Includes bibliographical references (p. 22-23). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

Includes bibliographical references (p. 64-73). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

The possible trends for atmospheric carbon monoxide in the next 100 yr have been illustrated using a coupled atmospheric chemistry and climate model driven by emissions predicted by a global economic development model. Various model runs with different assumptions regarding emissions or model parameters have been carried out to investigate the impacts of model and emission uncertainties on the predictions. We have found complicated interactions among emissions, atmospheric chemistry, and climate regarding the distributions and evolution of CO in the atmosphere. Based on the predicted emissions of methane and carbon monoxide, the model predicts an increasing trend of carbon monoxide in the next century with a tropospheric mole fraction of CO in 2100 double its present-day value. Methane emissions are found to have the most important effect on the future atmospheric CO budget. High methane emissions cause significant depletion of tropospheric OH, increase of CO concentrations, and lengthening of lifetimes of many chemical species including CO and CH4. The global average atmospheric lifetime of CO is predicted in our reference model run to be about 0.6 month longer than its present value (~2 months). The predicted emissions of CO increase only slightly over the next century, so the impact of CO emissions on the predicted CO abundance appears to be less important than that of methane. Consequently, maintaining the emissions of CH4 at their current levels can prevent significant future changes in tropospheric chemistry, while similar controlling emissions of CO cannot achieve the same result. This study also indicates that climate variations, especially those causing changes in H2O concentrations, can influence atmospheric trends of carbon monoxide. A two-way interaction between chemistry and climate regarding CO is evident. Specifically, the budget of atmospheric CO affects the destruction of methane and the production of CO2, ozone, and sulfate aerosols and thus affects climate, while the resultant changes in climate modify the budget of CO-CH4 in turn through their effects on H2O and temperature. / Includes bibliographical references (p. 11). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

Using a coupled global atmospheric chemistry and climate model we have predicted the evolution of tropospheric concentrations of chemical species along with climate parameters, based on a set of economic model predictions for anthropogenic emissions of chemically and radiatively important trace gases in the next 120 years. In particular, our predictions for tropospheric hydroxyl radical (OH) concentrations indicate the potential for substantial future changes affecting both atmospheric chemistry and climate. OH is arguably the most important free radical in the troposphere because it is the primary removal mechanism for most gases entering the atmosphere, and therefore, determines the lifetimes of these species. Our research indicates that if CH4 and CO emissions continually increase as expected through the next century, the tropospheric concentration of OH could decrease by as much as 29% from its current value. As a result, the lifetime of CO in the year 2100 is predicted to lengthen by 0.6 months beyond its current value of 2 months, and the CH4 lifetime in 2100 would exceed its current value (9 years) by 2.5 years in our reference case. / Includes bibliographical references. / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

To deepen understanding of the relation between economic development and energy demand, this study estimates the Engel curves that relate per-capita energy consumption in major economic sectors to per-capita GDP. Panel data covering up to 123 nations are employed, and measurement problems are treated both in dataset construction and in estimation. Time and country fixed effects are assumed, and flexible forms for income effects are employed. There are substantial differences among sectors in the structure of country, time, and income effects. In particular, the household sector's share of aggregate energy consumption tends to fall with income, the share of transportation tends to rise, and the share of industry follows an inverse-U pattern. / Includes bibliographical references (p. 15-16). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

The authors offer a provisional assessment of where the Kyoto negotiations have left the climate change issue. They present a few widely divergent assesments of what the Kyoto Protocol on Climate Change will accomplish, and describe some differing interpretations of its text in the context of the underlying international disagreement, as well as in differing perceptions of the underlying science and economics. The paper includes a brief but up-to-date summary of what we know and don't know about human influences on climate, and what it might take to restrain them. / Includes bibliographical references. / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

Includes bibliographical references (p. 21-23). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

In order to analyze competing policy approaches for addressing global climate change, a wide variety of economic-energy models are used to project future carbon emissions under various policy scenarios. Due to uncertainties about future economic growth and technological development, there is a great deal of uncertainty in emissions projections. This paper demonstrates the use of the Deterministic Equivalent Modeling Method, an efficient means for propagating uncertainty through large models, to investigate the probability distributions of carbon emissions from the MIT Emissions Prediction and Policy Analysis model. From the specific results of the uncertainty analysis, several conclusions with implications for climate policy are given, including the existence of a wider range of possible outcomes than suggested by differences between models, the fact that a "global emissions path through time" does not actually exist, and that the uncertainty in costs and effects of carbon reduction policies differ across regions. / Includes bibliographical references (p. 31-32). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

Includes bibliographical references (p. 14). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)

The Terrestrial Ecosystem Model (TEM version 4.1) is applied to assess the sensitivity of net ecosystem production (NEP) of the terrestrial biosphere to transient changes in atmospheric CO2 concentration and climate in the 21st century. These NEP estimates provide a measure of the potential for various vegetated regions and countries to act as sinks or sources of atmospheric CO2. We use three transient climate change predictions over the period of 1977-2100 from the MIT Integrated Global System Model for assessment of the effects of different climate changes. Global annual NEP has large interannual variations and increases over time, thus representing a growing net carbon flux from the atmosphere to the biosphere. Latitudinal distribution of total annual NEP along 0.5 degree resolution latitudinal bands has a significant shift from the tropics to the northern mid- and high-latitudes over time. The sums of annual NEP over the period of 1990-2100 differ substantially among the twelve economic regions of the world. The results show that temporal dynamics and spatial distribution of annual NEP are very sensitive to the magnitudes and paths of temporal changes in atmospheric CO2 concentration and climate. / Includes bibliographical references (p. 13-16). / Abstract in HTML and technical report in HTML and PDF available on the Massachusetts Institute of Technology Joint Program on the Science and Policy of Global Change website (http://mit.edu/globalchange/www/)