What is Greenhouse gas: Definition and 15 Discussions

A greenhouse gas (GHG or GhG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). Without greenhouse gases, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F). The atmospheres of Venus, Mars and Titan also contain greenhouse gases.
Human activities since the beginning of the Industrial Revolution (around 1750) have increased the atmospheric concentration of carbon dioxide by almost 50%, from 280 ppm in 1750 to 419 ppm in 2021. The last time the atmospheric concentration of carbon dioxide was this high was over 3 million years ago. This increase has occurred despite the absorption of more than half of the emissions by various natural carbon sinks in the carbon cycle.At current greenhouse gas emission rates, temperatures could increase by 2 °C (3.6 °F), which the United Nations' Intergovernmental Panel on Climate Change (IPCC) says is the upper limit to avoid "dangerous" levels, by 2050. The vast majority of anthropogenic carbon dioxide emissions come from combustion of fossil fuels, principally coal, petroleum (including oil) and natural gas, with additional contributions from deforestation and other changes in land use.

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  1. O

    Chemical Engineer - MBA in Chemical Industry

    Experience in the fertilizer industry, with focus on environmental issues and energy recovery, clean technologies, process design and simulation, GHG balance. Published several studies on low carbon technologies as well as on Kyoto Protocol Communications.
  2. W

    Perception of Intl Journal of Greenhouse Gas Control - Impact Factor 4

    The international Journal of Greenhouse Gas Control. It has an Impact Factor of around 4, but what's the perception? Is it respected? Is it considered a good journal? There isn't a qualitative judgment online. My boss seems to look down on it, but it has a good impact factor.
  3. T

    Variations in Emissions Inventories?

    Are there multiple sources for an emissions inventory? For instance, how debated is the UNFCCC GHG inventory? (http://unfccc.int/ghg_data/items/3800.php) And is there any international inventory that has an emissions breakdown like the Australian governments? (http://ageis.climatechange.gov.au/#)
  4. Stephanus

    B Terraforming Venus: Why Nobody Discusses It?

    Dear PF Forum, Why nobody ever thinks of terraforming Venus? Many propose Mars, even as far as Europa (not the continent!) or Titan. Mars has very little atmosphere compared to Earth. Titan has thick atmosphere but too cold. I once read that Carl Sagan proposed the idea by spreading bacterias in...
  5. G

    Percent water vapor - greenhouse gas

    I'm have armchair interest in greenhouse gases. One of the interesting points is the amount of greenhouse effect that CO2 has versus water vapor. I go to this page http://www.climate4you.com/GreenhouseGasses.htm and find that the relative percentage of atmospheric humidity is 45%. I...
  6. F

    How exactly does CO2 behave as a greenhouse gas?

    Hi everyone, This is my very first post here, so hi! I've got a few questions about CO2 that maybe a physics buff can help me out with. I understand the basics about CO2 warming the atmosphere via absorption and re-emission (radiatively or kinetically) of Outgoing Longwave Radiation...but...
  7. I

    Greenhouse Gas Misunderstanding?

    Okay so I am a first time poster, hello to my fellow scientists. I need an expert opinion on a simple question I can't get around: I understand that Carbon Dioxide will absorb more energy from whatever radiation it comes into contact with than, say, Oxygen. That being said, I imagine the...
  8. R

    Model CO2 as Greenhouse Gas: Tips & Results

    I recently came across several apparently reputable sources (e.g., NASA, PBS) that describe a simple, elegant experiment intended to demonstrate carbon dioxide's role as a greenhouse gas. Each of them involves two sealed containers with thermometers - one containing air, the other containing...
  9. D

    Earthward Upper Stratospheric IR Radiation Cancels Most Greenhouse Gas Effect

    Atmospheric gases play a role in planetary temperature regulation Carbon dioxide levels have been rising rapidly in the Earth’s atmosphere and are linked by the IPCC to “global” warming. Recent failure of measured temperatures to advance with increasing carbon dioxide has called this assertion...
  10. R

    Is the Greenhouse Gas Equation Wrong?

    Hungarian scientist Ferenc Miskolczi has discovered the greenhouse gas equation Arthur Milne developed in 1922 contains a serious flaw. Milne mistakenly solved the differential equation involved by assuming an infinitely thick atmosphere. Miskolczi was working for NASA at the time and NASA...
  11. O

    Are Volcanic Emissions Really Greater Than Man-Made Greenhouse Gases?

    is it true that there are more greenhouse gasses released from a single Volcanic eruption than all of the gasses produced by man since the industrial revolution? If so, shouldn't that silence the global-warming advocates?
  12. A

    How the Greenhouse Gas Effect works

    How the Greenhouse Gas Effect Works We all know by now that the greenhouse gas effect depends upon absorption by greenhouse gas molecules of infrared energy radiated from the Earth’s surface, and which is then re-radiated by these molecules in all directions. Effectively, half the energy is...
  13. A

    Greenhouse Gas Effect and Carbon Dioxide

    Greenhouse Gas Effect and Carbon Dioxide I have been having some difficulty with this, so perhaps someone could please sort out any mistakes, and let me know. Consider a vertical column of the Earth’s atmosphere based on a square of area 1 m^2. This air column has a mass of 1.01×10^4...
  14. R

    Water vapour overlooked as greenhouse gas ?

    Hello all It seems that water vapour doesn't figure in greenhouse gas calcs & global warming. This site claims.. "Water vapor overwhelms all other natural and man-made greenhouse contributions." http://www.clearlight.com/~mhieb/WVFossils/greenhouse_data.html Are they right ? cheers
  15. B

    Calculating Earth's Greenhouse Gas Absorption

    Ok, here's the question. Without the greenhouse gases in Earth's atmosphere the temperature would be 250K. With them it is 40K higher (290K). Using the Stefan-Boltzman equation for flux ( F = σT4) what is the percentage of infrared radiation leaving the Earth's surface taht is...