Conservation and Sustainable Use of the Biosphere - WBGU

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Conservation and Sustainable Use of the Biosphere - WBGU

Biospheric control over the climate system and the global hydrological cycle F 2.3

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ence of climatic conditions favourable to their

existence. It does become problematic however

for the whole Northern part of the Indian sub-continent,

the North of China and Southern Siberia,

the Australian steppes and the savannah zones in

Africa, the Western parts of North America and

the Andean region.

• In the Global Forest scenario the forest regions

increase dramatically and the current core areas of

desert and steppe retain their original form: the

desert belt of the ancient world from the Maghreb

and the Sahara over the Middle East into portions

of the Thar and Gobi deserts, Western Australia

and Western South Africa, Patagonian, the Atacama

and the south western part of North America.

There, no favourable climatic conditions can

be established for forest. Changes cannot simply

be maintained by afforestation and climatic conditions

alone. Irrigation is a provisional option, but

not a sustainable solution for these areas.

F 2.3

Biospheric control over the climate system and

the global hydrological cycle

These new simulations provide an initial evaluation

of the maximum biospheric control over our climate

system and the global hydrological cycle. What was

not considered is the exchange of many greenhouse

gases such as carbon dioxide that are controlled by

the biosphere. Also left unconsidered are the

exchange processes between ocean and atmosphere

that would influence many of the results. However,

the general conclusion that may be derived is that the

biosphere does indeed exercise an extensive control

function over the climate system. This control is particularly

strong in the global energy levels as a result

of the cooling effect of vegetation and in the global

hydrological cycle through increased evaporation,

determined by evapotranspiration. Its influence is on

the same scale to the changes that are anticipated as

a result of doubling the CO 2

concentration (IPCC,

1996a).

The geographic and temporal effect of the biosphere

is seen above all in the fact that the biological

influences are strongest during periods of maximum

solar radiation, whereas the increased carbon dioxide

concentration influences above all the winter period

in the upper latitudes.

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