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A polycarbonate is an oxocarbon dianion consisting of a chain of carbonate units, where successive carbonyl groups are directly linked to each other by shared additional oxygen atoms. That is, they are the conjugate bases of polycarbonic acids , the conceptual anhydrides of carbonic acid , or polymers of carbon dioxide .
Greenhouse gases make the atmosphere near Earth's surface mostly opaque to longwave radiation. The atmosphere only becomes transparent to longwave radiation at higher altitudes, where the air is less dense, there is less water vapor, and reduced pressure broadening of absorption lines limits the wavelengths that gas molecules can absorb. [56] [46]
Although single layer polycarbonate sheeting is more flexible than polycarbonate in twinwall configuration, it still retains significant advantages over alternative materials, including glass. A typical 6mm sheet has a density of 0.72 g/cm^2 [6] and a thermal insulation R value of 0.3 m^2°C/W, while allowing 80% of visible light pass through. [7]
Polycarbonate sheeting in a greenhouse The second largest consumer of polycarbonates is the construction industry, e.g. for domelights, flat or curved glazing, roofing sheets and sound walls . Polycarbonates are used to create materials used in buildings that must be durable but light.
where σ is the absorption cross section of a single CO 2 molecule, and n(y) is the number density of these molecules at altitude y. Due to the high dependence of the cross section in wavelength, the OD changes from around 0.1 at 13 microns to ~10 at 14 microns and even higher beyond 100 at 15 microns, then dropping off to ~10 at 16 microns, ~1 ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 27 February 2025. Gas in an atmosphere with certain absorption characteristics This article is about the physical properties of greenhouse gases. For how human activities are adding to greenhouse gases, see Greenhouse gas emissions. Greenhouse gases trap some of the heat that results when sunlight heats ...
Absorptions bands in the Earth's atmosphere created by greenhouse gases and the resulting effects on transmitted radiation. In spectroscopy, an absorption band is a range of wavelengths, frequencies or energies in the electromagnetic spectrum that are characteristic of a particular transition from initial to final state in a substance.
RCP 2.6 is a "very stringent" pathway. [6] According to the IPCC, RCP 2.6 requires that carbon dioxide (CO 2) emissions start declining by 2020 and go to zero by 2100.It also requires that methane emissions (CH 4) go to approximately half the CH 4 levels of 2020, and that sulphur dioxide (SO2) emissions decline to approximately 10% of those of 1980–1990.