45
carbon dioxide
(shells and their metamorphosed products). By partly absorbing long-wave
radiation from earth to space, the atmospheric carbon dioxide has been and
still is acting as an insulator, helping planet earth to maintain an overall
higher temperature than otherwise would have been possible: the greenhouse earth. Organic forms of carbon constitute all living biomass as well as
organic matter in soils and sediments and organic gases like methane in the
atmosphere. Through photosynthesis, plants (on land) as well as algae (in the
sea) are converting inorganic carbon dioxide into an immense variety and
complexity of organic compounds. Most of this is being recycled by animal
respiration or bacterial breakdown, but a small portion escapes and
throughout geological times this has led to the formation of reservoirs of
organic carbon (~carbon, organic), as coal, petroleum, and natural (methane)
gas. The increased rate of combustion of such fossil fuels by mankind has
led to the rapid increase of atmospheric carbon dioxide, at the risk of rapidly
enhancing the insulating or greenhouse effect, possibly leading to global warming. Sources are less well defined for atmospheric levels of methane, which
are also rising rapidly and similarly affecting the heat balance of the earth.
Throughout geological times relatively slow shifts in the carbon cycle are
known to have been critical for corresponding climatic changes.
carbon dioxide (C0 2 ) gas resulting from oxidation (e.g., combustion) of elemental carbon (C) or reduced (i.e., organic) C; the only stable form of C when
following the laws of chemical thermodynamics, which, however, only apply
to equilibria in closed systems. Earth is an open system and the continuous
flow of solar energy has given rise through conversion of CO 2 by photosynthesis to the existence of all biota: the living planet. Carbon dioxide is dissolved in seawater where it is equilibrated with several other dissolved
forms, the bicarbonate ion (HC0 3 -) being very predominant. The total
amount of various forms of carbon dioxide (gaseous CO 2 , H 2 C0 3 , HC0 3 -,
CO/-) in ocean waters is 40 10 18 g C, exchanging at an annual rate of about
100 1015 g C with the 700 1015 in the atmosphere. The latter corresponds to
about 0.0353 % of the atmosphere consisting of carbon dioxide. This atmospheric concentration of 353 ml m- 3 in 1990 is higher than ever before in the
past 160000 years (as estimated from air bubbles trapped in the Antarctic
ice sheet) and increasing at an annual rate of about 2 ml m-3 as a result of
fossil fuel burning and rapid deforestation, possibly giving rise to global
warming. Currently, mankind introduces CO 2 at about 5.1 1015 g C per year
from fossil fuel burning, presumably another amount of CO 2 , about 2 1015 g
C per year, by deforestation. Of this total input of about 7 1015 g C per year
only about 2 1015 g C is retained in the atmosphere (causing the increasing
CO 2 concentration), the remaining about 5 10 15 g C presumably annually
being taken up by the biosphere and the oceans, slowly adding to the already
immense reservoir of CO 2 in seawater.
carbon dioxide
(shells and their metamorphosed products). By partly absorbing long-wave
radiation from earth to space, the atmospheric carbon dioxide has been and
still is acting as an insulator, helping planet earth to maintain an overall
higher temperature than otherwise would have been possible: the greenhouse earth. Organic forms of carbon constitute all living biomass as well as
organic matter in soils and sediments and organic gases like methane in the
atmosphere. Through photosynthesis, plants (on land) as well as algae (in the
sea) are converting inorganic carbon dioxide into an immense variety and
complexity of organic compounds. Most of this is being recycled by animal
respiration or bacterial breakdown, but a small portion escapes and
throughout geological times this has led to the formation of reservoirs of
organic carbon (~carbon, organic), as coal, petroleum, and natural (methane)
gas. The increased rate of combustion of such fossil fuels by mankind has
led to the rapid increase of atmospheric carbon dioxide, at the risk of rapidly
enhancing the insulating or greenhouse effect, possibly leading to global warming. Sources are less well defined for atmospheric levels of methane, which
are also rising rapidly and similarly affecting the heat balance of the earth.
Throughout geological times relatively slow shifts in the carbon cycle are
known to have been critical for corresponding climatic changes.
carbon dioxide (C0 2 ) gas resulting from oxidation (e.g., combustion) of elemental carbon (C) or reduced (i.e., organic) C; the only stable form of C when
following the laws of chemical thermodynamics, which, however, only apply
to equilibria in closed systems. Earth is an open system and the continuous
flow of solar energy has given rise through conversion of CO 2 by photosynthesis to the existence of all biota: the living planet. Carbon dioxide is dissolved in seawater where it is equilibrated with several other dissolved
forms, the bicarbonate ion (HC0 3 -) being very predominant. The total
amount of various forms of carbon dioxide (gaseous CO 2 , H 2 C0 3 , HC0 3 -,
CO/-) in ocean waters is 40 10 18 g C, exchanging at an annual rate of about
100 1015 g C with the 700 1015 in the atmosphere. The latter corresponds to
about 0.0353 % of the atmosphere consisting of carbon dioxide. This atmospheric concentration of 353 ml m- 3 in 1990 is higher than ever before in the
past 160000 years (as estimated from air bubbles trapped in the Antarctic
ice sheet) and increasing at an annual rate of about 2 ml m-3 as a result of
fossil fuel burning and rapid deforestation, possibly giving rise to global
warming. Currently, mankind introduces CO 2 at about 5.1 1015 g C per year
from fossil fuel burning, presumably another amount of CO 2 , about 2 1015 g
C per year, by deforestation. Of this total input of about 7 1015 g C per year
only about 2 1015 g C is retained in the atmosphere (causing the increasing
CO 2 concentration), the remaining about 5 10 15 g C presumably annually
being taken up by the biosphere and the oceans, slowly adding to the already
immense reservoir of CO 2 in seawater.