Page 15 - Managing Global Warming

Why do we have global warming? 9

Table 1.3 Properties of some GHGs related to global warming
Property GHG
N 2 O CFCs
CO 2
CH 4
Concentration (ppm) 413 1.7 0.32 0.0009
Lifetime (years) 50–200 12 120 45–1700
Contribution to overall
Greenhouse effect (%) 63 18 6 13
Global warming potential 1 25 120 6130–14,400
Data from Table 2 of reference Tuckett RP. The role of atmospheric gases in global warming. In: Letcher TM, editor.
Climate change, observed impacts on planet earth. 2nd ed. Oxford: Elsevier; 2016; p. 375–98.

The table also highlights the atmospheric concentrations, estimated life time in the
atmosphere, greenhouse effect percentage, and the potential for global warming of
greenhouse gases, taking CO 2 as unity.
Overall, human sources of CO 2 are much smaller than the natural emissions from
animals, plants, decaying animals, vegetation, and volcanoes [27]. However, human
activity has upset the balance in a cycle that has existed for thousands of years. The
amount of carbon on the earth and in the atmosphere is fixed, but it is in a dynamic
and equilibrium cycle, moving between living and nonliving things, and changing
into different carbon compounds such as carbon dioxide in the air and in the oceans,
solid carbonate rock, and the living cells of plants and animals. In the first step of the
cycle, plants take up CO 2 from the air through the process of photosynthesis and
release oxygen. The CO 2 is then converted into living cells. In the next step, the
animals eat the plants, and the carbon in the plant cells are used to build animal
tissue and cells. Animals also breathe in oxygen and exhale carbon dioxide, which
in turn enter the atmosphere and the cycle continues. Dead plants and dead animals
decompose and carbon is either released as CH 4 and CO 2 or stored in the soil.
Superimposed on this cycle is the exchange of CO 2 between the atmosphere and
the oceans. These processes were in near-perfect equilibrium before the industrial
revolution [27,28].

1.4 Indicators of climate change

The evidence that global warming is altering our climate is very well documented, and
almost no day goes by without more evidence for climate change. The indicators
include more extreme weather events in the future; melting of Arctic sea ice; Antarctic
Sea changes; land ice behavior (including glaciers and ice sheets); weather pattern
changes; bird ecology changes (including migration); mammal and insect ecology
changes and biodiversity loss; sea life and coral reef changes; marine diversity and
intertidal indicators; plant ecology and plant pathogen changes; rising sea levels;
and ocean acidification [29].