Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

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Climate Change 2007: The Physical Science Basis.

The Intergovernmental Panel on Climate Change (IPCC) Technical Paper Climate Change and Water draws together and evaluates the information in IPCC Assessment and Special Reports concerning the impacts of climate change on hydrological processes and regimes, and on freshwater resources – their availability, quality, use and management. It takes into account current and projected regional key vulnerabilities, prospects for adaptation, and the relationships between climate change mitigation and water. Its objectives are:

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Climate change and water.

he prospect that increases inatmospheric concentrationsof greenhouse gases willhave measurable effects on theearth’s climate over the next fewdecades has attracted a vastresearch effort. Climatologistshave faced two main challenges.The first has been to distinguishthe signal of human-induced cli-mate change from the noise ofinterannual and decadal naturalvariability. The second has been topredict probable climate scenariosfor the future. Climate monitoringover the past century and long-term reconstructions of climateover the past millennium indicatethat the earth is indeed warmingup (Fig. 1)

http://uni-landau.de/umwelt/study/content/files/archiv/h.schulz/ws09/biodiversitaet_und_naturschutz/hughes 2000.pdf

Biological consequences of global warming: is the signal already

Increasing greenhouse gas concentrations are expected to have significant impacts on the world's climate on a timescale of decades to centuries. Evidence from long-term monitoring studies is now accumulating and suggests that the climate of the past few decades is anomalous compared with past climate variation, and that recent climatic and atmospheric trends are already affecting species physiology, distribution and phenology.

Biological consequences of global warming: is the signal already apparent?

Large changes in the wintertime atmospheric circulation have occurred over the past two decades over the ocean basins of the Northern Hemisphere, and these changes have had a profound effect on regional distributions of surface temperature and precipitation. The changes over the North Pacific have been well documented and have contributed to increases in temperatures across Alaska and much of western North America and to decreases in sea surface temperatures over the central North Pacific. The variations over the North Atlantic are related to changes in the North Atlantic Oscillation (NAO). Over the past 130 years, the NAO has exhibited considerable variability at quasi-biennial and quasi-decadal time scales, and the latter have become especially pronounced the second half of this century. Since 1980, the NAO has tended to remain in one extreme phase and has accounted for a substantial part of the observed wintertime surface warming over Europe and downstream over Eurasia and cooling in the northwest Atlantic. Anomalies in precipitation, including dry wintertime conditions over southern Europe and the Mediterranean and wetter-than-normal conditions over northern Europe and Scandinavia since 1980, are also linked to the behavior of the NAO. Changes in the monthly mean flow over the Atlantic are accompanied by a northward shift in the storm tracks and associated synoptic eddy activity, and these changes help to reinforce and maintain the anomalous mean circulation in the upper troposphere. It is important that studies of trends in local climate records, such as those from high elevation sites, recognize the presence of strong regional patterns of change associated with phenomena like the NAO.

Decadal Variations in Climate Associated with the North Atlantic Oscillation

Natural hazards in forests - glacier and permafrost effects as related to climate changed

https://www.zora.uzh.ch/id/eprint/52577/1/2011_EgliM_Boehlert_etal_Geomorphology_2011.pdf

Application of a combination of dating techniques to reconstruct the Lateglacial and early Holocene landscape history of the Albula region (eastern Switzerland)

Data on temperature and accumulation of high altitude firn in the Alps are compiled and discussed Firn temperature varies with incoming radiation (slope aspect) at a given altitude The altitudinal gradient of temperature in highly permeable firn bodies appears to be about twice as high as the mean lapse rate of air temperature "Cold infiltration" takes place above about 3500 m as! Firn temperatures on the highest peaks are around -15 'c Accumulation (net balance) also decreases with increasing altitude from about 3m H20 at 3500 m as! to around 05 m H20 at wind exposed sites between 4300 and 4800 m asl Probably this is strongly due to wind erosion and topographical effects However, temperature and accumulation not only appear to be interrelated, but also seem to be positively correlated to the heat applied to the surface Assuming the observed altitudinal gradients have remained constant in time, it can be estimated that high altitude firn bodies have become considerably warmer since the last century CO2-induced atmospheric warming could lead to a drastic change in the mass turnover and flow activity of high glaciers, in wind-exposed places where wind erosion of the snowpack becomes a controlling factor of accumulation INTRODUCTION Studies on mass and heat exchange at the surface of alpine firn have usually been carried out at altitudes below about 3500 m as!, where firn is temperate and accumulation is high (eg Lang and others 1977, Muller 1977) Access to firn regions of higher altitudes is difficult However, rather unusual construction work (eg Refuge lenkins on Mont Blanc), and a number of tunnels dug into the firn of the Monte Rosa region by J E Fisher in the 1950s, furnished some information which indicated that at high altitudes, firn is cold and accumulation does not further increase with altitude Interest in temperature and accumulation of high altitude firn has grown recently in connection with (I) englacial temperatures, (2) ice avalanches, and (3) alpine core drilling Temperature distribution in the tongue of Grenzgletscher, one of the largest ice bodies in the Alps, must be caused by advection of cold ice from high altitudes (Blatter and Haeberli 1984) The frequency of ice avalanches ultimately depends on the accumulation of firn (Alean 1985), and the stability of steep mountain glaciers seems to depend on firn and ice temperatures (Rothlisberger 198 1, Alean 1984) Finally, core drilling projects in cold, high alpine firn and ice provide important information about the evolution of the composition of the atmosphere in heavily industrialized regions over past decades and centuries (eg Wagenbach and others in press), but require knowledge about the distribution of accumulation in space and time The aims of the present study are to compile information available and point to possible effects of recent atmospheric warming FIRN TEMPERATURE Temperature measurements from deep pits, tunnels, and shallow bore-holes in high altitude firn of the Alps have been compiled by Haeberli (1976, cf also Hooke and others 1983) New information is available from Chli Titlis, Jungfraujoch/Sphinxgrat and Monte Rosa/Colle Gnifetti (all Swiss Alps) At Chli Titlis, 3070 m asI, 15 m-temperature in the summit's 22 m thick firn and ice was -07'C ( 1979/80, cf Haeberli and others 1979) Temperatures in the Sphinxgrat crest were measured in a 70 m borehole through firn, ice and perennially frozen rocks, in connection with recent construction work at the Jungfraujoch The ice-rock interface, 10 m below the surface at 3525 m as!, had a temperature close to -6'C (198 1) Temperatures around 14'C at 15 m depth were registered in all core drilling boreholes made so far on Colle Gnifetti (4450 m as!) The fim-ice transition in this cold firn saddle occurs about 40 m below the surface (Schotterer and others 1981) When presently-known firn temperatures are compiled (Figure I) two groups seem to exist Group I incorporates summits, crests and probably also very steep slopes (�45') which mainly consist of impermeable ice or high density firn with high concentrations of ice layers Temperatures in such ice bodies decrease with increasing altitude at a rate (about I 'C/IOO m) which is slightly higher than the assumed lapse rate of mean annual air temperature (065 'C/IOO m) No temperate firn bodies are known in such situations In contrast, more gentle slopes and basins (group 2) where highly permeable firn accumulates, are temperate up to about 3600 m as! Above this upper boundary of the "warm infiltration zone" of the Alps, percolating meltwater cannot

Temperature and accumulation of high altitude firn in the Alps

Managing risks and future options from new lakes in the deglaciating Andes of Peru: The example of the Vilcanota-Urubamba basin.

Subsurface ice fillings were first described in the Jura Mountains at the end of the sixteenth century. In order to assess the impact of climate change on low-altitude cave ice a detailed inventory has been drawn up and more than 50 objects have been identified. Comparisons between older cave maps, photographic documents and present-day observations outline a negative trend in ice mass balances, a trend that increased at the end of the 1980s. As most of these ice caves act as cold air traps, this negative mass balance is mainly attributed to higher winter temperatures and to reduced snow precipitation at low altitudes. The equilibrium line altitude of ice caves is believed to have increased several hundred metres between AD 1978 and 2004. Photographic comparisons and proxy records in some of the caves studied provide evidence of a rapid mass turnover. Ice ages range between less than a few decades and a millennium. Climatic records in these ice fillings will therefore present only short time series compared with other cave sediments. However, indications of former ice fillings have been found in different caves of the Jura Mountains and outline their potential role as palaeoclimatic markers.

Wilfried Haeberli

Papers

Natural hazards in forests - glacier and permafrost effects as related to climate changed

Application of a combination of dating techniques to reconstruct the Lateglacial and early Holocene landscape history of the Albula region (eastern Switzerland)

Temperature and accumulation of high altitude firn in the Alps

Managing risks and future options from new lakes in the deglaciating Andes of Peru: The example of the Vilcanota-Urubamba basin.

Ice caves as an indicator of winter climate evolution: a case study from the Jura Mountains