Ecoinformatics Problems of Global Climate Change - New Ecoinformatics Tools in Environmental Science: Applications and Decision-making - page 397

are well-mixed, and take many years to leave the atmosphere. Greenhouse gases in
the atmosphere absorb and re-emit some of the outgoing energy radiated from the
Earth

s surface, causing that heat to be retained in the lower atmosphere. The global
warming potential (GWP) depends on both the ef

'

ciency of the molecule as a
greenhouse gas and its atmospheric lifetime (Table 5.8 ).
From 1750 till now the CO 2 concentration in the atmosphere has increased by
about one third, reaching the highest level for the last 420 thousand years (and,
probably, during the last 20 million years), which is illustrated by the data from ice
cores (IPCC 2001, 2007). The growth of CO 2 concentration by about two thirds
during the last 20 years is explained by emissions to the atmosphere from fossil fuel
burning (contributions of deforestation and, to a lesser extent, cement industry
constitute one third). Figure 5.13 characterizes this data. It is of interest that by the
end of 1999, CO 2 emissions in the USA exceeded their 1990 level by 12 %, and by
2013 their further increase should raise this value by another 10 %. Nevertheless,
according to the Kyoto Protocol, the emissions should be reduced by 7 % by 2013
compared to the level of 1990, which requires a total reduction in emissions of by
about 25 %.
According to available observational data, both the World Ocean and land are
currently global sinks for CO 2 . In the ocean, both chemical and biological processes
are responsible; on land we observe an enhanced

“ ”

of vegetation due to
increased concentrations of CO 2 and nitrogen, as well as with changes in land use.
Yet much remains unclear about the global carbon cycle (Kondratyev et al. 2003c).
In particular, contradictions in the estimates of the role of the biosphere and ocean
in the global carbon cycle remain to be resolved.
There is no doubt that fossil fuel burning will remain the main factor in the
growth of CO 2 concentration in the 21st century. The role of the biosphere (both the
ocean and land) as a barrier to the growth of CO 2 concentration will be reduced in
time. According to the IPCC-2001 Report,

fertilization

the probable interval of CO 2

Table 5.8 Atmospheric lifetime and GWP relative to CO 2 at different time horizon for various
greenhouse gases ( http://en.wikipedia.org/wiki/Global-warming_potential )
Gas name Chemical formula Lifetime (years) Global warming potential

(GWP) for given time horizon
20-year 100-year 500-year

Carbon dioxide CO 2 30 95 1 1 1

-

Methane CH 4 12 72 25 7.6

Nitrous oxide N 2 O 114 289 298 153

CFC-12 CCl 2 F 2 100 11,000 10,900 5,200

HCFC-22 CHClF 2 12 5,160 1,810 549

Tetra fl uoromethane CF 4 50,000 5,210 7,390 11,200

Hexafluoroethane C 2 F 6 10,000 8,630 12,200 18,200

Sulfur hexa fl uoride SF 6 3,200 16,300 22,800 32,600

Nitrogen tri fl uoride NF 3 740 12,300 17,200 20,700