Climate Change Primer
Climate Change Consequences
If greenhouse gases continue to be emitted into the Earth’s atmosphere at roughly the current rates, the resulting consequences will have far-reaching impacts:
The average surface temperature of the planet is expected to increase by about 0.2oC (0.3oF) per decade (IPCC 2007), reaching from 1.8oC to 4.0oC (3.2oF to 7.2oF) by the end of this century. Climate models estimate that increases in temperature will raise sea level between 0.28m and 0.42m by the end of the century, relative to the 1980-1999 mean sea level. But these estimates are conservative, as they are based on rates of ice flow from Greenland and Antarctica observed from 1993 to 2003. Other processes that affect ice flow were not included in the models, and more recent observations suggest that warming could increase the vulnerability of the ice sheets, increasing future rates of sea level rise above projections.
Warming tends to reduce the uptake of carbon by the oceans and terrestrial ecosystems, thereby increasing the fraction of carbon emissions that remain airborne and, thus, increasing the rate of CO2 increase in the atmosphere and the rates of warming above those projected by models.
Because of the intensification of the hydrological cycle with warming, heavy precipitation events will become more frequent, and future hurricanes and typhoons will be more intense. Snow cover is expected to contract; permafrost to thaw; and sea ice to shrink. Furthermore, the warming will not be evenly distributed over the surface of the earth but greater at high latitudes. Because as much as a third of the world’s terrestrial carbon is stored in the soils and peats of these high-latitude systems, the increased temperatures and permafrost thawing have the potential to release large quantities of CO2 to the atmosphere. This positive feedback could reverse the natural terrestrial sink that has prevailed over the last decades.
The increasing concentrations of carbon dioxide will also continue to increase the acidification of the oceans.
In short, the average global warming of 0.75oC (1.3oF) since the late 1800s has already increased the frequency of droughts, fires, floods in different parts of the world, increased the number and intensity of heat waves, and contributed to the spread of infectious diseases. To prevent further climatic disruption, including reduced productivity of food crops, emissions must not be allowed to increase, or even to remain constant. They must be reduced dramatically and quickly. The effects of the warming already observed indicate that an average warming of 2.0oC (3.6oF) is too much. The concentration of CO2 in the atmosphere must not be allowed to increase above 400 ppm and should be restored to 350 ppm or less.