The Threat of Climate Change - Energy and Climate: How to Achieve a Successful Energy Transition - page 28

Other positive retroaction phenomena are likely to increase the imbal-
ance: thus, disappearance of the reflective effect of pack ice with respect to
solar radiation, the so-called 'albedo' effect,will contribute to increasing the
quantityofheat absorbedby thegroundandtherefore toheating the surface.
The temperature increase could also affect the tropical forests, which
currently capture some of the CO 2 in the atmosphere. If these forests should
disappear, they would release the carbon they have stored until now. These
risks concern in particular the subtropical forests, whose disappearance
could accelerate if the temperature reaches a certain threshold. A reduction
in their area, by modifying the rainfall, would reduce the quantity of water
received by the remaining forest, causing a chain reaction. Repeated heat
waves also promote outbreaks of forest fires. The Amazonian forest could
therefore disappear in a relatively short time.
Lastly, a major risk identified by the IPCC in its last report concerns a
reduction, caused by a rise in temperature, of the ability of the oceans to
act as a carbon sink, thereby increasing the atmospheric CO 2 content.
All these examples demonstrate that the effects of climate change could
increase suddenly above a certain point which could be reached in the
relatively short term. Survival of all ecosystems on the surface of the Earth
is concerned with such 'tipping points'.
The dramatic consequences of a temperature elevation are increasing
rapidly. For a 1 C elevation, it is estimated that acidification of the oceans
would cause serious damage to the coral reefs and to the ecosystems of the
Arctic region.
For a 1.5 C elevation, we would observe irreversible thawing of the
polar ice cap in Greenland. Between 2 C and 3 C, numerous ecosystems,
especially the Amazonian ecosystem, would be threatened. At 3 C, we
would be facedwith conditions leading tomassive extinction of numerous
plant and animal species, under conditions similar to those which led to
the major extinctions which occurred during the geological ages [21].
It therefore seems vital not to exceed a temperature elevation of 2 C.
According to themodels produced, to achieve this it is essential to limit the
atmospheric CO 2 content which will be reached in 2050 to a value of
between 400 ppm and 450 ppm.
The vulnerability of each country varies according to its geographic
position and its ability to adapt. The northern industrialised countries are
less vulnerable than the developing countries in the southern hemisphere, in
view of their latitudes and also their ability to invest to adapt to climate
change. Emerging countries like India andChina are highly exposed to the risk
of climate change, which could hinder their development. A very large
proportion of the world population is therefore seriously concerned [22].