Proposed Research on Long-Term Climate Change and Urban Heat Island Mitigation
Gaskill recommended that global and mesoscale (regional) modeling of the impact of the GAEP be performed by LLNL and Altostratus, Inc. possibly using conditions in previous LLNL published studies for comparison. The impact of incremental vs. instantaneous coverage would be studied. Similarly, global and mesoscale modeling by LBNL and Altostratus of the application of the GAEP to land surrounding urban heat islands could be studied for the 100 largest cities and for selected urban areas in the U.S. for which the GAEP may be applicable, comparing this with the albedo enhancement of pavement and roof tops.
At this point, Mr. Conover had to leave to attend another meeting, indicating he would email the presentations to others in DOE. Gaskill, MacCracken and Caldeira remained and discussed issues related to hurricane mitigation and abrupt climate change.
In written comments submitted later, Drs. MacCracken and Caldeira recommended that an evaluation be conducted of various engineering approaches to solving the problem of global climate change including the GAEP and such no regrets alternatives as massive introduction of photovoltaic (PV) arrays. Gaskill estimates that replacement of all 21st century electricity, transportation and heating needs with energy from PV arrays would require coverage of around 200,000 square miles, about 5% of the area of the maximum GAEP coverage.
Caldeira said that a lot of careful analysis should be done before we embark on any course that could significantly alter climate on a large scale. The main question he had about the GAEP was one of scale, noting that a square meter can be sheeted over with plastic with little harm; a square kilometer, perhaps; hundreds of thousands of square kilometers and there is some concern about impacts and feasibility.
Gaskill noted that massive heat island mitigation as proposed by LBNL and the CEC would involve altering the surface reflectivity of around 100,000 square miles, also a very large area, albeit spread out across the globe. The GAEP could also cover a large area spread out across the globe. Although most of the attention of this plan has focused on the Sahara, there are other deserts and the modeling may show that we can get away with covering a great deal of surface area by proper spacing of the coverage before any regional climate impacts are felt.
Caldeira said that we need to take albedo changes into consideration in thinking about human impacts on climate. “This is perhaps most clear in the attempts to ameliorate urban heat islands. From a research point of view, the question of how surface changes in one area might affect climate in a distant area is interesting. How would increasing reflectivity in the Sahara affect climate in New York or Mumbai (Bombay)? Would they see a cooling? Would they see changes in the hydrological cycle or winds? What are the distal consequences of tropical deforestation?”
Caldeira then noted, “It is becoming clearer that, because of albedo effects, it would not make sense to (deliberately) expand boreal forests to increase carbon storage. If albedo would need to be taken into account for crediting carbon storage in forests, this has the potential to complicate proposed carbon trading schemes and could possibly lead to economic value for albedo changes.”
