Impact of climate change on water resources
in
(1) Dipartimento di Pianificazione e Scienza del Territorio, Università di Napoli Federico II, Napoli, Italy; fortolan@unina.it
(2) ISAFOM, CNR, via Cupa Patacca, Ercolano, Napoli, Italy; pagliuca@ispaim.na.cnr.it
KEY WORDS:
climate change, water resources,
The
main result achieved with geoarchaeological research
consists in the identification of cyclicity (period
of about 1000 years) of the major climate and environmental changes that have
resulted in real environmental crises lasting between 100 and 200 years in the
Mediterranean area (figure 1). There is clearly a close
correlation between climatic and environmental changes and solar activity
(concurrence of prolonged maxima of solar activity and warm greenhouse effect
periods and concurrence of repeated minima of solar activity and cold periods,
such as the Little Ice Ages).
Figure 1 - Stratigraphic
reconstructions and palaeoclimatic interpretation of
sediments accumulating in
Figure 2 - 1500-2002
climatic evolution and forecast for the near future ("Third Millennium
Climatic Tongs").
Figure
3 - Correlation between climatic evolution of the last 500 years and variation
in the concentration of atmospheric CO2 from 1750 to today and forecast for the
near future (Third Millennium Climatic Tongs).
The
climatic and environmental data concerning the Warm Medieval Period examined
for the Mediterranean area, the results achieved with research into geoenvironmental changes linked to climatic variations of
the historical period, especially of the last few centuries, and the various
multidisciplinary data obtained with research in various parts of the world,
represent a valid frame of reference for assessing and quantifying the changes
that will occur at different latitudes during the enhanced Greenhouse Effect of
the Third Millennium.
The
history of mankind and the environment in the last few millennia highlights a
progressive, cyclical climatic and environmental change which is occurring
consistently in multicentennial periods (figure 1).
On the left-hand side of figure 2 we propose the climatic reconstruction of the
past 500 years, using instrumental data and those obtained from natural
archives (temperatures) and deduced from the flows of the River Rhone
(reconstructed rainfall from 1500 to 1995). The variations in rainfall are
represented as percentages of current values. On the right-hand side of figure
6 we advance a scenario of changes in temperatures and rainfall on the basis of
millennial cyclicity and assuming that climatic
evolution occurs with a similar trend to the previous Medieval Warm Period,
resulting in environmental conditions linked to the new greenhouse effect that
we term “Third Millennium enhanced Greenhouse Effect”.
Undoubtedly in the last 150 years human activity has resulted in the largest
emission into the atmosphere of greenhouse gases (carbon dioxide, methane
etc.). Logically, such pollution has to be reduced and international action has
to be taken to protect the atmosphere. Clearly, during a natural period of
greater solar activity the increase in the greenhouse effect (connected to
anthropogenic gases) could contribute to changing the effects of the
temperature rise on the Earth’s surface.
In the left-hand part of figure 3 (graph 2) we propose the increase in
atmospheric CO2 concentration in the past 250 years. In the right-hand part of
figure 6 the hypothesised trend in climatic variation according to natural cyclicity is correlated with the hypothesised trend in
atmospheric CO2 concentration on the basis of variable emission values.
Assuming that climate change follows the reconstructed pattern during the
medieval Warm Period (graph 1), it is forecast that the further temperature increase
will lead the environmental threshold to be exceeded, triggering abundant carbonatic sedimentation in shallow marine waters (figure
2). This scenario, as occurred during the medieval Warm Period, could have an
appreciable effect on atmospheric CO2 concentrations, sequestering considerable
percentages. The natural environmental balance would occur again at the end of
the postulated new period of considerable solar activity. The right-hand side
of graph 2 shows that the trend in the CO2 percentage, as anthropogenic
emissions are reduced, is similar to that forecast according to the natural
evolution of climatic variation (graph 1).
Figure
4 - Reconstruction of climatic variation and the variation in renewable water
resources from 1884 to today, prediction of expected changes for the next 100
years in coastal zones and inland Apennine areas in the regions of Campania, Molise and Basilicata, characterised by limestone
aquifers and chiefly clayey rocks (graphs 1, 2 and 3) and correlation with soil
formation, soil erosion and evolution of silicoclastic
littorals (graphs 3 and 4).
We
believe that it is a serious mistake to attribute current climatic changes
exclusively to the production of harmful anthropogenic gases; it appears clear
that human activity has happened to intensify precisely in the period of
natural climatic transition; this concomitance may result in misleading
conclusions being drawn by those who fail to appreciate the complexity and cyclicity of climatic and environmental evolution.
Importantly, cyclical climatic variation, as occurred
in the past, will result in new environmental conditions along the belts
bordering current climatic zones, establishing environmental conditions that
will at times be better and at times will be worse than those established with
the Little Ice Age. In particular, it will transform into humid areas a large part
of the areas which are currently subtropical deserts.
The scientific limitations to the debate on climate
change and the consequent inadequacy of international action have caused a
major delay in taking responsible steps to "prepare" the environment
of the Mediterranean area (e.g. elimination of water waste, treatment and
re-use of waste waters, accumulation of run-off into large and small basins, geoenvironmental restoration of littorals, etc.) so as to
attenuate the "environmental damage" forecast for the near future
when, especially in central-southern Italy, rainfall will fall sharply with a
serious impact on freshwater availability on which much of the country’s
socio-economic activity is based.
On
the basis of scientific data acquired with geoenvironmental
research conducted in the Mediterranean basin, it is possible to predict
climatic and environmental changes expected in the next 100 years. The most
serious environmental changes are expected in coastal areas where a sharp
reduction in rainfall and a marked temperature rise are expected, such as to
cause climatic desertification (annual rainfall about 200-
Considerable
problems for irrigation, industrial and domestic uses will arise from the
serious reduction in renewable water resources that will affect the limestone
aquifers (over 50% less).
The
serious environmental changes predicted for the next 100 years will result in regional and interregional social conflict over water
uses. Responsible steps should be taken to prevent and reduce damage,
including: adequate laws for the social use of water resources and environmental
re-balance by defining a "royalty", to be invested in zones from
which the resource is extracted, on water extracted and transported elsewhere;
interventions to defend and protect aquifers; exploitation of undersea sources;
research and identification of strategic groundwater resources; research for
artificially recharging aquifers; plans to capitalise on micro-resources for
multiple uses; wastewater treatment and re-use; strategic interventions to
eliminate aqueduct losses; research into desalination.