[SOLVED] Why is CO2 a green house gas? [CLOSED]

[ljcox]

What happens when a CO2 gas molecule in the atmosphere absorbs a photon of infrared radiation which has been emitted by the Earth’s surface?

What about photons that are coming in from the Sun?

As far as I can see, incoming photos would also collide with some of the CO2 molecules.

So why does more heat come in than goes out? Any assistance will be appreciated.

 

[andre_luis]

Re: Why is CO2 a green house gas?

It is just a matter of absorption efficiency of gases along with their concentration in Atmosphere, in fact all gases absorb energy from EM waves, however CO₂ in particular, has a maximum absorption efficiency close to the wavelength of the outgoing wavelength that emanates from the Earth's surface. Note that the energy coming from the Sun upon the Earth has a spectrum that is not the same as that radiated from the Earth. Refer to this graph:

 

[wwfeldman]

Re: Why is CO2 a green house gas?

EM radiation from the sun is approximately a black body (cavity radiator) at about 5500 kelvin
EM radiation from the earth is approximately a black body (cavity radiator) at about 300 kelvin

CO2, CO, Methane act as green house gases because they allow EM from sun in.
in andre's graph, the incoming solar radiation peaks in the visible range, and passes through the atmosphere
while the outgoing earth radiation peaks in the infrared/microwave region where at least some
of the radiation does not escape.

Green houses and parked cars work this way. Solar radiation comes in, passing through the glass walls,
(cavity radiator, 5000 kelvin) warms the plants and whatever is in the greenhouse (car).

The stuff in the greenhouse (car) re-radiates (cavity radiator about 300 kelvin) but the glass walls do not pass the
wavelength of the outgoing radiation, so the heat is trapped inside

 

[andre_luis]

Re: Why is CO2 a green house gas?

Another point to consider is that due to the complexity of the structure of the chemical compounds present in the atmosphere, from the simplest (atoms) to the most complex (molecules), there are multiple frequencies at which such absorptions occur at each substance as well as varying along the EM spectrum, so strictly speaking a more accurate value of the % absortion of each substance would be a bit more complex.

 

[Ratch]

Re: Why is CO2 a green house gas?

To the Ineffable All,

I really laugh when I hear all the outcries about climate change due to CO2. Climate change has been with us since the dawn of time, no doubt about that. It's about time folks learned a few facts. CO2 and water vapor have about the same thermal conductivity, or inversely, insulating value. But, CO2 content in the atmosphere is miniscule compared to water vapor. Even if we tax the US a trillion dollars in carbonated credits, India and China and the developing states of North Africa and Southeast Asia will be more that happy to fill the quota for free. And, don't forget the 100 or so of volcanoes and fumaroles around the world that are pumping out CO2 like crazy without buying carbon credits. And yet we have an infinitesimal amount of CO2 in the atmosphere. So what is causing the increase in the CO2? Probably the increase in the average temperature of the climate. So what is causing the increase in the temperature? Remember back a few ten thousand years ago when the Earth was covered with a ice sheet. There was no man-made CO2 source then, was there? And yet, the Earth warmed without CO2 to what it is today. So what is the mechanism that controls the heat the Earth receives.

The answer is is of course the SUN. The Sun outputs two things: particles call "solar wind", and infrared radiation. The solar wind we can observe as Northern and Southern Lights, and the infrared radiation needs no explanation. The Earth is also bombarded with cosmic radiation from interstellar space, which can be observed in a Wilson Cloud Chamber. These cosmic rays help form clouds which shield the Earth from the infrared rays of the Sun and keep it cooler. However, when the Sun, becomes "active" and spews out an excessive amount of solar wind, it interacts with the magnetic field of the Earth and "chases" away the cosmic rays, thereby causing less clouds to form and allowing the Earth to become warmer. These changes are not immediate, but given a sufficient time become inevitable. When the Earth warms, CO2 is released from the water and soil. Therefore, the increase in CO2 is an effect of temperature increase and not the cause of temperature increase.

I only know of one Entity that can control the Sun and thereby the global climate of Earth. It is not humankind.

Ratch

 

[wwfeldman]

Re: Why is CO2 a green house gas?

i am not an expert in geophysics, atmospheric physics, ocean chemistry and physics etc etc
and i doubt you are

i have yet to hear from any source that the sun is behaving differently in the last 10, 20 50 years than it has previously
NASA, NOAA, the solar physics community, etc would have reported it
it would be all over the news

the sun radiates like a black body (cavity radiator) at about 5500 kelvin
that include all frequencies, not just infrared

water and water vapor are not greenhouse gases
they let energy in from the sun, and let it back out when earth re-radiates, as noted above
CO, CO2 and methane let the energy in from the sun, but trap the re-radiated energy from earth

i do not think the solar wind chases away cosmic rays
they all interact with the earth's magnetic field - do you have a source?

you're right about all the volcanoes and etc

as for THE CREATOR adjusting the sun, the question is why?
one cannot know since we have an incognito creator (that is, we cannot know the mind of G-d)
if G-d is responsible, i posit that its because we aren't taking good care of his planet

so we need to clean up our act and the planet

you have moved the question out of the realm of physics and into the realm of religion
i expect there's a forum for that