Climate Change and the European Water Dimension - Agri ...

Figure VI.C.2. Daily flows in Ebro river from 1913 to 2001 (PHN, 2000).
There is increasing evidence that global climate is changing and most of the warming
observed since pre-industrial era is attributable to human activities (IPCC, 2001).
Observed changes in sea level, snow cover, ice extent and precipitation patterns are
consistent with the current scenario of higher temperatures. Based on current trends
it is reasonable to assume that the global hydrologic cycle will be accelerated, with
greater event variability and extremes.
Impacts of climate change can be evaluated using three different approaches; in
order of increasing prediction uncertainty those are:
• analysis of changes recorded in the current geophysical record;
• analysis of changes predicted from Global Circulation Models (GCMs);
• analysis of changes determined from various assumed scenarios of the
impact of global climate change.
All three approaches have been adopted for the Ebro river basin.
The three factors of global climate change that could most impact the hydrology of
the Ebro watershed are: increasing air temperature, changes in precipitation (leading
to variations in annual runoff), and sea level rise. Findings from the various studies,
highlighting the effects of climate change on some components of its hydrologic
cycle, as well as on the ecological status of the river and its delta area, are
summarized in the following paragraphs. Some of the problems arising when trying
to assess and quantify the effects of climate change are also presented.
VI.C.2. Climate Change Impacts
Temperatures
According to IPCC (2001), global mean temperature has increased by about 0.6°C
over the past 100 years. Globally the 1990s were the warmest decade on record,
and 1998 the warmest year. It is likely that the increase in temperature in the 20 th
century was the largest of any century during the past 1000 years. There is new and
stronger evidence that most of the warming observed over the past 50 years is
attributable to human activities. Based on predictions from seven GCMs, IPCC
(2001) reports that there is a potential for increases in average air temperature by the
year 2100, ranging from +2 to +4.2 °C,. Under IPCC emission scenarios, global
average temperature are projected to rise by 1.4°C to 5.8°C between 1990 and 2100,
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