185
them. Besides the great circulation, therefore, a
global ocean water circulation also exists, and the
two flow system transforms the spatial distribution of energy arriving from the Sun: around half
of the energy excess of the tropical zone is transported towards higher latitudes. The flow of air is
much faster (up to two orders of magnitude) that
that of water flowing in marine currents.
Furthermore, the movement of water in oceanic
basins is limited not like that of air. Taking these
differences and the heat capacity of the two
media into account, calculations revealed that the
heat transfer of the world ocean and the atmosphere directed from the Equator towards the
poles (regarding the average on the entire globe)
are practically similar in extent and could be very
different among areas.
A fine example of this is the climate of Europe.
The continent receives one of the greatest heat
excess on Earth as a result, of the heat transfer of
the Golf Current and the North Atlantic current,
and this makes the climate of Europe beneficial
causing a positive temperature anomaly (mild
winters). An opposite example would be the
north-eastern coast of North America with a significant cooling effect caused by the Labrador
Current. Certain scientists presume that the
warming of the climate could influence primarily
the water descending mechanism of the North
Atlantic Current: melting of marine and terrestrial
ice, increasing water discharge of rivers reduces
the density of saline marine water. As a result,
water subsidence could be halted in the northern
region of the Atlantic Ocean and also the great
marine conveyor belt as well. This would bring
changes in the tropical zone as well. The amount
of water entering the atmosphere would be
changed that would also contribute to global climate change. Regarding the world ocean, other
mechanisms have to be taken into account as well
(e.g. changing carbon dioxide uptake of marine
photosynthesising living beings) scientific uncertainties of the resultant effects of which are high.
Continents also contribute to the shaping of
the climate with several of their characteristics.
In this respect conditions of the surface cannot be
separated from the role of biosphere and especially that of vegetation. The ratio of reflected
and absorbed radiation, albedo and thus the
energy input of the Earth’s surface is determined
by soil and rock properties and vegetation cover
of the surface. Areas covered with continuous
forests, for example, reflect less radiation than
non-vegetated surfaces, i.e. major forest clearings reduce the total energy input of the planet.
Also, less forest can bind less carbon dioxide,
leaving more of it in the atmosphere and thus
increasing greenhouse effects. Regarding the two
opposite effects, the latter is stronger, i.e. decreasing forest areas contribute to the warming of the
climate. It has to be mentioned also that greater
atmospheric carbon dioxide concentration
directly and beneficially affects vegetation as
CO 2 is a fundamental material of photosynthesis.
The effects of this fact on the climate are not
known adequately.
In natural conditions terrestrial ecosystems are
slow to absorb carbon. This natural state, however, has been changed by humanity; therefore,
the present biosphere is now far from this nearbalance state. Regarding the above, the following
important processes have to be mentioned:
• timber productivity of woodlands significantly
increased in the last decades (“CO 2 fertilisation”—presumable due to the CO 2 excess
coming from fossil fuel burning) and this
intensifies carbon binding;
• forest and bush fires increase carbon
emission;
• the area of forests decreases globally as discussed in Sect. 4.4 (especially due to clearings
of tropical rainforests), reducing carbon
binding;
• agricultural cultivation extending over new
territories, inappropriate forestry, and intensifying soil erosion result in significant carbon
emission from the soil.
In a shorter time horizon (a few thousand
years) the greenhouse effects of atmospheric
gases and water vapour among the above listed
factors determine to the largest degree global climate. Without such effects the average temperature of near surface air would be 33 °C lower than
the present value.
4.5 Changes in the Atmosphere Owing to Human Impacts and Their Consequences
them. Besides the great circulation, therefore, a
global ocean water circulation also exists, and the
two flow system transforms the spatial distribution of energy arriving from the Sun: around half
of the energy excess of the tropical zone is transported towards higher latitudes. The flow of air is
much faster (up to two orders of magnitude) that
that of water flowing in marine currents.
Furthermore, the movement of water in oceanic
basins is limited not like that of air. Taking these
differences and the heat capacity of the two
media into account, calculations revealed that the
heat transfer of the world ocean and the atmosphere directed from the Equator towards the
poles (regarding the average on the entire globe)
are practically similar in extent and could be very
different among areas.
A fine example of this is the climate of Europe.
The continent receives one of the greatest heat
excess on Earth as a result, of the heat transfer of
the Golf Current and the North Atlantic current,
and this makes the climate of Europe beneficial
causing a positive temperature anomaly (mild
winters). An opposite example would be the
north-eastern coast of North America with a significant cooling effect caused by the Labrador
Current. Certain scientists presume that the
warming of the climate could influence primarily
the water descending mechanism of the North
Atlantic Current: melting of marine and terrestrial
ice, increasing water discharge of rivers reduces
the density of saline marine water. As a result,
water subsidence could be halted in the northern
region of the Atlantic Ocean and also the great
marine conveyor belt as well. This would bring
changes in the tropical zone as well. The amount
of water entering the atmosphere would be
changed that would also contribute to global climate change. Regarding the world ocean, other
mechanisms have to be taken into account as well
(e.g. changing carbon dioxide uptake of marine
photosynthesising living beings) scientific uncertainties of the resultant effects of which are high.
Continents also contribute to the shaping of
the climate with several of their characteristics.
In this respect conditions of the surface cannot be
separated from the role of biosphere and especially that of vegetation. The ratio of reflected
and absorbed radiation, albedo and thus the
energy input of the Earth’s surface is determined
by soil and rock properties and vegetation cover
of the surface. Areas covered with continuous
forests, for example, reflect less radiation than
non-vegetated surfaces, i.e. major forest clearings reduce the total energy input of the planet.
Also, less forest can bind less carbon dioxide,
leaving more of it in the atmosphere and thus
increasing greenhouse effects. Regarding the two
opposite effects, the latter is stronger, i.e. decreasing forest areas contribute to the warming of the
climate. It has to be mentioned also that greater
atmospheric carbon dioxide concentration
directly and beneficially affects vegetation as
CO 2 is a fundamental material of photosynthesis.
The effects of this fact on the climate are not
known adequately.
In natural conditions terrestrial ecosystems are
slow to absorb carbon. This natural state, however, has been changed by humanity; therefore,
the present biosphere is now far from this nearbalance state. Regarding the above, the following
important processes have to be mentioned:
• timber productivity of woodlands significantly
increased in the last decades (“CO 2 fertilisation”—presumable due to the CO 2 excess
coming from fossil fuel burning) and this
intensifies carbon binding;
• forest and bush fires increase carbon
emission;
• the area of forests decreases globally as discussed in Sect. 4.4 (especially due to clearings
of tropical rainforests), reducing carbon
binding;
• agricultural cultivation extending over new
territories, inappropriate forestry, and intensifying soil erosion result in significant carbon
emission from the soil.
In a shorter time horizon (a few thousand
years) the greenhouse effects of atmospheric
gases and water vapour among the above listed
factors determine to the largest degree global climate. Without such effects the average temperature of near surface air would be 33 °C lower than
the present value.
4.5 Changes in the Atmosphere Owing to Human Impacts and Their Consequences