The land to be used was provided free in return for jobs and debt forgiveness where applicable. No allowance was made for inflation or increase in resin prices due to crude oil price rises. The cover was installed over a 60-year period and kept in place 150 years.
These assumptions resulted in a cost at the end of 150 years of $75 trillion or $500 billion/year or $19 million/square mile. If the cover project is concluded before the 150-year period, but after 60 years, the costs will be progressively lower the sooner it ends.
Noteworthy is the fact that the cost of the plastic film is almost 80% of the total cost of the project and bringing it down an important step. This must be weighed against the performance that is also of paramount importance.
Gaskill said the project could be paid for by the purchase of thermal credits relatable to GHG emissions under a successor treaty to Kyoto. The cost per tonne (metric ton) of carbon emissions equivalent whose radiative forcing is offset by the cover is based on a future scenario in which an average of 19.5 GtC/year are emitted from 2010-2070 or 1170 GtC. This results in an average cost per tonne of $64. Looking at this from the perspective of some future exchange traded commodity, the GAEP offsets approximately 300,000 tonnes of carbon per square mile or around 0.01 tonnes (24 lbs)/SF. Thus, a SF of coverage should trade for around $0.69. Valued equally over the 60 year period, then, each year that square foot is worth $0.01.
Gaskill presented a pro forma schedule in which the modeling is completed by the end of 2004 and cover development and increasingly larger field trials occur from 2005-2012, culminating in full-scale implementation starting around 2012. Caldeira said that the global modeling could be completed in one month, but analyses of the data might take an additional 4 months, so at least the global modeling could fit this schedule. Dr. Taha from Altostratus, Inc. says that the mesoscale modeling will take much longer to complete, around one year per region chosen due to the time needed for the computers to produce results.
Gaskill addressed several other issues. He said that GHG emissions from the production, transportation, installation and recycling of the plastic film would result in emissions of 1.8% of total present day GHG emissions, dropping proportionally as global emissions rise. Thus, although these emissions are not insignificant, the cover would offset around 100X the emissions its production and deployment would produce. Capture and sequestration of the GAEP emissions would reduce this even further.
Alteration of desert dust storms might affect the Amazon and N. Atlantic, which depend on Saharan dust transported by upper level winds across the Atlantic for iron in both the Amazon and N. Atlantic and for phosphorous in the Amazon. Nearly 50% of the iron needed by phytoplankton in the N. Atlantic is supplied by Saharan dust, while almost all the phosphorous needed to support the bromeliad ecology of the Amazon comes from this source. The potential impact of altering these nutrient flows must be studied by climate modeling.
The geopolitical consequences of a GAEP must be considered as the land involved includes politically unstable and volatile nations, oil producing nations and large emitters like China. There is also a 1977 UN treaty prohibiting hostile use of weather/climate modification.
Gaskill recommended an international treaty indemnifying all involved with the project from lawsuits resulting from alleged or actual damage to the climate or economy of a country or region due to the GAEP.
