Most of the current land surface parameterization schemes lack any representation of regional groundwater aquifers. Such a simplified representation of subsurface hydrological processes would result in significant errors in the predicted land surface states and fluxes especially for the shallow water table areas in humid regions. This study attempts to address this deficiency. To incorporate the water table dynamics into a land surface scheme, a lumped unconfined aquifer model is developed to represent the regional unconfined aquifer as a nonlinear reservoir, in which the aquifer simultaneously receives the recharge from the overlying soils and discharges runoff into streams. The aquifer model is linked to the soil model in the land surface scheme [Land Surface Transfer Scheme (LSX)] through the soil drainage flux. The total thickness of the unsaturated zone varies in response to the water table fluctuations, thereby interactively coupling the aquifer model with the soil model. The coupled model (called LSXGW) has been tested in Illinois for an 11-yr period from 1984 to 1994. The results show reasonable agreements with the observations. However, there are still secondary biases in the LSXGW simulation partially resulting from not accounting for the spatial variability of water table depth. The issue of subgrid variability of water table depth will be addressed in a companion paper.

© American Meteorological Society 2005

This paper uses bottom-up engineering information as a basis for modeling new technologies within the MIT Emissions Prediction and Policy Analysis (EPPA) model, a computable general equilibrium model of the world economy. Natural gas combined cycle (NGCC) without carbon capture and sequestration (CCS), natural gas combined cycle with CCS, and integrated coal gasification with CCS power generation technologies are introduced into the EPPA model. These compete in the electricity sector with conventional fossil generation, nuclear, hydro, wind, and biomass power generation. Engineering cost data are used together with EPPA data, including the underlying Social Accounting Matrix (SAM) and supplementary physical energy accounts, to assure that technologies, when simulated within the model, meet thermodynamic efficiency limits, and that they reflect regional differences in the cost structure of the electric sector. Alternative capital vintaging approaches are investigated and an explicit treatment of market penetration of new technologies is developed. Simulations through 2100 show the introduction of the new technologies and their decline as fuel and input prices, and carbon policies, change. A general result is that NGCC plants with or without capture, while currently less costly methods of abating carbon emissions from the electric sector based on engineering data, play only a limited and short-term role in meeting carbon limits. By 2050 the coal CCS plants, currently the most costly of the three technologies, dominate in the simulated policy scenarios because rising gas prices raise the cost of the gas-based technologies.

The authors used the terrestrial ecosystem model (TEM, version 4.0) to estimate global responses of annual net primary production (NPP) and total carbon storage to changes in climate and atmospheric CO2, driven by the climate outputs from the 2-dimensional MIT L-O climate model and the 3-dimensional GISS and GFDL-q atmospheric general circulation models (GCMs). For contemporary climate with 315 ppmv CO2, TEM estimates that global NPP is 47.9 PgC/yr and global total carbon storage is 1658 PgC: 908 PgC of vegetation carbon and 750 PgC of reactive soil organic carbon. For climate change associated with a doubling of radiative forcing and an atmospheric level of 522 ppmv CO2, the responses of global NPP are +17.8% for the MIT L-O climate, +18.5% for the GFDL-q climate and +20.6% for the GISS climate. The responses of global total carbon storage are +6.9% for the MIT L-O climate, +8.3% for GFDL-q climate and +8.7% for the GISS climate. Among the three climate change predictions, the changes in latitudinal distributions of cumulative NPP and total carbon storage along 0.5^o latitudinal bands vary slightly, except in high latitudes. There are generally minor differences in cumulative NPP and total carbon storage for most of the 18 biomes, except for the responses of total carbon storage in boreal biomes for the 2-D MIT L-O climate change. The results demonstrate that the linkage between the TEM and the 2-D climate model is useful for impact assessment and uncertainty analysis within an integrated assessment framework at the scales of the globe, economic regions and biomes, given the compromise between computational efficiency in the 2-D climate model and more detailed spatial representation of climate fields in 3-D GCMs.

The international allocation of responsibilities for reductions in greenhouse gas emissions, as foreseen in the Kyoto Protocol, would create a public good. Yet the 1990 level of emissions that is used in the Protocol, as the base from which the reductions would be made, and the reductions targets themselves, are quite arbitrary and not based on a specific target for the future world climate. In addition, the particular allocations of greenhouse gas emissions restrictions among countries do not have a principled logic. This arbitrariness has led to allocations that impose sharply different costs on the participating countries that have no consistent relation to their income or wealth.
        Calculations are presented of the implications of alternative allocations of emissions reductions that do have a plausible ethical basis: equal per capita reductions, equal country shares in reductions, equalized welfare costs, and emulation of the allocations of the United Nations budget. All of these would reach the overall Kyoto target at lower overall costs than the emissions allocations in the Protocol itself. This would be achieved through the participation of the developing countries, in which the costs of emissions reductions are relatively low. In addition, use of any of the alternative allocations analyzed here would eliminate the wholly capricious accommodation given to the countries of the Former Soviet Union and Eastern Europe.
        The additional costs to the developing countries, for most of the alternative allocations, are so low that the Annex B countries could pay them to accede to a new emissions reduction schedule and still have lower costs than those imposed by the Kyoto allocations. This conclusion puts the Annex B countries in the anachronistic position of advocating an arbitrary and relatively high cost allocation of emissions reductions. The lower cost alternative is to make such an unequivocal commitment for reimbursement to the non-Annex B countries that they would be persuaded to reduce their own emissions. Everyone would gain from that.