GLOBAL WARMING AND CLIMATE

GLOBAL WARMING AND CLIMATE

Determining that there is a strong relation between population size and global warming does not tell us what the underlying mechanisms are. However, documentation of the relationship between human activities and the release of greenhouse gases produces a strong inference that population size and global warming are closely related (Gribbin, 1990). Forecasting the future is risky business. Growth rates for greenhouse-gas concentrations and MGT could decline from those at present due to unanticipated innovations or natural events. For example, volcanoes can spew enough ash into the atmosphere to block sunlight and temporarily reduce MGT slightly. However, short-term continued growth at current rates is probably an underestimate. Although population growth rate has slowed, the population is still growing. The dominating factor is that per-capita energy and resource consumption rates are increasing much faster than the population. This is not only due to anticipated increases in standards of living in underdeveloped countries, but also to future increases in the demand for energy in the developed countries (e.g., air conditioning) as summer temperatures rise. Since most of the energy will come from fossil fuels, at least for the next few decades, we can expect the atmospheric concentrations of greenhouse gases and MGT to rise in the short-term future at a faster rate than they have recently. As MGT rises, water vapor, another greenhouse component, will become a more and more significant factor due to increased evaporation. Although a 1.5oC increase in MGT above where we were in 1990 (1990 to 2025 in Fig. 2) does not seem like much of a change, it is enough to precipitate major changes in climate. A 1.5oC drop in MGT from where we were in 1990, for example, would put the ecosystem on the verge of an ice-age. Already, there is a suspicion that, since 1975, the persistent El Nino is the first sign of the relation between global warming and climate (Kerr, 1994). As MGT increases further, we can expect more frequent and severe hurricanes and perpetual summertime droughts in many places, particularly in the US Midwest. Paradoxically, more intense winter storms will occur in some places and climatic conditions for agriculture will improve in some areas, such as in Russia (Gribbin, 1990; Bernard, 1993). There has been considerable debate over the ecosystem's carrying capacity for humans. If we define that carrying capacity as the level that the ecosystem can support without changing state more than it has over the duration of human history, then Figures 2 and 3 indicate that we exceeded that capacity in 1975. This is the point in time where exponential growth began to push MGT along a path which has taken it outside the previous range. This does not necessarily mean that humans could not survive if MGT is about 2oC higher than it has ever been in their history. However, we will have to adapt to a radically different climate pattern and, if MGT goes any higher than that, there could be disastrous problems. If MGT continues to increase beyond 2025 to 4oC above that in 1990, high- northern-latitude temperatures could be as much as 10oC higher than at the equator. The Arctic ice-cap would begin to melt and the permafrost under the tundra would start thawing out. As a consequence, a thick layer of rotting peat would contribute further to atmospheric CO2 and CH4 concentrations (Gribbin, 1990). With a number of human-made and natural positive-feedback elements in operation simultaneously, a threshold could be crossed (Meyers, 1995; Overpeck, 1996). Are these risks that we should be willing to take for the sake of short- term gains?