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For the last 25 years, CO-PDD (Cézeaux-Aulnat-Opme-puy de Dôme) has evolved to become a full instrumented platform for atmospheric research. It has received credentials as a national observing platform in France and is internationally recognized as a global station in the GAW (Global Atmosphere Watch) network. It is a reference site of European and national research infrastructures ACTRIS (Aerosol Cloud and Trace gases Research Infrastructure) and ICOS (Integrated Carbon Observing System). The site located on top of the puy de Dôme mountain (1465 m a.s.l.) is completed by additional sites located at lower altitudes and adding the vertical dimension to the atmospheric observations: Opme (660 m a.s.l.), Cézeaux (410 m), and Aulnat (330 m). The integration of different sites offers a unique combination of in situ and remote sensing measurements capturing and documenting the variability of particulate and gaseous atmospheric composition, but also the optical, biochemical, and physical properties of aerosol particles, clouds, and precipitations. Given its location far away from any major emission sources, its altitude, and the mountain orography, the puy de Dôme station is ideally located to sample different air masses in the boundary layer or in the free troposphere depending on time of day and seasons. It is also an ideal place to study cloud properties with frequent presence of clouds at the top in fall and winter. As a result of the natural conditions prevailing at the site and of the very exhaustive instrumental deployment, scientific studies at the puy de Dôme strongly contribute to improving knowledge in atmospheric sciences, including the characterization of trends and variability, the understanding of complex and interconnected processes (microphysical, chemical, biological, chemical and dynamical), and the provision of reference information for climate/chemistry models. In this context, CO-PDD is a pilot site to conduct instrumental development inside its wind tunnel for testing liquid and ice cloud probes in natural conditions, or in situ systems to collect aerosol and cloud. This paper reviews 25 years (1995–2020) of atmospheric observation at the station and related scientific research contributing to atmospheric and climate science. [ABSTRACT FROM AUTHOR]

Future development and renewal of transport infrastructures have to take into account how the effects of climate change will affect these complex sociotechnical systems. This article aims at understanding how to raise this issue to ensure an efficient and systemic uptake of climate change by infrastructure managers. It reports the results of an in-depth case study conducted on the French railway company. This study identifies several adaptation dynamics: one is top-down and stems from climate change impacts; others are more bottom-up and focused on vulnerabilities. However, both types of approaches have, so far, yielded limited results. Building on the existing literature, this paper reveals critical bottlenecks to overcome in order to get the organization ready to adapt. It suggests key components of an enabling framework for a more proactive preparation to climate change and mainstreaming climate adaptation into major organisational decisions. [ABSTRACT FROM AUTHOR]

• French people have limited knowledge about climate change but worry about it. • They prefer green investments or regulations to a tax and dividend. • Distributive effects and lack of alternatives prevent carbon tax acceptance. • Improving knowledge is predicted to increase ecological attitudes and concern. • Unlike in the US, partisanship does not interact with education to shape perceptions. This paper aims to assess the prospects for French climate policies after the Yellow Vests crisis halted the planned increase in the carbon tax. From a large representative survey, we elicit knowledge, perceptions and values over climate change, we examine opinions relative to carbon taxation, and we assess support for other climate policies. Specific attention is given to the link between perceptions of climate change and attitudes towards policies. The paper also studies in detail the determinants of attitudes in terms of political and socio-demographic variables. Among many results, we find limited knowledge but high concern for climate change. We also document a large rejection of the carbon tax but majority support for stricter norms and green investments, and reveal the rationales behind these preferences. Our study entails policy recommendations, such as an information campaign on climate change. Indeed, we find that climate awareness increases support for climate policies but no evidence for the formation of opinions through partisan cues as in the US, suggesting that better access to science could foster support for climate policies. [ABSTRACT FROM AUTHOR]

This paper introduces an original method for climate change detection, called temporal optimal detection method. The method consists in searching for a smooth temporal pattern in the observations. This pattern can be either the response of the climate system to a specific forcing or to a combination of forcings. Many characteristics of this new method are different from those of the classical “optimal fingerprint” method. It allows to infer the spatial distribution of the detected signal, without providing any spatial guess pattern. The spatial properties of the internal climate variability doesn’t need to be estimated either. The estimation of such quantities being very challenging at regional scale, the proposed method is particularly well-suited for such scale. The efficiency of the method is illustrated by applying it on real homogenized datasets of temperatures and precipitation over France. A multimodel detection is performed in both cases, using an ensemble of atmosphere-ocean general circulation models for estimating the temporal patterns. Regarding temperatures, new results are highlighted, especially by showing that a change is detected even after removing the uniform part of the warming. The sensitivity of the method is discussed in this case, relatively to the computation of the temporal patterns and to the choice of the model. The method also allows to detect a climate change signal in precipitation. This change impacts the spatial distribution of the precipitation more than the mean over the domain. The ability of the method to provide an estimate of the spatial distribution of the change following the prescribed temporal patterns is also illustrated. [ABSTRACT FROM AUTHOR]

In this paper we investigate the impacts of future climatic change on the occurrence of debris flows in the Massif des Ecrins (French Alps). Two distinct aspects are discussed: the impact of future climatic change on the evolution of the process, and changes in the spatial distribution. Three climate simulations are presented for the current period (1970–1999) and for future periods (2070–2099) using GCM ARPEGE CLIMAT model developed by Météo-France. Simulated data are then statistically downscaled to obtain a higher spatial resolution. In the first step, we compare occurrence probabilities in the current period and in the next century. In the second step, we estimate which zones would be affected by the process in the future at the scale of the Massif des Ecrins. For the current period, the best model was obtained between debris flows and the number of days between June 15th and October 15th with more than 20 mm calculated either from observed meteorological or simulated data. Results of the ARPEGE model considering the A2 hypothesis (IPCC ) showed that the most significant climatic trends for the end of the century will be a decrease in intense rainy events and an increase in temperature. These trends are expected to reduce the occurrence of hill slope debris flows in the Massif des Ecrins. From a spatial point of view, the increase in temperature should result in a shift of the 0°C isotherm to a higher elevation which, in turn, should result in a 20% reduction of the number of slopes affected by the process. [ABSTRACT FROM AUTHOR]

In August 2003, Western Europe experienced a deadly heat wave. It is estimated that 15,000 people died in France from its direct effects. Applying an indirect estimation technique to the monthly number of deaths by sex, age, and place of residence for the period 1996-2003, we estimate the number of years that would have remained to those who died from the heat wave had they been spared. The paper also evaluates the role of the 'harvesting' effect of the 2003 heat wave in explaining the deficit of deaths recorded in 2004 - estimated at 23,000 out of an expected total of 535,000 deaths. The harvesting effect was modest and accounted for fewer than 5,000 of the 'missing' deaths in 2004. The mortality decline in 2004 is thus due mainly to other factors. One hypothesis is that special efforts have been directed towards isolated older people as a consequence of the heat wave. [ABSTRACT FROM AUTHOR]

This paper reviews the climatic history of northern France from the grape harvest dates of the Burgundian vineyards. The grape harvest date is constrained by the mean surface air temperature during the growing season (April–August). At the start of the grape harvest dates series – during the 1380s and from 1415 to 1435 – the tendency is towards early harvest dates and warmer conditions, starvation due to crop scorching in 1420 included. During the second half of the 'Quattrocento', there are later harvest dates and cooler springs/summers, exemplified by the 1481 famine, due to rain and cold. The 1500s, 20s, 30s and 50s are characterised by blasts of warmer summers. The 'midsummer night's dream' (1596/7) can turn into a nightmare ... Then, a cold 'long seventeenth century'? This is quite pronounced from 1570 to 1630, with, however, a slight improvement around 1600–20. Major waves of hot summers were experienced during the 1630s, 60s and 80s. Is the Maunder minimum, between 1645 and 1715, responsible for a slight, synchronous, cooling? In this case, it would be mainly the Late Maunder Minimum (1675–1715), with the chill of 1675, the 1690s and 1709–1715. Then the great warming of the eighteenth century: the years 1704–07, 1718/9, the 1720s and 30s, 1757–65, the 1780s and above all 1778–81 all favour this interpretation, though we must not forget the cold, wet years 1725, 1740 and 1770. The years 1812–17 are not only snowy but also globally cold (due to the Tambora eruption in 1815 and the Dalton minimum?). And then there is the 1846 heatwave, so harmful to cereals. The Little Ice Age ends in 1860, with no return up to the present, the twentieth century warming from 1900, with an intensification of the phenomenon from 1976 and particularly the 1990s. [ABSTRACT FROM AUTHOR]