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Climate is not changing uniformly within geographical regions, and long-term changes can be cyclical or irregular in some regions. The latter means that the standard statistical methods for analysing meteorological data that produce linear outputs can give misleading trends, with consequent misleading environmental and socio-economic outputs of models using such trends as inputs. Additionally, national and regional climate trends do not necessarily match international climate model outputs, so the latter need to be tested for relevance before being used in national or regional environment-related studies. [ABSTRACT FROM AUTHOR]

The groundwater contamination risk in future climates was investigated at three locations in Sweden. Solute transport penetration depths were simulated using the HYDRUS-1D model using historical data and an ensemble of climate projections including two global climate models (GCMs), three emission scenarios and one regional climate model. Most projections indicated increasing precipitation and evapotranspiration until mid-century with a further increase at end-century. Results showed both increasing and decreasing groundwater contamination risks depending on emission scenario and GCM. Generally, the groundwater contamination risk is likely to be unchanged until mid-century, but higher at the end of the century. Soil and site specific relationships between Δ(P – PET) (i.e. change in the difference between precipitation, P, and potential evapotranspiration, PET) and changes in solute transport depths were determined. Using this, changes in solute transport depths for other climate projections can be assessed. [ABSTRACT FROM AUTHOR]

Climate science and nuclear weapons testing have a long and surprisingly intimate relationship. The global networks that monitored the Fukushima radiation plume and forecasted its movement are the direct descendants of systems and computer models developed to trace fallout from weapons tests. Tracing radioactive carbon as it cycles through the atmosphere, the oceans, and the biosphere has been crucial to understanding anthropogenic climate change. The earliest global climate models relied on numerical methods very similar to those developed by nuclear weapons designers for solving the fluid dynamics equations needed to analyze shock waves produced in nuclear explosions. The climatic consequences of nuclear war also represent a major historical intersection between climate science and nuclear affairs. Without the work done by nuclear weapons designers and testers, scientists would know much less than they now do about the atmosphere. In particular, this research has contributed enormously to knowledge about both carbon dioxide, which raises Earth’s temperature, and aerosols, which lower it. Without climate models, scientists and political leaders would not have understood the full extent of nuclear weapons’ power to annihilate not only human beings, but other species as well. In the post-Cold War era, US national laboratories built to create the most fearsome arsenal in history are now using their powerful supercomputers, their expertise in modeling, and their skills in managing very large data sets to address the threat of catastrophic climate change. [ABSTRACT FROM PUBLISHER]

This study aimed to quantify possible climate change impacts on runoff for the Rheraya catchment (225 km2) located in the High Atlas Mountains of Morocco, south of Marrakech city. Two monthly water balance models, including a snow module, were considered to reproduce the monthly surface runoff for the period 1989‒2009. Additionally, an ensemble of five regional climate models from the Med-CORDEX initiative was considered to evaluate future changes in precipitation and temperature, according to the two emissions scenarios RCP4.5 and RCP8.5. The future projections for the period 2049‒2065 under the two scenarios indicate higher temperatures (+1.4°C to +2.6°C) and a decrease in total precipitation (−22% to −31%). The hydrological projections under these climate scenarios indicate a significant decrease in surface runoff (−19% to −63%, depending on the scenario and hydrological model) mainly caused by a significant decline in snow amounts, related to reduced precipitation and increased temperature. Changes in potential evapotranspiration were not considered here, since its estimation over long periods remains a challenge in such data-sparse mountainous catchments. Further work is required to compare the results obtained with different downscaling methods and different hydrological model structures, to better reproduce the hydro-climatic behaviour of the catchment.EDITOR M.C. AcremanASSOCIATE EDITOR R. Hirsch [ABSTRACT FROM PUBLISHER]

Climate models and hydrological parameter uncertainties were quantified and compared while assessing climate change impacts on monthly runoff and daily flow duration curve (FDC) in a Mediterranean catchment. Simulations of the Soil and Water Assessment Tool (SWAT) model using an ensemble of behavioural parameter sets derived from the Generalized Likelihood Uncertainty Estimation (GLUE) method were approximated by feed-forward artificial neural networks (FF-NN). Then, outputs of climate models were used as inputs to the FF-NN models. Subsequently, projected changes in runoff and FDC were calculated and their associated uncertainty was partitioned into climate model and hydrological parameter uncertainties. Runoff and daily discharge of the Chiba catchment were expected to decrease in response to drier and warmer climatic conditions in the 2050s. For both hydrological indicators, uncertainty magnitude increased when moving from dry to wet periods. The decomposition of uncertainty demonstrated that climate model uncertainty dominated hydrological parameter uncertainty in wet periods, whereas in dry periods hydrological parametric uncertainty became more important.Editor M.C. Acreman; Associate editor S. Kanae [ABSTRACT FROM PUBLISHER]

Climate change could cause alpine treelines to shift in altitude or to change their spatial pattern, but little is known about the drivers of treeline dynamics and patterning. The position and patterns of tropical alpine treelines are generally attributed to land use, especially burning. Species interactions, in particular facilitation through shading, may also be important for treeline patterning and dynamics. We studied how fire in alpine vegetation and shade dependence of trees may affect the position and spatial pattern of tropical alpine treelines and their response to climatic warming, using a spatial minimal model of tree growth at treeline. Neighboring trees provided shade and protection from fire. The positive feedback that resulted from these neighbor interactions strongly affected the emergent treelines and always reduced the distance and speed of treeline advance after a temperature increase. Our model demonstrated that next to fire, shade dependence of trees can also lead to abrupt treelines and relatively low treeline positions. This implies that these patterns do not necessarily indicate human disturbance. Strong abruptness of a treeline may indicate that it will respond slowly to climatic changes. [ABSTRACT FROM AUTHOR]