Greenhouse Gas Emissions

Abstract

BackgroundA greenhouse gas (GHG) is an atmospheric gas that slows the rate at which heat radiates into space, thus having a warming effect on the atmosphere. GHGs include water vapor, carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide, chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs) and some other halogenated gases. Greenhouse gases in the atmosphere make the earth considerably warmer than it otherwise would be.1 However, excessive CO 2 emissions have caused an imbalance in the planet's natural ability to absorb or use CO 2 , resulting in steadily increasing CO 2 concentrations. Concentrations of other greenhouse gases are rising as well. Atmospheric concentrations of CO 2 (379ppm) and CH 4 (1774 ppb) in 2005 exceed by far the natural range over the last 650,000 years. Global increases in CO2 concentrations are due primarily to fossil fuel use, with land-use change providing another significant but smaller contribution.2 Emissions of GHGs are substantially larger than emissions of other manmade pollutants. The United States alone released more than 5.7 billion metric tons of CO 2 from combustion in 2005, and net U.S. emissions of GHGs, expressed as CO 2 equivalents, 3 totaled 6.4 billion metric tons in that year.4 This is about 250 times the national emission of other major pollutants such as nitrogen oxides (NO x ), sulfur dioxide (SO 2 ), and volatile organic compounds (VOCs).

Designing Mesoporous Photonic Structures for High-Performance Passive Daytime Radiative Cooling

“…Cooling and refrigeration are becoming increasingly important for human society due to climate change, industrial development, and the improvement of living standards . Current mainstream electricity-powered compression-based technologies are energy consuming and generate greenhouse and/or ozone-depleting gases . They also have a net heating effect, since heat is not lost outside the terrestrial environment and the work used is ultimately dissipated as heat too .…”