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The hydrological cycle is a fundamental component of the Earth’s climate system. Modelingthe time response of this cycle and the implied physical processes challenges thegeneral circulation models (GCM) used to study the climate system and to projectfuture climate. Water stable isotopes (H216O, H218O and HD16O) are integratedtracers of climate processes occurring in various branches of the hydrological cycle.Changes of the isotopic composition, which can be measured in various naturalclimate archives, have been used, for example, to reconstruct past temperatureschanges at high resolution or to study the past dynamics of the monsoon. However, thequantitative translations of isotope signals recorded in the natural archives to climatevariables is still challenging. The explicit modeling of these isotopes in GCMs isone way to improve our understanding of the mechanisms controlling the waterisotopes distribution link with the variations of climate and to evaluate the modelperformance. We present here the results, under pre-industrial (PI) and mid-Holocene (6k) conditions,of the new isotope-enhanced version of the fully coupled Earth system model MPI-ESM,called hereafter MPI-ESM-wiso. For that, the water isotopes have been implementedin all the components of the model (ECHAM6: atmosphere, JSBACH: dynamicvegetation, MPIOM: ocean/sea-ice). The related isotope masses of H216O, H218Oand HD16O are exchanged between the atmosphere and the ocean via the couplerOASIS3. The mid-Holocene, one of the PMIP4-CMIP6 entry cards to evaluate theperformance of the coupled GCMs [1], provides the opportunity to evaluate the modelresponse to changes in the seasonal and latitudinal distribution of insolation induced bydifferent orbital forcing conditions. Especially, this period is characterized by enhancedAfrican and Indian monsoons with depleted isotopic contents of precipitation. Inaddition to classical variables (temperatures, precipitation amount...), we evaluatethe isotopic composition of precipitation, water vapor, ocean, etc. simulated byMPI-ESM-wiso against available observations. We also investigate the variability of theisotope-to-climate gradients (spatial and temporal) during and between the PI and 6kperiods. This work will be an important contribution to the Paleoclimate ModellingIntercomparison Project. Indeed, the models with an explicit water stable isotope diagnosticsmake it possible to perform direct comparisons, at different time periods, with environmentalrecords and to reduce the uncertainties resulting from the interpretation of these records interms of climate signals in model-data comparisons. The project is part of the PalModinitiative ("Paleo Modelling: A national paleo climate modelling initiative"), funded by theGerman Federal Ministry of Education and Science (BMBF). [1] Kageyama et al., Geosci. Model Dev., 11, 1033-1057, 2018. [ABSTRACT FROM AUTHOR]

This study presents the first insights into the intensifying impact of global warming on extreme hydrological shifts between wet and dry conditions at the sub-seasonal to seasonal scale. For instance, the flood in England during the summer of 2007 was followed by heavy drought conditions, and a switch took place in the recent past from extreme drought to severe flooding in California. Most recently, the 2018 flood to drought transition in Japan brought on one of the most intense heatwaves the country has ever faced. These are just a few real-world examples. Considering the interconnected nature of the processes governing the increases in wet and dry events, we introduce a new index called 'Event to event variability (E2E)' as a proxy of the hydrological cycle, taking the aforementioned shifts in wet to dry (or dry to wet) transition into account. Based on multi-model large ensemble climate simulations, we assessed the impact of half a degree of additional warming from 1.5°C to 2°C for the global mean temperature, reflecting the warming targets of the Paris agreement of 2015 that were adopted at the 21st Conference of the Parties (COP) of the United Nations Framework Convention on Climate Change (UNFCC). Our results show that for an additional 0.5°C warming, mean intensification of the wet-dry (or dry-wet) transition will be significant on a global scale. The E2E index was further utilized to investigate the extreme conditions of said intensification, which showed extremes will increase 10 times compared to the mean state intensification. We found that event-to-event variability increases with warming for Western North America, Japan, and the UK, exhibiting intensification in both wet and dry conditions, which is potentially attributable to the increased occurrence of the aforementioned extreme events. We believe that our study will provide a new perspective into hydroclimatic stress under the future climate, in particular, for the additional 0.5°C warming and the importance of adhering to the Paris Agreement. [ABSTRACT FROM AUTHOR]

We are faced with negative changes concerning social and the natural environment induced the degradation of permafrost, which is related to recent global warming. Thawing permafrost affects the hydrological cycle, geomorphological processes, as well as vegetation changes. Mongolia territory is by about 63 % within permafrost zone. Therefore, it is important to understand the dynamic of the process and controlling factors responsible for the permafrost degradation. We studied two peatlands Khar Zurkhnii Khukh Nuur in the Khentii mountain range (NE Mongolia). This part of Mongolia is characterized by the occurrence of the forest-steppe mosaic in the area of discontinuous permafrost. We aimed to reconstruct dependence between vegetation composition, fire regime shift and timing of permafrost degradation during the last 1600 years from two peat archive. For this purpose, we worked on peat archive and used multi-proxy analysis (pollen, plant macrofossils, testate amoebae, Cladocera, macro-charcoal, and geochemistry). Two profiles: 36-cm (KH-1) and 55-cm (KH-2) have been extracted from two nearby peatlands, which are only 1 km away. Chronology of the KH-1 core was based on 6 AMS 14C dates, 137Cs, and 210Pb analyses, while the second core KH-2 was based on 11 AMS 14C dates. Respectively, the core KH-1 covers the last 250 years and the core KH-2 covers the last 1600 years. Our first results indicate a strong relationship between degradation permafrost, droughts, vegetation forest-steppe mosaic composition and fire regime shifts, which caused intensified erosion in the catchment. Palaeoecological and geochemical data allowed tracing the dynamics of degradation permafrost and impact of fire regime shifts on the ecosystems, both triggered by recent and past climate changes. The research was funded by the National Science Centre (Poland) – grants 2017/01/X/ST10/01216 [ABSTRACT FROM AUTHOR]

The Future Climate For Africa programme aims to generate fundamentally new climate science focused on Africa, and to ensure that this science has an impact on human development across the continent. Funded by the UK Department for International Development and the Natural Environment Research Council, this programme is generating new insights into drivers of climate variability and change in the different regions of Africa. The programme has a focus on areas of climate science which can inform development decisions with long-term consequences. For example, the considerable investments being made in new infrastructure across the continent need to be future-climate proofed. This drives a need to improve knowledge of how climate change will affect, amongst other things, the frequency and severity of intense storms and droughts, and the occurrence of agriculturally-damaging dry spells. The provision of reliable future climate information for Africa is compromised by uncertainties in the water cycle and in the projections of variability of regional circulations within CMIP5 and CORDEX simulations. The representation of extreme rainfall is considered to be particularly uncertain due to the limitations of convective parameterisations used within global and regional climate models. We will present examples of new insights from the programme, including analysis of a unique convection-permitting pan-African simulation of current and future climate. [ABSTRACT FROM AUTHOR]