SRES scenarios are often used in
climate modeling and to predict what if scenarios when modeling the implication
of some system on climate. SRES stands for Special Report on Emissions
Scenarios which was a report produced by the IPCC first published in 2000 in
the 3rd IPCC. The 4th IPCC in 2007 saw an update of SRES
available for scientists to use. They are widely referred to in a wide range of
materials such as RAMSAR report and others. Ramsar
Convention is an international treaty, which seeks to encourage conservation
and sustainable utilization of wetlands. The convention was named after an
Iranian city- Ramsar, where it was first signed in 1971. It recognizes the
essential ecological function of wetlands and their economic, cultural,
scientific and recreational values. They are also widely used by
hydrologists and climatologists as well as meteorologists and geologists when
trying to predict the future climate or its particular aspects. They are
different world scenarios that consider population growth, globalization and
world economics, the cleanliness of technologies and world environmental
priorities (Ramsar Report, 2002).
I mentioned them
in the previous blog post in a study about geology and CCS implications so I
thought I’d write a little blog post about SRES scenarios themselves too. Other
examples of studies involving the use of these are the example of Nicholls’
2004 study on how the impact of a particular climate change- sea-level rise in
his case, would be affected under SRES and thus what is the climate likely to
look like in the future. Nicholls used SRES to improve his original study of
sea-level rise and how it would effect coastal wetlands due to increased
flooding (Nicholls, 2004).
The scenarios are four scenarios
which each has their own GHGs trajectories for the future where A1 and A2 has
high GHGs which continue to increase beyond 2100 and B1 and B2 have mid to low
levels of GHGs with rates of increase showing signs of slowing by the end of
2100. Figure 1 below summarizes these scenarios.
Source: Ramsar Report, 2002 Description of SRES scenarios.
Using full range of SRES scenarios,
the atmospheric CO2 concentrations are projected to increase from the 1990
level to 475-1100 ppm by 2100. The mean global temperatures are projected to be
1.4C-5.8C higher by 2100 with variation in the increase in different regions on
Earth. Generally temperatures are projected to increase the most in mid to high
latitudes of the northern hemisphere. Precipitations changes are also to occur
on much smaller scales of only 5-20% and also show regional variation. Although
these changes could be enough for serious hydrological, ecological and global
climate implications (Ramsar Report,2002).
The potential implications of SRES are shown below by
figure 2.
Figure 2.
Source: United States EnvironmentalProtection Agency, 2015. Projected changes over the 21st
Century in the atmospheric concentrations of 3 GHGs: CO2, methane and nitrous
oxide (N2O).
The 5th IPCC, published
in 2014 updated SRES yet again now renaming them as RCPs (Representative
Concentration Pathways). They are four scenarios yet again used for climate modeling
and research. They also depend on GHGs emissions into the atmosphere mainly up to
2100 but also give some predictions beyond that into the 22nd
century. We have to think well beyond the 21st century and at least
about the 22nd century as the potential effects of GHGs on the
planet lag due to slow responses of global earth systems such as ocean
circulation thus lagging impacts such as sea level rise which in turn also has
further ability to create positive feedbacks on climate change. The four RCPs are named RCP2.6, RCP4.5,
RCP6, and RCP8.5. RCP2.6 assumes the peak of GHG emissions between 2010 and
2020; RCP4.5 peak around 2040 then decline; RCP6 emissions peak around 2080 and
RCP8.5 emissions continue to rise throughout the 21st century. These
are portrayed by Figure 3 below.
Figure 3.
Source. All forcing agents’ atmospheric CO2 equivalent
concentrations (in ppmv) according to four RCPs.
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