Manolis G. Grillakis

Evaluation of precipitation and temperature simulation performance of the CMIP3 and CMIP5 historical experiments

Abstract The fifth phase of the Coupled Model Intercomparison Project (CMIP5) is the most recent coordinated experiment of global climate modeling. Compared to its predecessor CMIP3, the fifth phase of the homonymous experiment—CMIP5 involves a greater number of GCMs, run at higher resolutions with more complex components. Here we use daily GCM data from both projects to test their efficiency in representing precipitation and temperature parameters with the use of a state of the art high resolution gridded global dataset for land areas and for the period 1960–2005. Two simple metrics, a comprehensive histogram similarity metric based on the match of simulated and observed empirical pdfs and a metric for the representation of the annual cycle were employed as performance indicators. The metrics were used to assess the skill of each GCM at the entire spectrum of precipitation and temperature pdfs but also for the upper and lower tails of it. Results are presented globally and regionally for 26 land regions that represent different climatic regimes, covering the total earth’s land surface except for Antarctica. Compared to CMIP3, CMIP5 models perform better in simulating precipitation including relatively intense events and the fraction of wet days. For temperature the improvement is not as clear except for the upper and lower hot and cold events of the distribution. The agreement of model simulations is also considerably increased in CMIP5. Substantial improvement in intense precipitation is observed over North Europe, Central and Eastern North America and North East Europe. Nevertheless, in both ensembles some models clearly perform better than others from a histogram similarity point of view. The derived skill score metrics provide essential information for impact studies based on global or regional land area multi-model ensembles.

Climate Change Impact on Photovoltaic Energy Output: The Case of Greece

Solar power is the third major renewable energy, constituting an increasingly important component of global future—low carbon—energy portfolio. Accurate climate information is essential for the conditions of solar energy production, maximization, and stable regulation and planning. Climate change impacts on energy output projections are thus of crucial importance. In this study the effect of projected changes in irradiance and temperature on the performance of photovoltaic systems in Greece is examined. Climate projections were obtained from 5 regional climate models (RCMs) under the A1B emissions scenario, for two future periods. The RCM data present systematic errors against observed values, resulting in the need of bias adjustment. The projected change in photovoltaic energy output was then estimated, considering changes in temperature and insolation. The spatiotemporal analysis indicates significant increase in mean annual temperature (up to 3.5°C) and mean total radiation (up to 5 W/m2) by 2100. The performance of photovoltaic systems exhibits a negative linear dependence on the projected temperature increase which is outweighed by the expected increase of total radiation resulting in an up to 4% increase in energy output.

Climate-Induced Shifts in Global Soil Temperature Regimes

Abstract Soil temperature is a key factor of plant growth and biological enzyme activities occurring in the soil, affected by the land cover, the evapotranspiration rate, the albedo, and the energy budget of the soil surface. In recent decades, efforts have been made to conserve soils against nonsustainable anthropogenic pressures. Changes in climate can impose additional threats on soil sustainability, as global scale soil temperature regime alterations are expected under global warming. Here, data from three well-established global climate models, spanning from 1981 to as far as 2120, are used to force the JULES (Joint UK Land Environment Simulator) model and produce simulations of soil temperature, calculating the water and energy budgets of the land surface. Modeled soil temperature data are used to estimate the climate-induced changes in the global soil temperature regimes at three different global warming levels. The results show significant shifts in the soil temperature regime for extended areas of the world, especially in the northern hemisphere. Pergelic and Cryic areas are reduced, whereas the Mesic and Thermic soils gain large areas in all three studied scenarios. Implications of the warming patterns might indicate the northward shift of various croplands in regions that until now their cultivation was not possible.

Freshwater vulnerability under high end climate change. A pan-European assessment

As freshwater availability is crucial for securing a sustainable, lower‑carbon future, there is a critical connection between water management and climate policies. Under a rapidly changing climate, it is more important than ever to estimate the degree of future water security. This is a challenging task as it depends on many different variables: the degree of warming and its consequent effects on hydrological resources, the water demand by different sectors, and the possible ameliorations or deteriorations of the effects due to climate change adaptation and mitigation strategies. A simple and transparent conceptual framework has been developed to assess the European vulnerability to freshwater stress under the present hydro-climatic and socioeconomic conditions, in comparison to projections of future vulnerability for different degrees of global warming (1.5°C, 2°C and 4°C), under the high-rate warming scenario (RCP8.5). Different levels of adaptation to climate change are considered in the framework, by employing various relevant pathways of socioeconomic development. A spatially detailed pan-European map of vulnerability to freshwater shortage has been developed at the local administrative level, making this approach extremely useful for supporting regional level policymaking and implementation and strategic planning against future freshwater stress.

Climate Impacts in Europe Under +1.5°C Global Warming

The Paris Agreement of the United Nations Framework Convention on Climate Change aims not only at avoiding +2°C warming (and even limit the temperature increase further to +1.5°C), but also sets long-term goals to guide mitigation. Therefore, the best available science is required to inform policymakers on the importance of and the adaptation needs in a +1.5°C warmer world. Seven research institutes from Europe and Turkey integrated their competencies to provide a cross-sectoral assessment of the potential impacts at a pan-European scale. The initial findings of this initiative are presented and key messages communicated. The approach is to select periods based on global warming thresholds rather than the more typical approach of selecting time periods (e.g., end of century). The results indicate that the world is likely to pass the +1.5°C threshold in the coming decades. Cross-sectoral dimensions are taken into account to show the impacts of global warming that occur in parallel in more than one sector. Also, impacts differ across sectors and regions. Alongside the negative impacts for certain sectors and regions, some positive impacts are projected. Summer tourism in parts of Western Europe may be favored by climate change; electricity demand decreases outweigh increases over most of Europe and catchment yields in hydropower regions will increase. However, such positive findings should be interpreted carefully as we do not take into account exogenous factors that can and will influence Europe such as migration patterns, food production, and economic and political instability.

Modeling Soil Salinity in Greenhouse Cultivations Under a Changing Climate With SALTMED: Model Modification and Application in Timpaki, Crete

Abstract Soil salinity is a major soil degradation threat especially for arid coastal environments where it hinders agricultural production, thus imposing a desertification risk. In the prospect of a changing climate, soil salinity caused by brackish water irrigation introduces additional uncertainties regarding the viability of deficit irrigation and intensive cultivation practices such as greenhouse cropping. Here, we propose a modification of the SALTMED leaching requirement model to account for greenhouse cultivation conditions. The model is applied in the RECARE Project Case Study of Timpaki, a semiarid region in south-central Crete, Greece, where greenhouse horticulture is an important land use. Excessive groundwater abstractions toward irrigation have resulted in a drop of the groundwater level in the coastal part of the aquifer, thus leading to seawater intrusion and in turn to soil salinization. Crop yield and soil profile electrical conductivity (EC) sensitivity to initial soil EC (up to 2 dS m−1) and irrigation water EC (up to 3 dS m−1) are modeled for the locally popular horticultural crops of Solanum lycopersicum, Solanum melongena, and Capsicum annuum. Climate model data obtained from nine general circulation models for the “worst case” representative concentration pathway of 8.5 W m−2 of the fifth phase of the Coupled Model Intercomparison Project are corrected for bias against historical observations with the Multisegment Statistical Bias Correction method and used to estimate crop yield and soil profile EC sensitivity in a warmer future. Results show that the effects of climate change on S. lycopersicum greenhouse cultivations of Timpaki will be detrimental, whereas S. melongena and C. annuum cultivations may show greater resilience.

A method to preserve trends in quantile mapping bias correction of climate modeled temperature

Bias correction of climate variables is a standard practice in climate change impact (CCI) studies. Various methodologies have been developed within the framework of quantile mapping. However, it is well known that quantile mapping may significantly modify the long-term statistics due to the time dependency of the temperature bias. Here, a method to overcome this issue without compromising the day-to-day correction statistics is presented. The methodology separates the modeled temperature signal into a normalized and a residual component relative to the modeled reference period climatology, in order to adjust the biases only for the former and preserve the signal of the later. The results show that this method allows for the preservation of the originally modeled long-term signal in the mean, the standard deviation and higher and lower percentiles of temperature. To illustrate the improvements, the methodology is tested on daily time series obtained from five Euro CORDEX regional climate models (RCMs).