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Many scientists agree that the earth is warming up due to the addition of anthropogenically produced greenhouse gases (CO2, CH4, NOx) to the atmosphere. Current estimates place the expected level of global warming over the next century to be between 1.0 and 4.5 oC. Recent ocean research suggests that the higher end estimate is closer to the truth based on increased heat storage in the oceans.
An increase of 3oC would make this the warmest period in the past 100,000 years, while an increase of 4oC would make the earth the warmest its been since the Eocene Epoch about 40,000,000 years ago.
While the absolute degree change would not make the planet warmer than it has been in the past, the rate at which that change takes place could have major effects on species diversity. Current estimates would put the rate of change at between 15 and 40 times the rate of past natural changes.
Changes is the global temperature patterns would trigger widespread alterations in the rainfall pattern, with some areas receiving a major increase in rainfall, while others experience major droughts. A long term drying trend is predicted for summers in midlatitude interior continental regions, with up to a 40% decrease in precipitation in the Great Plains.
Increased concentrations of CO2 may accelerate the growth of some plants at the expense of others which would destabilize natural communities. Greater warming is expected to occur in higher latitudes, suggesting that temperate and arctic species would be placed in greater danger than their tropical relatives. While continued melting of the ice caps would raise sea level, flooding coastal areas.
SHIFT OF SPECIES RANGES
The most obvious effect of global warmnimng will be the shift in species ranges, since species generally track climatic optima. There is, for instance, abundant fossil evidence from the Pleistocene for shifting plant and animal ranges due to climatic warming and cooling.
Species can shift their ranges both latitudinally (north to south) or through change in elevation (see Figure below). Remember, that a 3oC change in temperature can equally be achieved by a roughly 500m. change in elevation of a 250 km. change in latitude. In the example below species "A" will go extinct locally due to warming, while species "B" will suffer a severe range reduction leading to intensified intra-specific competition for space.