Environmental Engineering Reference
In-Depth Information
1.0
observed
model simulation
0.5
0.0
-0.5
1850
1900
1950
2000
Figure 1.3 Natural factors cannot explain recent warming. (© Crown copyright 2007, the Met
Offi ce)
The basic evidence that provides confi rmation that global warming is due to human-made
factors was provided by a climate model developed at the Hadley Centre for Climate Predic-
tion and Research in the UK. In Figure 1.3, the observed global temperature since the early
1900s is shown by the bold line. The climate model was driven over that period by natural
factors such as output of the sun, changes in the optical depth of the atmosphere from volcanic
emissions and the interactions between the atmosphere and oceans. The predictions of the
model are shown by the fuzzy band. This clearly disagrees with the observations particularly
since about 1970, that observed temperatures have risen by about 0.5 °C, but those simulated
by natural factors have not changed at all.
If the climate model is now driven by natural factors as previously but in addition by man-
made factors - change in greenhouse gas concentrations and sulfate particles - the model
simulation predictions in Figure 1.4 are in much better agreement with the temperature record.
Climate modelling studies by other research centres have arrived at the same broad
conclusions.
1.2.3 The Kyoto Protocol
The effects of climate change are global and hence mitigation requires coordinated interna-
tional effort. Signed in 1997, the Kyoto Protocol aims at reducing greenhouse gas emissions
in the period 2008 to 2012 to 5.2% below those in 1990. Emissions of greenhouse gases by
the US are currently 20% higher than in 1990 while the target fi gure in Kyoto was a cut of
7%. In the long run however it is prudent for industrialized countries to reduce their emissions
by 60% by 2050 if the worst effects of climate change are to be mitigated with any confi dence.
This is a major challenge, to individuals, to governments and to supranational bodies. Greatest
responsibility rests of course with the nations producing the largest CO 2 emissions per capita
and those moving fast up the emissions table. Table 1.1 illustrates the variation in emissions
per head and how this is partly driven by the income per head. Emissions from China are
expected to surpass those of the US by 2025 so there is much to be done.
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