CLIMATE CHANGE AND ITS IMPACT ON ROAD CONDITIONS IN WINTER

摘要

In the Summary for Policy Makers of the IPCC WG1’s contribution to its FourthAssessment Report, the IPCC declares that warming of the climate system is unequivocaland that most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas.This change is observed in most of the world and it is particularly important at highlatitudes of the northern Hemisphere and over Western Europe. In France, the observedtemperature has increased by almost 1°C during the last century and this rise has mainlyoccurred since the 1970s.The IPCC projects that the increase in temperatures will continue during the next decades.For most greenhouse gas emission scenarios, climate models calculate a global warmingof about 0.2°C per decade at the beginning of the XXIe Century. It is very likely thatwarming will accelerate after 2050 at a rate depending on the emission scenarios taken forhypothesis. Increase in temperature will be stronger over continental regions at midlatitudeswhich concentrate a major part of the roads and of the traffic in the world. Thereis no doubt that climate change will have in these regions an important impact on themaintenance activities of the roads in winter. In a nutshell, the number of frost days, ofcold waves and snowfalls will significantly decrease. This will probably limit the damage byfrost of the road structures and the number of days when the traffic will be disturbed bysnow. However, less favorable factors have to be taken into account, such as the rise ofthe summer temperatures or the increase in the intensity of winter precipitations in certainregions.A sound assessment of the impact of climate change on the roads and their wintermaintenance needs a solid understanding of the processes intervening between thepavement and the meteorological conditions. The use of physically-based simulationmodels is necessary to quantify the respective role of various factors like the airtemperature and humidity, the cloudiness, the precipitation or the physical properties of theroad structure. It also needs realistic climate scenarios on a regional scale which are nowavailable. Because snow and frost conditions are common but not very frequent, France isa particularly interesting case to assess the impact of climate change on road maintenanceactivities in winter. Recent results will be presented to illustrate the possible impact ofvarious climate scenarios to be expected on the number frost and snow days. Particularattention will be devoted to the number of days when snow is likely to stay on the roads.