The contribution of methane (CH4) to anthropogenic radiative forcing, including direct and indirect effects, is about 0.7 W/m2, or roughly half that of CO2. Also, changes in the load of CH4 feed back into atmospheric chemistry, affecting the concentrations of hydroxyl (OH) and ozone (O3). The increase in CH4 since the pre-industrial era is responsible for about half of the estimated increase in background tropospheric O3 during that time. It should be noted that changes in OH concentration affect the lifetimes of other greenhouse gases such as hydrochlo-rofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs).

In 2003, CH4 increased by about 5 ppb (parts per billion, 109, by dry air mole fraction), primarily due to increases in the Northern Hemisphere. This was followed by a small decrease in 2004 and little change from those levels in 2005. The globally averaged methane (CH4) concentration in 2005 was 1774.8 ppb, or 2.8 ppb less than in 2004.

Stratospheric ozone over Antarctica on September 29, 2005, reached a minimum of 110 Dobson units (DU). This represented the 10th lowest minimum level in the 20 years of measurement of stratospheric ozone. A Dobson unit is the most basic measure used in ozone research. The unit is named after G. M. B. Dobson, one of the first scientists to investigate atmospheric ozone. He designed the Dobson spectrometer, which is the standard instrument used to measure ozone from the ground. The Dobson spectrometer measures the intensity of solar UV radiation at four wavelengths, two of which are absorbed by ozone and two of which are not. One Dobson unit is defined to be 0.01 mm thickness at STP (standard temperature and pressure = 0°C and 1 atmosphere pressure). For example, when in an area all the ozone in a column is compressed to STP and spread out evenly over the area and forms a slab of 3 mm thick, then the ozone layer over that area is 300 DU.

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Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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