Environmental Engineering Reference
In-Depth Information
TheSRESscenariosarenow(post2013)beingsupersededbyfourrepresentative con-
centration pathways (RCPs) that will enable the consideration of global mitigation actions.
However, I opted to devote several paragraphs to the SRES-based approach because it was
used in most of the available relevant scientific literature up to 2013. The first IPCC assess-
ment to use the RCPs was the AR5 that appeared in 2013. Each of the four pathways has
a different signature of possible levels of radiative forcing in the year 2100. Therefore, we
have RCP2.6, RCP4.5, RCP6.0 and RCP8.5. The numbers refer to the different possible
levels of radiative forcing in watts per square metre (W/m
2
) in the year 2100 relative to
preindustrial values.
Here are the primary characteristics of the RCPs relative to the present century:
·
In RCP8.5, the GHG emission increase over time leads to increasing radiative for-
cing without stabilization and a global temperature anomaly (relative to preindus-
trial times) that passes through 4.9°C (again without stabilization) by 2100.
·
In RCP6.0, the GHG emission reduction leads to a stabilization of global radiative
forcing soon after 2100, giving a global temperature anomaly that stabilizes at
3.0°C.
·
In RCP4.5, a more aggressive GHG emission reduction leads to a stabilization of
global radiative forcing soon after 2100, giving a global temperature anomaly that
stabilizes at 2.4°C.
In RCP2.6, radiative forcing rises to about 3.1 W/m
2
by the middle of the century
and then falls to 2.6 W/m
2
by 2100. This scenario requires a very aggressive GHG
emission reduction to begin within the next few years. It would lead to a global
temperature anomaly that stabilizes at 1.5°C.
·
This approach indicates that hopes of the world achieving a total temperature rise by 2100
of less than 2.0°C are fading and we may be tracking a path that exceeds RCP6.0 or per-
haps much more.
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