chapter - Atmospheric and Oceanic Science

The new climate conditions have rendered obsolete a great part of the infrastructure
related to water management, since it was designed for a different climate
Much of this toll could be avoidable in the future, if part of the infrastructure were
modified to meet the new conditions, and the new constructions were built according
to the new and future hydrometeorological conditions. With few exceptions,
none of these things are being done. Specifically, most of the infrastructure was,
and still is, designed with the implicit assumption of a stationary climate. The few
appropriate methods available to assess future climate under non-stationary climate
conditions, some of which are still evolving, are neither known nor used. This attitude
reflects the lack of awareness of the technical community about the regional
climate trends and their hydrological consequences.
For these reasons, the second purpose of this book is to draw attention on the
climate and hydrological trends showing its territorial dimension in order that the
local trends not to be misinterpreted as random and unrelated symptoms. The
description of these trends is made in chapters 5, 6 and 7 and for its better understanding,
in chapters 2, 3 and 4 the most general features of the regional climate and
hydrology are previously approached.
1.3. Climate forcings
Introduction
Carbon dioxide and other greenhouse gases emissions (GGE) are considered
responsible for at least part of the global temperature increase during the twentieth
century and it will be the main drive for climate change during the twenty first century.
The evolution of the GEG emissions in the future will depend on numerous
factors whose prediction is quite complex. They are the economic and demographic
growth, the technological changes and even the development toward a society
with more or less equity; and last, but not less important, on the humanity's collective
decision to reduce or at least to diminish the rate of growth of the emissions.
Since all this is very difficult to be foreseen, it is only possible to build possible
future socioeconomic scenarios. The different scenarios presuppose levels of economic
activity that imply in turn different scenarios of emissions. The construction
and characteristic of these scenarios are discussed in chapter 12.
The global climate change issue is summarized in chapter 9. Long-term
changes in global climate are assessed using global climate models (GCMs), which
simulate the responses to the changes in the atmospheric constituents that have
been observed in the past or that will be expected in the future. GCMs are also used
to simulate other changes that can modify climate, as deforestation and changes of
vegetation and in the use of soil. These and other regional forcings are treated in
chapter 10.
11