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  • Anthropogenic climate change: Climate change caused by human activity, most importantly the effect that the human use of fossil fuels has on increasing the average temperature of the Earth's atmosphere.
  • deg C, degrees Celsius: The measure of temperature used in scientific papers about climate change. One deg C is equal to 1.8 deg Fahrenheit.
  • ppm: parts per million. The standard form of measurement for CO2 and other greenhouse gasses in the atmosphere. 10,000 ppm equals 1%. While parts per million may seem like a small amount, here are some numbers to compare: 50 million years ago CO2 levels were 3500 ppm, which was enough to allow temperate forests to grow on Antarctica; the last ice age had CO2 levels of about 85 ppm; and in 1500 AD, before industrialization became common, CO2 was at 290 ppm. It is now at around 385 ppm.
  • Greenhouse effect: The absorption or reflection by the atmosphere of heat radiating from the Earth's surface--effectively a global insulator or blanket. The same reason that gardeners use a greenhouse (house with glass walls and ceilings) to protect plants in cold weather: sunlight entering through the glass is absorbed by the soil and reradiated as infrared energy, which is trapped and reflected back to the soil by the glass, keeping the greenhouse warm.
  • Greenhouse gas: A gas that contributes to the greenhouse effect by absorbing or reflecting escaping heat and light back towards the Earth. There are 14 greenhouse gases, but the most important by far are carbon dioxide, methane, and nitrous oxide.
  • Albedo: the amount of radiant energy that an object or material reflects. Changes in the Earth's albedo will have a major role to play in any future change in the climate.
  • Geoengineering: Engineering on a planetary scale. With reference to climate change, this refers to ways to reduce the amount of sunlight hitting the earth to balance the increased amount of energy trapped by greenhouse gasses. One proposal is to place a semi-reflective screen at the L1 Point, a stable orbit that always remains between the earth and the sun. Other proposals would raise the earth's albedo by injecting finely ground sulfur particles or other reflective substances into the upper reaches of the atmosphere; it is well known that large volcanoes can cause worldwide cooling by this method. Other albedo-enhancing proposals involve cloud-seeding (to make the atmosphere cloudier and more reflective) as well as more mundane proposals to require all new buildings to have reflective or energy-absorbing (solar or garden-style) roofs and all paved surfaces to be built with high-reflectivity concretes instead of macadam or "blacktop." Geoengineering could help "buy time" for a solution by slowing down the increase in temperature due to increased greenhouse gasses. Early models indicate that aggressive use of an orbital screen or a high-altitude injection process could allow us to maintain a fairly constant global average temperature in this century, but at the cost of reduced total rainfall and other side-effects.



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FutureoftheUS 		Latest page update: made by FutureoftheUS , Oct 4 2008, 9:06 PM EDT (about this update About This Update FutureoftheUS Edited by FutureoftheUS


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