610
Climatic Geomorphology
As a result of it, a partial ice cap melting could happen and see level could raise 5 to 6 cm
on average in one decade.
These variations will generate intense modifications of natural systems producing
important socioeconomic implications that would seriously affect human life. For this
reason, during the summit in Rio de Janeiro in 1992 a Covenant on Climate Change was
signed (CCC). In the agreement a group of programs was proposed to mitigate future
climate change, as well as to promote new technologies to reduce greenhouse gases.
From IPCC in 1990 to the one in 1995 (Houghton et al., 1996), relevant progress has
been made. This lies in the application of more powerful simulation models, as well as the
consideration of the effects of sulphate aerosols and the reduction of the stratospheric and
anthropic ozone, which highly affect climate change (Santer et al., 1996). All that research
led IPCC in 1995 to the development of new scenarios for the period 1990 to 2100, on
the basis of different hypothesis. For the average scenario (IS92a) an increase of 2~ in
the temperature of the air in 2100 is estimated, and 1 to 2.5~ in the case of extreme
suppositions (IS92c and IS92e). The sea level rise due to ice masses melting and the
thermal expansion of the oceans are calculated for the year 2100 as 50 cm (scenario IS92a)
and 15 to 95 cm in the case of other extreme scenarios (Houghton et al., 1990). These new
values reduce quite a lot the most catastrophic forecasts of the IPCC in 1990. This
important decrease is basically due to the consideration of sulphate aerosols in predictions
and to the application of new atmosphere-ocean models.
Nevertheless, Houghton et al. (1996, p. 5) indicated that in the predictions of climate for
the future:
important uncertainties remain which come from vague estimates of future gas emissions,
from the representation in climatic processes models (as those associated to clouds, ocean,
marine ice, and vegetation) and from the systematic capture of climatic variables. Furthermore, short- and long-term climate changes are difficult to predict, because the nonlinearity of
the climatic system, so that, numerous "surprises" can occur.
The most important finding of the IPCC third assessment report, was the statement:
"There is now new and stronger evidence that most of the warming observed over the last
50 years is attributable to human activities." This represents a significant strengthening
of the analogous statement issued by the IPCC (1996): "The balance of evidences suggest
a discernible human influence on global climate." The globally-averaged surface air
temperature has increased by about 0.6 +/-0.2~
over the 20th century. Most of this
warming has occurred during two periods: 1910 to 1945 and 1976 to 2000, with gradual
cooling during the intervening period. The range, reported in the IPCC Third Assessment
Report (IPCC, 2001), is higher than the 1.0 to 3.5~ range reported in the Second
Assessment Report (IPCC, 1996) probably because a greater range of scenarios are now
being used. In the 1966 report only six scenarios were used, whereas now 40 scenarios
are used.
Although there is a general consensus on the fact that global warming will occur in the
near future, some opinions disagree or express doubts about discrepancies. Dickinson
(1986) showed that general models of circulation (GCMs) have many limitations and
should be carefully used. Sundquist (1993), in a study about the emissions from ice during
the last interglacial period and the absorption balance in the oceans, indicated that there are
significant uncertainties in relation to anthropogenic CO2, considering its later effects.
Climatic Geomorphology
As a result of it, a partial ice cap melting could happen and see level could raise 5 to 6 cm
on average in one decade.
These variations will generate intense modifications of natural systems producing
important socioeconomic implications that would seriously affect human life. For this
reason, during the summit in Rio de Janeiro in 1992 a Covenant on Climate Change was
signed (CCC). In the agreement a group of programs was proposed to mitigate future
climate change, as well as to promote new technologies to reduce greenhouse gases.
From IPCC in 1990 to the one in 1995 (Houghton et al., 1996), relevant progress has
been made. This lies in the application of more powerful simulation models, as well as the
consideration of the effects of sulphate aerosols and the reduction of the stratospheric and
anthropic ozone, which highly affect climate change (Santer et al., 1996). All that research
led IPCC in 1995 to the development of new scenarios for the period 1990 to 2100, on
the basis of different hypothesis. For the average scenario (IS92a) an increase of 2~ in
the temperature of the air in 2100 is estimated, and 1 to 2.5~ in the case of extreme
suppositions (IS92c and IS92e). The sea level rise due to ice masses melting and the
thermal expansion of the oceans are calculated for the year 2100 as 50 cm (scenario IS92a)
and 15 to 95 cm in the case of other extreme scenarios (Houghton et al., 1990). These new
values reduce quite a lot the most catastrophic forecasts of the IPCC in 1990. This
important decrease is basically due to the consideration of sulphate aerosols in predictions
and to the application of new atmosphere-ocean models.
Nevertheless, Houghton et al. (1996, p. 5) indicated that in the predictions of climate for
the future:
important uncertainties remain which come from vague estimates of future gas emissions,
from the representation in climatic processes models (as those associated to clouds, ocean,
marine ice, and vegetation) and from the systematic capture of climatic variables. Furthermore, short- and long-term climate changes are difficult to predict, because the nonlinearity of
the climatic system, so that, numerous "surprises" can occur.
The most important finding of the IPCC third assessment report, was the statement:
"There is now new and stronger evidence that most of the warming observed over the last
50 years is attributable to human activities." This represents a significant strengthening
of the analogous statement issued by the IPCC (1996): "The balance of evidences suggest
a discernible human influence on global climate." The globally-averaged surface air
temperature has increased by about 0.6 +/-0.2~
over the 20th century. Most of this
warming has occurred during two periods: 1910 to 1945 and 1976 to 2000, with gradual
cooling during the intervening period. The range, reported in the IPCC Third Assessment
Report (IPCC, 2001), is higher than the 1.0 to 3.5~ range reported in the Second
Assessment Report (IPCC, 1996) probably because a greater range of scenarios are now
being used. In the 1966 report only six scenarios were used, whereas now 40 scenarios
are used.
Although there is a general consensus on the fact that global warming will occur in the
near future, some opinions disagree or express doubts about discrepancies. Dickinson
(1986) showed that general models of circulation (GCMs) have many limitations and
should be carefully used. Sundquist (1993), in a study about the emissions from ice during
the last interglacial period and the absorption balance in the oceans, indicated that there are
significant uncertainties in relation to anthropogenic CO2, considering its later effects.