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Climate change

Martin Beniston

Martin Beniston
Professor of Climatology, University of Geneva

Prof. Martin Beniston, born in the UK and a citizen of France and Switzerland as well as the UK, heads the Research Group on Climate Change and Climate Impacts at the University of Geneva. He is a lead author and reviewer for the International Panel on Climate Change (IPCC).

Financially supported by UNEP and with the help of DEWA/GRID-Europe, the Zurichbased World Glacier Monitoring Service (WGMS) reported in January 2007 that mountain glaciers around the world continue to melt. Tentative figures for 2005 indicate average thickness reduction for measured glaciers of roughly half a meter of ice. The new data confirms the trend in accelerated ice loss during the past two and a half decades and brings the average thickness loss since 1980 of the 30 reference glaciers of nine mountain ranges at about 9.6 meter water equivalent (w.e). On average, one meter w.e. corresponds to 1.1 meter ice thickness. Average annual ice loss since the year 2000 was 1.6 times more than the average of the 1990s and three times the loss rate of the 1980s.

View from a climatologist

Global warming and Switzerland: what to expect

The University of Geneva has a special group studying climate change and its effects in Switzerland. The group's leader, climatologist Martin Beniston, answers questions about the local effects.

Q: Over the next few decades, what will global warming mean for Switzerland?

A: In Switzerland, we expect the rapid warming of the global climate to translate into an average rise in winter temperatures of 2-4ºC and an increase in winter precipitation of 5-20% over today's values. Summers could be 5-7ºC warmer and have 10-30% less rain.We could describe this as a gradual progression toward a «Mediterranean climate», characterized by a distinct rainy season in winter and hot, dry summers.

Q: Might some people consider this desirable?

A: Hardly. Such a dramatic change in our regional climate would be accompanied by more heatwaves at least as intense as that of 2003, and an increase in the number and severity of droughts. Ironically, we can also expect more torrential rains of the sort that caused the disastrous flooding in Bern and Lucerne in August 2005, and for which we paid an enormous price in loss of human life and property. The floods washed away roads and railroad tracks, isolated villages, triggered mass evacuations, contaminated water supplies, cut power lines. Several people were drowned or buried under mudslides.

Q: What will climate change mean for the Geneva region, specifically?

A: The Rhone valley and the Léman (Lake Geneva) basin will naturally experience some direct effects from these changes. But the indirect impacts of what happens upstream, in the mountains, could be even more profound. This is where water for the river, its tributaries and eventually the lake comes from, and a dramatic change in the alpine climate will have important physical, biological and ecological knockon effects.

Q: Is there any truth to the reports that Swiss glaciers are rapidly melting?

A: In Switzerland the surface area of the «cryosphere» - the areas where we find glaciers, permanent snow cover and permafrost - has been decreasing for more than a century, and the rate of decline can only increase in the future. We fear that 50-90% of the mass of our mountain glaciers will disappear before the end of the 21st century, depending on the magnitude and rate of warming. In general, the snow limit moves up 150m for every extra degree of temperature. As for the permafrost, when this melts it causes the mountainsides to become more unstable. We can thus expect more avalanches, rockslides and mudslides. The consequences of such disasters in terms of human suffering and loss of infrastructure will be significant.

Q: How will this affect the River Rhone?

A: In terms of the region's hydrology, the flow of the Rhone and the smaller rivers that feed it will be affected by the seasonal changes in the precipitation regimes and by the fact that below 1500m rain will take the place of snow. Given that an important part of the Rhone's water comes from the melting of snow and glaciers, and that the snow will begin to melt earlier in the spring, the river's seasonal flow patterns will be affected. The hydrological changes that take place high in the mountains will be felt strongly in the valleys and plains and all the way to Lake Léman, where the need for water is a function of the region's high population density, extensive agriculture and industrial growth.

Q: What effects will this have on the environment of these regions?

A: It's hard to predict in detail, but we expect to see a decline in the biological diversity of mountain ecosystems. Plant species will migrate to higher altitudes, where growing conditions will match those of today. Species already found at high altitudes will have to adapt or disappear. Normal patterns of species competition will be disrupted, to the detriment of those who are less able to adapt or migrate. It might seem paradoxical that mountain vegetation, which is so robust and resistant in the face of extreme conditions, can be menaced with extinction by what seems to be a small change. This is because the plants are well-adapted to climate extremes, a very short growing season, poor soils, steep slopes and competition with other species. Thus they are able to survive within a very narrow «environmental bandwidth.» Any perturbation in the climate can disrupt the balance between these essential survival factors and spell disaster for some kinds of vegetation.

Q: What about the animals?

A: Mountain fauna will face many of the same pressures and obstacles as the plants, as their food supply migrates or diminishes, as their habitats become more unstable, and as their predators and competitors change their range and behavior.

Disruption of the hydrological cycle will affect the quality and quantity of the water supply, with resulting impacts on health and waterdependent activities and industry. The security of mountain hydroelectric plants, on which Switzerland is so dependent, will be compromised. The water quality of Lake Léman may be at risk, particularly during summer heatwaves, causing a proliferation of pathogenic bacteria.

Q: Is there a silver lining to this very dark cloud?

A: The only positive effect I can think of might be for agriculture. For example, the increased temperatures might lengthen the growing season and preclude the spring frosts that can damage fruit trees. But this is probably a false hope, offset by increased risk of drought and therefore a lack of water for irrigation.

Q: What can we do?

A: Unfortunately, global warming is now inevitable. But we can support efforts to reduce its amplitude, and here in Switzerland we can prepare for the winter floods and summer droughts that loom in our near future.