ALBERT

Description: Meteorological extreme events have great potential for damaging railway infrastructure and posing risks to the safety of train passengers. In the future, climate change will presumably have serious implications on meteorological hazards in the Alpine region. Hence, attaining insights on future frequencies of meteorological extremes with relevance for the railway operation in Austria is required in the context of a comprehensive and sustainable natural hazard management plan of the railway operator. In this study, possible impacts of climate change on the frequencies of so-called critical meteorological conditions (CMCs) between the periods 1961–1990 and 2011–2040 are analyzed. Thresholds for such CMCs have been defined by the railway operator and used in its weather monitoring and early warning system. First, the seasonal climate change signals for air temperature and precipitation in Austria are described on the basis of an ensemble of high-resolution Regional Climate Model (RCM) simulations for Europe. Subsequently, the RCM-ensemble was used to investigate changes in the frequency of CMCs. Finally, the sensitivity of results is analyzed with varying threshold values for the CMCs. Results give robust indications for an all-season air temperature rise, but show no clear tendency in average precipitation. The frequency analyses reveal an increase in intense rainfall events and heat waves, whereas heavy snowfall and cold days are likely to decrease. Furthermore, results indicate that frequencies of CMCs are rather sensitive to changes of thresholds. It thus emphasizes the importance to carefully define, validate, and—if needed—to adapt the thresholds that are used in the weather monitoring and warning system of the railway operator. For this, continuous and standardized documentation of damaging events and near-misses is a pre-requisite.

Description: Statistical bias-adjustment of climate models' outputs is being increasingly used for assessing the impact of climate change on several sectors. It is known that these techniques may alter the mean climate signal of the adjusted variable; however, the effect on the projected occurrence of climate extremes is less commonly investigated. Here, the outputs of an ensemble of high-resolution (0.11 ∘ ) regional climate models (RCM) from the Coordinated Regional-climate Downscaling Experiment for Europe (EURO-CORDEX) have been bias-adjusted, and a number of climate indices from the Expert Team on Climate Change Detection and Indices (ETCCDI) has been calculated for the present (1981-2010) and future (2071-2100) climate. Indices include absolute-thresholds indices, percentile-based indices, and indices based on the duration of an event. Results show that absolute-threshold indices are largely affected by bias-adjustment, as they depend strongly on both the present mean climate value (usually largely biased in the original RCMs) and its shift under climate change. The change of percentile-based indices is less affected by bias-adjustment, as that of indices based on the duration of an event (e.g., consecutive dry days, or heat waves) although the present climate value can differ between original and bias-adjusted results. Indices like R95ptot (the total amount of precipitation larger than the 95th reference percentile) are largely affected by bias-adjustment, although, when analysing an ensemble of RCMs, the differences are usually smaller than, or comparable to the inter-model variability.

Description: Severe, extreme, and exceptional heat waves, such as those that occurred over the Balkans (2007), France (2003), or Russia (2010), are associated with increased mortality, human discomfort and reduced labour productivity. Based on the results of a very high-resolution global model, we show that, even at 1.5 °C warming, a significant increase in heat wave magnitude is expected over Africa, South America, and Southeast Asia. Compared to a 1.5 °C world, under 2 °C warming the frequency of extreme heat waves would double over most of the globe. In a 1.5 °C world, 13.8% of the world population will be exposed to severe heat waves at least once every 5 years. This fraction becomes nearly three times larger (36.9%) under 2 °C warming, i.e. a difference of around 1.7 billion people. Limiting global warming to 1.5 °C will also result in around 420 million fewer people being frequently exposed to extreme heat waves, and ~65 million to exceptional heat waves. Nearly 700 milli...

Description: Discriminating climate impacts between 1.5 °C and 2 °C warming levels is particularly important for Central Africa, a vulnerable region where multiple biophysical, political, and socioeconomic stresses interact to constrain the region’s adaptive capacity. This study uses an ensemble of 25 transient Regional Climate Model (RCM) simulations from the CORDEX initiative, forced with the Representative Concentration Pathway (RCP) 8.5, to investigate the potential temperature and precipitation changes in Central Africa corresponding to 1.5 °C and 2 °C global warming levels. Global climate model simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5) are used to drive the RCMs and determine timing of the targeted global warming levels. The regional warming differs over Central Africa between 1.5 °C and 2 °C global warming levels. Whilst there are large uncertainties associated with projections at 1.5 °C and 2 °C, the 0.5 °C increase in global temperature is associated...

Description: We analyze the potential effect of global warming levels (GWLs) of 1.5 °C and 2 °C above pre-industrial levels (1861−1890) on mean temperature and precipitation as well as intra-seasonal precipitation extremes over the Greater Horn of Africa. We used a large, 25-member regional climate model ensemble from the Coordinated Regional Downscaling Experiment and show that, compared to the control period of 1971−2000, annual mean near-surface temperature is projected to increase by more than 1 °C and 1.5 °C over most parts of the Greater Horn of Africa, under GWLs of 1.5 °C and 2 °C respectively. The highest temperature increases are projected in the northern region, covering most parts of Sudan and northern parts of Ethiopia, and the lowest temperature increases are projected over the coastal belt of Tanzania. However, the projected mean surface temperature difference between 2 °C and 1. 5 °C GWLs is higher than 0.5 °C over nearly all land points, reaching 0.8 °C over Sudan and norther...

Description: Results from an 25 regional climate model simulations from the Coordinated Regional Downscaling Experiment Africa initiative are used to assess the projected changes in temperature and precipitation over southern Africa at two global warming levels (GWLs), namely 1.5 °C and 2.0 °C, relative to pre-industrial values, under the Representative Concentration Pathway 8.5. The results show a robust increase in temperature compared to the control period (1971–2000) ranging from 0.5 °C–1.5 °C for the 1.5 °C GWL and from 1.5 °C–2.5 °C, for the 2.0 °C GWL. Areas in the south-western region of the subcontinent, covering South Africa and parts of Namibia and Botswana are projected to experience the largest increase in temperature, which are greater than the global mean warming, particularly during the September–October–November season. On the other hand, under 1.5 °C GWL, models exhibit a robust reduction in precipitation of up to 0.4 mm day −1 (roughly 20% of the climatological va...

Description: ABSTRACT As a result of climate change in recent past and unsustainable land management, drought became one of the most impacting disasters and, with the projected global warming, it is expected to progressively cause more damages by the end of the 21st century. This study investigates changes in drought occurrence, frequency, and severity in Europe in the next decades. A combined indicator based on the predominance of the drought signal over normal/wet conditions has been used. The indicator, which combines the standardized precipitation index (SPI, which accounts for anomalous low rainfall), the standardized precipitation evapotranspiration index (SPEI, which accounts for high temperatures and scarce precipitations), and the reconnaissance drought indicator (RDI, similar to SPEI but more affected by extreme events), has been computed at 3- and 12-month accumulation scales to characterize trends in seasonal and annual events from 1981 to 2100. Climate data from 11 bias-adjusted high-resolution (0.11°) simulations from the EURO-CORDEX (coordinated regional climate downscaling experiment) have been used in the analyses. For each simulation, the frequency and severity of drought and extreme drought events for 1981–2010, 2041–2070, and 2071–2100 have been analysed. Under the moderate emission scenario (RCP4.5), droughts are projected to become increasingly more frequent and severe in the Mediterranean area, western Europe, and Northern Scandinavia, whereas the whole European continent, with the exception of Iceland, will be affected by more frequent and severe extreme droughts under the most severe emission scenario (RCP8.5), especially after 2070. Seasonally, drought frequency is projected to increase everywhere in Europe for both scenarios in spring and summer, especially over southern Europe, and less intensely in autumn; on the contrary, winter shows a decrease in drought frequency over northern Europe. We investigate future European drought trends using EURO-CORDEX bias-adjusted data. Under the RCP4.5 scenario, droughts are projected to become increasingly more frequent and severe over the Mediterranean, western Europe, and Scandinavia, whereas the European continent – except Iceland – will be affected by more frequent extreme droughts under RCP8.5, especially after 2070. Drought frequency is projected to increase everywhere in Europe in spring and summer (less intensely in autumn), especially over southern Europe, but to decrease in winter over northern Europe. Drought frequency (DRF), extreme drought frequency (ExDRF), and drought severity (DRS) are projected to largely increase over most of Europe in the far future compared to recent decades for both moderate (RCP4.5) and more extreme emission (RCP8.5) scenarios.

Description: There is a general lack of information about the potential effects of 1.5, 2 or more degrees of global warming on the regional climates within Africa, and most studies that address this use data from coarse resolution global models. Using a large ensemble of CORDEX Africa simulations, we present a pan-African overview of the effects of 1.5 and 2 °C global warming levels (GWLs) on the African climate. The CORDEX simulations, consistent with their driving global models, show a robust regional warming exceeding the mean global one over most of Africa. The highest increase in annual mean temperature is found over the subtropics and the smallest one over many coastal regions. Projected changes in annual mean precipitation have a tendency to wetter conditions in some parts of Africa (e.g. central/eastern Sahel and eastern Africa) at both GWLs, but models’ agreement on the sign of change is low. In contrast to mean precipitation, there is a consistent increase in daily precipitation int...

Description: We examine the impact of +1.5 °C and +2 °C global warming levels above pre-industrial levels on consecutive dry days (CDD) and consecutive wet days (CWD), two key indicators for extreme precipitation and seasonal drought. This is done using climate projections from a multi-model ensemble of 25 regional climate model (RCM) simulations. The RCMs take boundary conditions from ten global climate models (GCMs) under the RCP8.5 scenario. We define CDD as the maximum number of consecutive days with rainfall amount less than 1 mm and CWD as the maximum number of consecutive days with rainfall amount more than 1 mm. The differences in model representations of the change in CDD and CWD, at 1.5 °C and 2 °C global warming, and based on the control period 1971−2000 are reported. The models agree on a noticeable response to both 1.5 °C and 2 °C warming for each index. Enhanced warming results in a reduction in mean rainfall across the region. More than 80% of ensemble members agree that CDD w...

Description: ABSTRACT During the last decades, the effects of global warming have become apparent also in Europe, causing relevant impacts in many sectors. Under projected future global warming, such a tendency can be expected to persist until the end of this century and beyond. Identifying which climate-related impacts are likely to increase, and by how much, is an important element of any effective strategy for managing future climate risks. This study investigates whether energy demand for cooling and heating buildings can be expected to increase or decrease under climate change. Two indicators of weather-related energy consumption for heating and cooling buildings are considered: heating degree-days (HDD) and cooling degree-days (CDD). The evolution of these indicators has been analysed based on 11 high-resolution bias-adjusted EURO-CORDEX simulations for two emission representative concentration pathways (RCP4.5 and RCP8.5). Both indicators have been validated over the period 1981–2010 using an independent data set that contains more than 4000 station data, showing very high correlation over most of Europe. Trends of HDD and CDD from 1981 to 2100, together with their uncertainties, are analysed. For both RCPs, all simulations project a significant decrease for HDD, especially over Scandinavia and European Russia, and an increase of CDD which peaks over the Mediterranean region and the Balkans. Overall, degree-day trends do not show remarkable differences if population weighting is applied. If a constant population scenario is considered, the decrease in HDD will outbalance the increase in CDD in the 21st century over most of Europe. Thus the related energy demand (expressed as Energy Degree-days, EDD) is expected to decrease. If, however, population projections over the 21st century are included in the calculations, it is shown that despite the persisting warming, EDD will increase over northern Europe, the Baltic countries, Great Britain, Ireland, Benelux, the Alps, Spain, and Cyprus, resulting in an overall increase in EDD over Europe. Using 11 bias-adjusted EURO-CORDEX simulations, we computed heating (HDD) and cooling degree-days (CDD) for 1981–2100 over Europe under RCP4.5 and RCP8.5. A significant projected decrease in HDD under both scenarios is found, especially over Fennoscandia and Russia; the increase of CDD will peak over Mediterranean and Balkans. Under a constant population scenario, energy degree-days (EDD) are expected to decrease almost over the entire Europe. Using population projections, EDD will increase over northern Europe, the Baltic Republics, the British Isles, Benelux, the Alps, Spain, and Cyprus. Ensemble mean linear trends of HDD/year (left) and CDD/year (right) under RCP4.5 (top) and RCP8.5 (bottom). Over grey areas, fewer than 7 out of 11 simulations projected a significant trend at 95%. Population-weighting is not applied in this map.