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With federal policies to curb greenhouse gas emissions in the US stagnating, California has taken action on its own. We estimate the impact of California’s cap-and-trade program on the leakage of emissions to other regions using a calibrated general equilibrium model. Sub-national policies can lead to high leakage rates as state economies are generally closely connected to other economies, including integration of electricity markets. Measures that will prevent leakage from California’s cap-and-trade program include requiring permits to be surrendered for emissions embodied in imported electricity and legislation banning “resource shuffling”. Under a cap-and-trade policy without measures to reduce leakage, the price of emission permits is $12 per ton of CO2 and emissions in other regions increase by 46% of the reduction in emissions in California. When imported electricity is included in the program and resource shuffling is banned, the carbon price is $65, there is negative leakage to regions exporting electricity to California, positive leakage to other regions and the overall leakage rate is 2%. We conclude that although there is potential for large increases in emissions elsewhere due to California’s cap-and-trade policy, enforcement of requirements for imported electricity will be effective at curtailing leakage.

Bush-era tax cuts are scheduled to expire at the end of 2012, leading to interest in raising revenue through a carbon tax. This revenue could be used to either cut other taxes or to avoid cuts in Federal programs. There is a body of economic research suggesting that such an arrangement could be a win-win-win situation. The first win—Congress could reduce personal or corporate income tax rates, extend the payroll tax cut, maintain spending on social programs, or some combination of these options. The second win—these cuts in income taxes would spur the economy, encouraging more private spending and hence more employment and investment. The third win—carbon dioxide (CO2) pollution and oil imports would be reduced. This analysis uses the MIT U.S. Regional Energy Policy (USREP) model to evaluate the effect of a carbon tax as part of a Federal budget deal. A baseline scenario where temporary payroll cuts and the Bush tax cuts are allowed to expire is compared to several scenarios that include a carbon tax starting at $20 per ton in 2013 and rising at 4%. We find that, whether revenue is used to cut taxes or to maintain spending for social programs, the economy is better off with the carbon tax than if taxes remain high to maintain Federal revenue. We also find that, in addition to economic benefits, a carbon tax reduces carbon dioxide emissions to 14% below 2006 levels by 2020, and 20% below by 2050. Oil imports remain at about today’s level, and compared to the case with no carbon tax, are 10 million barrels per day less in 2050. The carbon tax would shift the market toward renewables and other low carbon options, and make the purchase of more fuel-efficient vehicles more economically desirable.

Three Questions With John Reilly:

Q: What led you to consider a carbon tax as part of a Federal budget deal?

A: There is clear need to reduce the Federal deficit but at the same time there is interest in maintaining at least some of the Bush tax cuts that will expire at the end of the year. This has led to interest among some in Congress in raising revenue through a carbon tax and using the revenue to either cut other taxes or to avoid draconian cuts in Federal programs. There is a body of research in economics suggesting the possibility that such arrangement could be a win-win, or even a win-win-win situation. The first win – Congress could reduce personal or corporate income tax rates, extend the payroll tax cut, maintain spending on social programs, or some combination. The second win – these cuts in income taxes would spur the economy, encouraging more private spending and hence more employment and investment. The third win – carbon dioxide pollution and oil imports would be reduced. While in principle it is possible to get such a positive result, in practice it can depend on the specific proposal. Recent interest in such a deal has focused on a $20 per ton tax on carbon dioxide emissions, starting soon, and rising at 4% per year in real terms – a carbon pricing approach the Congressional Budget Office had considered a couple of years back, but not as part of a deal that would use revenue to cut other taxes. There is also concern with how different tax cut and spending changes would affect lower and middle income households. So we thought it useful to complete a careful analysis of such a plan.

Q: How did you construct your study and what did you find?

A: We were able to make use of a model we have developed of the U.S. economy that has significant detail on the energy economy, taxes and taxation, and households of different income levels. We factored in the expiration of the Bush personal and corporate income tax cuts and the temporary payroll tax cut. If these are allowed to expire, that will go a long way toward reducing the deficit. Starting from that point, we used the CBO carbon pricing path. We calculated the net new revenue such a carbon tax would raise, and we used that revenue to cut tax rates or maintain spending on social programs. We also considered options where we used half of the revenue for an investment tax credit. In general, we found the win-win-win result we thought might be there. Whether we cut taxes or maintained spending for social programs, the economy was better off with the carbon tax than if we had to keep other taxes high to maintain Federal revenue. By allocating only net new revenue from the carbon tax, we assured that all of the options we considered were "revenue neutral." Congress will face many difficult tradeoffs in stimulating the economy and job growth while reducing the deficit. However, with the options we considered there were really no serious tradeoffs at the highest level – the macro economy improved, income taxes were lower, and pollution emissions reduced.

Among the detailed options we considered there are some smaller trade-offs. Those options where we used all of the net carbon revenue for cutting income taxes gave more benefits over the next 10 to 20 years compared to the options where half of the revenue was used for an investment tax credit. The investment tax credit diverts income away from consumption spending today and toward investment. This works for the economy just as in your personal life: when you save for the future, that leaves less spending for the present. But when those savings earn a return, you then have more to spend in the future. So the tradeoff with the investment tax credit is whether we would like to spur consumption immediately or build investment for the future. Given the current recession and unemployment, the balance might tip more toward options that increased spending today.

The other tradeoff was how the different plans affected households at different income levels. Not surprisingly, maintaining social programs was best for lower income households. Maintaining these programs also improved the economy because it shifted income to households with a higher propensity to consume. This created more consumption, but obviously less savings, so in the longer run this option was not as beneficial for the whole economy as other options. On the other end of the spectrum cutting personal and corporate income taxes, especially when combined with an investment tax credit, benefitted wealthy households the most. Wealthy households on average pay more taxes, and thus tax cuts benefit them more. They also are more likely to receive income from investments, and so expanding investment benefits them. The most neutral option was extension of the payroll tax cut. Because there is an income limit on this tax, cutting the rate has a limited benefit for households above the income limit, and the net effect is a more equal affect on all households.

But again, these are minor tradeoffs, as in most cases we are looking at benefits to all households.

Q: How would a carbon tax improve our environment and energy future?

A; Given the critical nature of economic growth, jobs and the budget deficit, the third win – environment and energy – almost doesn't matter. That said, we find the carbon tax reduces emissions to 14% below 2006 levels by 2020, and 20% below by 2050. We see no increase in oil imports, which by 2050 is 10 million barrels a day less than in our projection without the carbon tax. The carbon tax would shift the market toward renewables and other low carbon options, and make the purchase of more fuel-efficient vehicles more economically desirable. These are goals Congress has pursued using various tax credits. Those tax credits reduce tax revenue and contribute to the Federal deficit. By shifting to a carbon tax instead of such credits, we create similar incentives for cleaner energy technologies, but we raise revenue rather than spending it. Even if we ignore these environmental and energy benefits, this type of tax reform would still be a good thing for the economy.

The rapid recent decline of Arctic Ocean sea ice area increases the flux of solar radiation available for primary production and the area of open water for air-sea gas exchange. We use a regional physical-biogeochemical model of the Arctic Ocean, forced by the National Centers for Environmental Prediction/National Center for Atmospheric Research atmospheric reanalysis, to evaluate the mean present-day CO2 sink and its temporal evolution. During the 1996–2007 period, the model suggests that the Arctic average sea surface temperature warmed by 0.04°C a−1, that sea ice area decreased by ∼0.1 × 106 km2 a−1, and that the biological drawdown of dissolved inorganic carbon increased. The simulated 1996–2007 time-mean Arctic Ocean CO2 sink is 58 ± 6 Tg C a−1. The increase in ice-free ocean area and consequent carbon drawdown during this period enhances the CO2 sink by ∼1.4 Tg C a−1, consistent with estimates based on extrapolations of sparse data. A regional analysis suggests that during the 1996–2007 period, the shelf regions of the Laptev, East Siberian, Chukchi, and Beaufort Seas experienced an increase in the efficiency of their biological pump due to decreased sea ice area, especially during the 2004–2007 period, consistent with independently published estimates of primary production. In contrast, the CO2 sink in the Barents Sea is reduced during the 2004–2007 period due to a dominant control by warming and decreasing solubility. Thus, the effect of decreasing sea ice area and increasing sea surface temperature partially cancel, though the former is dominant.

© 2013 American Geophysical Union

Conducting probabilistic climate projections with a particular climate model requires the ability to vary the model's characteristics, such as its climate sensitivity. In this study, the authors implement and validate a method to change the climate sensitivity of the National Center for Atmospheric Research (NCAR) Community Atmosphere Model, version 3 (CAM3), through cloud radiative adjustment. Results show that the cloud radiative adjustment method does not lead to physically unrealistic changes in the model's response to an external forcing, such as doubling CO2 concentrations or increasing sulfate aerosol concentrations. Furthermore, this method has some advantages compared to the traditional perturbed physics approach. In particular, the cloud radiative adjustment method can produce any value of climate sensitivity within the wide range of uncertainty based on the observed twentieth century climate change. As a consequence, this method allows Monte Carlo-type probabilistic climate forecasts to be conducted where values of uncertain parameters not only cover the whole uncertainty range, but cover it homogeneously. Unlike the perturbed physics approach that can produce several versions of a model with the same climate sensitivity but with very different regional patterns of change, the cloud radiative adjustment method can only produce one version of the model with a specific climate sensitivity. As such, a limitation of this method is that it cannot cover the full uncertainty in regional patterns of climate change.

© 2012 American Meteorological Society

The extent, availability and reliability of solar power generation are assessed over Europe, and—following a previously developed methodology—special attention is given to the intermittency of solar power. Combined with estimates of wind power resource over Europe from a companion assessment, we assess the benefits of co-location of solar and wind power installations, particularly with respect to aggregate power generation and local mitigation of intermittency. Consistent with previous studies, our results show that the majority of solar potential is found in southern Europe, which also displays the strongest availability. We also found that higher latitude locations, around central Europe, benefit from medium to high solar power during the warm season. If a region’s availability of solar power is sufficient—as determined by a minimum technological threshold for photovoltaic extraction— it possesses the potential to reduce intermittency by aggregation and interconnection. We find these conditions occurring to a moderate extent over mainland central Europe. Finally, the result of co location of wind and solar power is increased power availability over the whole continent, especially in central Europe where neither resource is strong. In terms of local intermittency mitigation, the regions that benefit most are the Mediterranean and Baltic countries.

Wind power is assessed over Europe, with special attention given to the quantification of intermittency.  Using the methodology developed in Gunturu and Schlosser (2011), the MERRA boundary flux data was used to compute wind power density profiles over Europe. Besides of the analysis of capacity factor, other metrics are presented to further quantify the availability and reliability of this resource and the extent to which wind-power intermittency is coincident across Europe. The analyses find that, consistent with previous studies, the majority of European wind power resources are located offshore. The largest  wind power resources at onshore locations are found to be over Iceland, the United Kingdom, and along the northern coastlines of continental Europe. Other isolated pockets of higher wind power are found over Spain and along the Mediterranean coast of France. Overall, the availability of onshore wind power is low and is highly intermittent, while offshore locations show a high degree of persistence. However, for the strongest onshore locations of wind power—primarily over northern coastlines as well as the United Kingdom and Iceland—the evidence indicates that intermittency can be reduced by aggregation and interconnection of wind-power installations. 

The wind resource in Australia has been reconstructed and characterized in terms of its geographical distribution, abundance, variability, availability, persistence and intermittency. The impact of raising the wind turbine hub height on these metrics is analyzed. The Modern Era Retrospective Analysis for Research and Applications (MERRA) boundary layer flux data was used to construct wind power density (WPD) and wind speed at 50 m, 80 m, 100 m, and 150 m, which represent current and potential wind turbine hub heights. The wind speeds at 80 m were quantitatively and spatially similar to a map of wind sp

Wind resource in the continental and offshore United States has been reconstructed and characterized using metrics that describe, apart from abundance, its availability, persistence and intermittency. The Modern Era Retrospective-Analysis for Research and Applications (MERRA) boundary layer flux data has been used to construct wind profile at 50 m, 80 m, 100 m, 120 m turbine hub heights. The wind power density (WPD) estimates at 50 m are qualitatively similar to those in the US wind atlas developed by the National Renewable Energy Laboratory (NREL), but quantitatively a class less in some regions, but are within the limits of uncertainty. The wind speeds at 80 m were quantitatively and qualitatively close to the NREL wind map. The possible reasons for overestimation by NREL have been discussed. For long tailed distributions like those of the WPD, the mean is an overestimation and median is suggested for summary representation of the wind resource.

The impact of raising the wind turbine hub height on metrics of abundance, persistence, variability and intermittency is analyzed. There is a general increase in availability and abundance of wind resource but there is an increase in intermittency in terms of level crossing rate in low resource regions.

© 2012 the Authors

In this study, we introduce a new method of downscaling global population distribution, for which purpose conventional approaches have serious limitations in application. Our approach is “eclectic,” as it explores the intersection between an optimization framework and the empirical regularities involved in rank-size distributions. The novelty of our downscaling model is that it allows city-size distributions to interact with socioeconomic variables. Our contribution to the urban studies literature is twofold. One is our challenge to the conventional view that the proportionate growth dynamics underlies empirical rank-size regularities. We first show that the city-size distribution of a region can deviate substantially from a log-normal distribution with cross-regional and time variations, and then demonstrate that such variations can be explained by certain socioeconomic conditions that each region confronts at a particular time point. In addition to expanding academic debates on city-size distributions, our study can pave the way for various academic and professional research projects, which need spatial distribution of global population at fine grid cell levels as key input. Our model is applicable to the entire globe, including regions for which reliable sub-regional population data sets are limitedly available, and can be extended easily to function as a forecasting model.

This paper describes the use of the CliCrop model in the context of climate change general assessment modeling. The MIT Integrated Global System Model (IGSM) framework is a global integrated assessment modeling framework that uses emission predictions and economic outputs from the MIT Emission Prediction and Policy Analysis (EPPA) model and earth system modeling predictions from the IGSM to drive a land system component, a crop model (CliCrop) and a Water Resource System (WRS) model. The global Agriculture and Water System are dependant upon and interlinked with the global climate system. As irrigated agriculture provides 60% of grains and 40% of all crop production on 20% of global crop lands and accounts for 80% of global water consumption, it is crucial that the agricultural-water linkage be properly modeled. Crop models are used to predict future yields, irrigation demand and to understand the effect of crop and soil type on food productivity and soil fertility. In the context of an integrated global assessment, a crop water-stress and irrigation demand model must meet certain specifications that are different for other crop models; it needs to be global, fast and generic with a minimal set of inputs. This paper describes how CliCrop models the physical and biological processes of crop growth and yield production and its use within the MIT Integrated Global System Model (IGSM) framework, including the data inputs. This paper discusses the global data bases used as input to CliCrop and provides a comparison of the accuracy of CliCrop with the detailed biological-based crop model DSSAT as well as with measured crop yields over the U.S. at the country level using reanalyzed weather data. In both cases CliCrop performed well and the analysis validated its use for climate change impact assessment. We then show why correctly modeling the soil is important for irrigation demand calculation, especially in temperate areas. Finally, we discuss a method to estimate actual water withdrawal from modeled physical crop requirements using U.S. historical data.

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