Seite - 171 - in Water, Energy, and Environment - A Primer

While there is a release of CO2 from natural biological processes, the observed recent temperature changes clearly have another origin. These ‘extra’ CO2 emissions derive from the combustion of coal, oil, and natural gas in electricity production, the combustion of oil in transportation vehicles, and the combustion of fossil fuels in industrial processes. The increasing use of lower-cost natural gas (a powerful greenhouse gas) in power production and industrial processes, possibly resulting in increased leakage into the atmosphere through insufficiently sealed infrastructure, is also a major concern. In addition, the release of N2O, another powerful greenhouse gas, from increased use of agricultural fertilizers, is a topic of increasing scientific study and concern. Finally, it should be noted that as global warming proceeds, andmore andmorewater vapor enters the atmosphere, this can have a feedback effect on global warming. For example, more clouds can bounce more solar radiation back into space, reducing the heating effect (negative feedback); but the presence of more water vapor can also amplify the global warming effect because water vapor absorbs infrared re-radiation from the oceans and land masses, a positive feedbackmechanism.Volcanic eruptions can also have amixed impact: the clouds of material produced by these eruptions, which can circle the globe, can reflect sunlight, but the small, dark-colored particulate matter they introduce into the atmosphere can absorb the Sun’s radiation and increase the heating effect. Other positive feedback mechanisms exist as well. Melting of Arctic Ocean ice changes the albedo (reflectivity) of the ocean from reflecting to absorbing, allowing increased ocean heating. The thawing of cold region permafrost, frozen layers below the Earth’s surface, can also exacerbate global warming by releasing trapped CH4 and other hydrocarbons, which are powerful greenhouse gases. All in all, a complicated set of physical phenomena that many people are workinghard to understand. Policy considerations 171