Increasing the use of clean energy is a key means to reducing fossil fuel-induced carbon dioxide (CO2) emissions that are the largest contributor to global climate change.  Energy from the sun keeps the Earth warm enough for comfortable human habitation.  This natural greenhouse effect is created when gases in the atmosphere — water vapor, CO2, and others — trap heat to keep the Earth from freezing.  However, when the concentration of greenhouse gases becomes too high, problems arise in the Earth’s climate.

These problems are experienced mostly in the form of extreme weather conditions, such as severe or no winters and extremely hot summers, as well as floods and droughts.

Human activities — particularly burning of fossil fuels (coal, oil and natural gas) — increase atmospheric CO2, methane, nitrous oxide and other gases, which, when they accumulate, increase the intensity of the natural “greenhouse effect” and result in global warming. America’s use of fossil fuel energy currently produces about one-fourth of the world's CO2 emissions.  Projections show that, in the absence of policies to impose controls CO2 concentrations in 2100 could be anywhere from 30% to 150% higher than they are today.

According to experts, several other sources of energy have the potential to produce huge quantities of power without the polluting effects of CO2.  Possibilities for primary energy sources include solar and wind energy, biomass, wave/tidal technology, hydroelectricity and landfill gas.  Non-primary sources include efficiency improvements, hydrogen production, super-conducting global electric grids, and geo-engineering.  Some of these sources, such as wind energy and biomass, are already commercially viable; others will require further research and development.