Jökull - 01.01.2005, Blaðsíða 2

Wallace S. Broecker
Figure 1. Atmospheric CO2 contents for past times (blue), for the present (yellow) and for the future (red). The
scale on the left is concentration in parts per million. The scale on the right is for the temperature change asso-
ciated with each of these CO2 levels. The logarithmic spacing of the latter reflects the progressive saturation of
CO2’s absorption bands as its concentration increases. – Styrkur koltvíoxíðs í andrúmslofti í fortíð (blár litur),
nútíð (gulur) og í framtíð (rauður) ásamt samsvarandi hitabreytingum. Lógariþmíski kvarðinn endurspeglar
vaxandi mettun orkuísogs koltvíoxíðs með auknum styrkleika þess. Breytingar á hitastigi fyrir mismunandi
magn CO2 í andrúmslofti eru einnig sýndar.
CO2 produced as the result of deforestation, fossil fuel
burning accounts for the 30 percent increase which
has occurred since the beginning of the Industrial
Revolution. This cannot be disputed for the increase
is only half as large as would be the case if all the CO2
produced by coal, petroleum and natural gas combus-
tion had remained airborne. In several independent
ways, it has been documented that much of the other
half of this CO2 has been sucked up by the ocean
(Quay et al., 2003). The small unaccounted-for re-
mainder appears to have gone into increased storage
of carbon in vegetation and soils. Models which in-
clude the atmosphere, ocean and terrestrial biosphere
suggest that this 50–50 split between the atmosphere
on one hand and the ocean plus terrestrial biosphere
on the other will apply throughout the coming century.
The concentration of CO2 in the atmosphere has
already reached 380 parts per million (up 100 ppm
from its pre-industrial value of 280 parts per million;
see Figure 1). It is currently rising by nearly two parts
per million per year. But, if fossil fuels continue to
supply 85 or so percent of the world’s energy, as pop-
ulation increases and as the traditionally poor nations
industrialize, this rate of increase is expected to dou-
ble and perhaps even triple.
In this regard, it must be kept in mind that the rise
in CO2 will not be stemmed by a shortage of fossil
fuels. Although the reserves of petroleum and natu-
ral gas are finite, those of coal are virtually unlimited.
Further, as coal can be economically converted into
gasoline, there is no danger that fuel for our trans-
portation fleet will fall into short supply. Coal alone
2 JÖKULL No. 55, 2005