Infrared radiation1
which is reflected from the
Earth's
surface is of longer wavelength than the incident
solar radiation. That means that the carbon dioxide
(CO2)
and water (H2O) constituent gases in the atmosphere
offer an increased propensity to absorb the reflected radiant
energy than the incident radient energy. This absorption
asymmetry is known as the greenhouse effect. Without this
effect, the average temperature at the
Earth's
surface would be below the freezing point of water.
In addition to CO2, other
constituent greenhouse gases in the atmosphere which are of
present concern are methane (CH4),
nitrous oxide (N2O),
chlorofluorocarbons (CFC-11 and CFC-12), and the
halocarbons.2
The respective concentrations of these gases in the atmosphere
have been increasing markedly since the beginning of the
industrial era around
1750 ce,
as shown in the Figure below.
The dramatic spike in concentrations are of concern because the
respective gases are chemically stable in the atmosphere, and
therefore can persist for many decades, sometimes even centuries.
This means that increased emissions of these gases arising from
human activity can potentially have a very long-term influence on the
Earth's
climate.
Histories of the globally averaged normalised atmospheric
concentrations of the
carbon dioxide
(CO2),
methane
(CH4) and
nitrous oxide
(N2O)
greenhouse gases over the last 2000 years. The industrial
era began around 1750. Normalised concentrations are
expressed as the relative mole faction, i.e., as the number
of molecules of the gas in a well-mixed atmospheric sample
divided by the corresponding number in 1750. The plot
combines data from measurements of gas concentrations
trapped in ice cores at Law Dome, Antarctica, and of
directly measured marine surface annual mean data.
In the figure, data for the ice cores at Law Dome were accessed
from the US's National Oceanic and Atmospheric Administration
(NOAA).[1]
Marine surface annual mean data were also accessed from the
NOAA.[2][3][4]
1
I declare this to be my own work, entirely. In particular, no AI was used in any research, analysis, synthesis, writing, nor typesetting of this work. In short, AI was not recruited at any time in this work. Errors and inaccuracies are therefore proudly my own.
2
The halocarbons are a group of gases containing flourine, clorine and bromine.
[2]Ed Dlugokencky and Pieter Tans.Trends in Atmospheric Carbon Dioxide.Earth System Research Laboratory, Global Monitoring Division, National Oceanic and Atmospheric Administration.See also 'ftp://aftp.cmdl.noaa.gov/products/trends/co2/co2_annmean_gl.txt'.Accessed 10 March 2019.https://www.esrl.noaa.gov/gmd/ccgg/trends/gl_full.html
[3]Ed Dlugokencky and Pieter Tans.Trends in Atmospheric Methane.Global Monitoring Division, National Oceanic and Atmospheric Administration.See also 'ftp://aftp.cmdl.noaa.gov/products/trends/ch4/ch4_annmean_gl.txt'.Accessed 10 March 2019.https://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/
[4]Ed Dlugokencky.Combined Nitrous Oxide data.Earth System Research Laboratory, Global Monitoring Division, National Oceanic and Atmospheric Administration.See also 'ftp://ftp.cmdl.noaa.gov/hats/n2o/combined/HATS_global_N2O.txt'.Accessed 10 March 2019.https://www.n2olevels.org/
