Climate change/Global warming
The earth receives energy from the sun in the form of short wave radiation. About half of the radiation that reaches the outer atmosphere makes its way to the surface of the earth. Of this energy, about half is reflected back to space with its wave length unaltered. The other half is absorbed by the earth’s surface and is then re-radiated in the form of long-wave radiation. It is this long-wave radiation that becomes absorbed, or trapped in the atmosphere to warm the planet. Carbon dioxide (CO2), a triatomic gas, is the principal atmospheric gas, though not the only one, that traps the long-wave radiation. This phenomenon is often termed the greenhouse effect or the atmospheric effect. Without the greenhouse effect, the planet would be a much colder and uninhabitable place. Other triatomic gases like water vapor (H2O) and more complex gases such as methane (CH4) add to the effect.
(CC Image (left) Coutesy of Global Warming Art via WikiMedia)
Global warming occurs when the greenhouse effect is enhanced through the process of enriching the atmosphere with greenhouse gases. Of course, the natural concentrations of greenhouse gases are in a constant state of flux through the natural cycling of greenhouse gases. When forests burn, for example, the atmosphere becomes enriched with CO2. But, when trees grow, they absorb carbon once again. The global warming issue discussed today is not about the natural cycling of organic and other natural forms of short-term carbon enrichment, but rather it is about the sources that derive from human activities, especially those that release carbon from fossil fuels.
When we burn gasoline, coal, fuel oil, and natural gas, carbon is released and forms carbon dioxide in the atmosphere. Because the carbon stored in fossil fuels is not part of the short-term carbon cycle, levels of carbon dioxide in the atmosphere are on the rise and have been for about a century, and especially so during the last 50 years. Presently, the burning of fossil fuels is responsible for about 75% of the human-induced CO2 enrichment of the atmosphere.
(CC Image (below, right) of simple diagram of annual carbon cycle from the DOE via Wikimedia Commons)
Burning biomass also contributes to CO2 enrichment of the atmosphere, but its role is a bit more complicated than for fossil fuels. Like fossil fuels, carbon is released when biomass burns, but unlike fossil fuel, the CO2 can be recaptured through reforestation. Rapid deforestation and other forms of land disturbance are, nevertheless, responsible for a significant proportion of the carbon enrichment of the atmosphere.
Other gases such as methane from agriculture and artificial gases like coolants also contribute significantly to the enhancement of the greenhouse effect.
The critical points in understanding global warming are: 1) ample evidence suggests that it is occurring; 2) the evidence overwhelmingly points to enhanced radiative forcing through the enrichment of the atmospheric greenhouse gases that are being released by human industrial processes, primarily fossil carbon and equivalent emissions; 3) it has been accelerating and certain aspects of it have accelerated faster than early models predicted; 4) globally we are doing little to mitigate the causes and consequences; 5) adaptation (to the extent that adaptation is possible) requires that we implement many of the same strategies that were needed to avoid the impacts; and 6) many other environmental maladies would benefit from global warming mitigation measures (e.g., biodiversity loss).