Climate Change
Climate change, a more general term for global warming, is a global average change in temperature, precipitation, and other weather patterns due to the unprecedented emissions of geologically-stored carbon and chemically-changed nitrogen into the atmosphere.
Over millions of years, carbon in the earth-atmosphere system was stored through natural processes underground as coal, oil, and natural gas. Since the industrial revolution began, these three sources of carbon were mined and burned as sources of energy, resulting in billions of tons of stored carbon to be released to the atmosphere in only about 100 years (Fig. 1). Carbon emitted in this way becomes air pollutants such as carbon monoxide (CO), carbon dioxide (CO2), and methane (CH4) to name a few.
Figure 1: Atmospheric CO2 concentration over last 400 000 years, and it's correlation to temperature (Center for Climate and Energy Solutions)
On a similar scale, nitrogen in various chemical forms has been used extensively in agriculture to feed an increasing population, and is also emitted in toxic forms from combustion engines.
In addition to reducing air quality, CO2, CH4 and N2O are greenhouse gases (GHGs). GHGs – unlike oxygen (O2) and nitrogen (N2), which are radiatively inert – absorb infrared radiation, resulting in the warming of the lower atmosphere (Fig. 2). Atmospheric concentrations of CO2 and CH4 have increased 36% and 148% respectively since the industrial revolution began.
- Figure 2: Radiative energy balance of Earth with the role of GHGs circled (IPCC report, 2007).
The human-induced increase in the atmospheric GHG concentrations from natural levels has resulted in a global average temperature increase, melting of polar ice and glaciers, sea level rise, increased occurrence and severity of hurricanes and storms, a decrease in the recovery of the ozone hole, ocean acidification (because the ocean absorbs some of the excess atmospheric CO2), increased occurrence of wild fires and drought in some areas and flooding in others, increases in pests such as the North American pine beetle, increases in mosquito carrying diseases such as malaria, and so on.
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