This paper presents the probabilistic collocation method as a computationally efficient method for performing uncertainty analysis on large complex models such as those used in global climate change research. The collocation method is explained, and then the results of its application to a box model of ocean thermohaline circulation are presented. A comparison of the results of the collocation method with a traditional Monte Carlo simulation show that the collocation method gives a better approximation for the probability density function of the model's response with less than 20 model runs as compared with a Monte Carlo simulation of 5000 model runs. / Includes bibliographical references (p. 21). / 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 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 0.5o 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. / 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/).

A significant number of long-term climate change simulations are to be carried out in the Integrated Framework of the MIT Global Change Joint Program. Since Global Circulation Models (GCMs) require an enormous amount of computer time, the two-dimensional statistical-dynamic model developed by Stone and Yao was chosen to be used for the initial stage of the Joint Program. At MIT, the model has been modified to make it more suitable for the purposes of the Joint Program, including developing a new scheme for a surface flux calculation. A number of simulations with the modified version of the model have been performed in which a few schemes for cloud and ocean heat transport calculation have been tested. Comparisons of the results of the present climate simulations with observational data show that the model reasonably reproduces main features of zonally averaged atmospheric circulation. A climate sensitivity produced by the model coupled with a mixed layer ocean model in response to the doubling of the atmospheric CO2 concentration lies in the range of the results obtained with GCMs. The results of the simulations with a gradual increase of the greenhouse gas concentrations in the atmosphere, in which diffusion of heat into the deep ocean was taken into account, are also similar to those obtained in the analogous simulations with GCMs. As a whole, presented results demonstrate that the modified version of the two-dimensional model can be successfully used for climate change predictions in the Integrated Framework of the Joint Program. / Includes bibliographical references (p. 13-14). / 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/).

Achieving agreement about whether and how to control greenhouse gas emissions would be difficult enough even if the consequences were fully known. Unfortunately, choices must be made in the face of great uncertainty, about both likely climate effects and the costs of control. Because several of the greenhouse gases have residence times of decades to centuries, any economic and environmental consequences are for practical purposes irreversible on those time scales. On the other hand, the commitment of resources to emissions control also has an irreversible aspect: investment foregone leaves a permanent legacy of reduced human welfare. Neither of the extreme positions, to take urgent action now or do nothing awaiting firm evidence, is a constructive response to the climate threat. Responsible treatment of this issue leads to a difficult position somewhere in between. / Includes bibliographical references (p. 32-34). / 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/).

Christoforos N. Hadjicostis. / Also issued as Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999. / Includes bibliographical references (p. 189-196). / Sponsored through a contract with Sanders, A Lockheed Martin Company.

John A. McKenzie. / "June 1999." / Includes bibliographical references (leaves [1]-[2]).

Shawn M. Verbout. / "June 1999." / Includes bibliographical references (p. [225]-240). / Sponsored by the U.S. Air Force. F49620-96-1-0072 Supported by the U.S. Army Research Laboratory under Cooperative Agreement, DAAL01-96-2-001

Warren M. Lam and Gregory W. Wornell. / "October 1998"--Cover. / Includes bibliographical references (p. 33-34). / Supported by DARPA monitored by ONR. N00014-93-1-0686, N00014-96-1-0930 Supported by AFOSR. F49620-1-0072

hosted [and edited] by J. Kennedy Salisbury and Mandayam A. Srinivasan. / "December, 1998." / Includes bibliographical references. / Sponsored by SensAble Technologies, Inc., Cambridge, MA.

Haralabos Christos Papadopoulos. / Includes bibliographical references (p. 163-165). / Also issued as a Ph.D. thesis, Dept. of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 1998. / Sponsored by the Advanced Research Projects Agency monitored by the Office of Naval Research. N00014-93-1-0686 Sponsored by the Air Force Office of Scientific Research. F49620-96-1-0072 Sponsored in part by the U.S. Army Research Laboratory under the Federated Laboratory Program. Cooperative Agreement No. DAAL01-96-2-0002