From wiki:
Quote:The explanation given in most sources for the warmer temperature in a greenhouse is that incident solar radiation (the visible and adjacent portions of the infrared and ultraviolet ranges of the spectrum) passes through the glass roof and walls and is absorbed by the floor, earth, and contents, which become warmer and re-emit the energy as longer-wavelength infrared radiation. Glass and other materials used for greenhouse walls do not transmit infrared radiation, so the infrared cannot escape via radiative transfer. As the structure is not open to the atmosphere, heat also cannot escape via convection, so the temperature inside the greenhouse rises. This is known as the "greenhouse effect".[14][15] The greenhouse effect, due to infrared-opaque "greenhouse gases", including carbon dioxide and methane instead of glass, also affects the earth as a whole; there is no convective cooling as air does not escape from the earth.
https://en.wikipedia.org/wiki/GreenhouseThat is simple enough to understand: visible light passes through glass or transparent or translucent plastic easily enough (some gets reflected and that is why we can see the bally greenhouses
) some gets absorbed and the wavelength lengthens from visible light to infrared as the light loses energy. The walls of the greenhouse prevent IR from escaping, heating the greenhouse.
I think everyone agrees that it is warmer in a greenhouse than outside it? I mean, if it wasn’t farmers wouldn’t go to the trouble and expense of building the blessed things, right?
Now, as the last couple of sentences of the wiki article indicate, certain gases in the atmosphere can also block infrared radiation. That is why it is said that the earth is warming from “the greenhouse effect.” This property of carbon dioxide in particular has been known since the 19th century.
That carbon dioxide can block infrared radiation can be easily demonstrated in the lab by holding a glass container of CO2 in between a heat source and a spectrometer or even a sensitive thermometer. A container of air or pure oxygen or pure hydrogen etc does not block IR.Have a look here for one such demonstration:
So as we burn more fossil fuels we put more and more carbon dioxide, CO2, into the atmosphere and so increase the greenhouse effect of the atmosphere, warming the earth. Nobody has a credible set of global temperatures over time showing that the global temperature is static or declining. Nobody!
We know other gases have an even stronger greenhouse effect: methane, CH4, a carbon atom bonded to four hydrogen atoms. Methane is being released as the Arctic tundra thaws due to the greenhouse effect. Methane has a much stronger greenhouse effect than carbon dioxide. Fortunately, methane has a shorter life than carbon dioxide and over time changes into carbon dioxide. But there is another greenhouse gas (GHG) with an even stronger greenhouse effect than methane: nitrous oxide:
Quote:Nitrous oxide (N2O): Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.
https://www.epa.gov/ghgemissions/overview-greenhouse-gasesFortunately, nitrous oxide is only present in minute quantities but it is concerning that its concentration is increasing:
Quote:There’s a greenhouse gas whose concentration is on the rise because of human activities. But it’s not the one you’d expect: it’s nitrous oxide (N2O), also known as laughing gas. It’s been accumulating in the atmosphere since the 1700s, and it’s powerful and persistent. One molecule of N2O has the same greenhouse warming power of 300 molecules of carbon dioxide. Once that N2O molecule gets into the upper atmosphere, it can stay there for more than 100 years before it’s destroyed naturally.
Fortunately, air has about 1,000 times less N2O than carbon dioxide. But the rise in N2O has accelerated over the past two decades. And while we know where the excess carbon dioxide is coming from, we don’t know precisely how N2O is produced.
http://www.whoi.edu/oceanus/feature/another-greenhouse-gas-to-watch--nitrous-oxi...But N2O is being released faster at the poles than was thought:
https://www.scientificamerican.com/article/nitrous-oxide-poses-fresh-threat-to-t...http://www.sciencedirect.com/science/article/pii/S1352231002003400So the more powerful GHGs methane and nitrous oxide are starting to enter the atmosphere faster as global warming continues. No wonder we see that the fifteen years recording the highest temperatures have all occurred this century—which is only 17 years old!
Climate sensitivityClimate sensitivity is the degree of change in global temperature in response to a change in GHG concentrations. Since the globe is warming due to the greenhouse effect climate sensitivity is measured as the increase in global temperature per doubling of CO2 concentration in the atmosphere:
Quote:Climate sensitivity has been hard to pin down accurately. Climate models give a range of 1.5-4.5℃ per doubling of CO₂, whereas historical weather observations suggest a smaller range of 1.5-3.0℃ per doubling of CO₂.
https://theconversation.com/why-the-climate-is-more-sensitive-to-carbon-dioxide-...To be cont’d
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