Methane

The primary sources of methane in the atmosphere are agriculture and the use of fossil fuels. The main natural sources of methane are from decomposition of organic matter in wetlands, rice paddies, and bogs. Termites are also a source of methane. Methane was once called swamp gas and marsh gas because it was commonly observed to evolve from wetland areas filled with decaying organic material such as leaves and other vegetation. Methane is a by-product of the digestion of farm animals such as...

Ethanol Corn Sugar Cellulose

Ethanol, or grain alcohol, can be produced from corn, sugar beets, sugar cane, or other crops primarily by fermentation. Ethanol came onto the scene largely as a means of moving toward energy independence. Brazil currently uses ethanol to meet an estimated 40 percent of its transportation requirements. Presently, roughly 20 percent of the corn grown in the United States is converted to ethanol. Current farming methods use a high percentage of petrochemicals, which to some extent defeats the...

Emissions Trading Cap and Trade

Emissions trading is an approach that governments use to reduce pollutants, including greenhouse gases, to certain target levels. Incentives are provided to companies or organizations to reduce the release of these gases. The government sets a cap or limit on the amount of the greenhouse gas that can be released. If a company operates below the established cap, it has a credit that it can then trade or sell to another company that is having greater difficulties meeting the cap. Enforcement of...

Origin and Impact of Greenhouse Gases

The climate of the earth has gone through a recurring pattern of temperature changes which has brought the earth in and out of a series of historic ice ages. Gases in the atmosphere also have ebbed and flowed with the temperature cycles. However, the levels of greenhouse gases building up in the atmosphere today have never been this high throughout Earth's history. This chapter will explore where these greenhouse gases are coming from and how they are driving climate changes. There are several...

Solar Electricity Photovoltaics

Global Thermal Balance

Enough energy from the sun strikes the earth in 1 hour to provide all the energy consumed by the earth's entire population in 1 year. In most places, sufficient sunlight strikes the earth's surface to power an (energy-efficient) home and support a plug-in hybrid car. Solar energy stands out as an opportunity that overshadows all the other renewable energy sources and fossil fuels combined. Today, only a small fraction of this vast potential has been exploited. Solar cells were developed (by...

Burning Fossil Fuels

The fossil fuels are coal, oil, and natural gas. The name fossil fuels derives from the origin of these fuels from the remains of organic matter preserved from prehistoric times. Most of our energy used for electricity and transportation today comes from the burning of fossil fuels, which generates carbon dioxide as a by-product. As a result of fossil fuel combustion, carbon dioxide in the atmosphere is now 35 percent higher than it was a century and a half ago. Whenever anything containing...

Drought

Global Thermal Balance

Drought has become more common, especially in the tropics, since 1970. Droughts are becoming longer and more severe and are affecting a wider area. This is consistent with decreased precipitation in some areas and higher temperatures causing drying conditions. Increasing sea surface temperatures and loss of snow are direct contributors to drought. An index called the Palmer Drought Severity Index (PDSI) is used to compare the extent of local loss of surface land moisture. Figure 3-27 shows that...

Sunspot Cycles

In order to identify how much human activities are influencing the temperature of the earth, it is important to isolate changes that would be taking place without the presence of humans. Accurate measurements of solar output date back only as far as 1978, when satellites began measuring solar intensity outside the interfering influence of the earth's atmosphere. Details about how these satellites monitor the various aspects of the earth's climate can be found in Appendix C. Satellite...