chinese household transport sector in the MIT Emissions Prediction & Policy Analysis (EPPA) computable general equilibrium (CGE) model, implementing income elasticities of demand for vehicle travel and vehicle stock growth based on historical data. To bracket uncertainty in the literature, I impose three scenarios of future growth in demand for purchased (air, rail and marine) and vehicle modes. These are explored under a no-policy baseline, a climate-stabilization policy, and with a policy that extends the emissions-intensity goal of China’s Twelfth Five-Year Plan—both policies are modelled as caps creating prices on carbon. Examining the results, I find that trends in growth are only modesty affected by policy continuing present energy-intensity goals, with small decreases in travel activity and energy intensity of vehicles combining for a reduction in refined oil use; such a policy has modest cost and affects household transport less than other sectors. In contrast, my results show that a stringent emissions cap has large impacts on vehicle efficiency, limits vehicle ownership and general travel activity levels. Compared to the no-policy baseline, a smaller vehicle fleet (250 million total, or 200 per 1000 capita). Sixteen percent of the fleet is new energy vehicles (plug-in hybrid-electrics), while total refined oil use increases by 2050 to nearly three times its 2010 level. However, these effects come with a reduction in total primary energy as the policy is introduced, and large costs economy-wide. Chinese national and municipal policies include objectives of promoting vehicle ownership and mobility on the one hand, and of reducing dependence on carbon-intensive refined oil on the other. My findings illustrate that 3 these goals are at odds, and offer inputs to policy design related to vehicle sales, public transit, congestion, pollution and energy security.

Policy: Carbon emissions in China's trade

China is a global carbon crossroads. Wealthy eastern coastal provinces import carbon-intensive goods from the country's less affluent centre and west. But China also exports carbon to consumers abroad, particularly in Europe, Japan and the United States. A key question is whether and how policy can hold consumers responsible for the direct and indirect emissions in the goods they buy. Writing in the Proceedings of the National Academy of Sciences of the USA, Feng and colleagues1 illustrate the magnitude of this challenge by linking over half of China's domestic emissions to consumption in the wealthy parts of China and overseas.

Possible climate change over Northern Eurasia

In this study, we investigate possible climate change over Northern Eurasia and its impact on extreme events and permafrost degradation. Northern Eurasia is a major player in the global carbon budget because of boreal forests and peatlands. Circumpolar boreal forests alone contain more than five times the amount of carbon of temperate forests and almost double the amount of carbon of the world's tropical forests. Furthermore, severe permafrost degradation associated with climate change could result in peatlands releasing large amounts of carbon dioxide and methane. Meanwhile, changes in the frequency and magnitude of extreme events, such as extreme precipitation, heat waves or frost days are likely to have substantial impacts on Northern Eurasia ecosystems. For this reason, it is very important to quantify the possible climate change over Northern Eurasia under different emissions scenarios, while accounting for the uncertainty in the climate response and changes in extreme events.

Possible future changes in extreme events over Northern Eurasia

In this study, we investigate possible future climate change over Northern Eurasia and its impact on extreme events. Northern Eurasia is a major player in the global carbon budget because of boreal forests and peatlands. Circumpolar boreal forests alone contain more than ï¬ve times the amount of carbon of temperate forests and almost double the amount of carbon of the world’s tropical forests. Furthermore, severe permafrost degradation associated with climate change could result in peatlands releasing large amounts of carbon dioxide and methane. Meanwhile, changes in the frequency and magnitude of extreme events, such as extreme precipitation, heat waves or frost days are likely to have substantial impacts on Northern Eurasia ecosystems. For this reason, it is very important to quantify the possible climate change over Northern Eurasia under different emissions scenarios, while accounting for the uncertainty in the climate response and changes in extreme events.

For several decades, the Massachusetts Institute of Technology (MIT) Joint Program on the Science and Policy of Global Change has been investigating uncertainty in climate change using the MIT Integrated Global System Model (IGSM) framework, an integrated assessment model that couples an earth system model of intermediate complexity (with a 2D zonal-mean atmosphere) to a human activity model. In this study, regional change is investigated using the MIT IGSM-CAM framework that links the IGSM to the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM). New modules were developed and implemented in CAM to allow climate parameters to be changed to match those of the IGSM.

The simulations presented in this paper were carried out for two emission scenarios, a “business as usual” scenario and a 660 ppm of CO2-equivalent stabilization, which are similar to, respectively, the Representative Concentration Pathways RCP8.5 and RCP4.5 scenarios. Values of climate sensitivity and net aerosol forcing used in the simulations within the IGSM-CAM framework provide a good approximation for the median, and the lower and upper bound of 90% probability distribution of 21st century climate change. Five member ensembles were carried out for each choice of parameters using different initial conditions. With these simulations, we investigate the role of emissions scenarios (climate policies), the global climate response (climate sensitivity) and natural variability (initial conditions) on the uncertainty in future climate changes over Northern Eurasia. A particular emphasis is made on future changes in extreme events, including frost days, extreme summer temperature and extreme summer and winter precipitation.

Potential influence of climate-induced vegetation shifts on future land use and associated land carbon fluxes in Northern Eurasia

Climate change will alter ecosystem metabolism and may lead to a redistribution of vegetation and changes in fire regimes in Northern Eurasia over the 21st century. Land management decisions will interact with these climate-driven changes to reshape the region’s landscape. Here we present an assessment of the potential consequences of climate change on land use and associated land carbon sink activity for Northern Eurasia in the context of climate-induced vegetation shifts. Under a ‘business-as-usual’ scenario, climate-induced vegetation shifts allow expansion of areas devoted to food crop production (15%) and pastures (39%) over the 21st century. Under a climate stabilization scenario, climate-induced vegetation shifts permit expansion of areas devoted to cellulosic biofuel production (25%) and pastures (21%), but reduce the expansion of areas devoted to food crop production by 10%. In both climate scenarios, vegetation shifts further reduce the areas devoted to timber production by 6–8% over this same time period. Fire associated with climate-induced vegetation shifts causes the region to become more of a carbon source than if no vegetation shifts occur. Consideration of the interactions between climate-induced vegetation shifts and human activities through a modeling framework has provided clues to how humans may be able to adapt to a changing world and identified the trade-offs, including unintended consequences, associated with proposed climate/energy policies.

MIT Global Change

Regional Analysis

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