Climate Change and the Mediterranean Region
Executive Summary
Water shortages and poor harvests during the droughts of the early 1990s exposed the acute vulnerability of the Mediterranean region to climatic extremes. Against this backdrop, the prospect of a major climate change brought about by human activities is a source of growing concern, raising serious questions over the sustainability of the region.
This report examines the potential implications of global climate change for the Mediterranean region. Drawing on the results of recent studies, it reviews possible changes in climate together with recent trends, the potential impacts of climate change and the implications for sustainable development.
One key finding is that future climate change could critically undermine efforts for sustainable development in the Mediterranean region. In particular, climate change may add to existing problems of desertification, water scarcity and food production, while also introducing new threats to human health, ecosystems and national economies of countries. The most serious impacts are likely to be felt in North African and eastern Mediterranean countries.
The report concludes that while there is some scope for adaptation, ensuring the long-term sustainability of the region requires urgent action to cut global emissions of greenhouse gases.
Specific findings are summarised below.
Hotter and drier times ahead?
If current trends in emissions of greenhouse gases continue, global temperatures are expected to rise faster over the next century than over any time during the last 10,000 years. Significant uncertainties surround predictions of regional climate changes, but it is likely that the Mediterranean region will also warm significantly.
The outlook for precipitation is much less certain, but most projections point to more precipitation in winter and less in summer over the region as a whole. A common feature of many projections is declining annual precipitation over much of the Mediterranean region south of 40 or 45° N, with increases to the north of this. Even areas receiving more precipitation may get drier than today due to increased evaporation and changes in the seasonal distribution of rainfall and its intensity.
As a consequence, the frequency and severity of droughts could increase across the region. Changes in large-scale atmospheric circulation - as represented by the El Niņo-Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO) - would further effect the occurrence of extreme events.
An indication of the scale of possible changes is given by one scenario based on the output from four climate models. This suggests that temperatures could rise by over 4°C by 2100 over many inland areas and by over half of this over the Mediterranean Sea. Over the same period, annual precipitation is projected to decline by 10 to 40% over much of Africa and southeastern Spain, with smaller - but potentially significant - changes elsewhere.
Aerosol emissions may counter some of the effects of greenhouse gases in some areas. But, in the long term prospect remains one of hotter, drier conditions throughout the Mediterranean region as the relative influence of greenhouse gases increases over time.
Coastal flooding and erosion
As the world warms, global sea levels will rise as oceans expand and glaciers melt. Around much of the Mediterranean basin, sea levels could rise by close to 1 m by 2100. As a consequence, some low-lying coastal areas would be lost through flooding or erosion, while rivers and coastal aquifers would become more salty. The worst affected areas will be the Nile Delta, Venice and Thessaloniki where local subsidence means that sea levels could rise by at least one-and-a-half times as much as elsewhere.
Climate shows possible signs of change
On a global scale, there is increasing evidence that climate is changing and of a discernible human influence. The high natural variability of the Mediterranean climate make both the detection of climate change and attribution of its cause very difficult. Nevertheless, observations suggest that climate may already be changing in the region.
Land records for the western Mediterranean show slight trends towards warmer and drier conditions over the last century. In contrast, parts of the eastern Mediterranean have experienced cooler, wetter conditions in recent times than earlier this century. Surface water temperature records for the last 120 years show little overall trend but deep water records for the western Mediterranean show a continuous warming trend since 1959.
During the period 1952 to 1992, the number and frequency of heat waves affecting the region has increased. The early 1990s were notable for recurrent droughts and for periods of intense rainfall in the western Mediterranean and for extreme cold events and rainfall in the east. Recent climatic extremes are linked with the exceptional behaviour of ENSO and of the NAO. Record-breaking NAO values occurred in 1983, 1989 and 1990, while the prolonged 1990 to 1995 El Niņo event was the longest on record.
While all such trends and extremes could have occurred naturally, they are broadly consistent with the potential effects of greenhouse gas emissions and aerosol emissions to-date.
Increase in extent and severity of desertification
While much desertification is attributed to poor land use practices, hotter and drier conditions would extend the area prone to desertification northwards to encompass areas currently not at risk. In addition, the rate of desertification would increase due to increases in erosion, salinisation and fire hazard and reductions in soil quality. As a result, the process of desertification is likely to become irreversible.
The economic and human costs of an increase in desertification would be tremendous - even today, the annual costs of desertification in Tunisia and Spain are US$100 million and US$200 million, respectively.
Increased frequency of water shortages and decline in water quality
It is likely that the first impacts of climate change will be felt in the Mediterranean water resource system. Reductions in water availability would hit southern Mediterranean countries the hardest. In Egypt, Libya, Tunisia, Algeria, Morocco, Syria, Malta and the Lebanon, water availability already falls below, or approaches 1,000 m3 per person per year - the common benchmark for water scarcity.
Even relatively well-endowed countries, such as Spain, Greece and Italy, could suffer ever-more frequent regional water shortages due to the twin problems of climate change and rising demand. Crete, for example, could experience serious water shortages in five out of six years by 2010.
Some water supplies could become unusable due to the penetration of salt water into rivers and coastal aquifers as sea level rises. Water pollution - already a major health hazard in the region - would become still worse as pollutants become more concentrated with reductions in river flow.
Food security threatened by falls in production and world price rises
Livestock production would suffer due to a deterioration in the quality of rangeland associated with higher concentrations of atmospheric carbon dioxide and to changes in areas of rangeland as climate boundaries move northwards. In the European Mediterranean, the area of unproductive shrubland is expected to expand, while in North Africa and the Near East, most of the steppe rangeland could give way to desert by 2050 or earlier.
Yields of grains and other crops could decrease substantially across the Mediterranean region due to increased frequency of drought. While losses may be partially offset by beneficial effects from carbon dioxide, crop production would be further threatened by increases in competition for water and the prevalence of pests and diseases and land losses through desertification and sea level rise.
Climate change effects combined with wider socio-economic factors could cause cereal production over much of southern Europe to become untenable. At Kardista in central Greece, for example, the chance of obtaining current yields of maize could drop to close to zero by 2050, while in Spain, irrigation problems could force maize out of production.
In North Africa and the Near East, changes in average climate associated with a doubling of carbon dioxide could cause yield losses of over 20% for wheat, corn and other coarse grains - even before allowance is made for losses through other causes. In coastal areas, large areas of productive land may be lost through flooding, saline intrusion and waterlogging. In Egypt, for example, agricultural production may cease altogether over an area extending 20 km inland.
World prices for many key commodities such as wheat, maize, soybean meal and poultry could rise significantly as a result of global climate changes. Not only might Mediterranean countries loose substantially in economic terms, but the combination of higher prices and crop losses would lead to a deterioration in levels of food security in, particularly, southern countries.
New, widespread risks to public health
Reductions in food security would increase the risks of malnutrition and hunger for millions in the south. The combination of heat and pollution would lead to an upsurge in respiratory illness among urban populations, while extreme weather events could increase death and injury rates. Water shortages and damaged infrastructure would increase the risk of cholera and dysentery. Higher temperatures would increase the incidence and extent of infectious diseases, such as malaria, dengue fever, schistosmaisis and yellow fever.
Many valuable ecosystems would be lost
Many valuable ecosystems could be lost as species fail to keep up with the shift in climate boundaries and/or find their migration paths blocked by human activities. Wetland sites will face the dual threats of drying out and sea level rise. Up to 85% of wetland sites in southern Europe could disappear with a 3 to 4°C rise in temperatures. In Tunisia, for example, rising temperatures could contribute to the loss of all food plants and breeding waterfowl and the disappearance of nationally important fisheries.
Economic activity undermined in coastal zones
Industries, infrastructure and heritage sites in the coastal zone would be threatened by inundation or erosion due to sea level rise. For example, a rise in sea level of just 0.5 m would flood the western part of Kastala Bay (Croatia) harbour and cause serious degradation to the historic cities of Cres (Croatia) and Venice (Italy). Hydroelectric power output could be constrained by water shortages, with potentially serious knock-on implications for both domestic and industrial users.
Serious social disruption as the livelihood of millions is threatened and international tensions over resources mounts.
Serious social disruption could occur as millions are forced from their homelands as a result of desertification, poor harvests and sea level rise, while international disputes over shared water resources could turn into conflict in the face of declines in water availability and increased demand.
Losses to national economies
National economies would be adversely affected not only by the direct impacts of climate change, but also through the cost of adaptive measures and the knock-on implications of changes elsewhere. Quantitative estimates of financial costs are unreliable but in general, developing countries are expected to suffer larger relative economic damages than developed countries.
Sustainable development hinges on international action to cut greenhouse gas emissions
Future climate change could critically undermine efforts for sustainable development in the Mediterranean region through its impacts on the environment and social and economic well-being. While in many respects climate change exacerbates existing problems rather than creates new ones, the sheer magnitude of the potential problem means it cannot be ignored.
There is some scope for adaptation, but the fact that many measures would be beneficial irrespective of climate change suggests that radical changes in policies and practices will be needed. It is also vital that developed countries meet their obligations to assist adaptation in developing countries through access to know-how and financial assistance.
Ultimately, however, the long-term sustainability of the Mediterranean region requires keeping climate change within tolerable bounds. Current understanding of safe limits points to the need for prompt international agreement - and action - to make the drastic cuts in emissions of greenhouse gases required to stabilise atmospheric concentrations of these gases.