Climate Change and Tourism - UNEP - Division of Technology ...

48 Climate Change and Tourism – Responding to Global Challenges
8.2 Advances in the Understanding of Global Climate Change
The methods used to explore future climate shows that the uncertainties are linked to research tools
currently available and some others to the evolution of human activities over the span of several decades
(e.g., population and economic growth, evolution and implementation of new technology). Climate
being a statistic of daily weather over a long period implies that it is necessary to work with statistics,
trends, indicators of variability, and confidence levels, all of which make it difficult to deliver clear
messages to diverse audiences.
Two types of approaches can be used to describe the nature of potential future climate change.
Scenarios
Scenarios are the main method used to explore the future of climate. In order to develop future climate
scenarios, the future of GHG emissions from human activities need to be considered. Two categories of
GHG emission scenarios must be distinguished; those that do not consider policies to mitigate emissions
(e.g., IPCC Special Report on Emission Scenarios (SRES)) and those that do (i.e., stabilisation scenarios).
The IPCC SRES scenarios are classified into four families according to their global-regional and the
development-environmental orientations:
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The A1 storyline and scenario family describes a future world with very rapid economic growth,
low population growth, and the rapid introduction of new and more efficient technologies.
The A2 storyline and scenario family describes a very heterogeneous world. The underlying theme
is self-reliance and preservation of local identities.
The B1 storyline and scenario family describes a convergent world with the same low population
growth as in the A1 storyline, but with rapid changes in economic structures toward a service and
information economy, with reductions in material intensity, and the introduction of clean and
resource-efficient technologies.
The B2 storyline and scenario family describes a world in which the emphasis is on local solutions
to economic, social, and environmental sustainability.
The different GHG emission trajectories over the 21st century from these SRES scenarios are outlined
in Figure 8.2.
When the SRES emission scenarios are run through several extensively validated Global Climate
Models (GCMs), the estimated range of global warming is 1.8° C to 4.0° C by the end of the 21st
century. 165 This range is due to the uncertainty about future GHG emissions linked to unpredictable
socio-economic conditions and to the different responses of GCMs to the same amount of emissions.
Thus, these scenarios deliver results that policy makers sometimes find difficult to use. Often, policy
makers want to know what they need to do in order to keep climate change within boundaries that they
perceive as ‘acceptable’. This is a question to which stabilisation scenarios are more suited to provide
an answer.
UNWTO, 9 July 2008