Climate Change Glossary (M-Z)
Methane : A hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 23 times that of carbon dioxide (CO2). Methane is produced through anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and petroleum, coal production, and incomplete fossil fuel combustion.Metric Ton: Common international measurement for the quantity of greenhouse gas emissions.Non-Methane Volatile Organic Compounds (NMVOCs): Organic compounds, other than methane, that participate in atmospheric photochemical reactions.Oxidize: To chemically transform a substance by combining it with oxygen.Ozone Layer: The layer of ozone that begins approximately 15 km above Earth and thins to an almost negligible amount at about 50 km, shields the Earth from harmful ultraviolet radiation from the sun.Ozone Precursors: Chemical compounds, such as carbon monoxide, methane, non-methane hydrocarbons, and nitrogen oxides, which in the presence of solar radiation react with other chemical compounds to form ozone, mainly in the troposphere.Particulate Matter (PM): Very small pieces of solid or liquid matter such as particles of soot, dust, fumes, mists or aerosols.Photosynthesis: The process by which plants take CO2 from the air (or bicarbonate in water) to build carbohydrates, releasing O2 in the process.Reforestation: Planting of forests on lands that have previously contained forests but that have been converted to some other use.Respiration: The process whereby living organisms convert organic matter to CO2, releasing energy and consuming O2.Solar Radiation: Radiation emitted by the Sun. It is also referred to as short-wave radiation.Trace Gas: Any one of the less common gases found in the Earth’s atmosphere. Nitrogen, oxygen, and argon make up more than 99 percent of the Earth’s atmosphere. Other gases, such as carbon dioxide, water vapor, methane, oxides of nitrogen, ozone, and ammonia, are considered trace gases.Troposphere: The lowest part of the atmosphere from the surface to about 10 km in altitude in mid-latitudes (ranging from 9 km in high latitudes to 16 km in the tropics on average) where clouds and “weather” phenomena occur.Ultraviolet Radiation (UV): The energy range just beyond the violet end of the visible spectrum. Although ultraviolet radiation constitutes only about 5 percent of the total energy emitted from the sun, it is the major energy source for the stratosphere and mesosphere, playing a dominant role in both energy balance and chemical composition.Wastewater: Water that has been used and contains dissolved or suspended waste materials.Water Vapor: The most abundant greenhouse gas, it is the water present in the atmosphere in gaseous form. Water vapor is an important part of the natural greenhouse effect. While humans are not significantly increasing its concentration, it contributes to the enhanced greenhouse effect because the warming influence of greenhouse gases leads to a positive water vapor feedback.