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Probabilistic Forecast for 21st Century Climate Based on Uncertainties in Emissions (without Policy) and Climate Parameters

The MIT Integrated Global System Model is used to make probabilistic projections of climate change from 1861 to 2100. Since the model's first projections were published in 2003 substantial improvements have been made to the model and improved estimates of the probability distributions of uncertain input parameters have become available. The new projections are considerably warmer than the 2003 projections, e.g., the median surface warming in 2091 to 2100 is 5.1°C compared to 2.4°C in the earlier study. Many changes contribute to the stronger warming; among the more important ones are taking into account the cooling in the second half of the 20th century due to volcanic eruptions for input parameter estimation and a more sophisticated method for projecting GDP growth which eliminated many low emission scenarios. However, if recently published data, suggesting stronger 20th century ocean warming, are used to determine the input climate parameters, the median projected warning at the end of the 21st century is only 4.1°C. Nevertheless all our simulations have a very small probability of warming less than 2.4°C, the lower bound of the IPCC AR4 projected likely range for the A1FI scenario, which has forcing very similar to our median projection. The probability distribution for the surface warming produced by our analysis is more symmetric than the distribution assumed by the IPCC due to a different feedback between the climate and the carbon cycle, resulting from a different treatment of the carbon-nitrogen interaction in the terrestrial ecosystem.

Probabilistic Forecast for 21st Century Climate Based on Uncertainties in Emissions (without Policy) and Climate Parameters

The MIT Integrated Global System Model is used to make probabilistic projections of climate change from 1861 to 2100. Since the model's first projections were published in 2003, substantial improvements have been made to the model, and improved estimates of the probability distributions of uncertain input parameters have become available. The new projections are considerably warmer than the 2003 projections; for example, the median surface warming in 2091–2100 is 5.1°C compared to 2.4°C in the earlier study. Many changes contribute to the stronger warming; among the more important ones are taking into account the cooling in the second half of the twentieth century due to volcanic eruptions for input parameter estimation and a more sophisticated method for projecting gross domestic product (GDP) growth, which eliminated many low-emission scenarios.

However, if recently published data, suggesting stronger twentieth-century ocean warming, are used to determine the input climate parameters, the median projected warning at the end of the twenty-first century is only 4.1°C. Nevertheless, all ensembles of the simulations discussed here produce a much smaller probability of warming less than 2.4°C than implied by the lower bound of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) projected likely range for the A1FI scenario, which has forcing very similar to the median projection in this study. The probability distribution for the surface warming produced by this analysis is more symmetric than the distribution assumed by the IPCC because of a different feedback between the climate and the carbon cycle, resulting from the inclusion in this model of the carbon–nitrogen interaction in the terrestrial ecosystem.

© 2009 American Meteorological Society

[Erratum]

Probabilistic policy experiments: The use of energy-economic-environmental models in the climate change policy process

This paper uses the Edmonds-Reilly model to explore an alternative approach for using energy- economic- environmental models when analysing future CO2 emissions. This approach - conducting probabilistic policy experiments - can be used to investigate the effectiveness of various policy options in the context of uncertainty. The analysis builds on work by Nordhaus and Yohe (1983) and Edmonds et al. (1986). A key feature of using a probabilistic approach is that it offers both analysts and policy- makers an opportunity to move away from arguing about which scenario is the 'right', best-guess scenario, and towards a discussion of which strategies are effective across an wide range of possible futures. This paper both develops a methodology for conducting probabilistic policy experiments and presents the results of five preliminary experiments using this approach.

© 1995 Inderscience Enterprises Limited

Process Modeling of Global Soil Nitrous Oxide Emissions

Nitrous oxide is an important greenhouse gas and is a major ozone-depleting substance. To understand and quantify soil nitrous oxide emissions, we expanded the Community Land Model with prognostic Carbon and Nitrogen (CLM-CN) by inserting a module to estimate annually- and seasonally-varying nitrous oxide emissions between 1978 and 2000. We evaluate our soil N2O emission estimates against existing emissions inventories, other process-based model estimates, and observations from two forest sites in the Amazon and one in the United States. The model reproduces soil temperature and soil moisture relatively well, and it reconfirms the important relationship between N2O emissions and these parameters. The model also reproduces observations of N2O emissions well in the Amazonian forests but not during the winter in the USA. Applying this model to estimate the past 23 years of global soil N2O emissions, we find that there is a significant decrease in soil N2O emissions associated with drought and El Ni˜no years. More study is necessary to quantify the high-latitude winter activity in the model in order to better understand the impact of future climate on N2O emissions and vice versa.

Prospects for Plug-in Hybrid Electric Vehicles in the United States and Japan: A General Equilibrium Analysis

The plug-in hybrid electric vehicle (PHEV) may offer a potential near term, low carbon alternative to today's gasoline- and diesel-powered vehicles. A representative vehicle technology that runs on electricity in addition to conventional fuels was introduced into the MIT Emissions Prediction and Policy Analysis (EPPA) model as a perfect substitute for internal combustion engine (ICE-only) vehicles in two likely early-adopting markets, the United States and Japan. We investigate the effect of relative vehicle cost and all-electric range on the timing of PHEV market entry in the presence and absence of an advanced cellulosic biofuels technology and a strong (450ppm) economy-wide carbon constraint. Vehicle cost could be a significant barrier to PHEV entry unless fairly aggressive goals for reducing battery costs are met. If a low cost vehicle is available we find that the PHEV has the potential to reduce CO2 emissions, refined oil demand, and under a carbon policy the required CO2 price in both the United States and Japan. The emissions reduction potential of PHEV adoption depends on the carbon intensity of electric power generation and the size of the vehicle fleet. Thus, the technology is much more effective in reducing CO2 emissions if adoption occurs under an economy-wide cap and trade system that also encourages low-carbon electricity generation.

Prospects for Plug-In Hybrid Electric Vehicles in the United States and Japan: A General Equilibrium Analysis

The plug-in hybrid electric vehicle (PHEV) may offer a potential near term, low-carbon alternative to today’s gasoline- and diesel-powered vehicles. A representative vehicle technology that runs on electricity in addition to conventional fuels was introduced into the MIT Emissions Prediction and Policy Analysis (EPPA) model as a perfect substitute for internal combustion engine (ICE-only) vehicles in two likely early-adopting markets, the United States and Japan. We investigate the effect of relative vehicle cost and all-electric range on the timing of PHEV market entry in the presence and absence of an advanced cellulosic biofuels technology and a strong (450 ppm) economy-wide carbon constraint. Vehicle cost could be a significant barrier to PHEV entry unless fairly aggressive goals for reducing battery costs are met. If a low-cost PHEV is available we find that its adoption has the potential to reduce CO2 emissions, refined oil demand, and under a carbon policy the required CO2 price in both the United States and Japan. The emissions reduction potential of PHEV adoption depends on the carbon intensity of electric power generation. Thus, the technology is much more effective in reducing CO2 emissions if adoption occurs under an economy-wide cap and trade system that also encourages low-carbon electricity generation.

© 2010 Elsevier

Prospects for Plug-In Hybrid Transportation in the United States: A General Equilibrium Analysis

The plug-in hybrid electric vehicle (PHEV) could significantly contribute to reductions in carbon dioxide emissions from personal vehicle transportation in the United States over the next century, depending on the cost-competitiveness of the vehicle, the relative cost of refined fuels and electricity, and the existence of an economy-wide carbon emissions constraint. Using a computable general equilibrium model, I evaluated the potential for the PHEV to enter the U.S. personal vehicle market before 2100 and alter electricity output, refined oil consumption, carbon dioxide emissions, and the economic welfare losses associated with the imposition of a strict climate policy. The PHEV is defined by its ability to run on battery-stored electricity supplied from the grid as well as on refined fuel in an internal combustion engine. Sectors that produce PHEV transportation as well as other electric-drive vehicle technologies were added to the MIT Emissions Prediction and Policy Analysis (EPPA) Model as a perfect substitute for internal combustion engine (ICE)-only vehicles. Engineering cost estimates for the PHEV, as well as information about the pre-existing fleet, were used to specify PHEV sector input shares and substitution elasticities in the model.

Based on the model results, several conclusions emerged from this work. First, lower vehicle cost markups may hasten PHEV market entry, especially in the absence of a climate policy. Second, in the short term, the lower cost of electricity compared with refined fuels on a per mile basis is likely to favor adoption of vehicles with longer all-electric ranges. However, realizing the electricity advantage will depend on whether or not current battery cost and performance limitations can be overcome. Third, the availability of biofuels as a carbon neutral fuel substitute could delay PHEV market entry, especially when a climate policy is imposed. Fourth, large-scale adoption of the PHEV will increase electricity demand, reduce refined oil consumption, and could offset the economic welfare cost of pursuing a climate policy, especially if biofuels are not available. Fifth, realizing the maximum carbon emissions reduction potential of grid-charged electric-drive vehicles such as the PHEV will depend on concurrent reductions in power sector emissions.

Kyoto and the Future of Coal

Natural gas will be more important than the Kyoto Protocol to coal's future. How, and whether, this ambitious international agreement is implemented will significantly affect coal's prospects. But the more important feature of coal's future is likely to be the possibility for displacement by other fuels, specifically natural gas, whose recent expansion is due far more to its newly found abundance than to its touted environmental attributes. Natural gas enjoys an ease of handling and environmental attributes that give it clear advantages in relatively small-scale uses typical of households, commercial establishments and general industry. Coal's only advantage is price. Low cost is not an insignificant advantage, but it is a relative one that depends as much on the competing fuel as it does on coal. Therein lies a threat, no less serious but more real than the prospects for meaningful implementation of the Kyoto Protocol.

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