INTERNATIONAL WORKSHOP ON OIL DEPLETION
Uppsala, Sweden, May 23-25, 2002
Organized by Uppsala University and ASPO, the Association for the Study of Peak Oil
Climate Change And Oil Depletion
by Rui Rosa
Évora Geophysics Centre, University of Évora,
Rua Romão Ramalho 59, 7000 671 Évora, Portugal.
Primary energy sources have progressively displaced each other and shared the supply in terms that can historically be described by a model proposed by Cesare Marchetti as a generalization of the Fisher and Pry law. So wood, coal, oil and natural gas have displaced or are displacing each other, each one following a logistic evolution until a maximum share is attained, afterward receiving in a symmetrically similar way, provided there is no exhaustion of the respective resource base, each one completing its lifecycle. On the other hand, the persistent growth of the total energy demand implies that the total amount of each one of the successive primary energy sources, required to complete its lifecycle, is growing as time lapses.
So it is realized that coal resources are much larger than its total lifecycle demand. The same is not the case of oil, whose resource base (estimate 2000 Gb) may be smaller than the integrated prospective demand unless this starts declining steadily. However, if the rate of growth of total energy demand persists, the amount of natural gas required to complete a similar lifecycle will likely exceed its actual resource base. One faces, therefore, two problems: the constraint on oil availability right now and a possible, even more severe, constraint on natural gas in about twenty years time.
Combustion of fossil fuels always produces CO2 emissions as well as nitrogen oxides. Except for natural gas, all other fuels also produce, to a variable extent, particulate matter (aerosols) and sulfur oxides. The permanent alteration of the chemical composition of the atmosphere as a result of all these emissions may affect the biogeochemical balance of the climate system. Such emissions produce recognized impacts of some sort at local and regional levels, either temporary or permanent. Whether real effects can be global and permanent is still under dispute, but the observed steady and simultaneous increase of the CO2 atmospheric content and the average earth surface temperature are being considered to be interrelated.
Carbon dioxide, water vapour, and clouds all act as greenhouse forcing agents; cloud cover on account of its high solar reflectivity also acts as a direct cooling agent. Aerosols are of great importance in the processes of cloud formation and precipitation initiation, thereby affecting the hydrological cycle; they also exhibit radiative forcing properties both direct and indirect, by way of the clouds, either positive or negative, according to their particular composition. These particular influences are not yet well known and not yet properly incorporated in the simulations of climate scenarios adopted by the IPCC. And uncertainty brackets are still rather large.
Notwithstanding, the results of these still incomplete climate scenarios have been taken as enough scientific evidence to decide upon imposing limits to greenhouse gas emissions. The European Union has already approved a European Climate Change Programme and took the political initiative in the Marrakesh COP of the UNFCCC in November 2001, to the effect of the implementation of the Kyoto Protocol (1997). It is a political option which, besides setting emissions targets and energy policy terms of reference, also sets emission taxes and opens a new financial market for the trade of emission rights or permits.
Evidence for the real strain put upon the fossil energy supply is rather stronger than the evidence for anthropogenic climate changes. Rather more attention should be drawn to the supply of alternative energy sources, to the development of new energy carriers, to the improvement of technologies for energy conversion and storage as weel as to the rationalization and moderation of demand at end use, so that a severe fossil energy supply crises might be avoided. In doing so, environmental and climatic consequences of any kind due to the rising worldwide level of energy demand would be reduced; and the growth of energy consumption by developing countries might be met free of unduly constrains.