Der globale Klimawandel und Aspekte des regionalen Klimawandels in der Region Berlin-Brandenburg

To obtain an estimate of the average temperature of the northern hemisphere during the last 1200 years, proxy data have been merged with instrumental recordings. These instrumental measurements are, with a few exceptions, only available for the recent 150 years. In the city of Berlin the temperature has been recorded since as early as 1701. However, during the first 150 years the measurements were problematic as location, measurement procedure and instruments changed frequently and without proper documentation. From 1847 onwards observations became more reliable once the Royal Prussian Meteorological Institute had been established. For the last 100 years temperature and precipitation measurements have been performed in parallel at Berlin-Dahlem and Potsdam. The datasets recorded in the city of Berlin and in Berlin-Dahlem have been merged to obtain a record of more than 300 years. It indicates that the temperature of Berlin has risen by 1.04°C during the last 100 years after correcting for the urbanisation effect. In the same period, the total number of frost days has significantly decreased by almost 17 days, and the number of summer days has significantly increased by about 12 days. Annual mean precipitation has hardly changed (decrease less than 0.2 %) during the last century. However, rainfall has decreased by about 4 % in summer and increased by 3 % in winter. All precipitation changes are below the 95 % significance level. Model projections indicate that warming will continue which means that Berlin-Brandenburg will experience a temperature rise of about 3-3.5°C by the end of this century for the IPCC scenario A1B. For the same scenario precipitation is expected to increase by 10-20 % in winter and to decrease by 10-30 % in summer: The seasonal precipitation changes compensate each other resulting in an almost unchanged annual mean

Global Climate Change and Aspects of Regional Climate Change in the Berlin-Brandenburg Region

To obtain an estimate of the average temperature of the northern hemisphere during the last 1200 years, proxy data have been merged with instrumental recordings. These instrumental measurements are, with a few exceptions, only available for the recent 150 years. In the city of Berlin the temperature has been recorded since as early as 1701. However, during the first 150 years the measurements were problematic as location, measurement procedure and instruments changed frequently and without proper documentation. From 1847 onwards observations became more reliable once the Royal Prussian Meteorological Institute had been established. For the last 100 years temperature and precipitation measurements have been performed in parallel at Berlin-Dahlem and Potsdam. The datasets recorded in the city of Berlin and in Berlin-Dahlem have been merged to obtain a record of more than 300 years. It indicates that the temperature of Berlin has risen by 1.04°C during the last 100 years after correcting for the urbanisation effect. In the same period, the total number of frost days has significantly decreased by almost 17 days, and the number of summer days has significantly increased by about 12 days. Annual mean precipitation has hardly changed (decrease less than 0.2 %) during the last century. However, rainfall has decreased by about 4 % in summer and increased by 3 % in winter. All precipitation changes are below the 95 % significance level. Model projections indicate that warming will continue which means that Berlin-Brandenburg will experience a temperature rise of about 3-3.5°C by the end of this century for the IPCC scenario A1B. For the same scenario precipitation is expected to increase by 10-20 % in winter and to decrease by 10-30 % in summer: The seasonal precipitation changes compensate each other resulting in an almost unchanged annual mean

On skillful decadal predictions of the subpolar North Atlantic

The North Atlantic is a crucial region for the prediction of weather and climate of North America and Europe and is the focus of this analysis. A skillful decadal prediction of the surface temperature was shown for several Earth system models, with the North Atlantic standing out as one region with higher predictive skill. This skill assessment concentrates on the rapid increase of the annual mean sea surface temperature of the North Atlantic subpolar gyre by about 1 K in the mid‑1990s and the adjacent years. This event-oriented analysis adds creditability to the decadal predictions and reveals the potential for improvements. The ability to simulate the observed sea surface temperature in the North Atlantic is quantified by using four versions of decadal predictions, which differ in model resolution, initialization technique, and the reanalysis data used in the assimilation run. While all four versions can reproduce the mid-1990s warming of the subpolar North Atlantic, the characteristics differ with lead time and version. The higher vertical resolution in the atmosphere and the higher horizontal resolution in the ocean improve the decadal prediction for longer lead times, and the anomaly initialization outperforms the full-field initialization for short lead times. The effect from the two different ocean reanalysis products on the predictive skill is strongest in the first two prediction years; a substantial cooling instead of the warming in the central North Atlantic reduces the skill score for the North Atlantic sea surface temperature in one version, whereas a too large interannual variability, compared with observations, lowers the skill score in the other version. The cooling patches are critical since the resulting gradients in sea surface temperature and their effect on atmospheric dynamics deviate from observations, and, moreover, hinder the skillful prediction of atmospheric variables

Assessment of precipitation climatology in an ensemble of CORDEX-East Asia regional climate simulations

An ensemble of regional climate simulations from the Coordinated Regional Downscaling Experiment in East Asia (CORDEX-East Asia) was analysed to evaluate the ability of 5 regional climate models (RCMs) and their ensemble mean in reproducing the key features of present- day precipitation (1989−2008). We emphasised (1) an extreme rainfall event, (2) seasonal climatology, (3) annual cycles and inter-annual variability and (4) the monsoon characteristics. We highlighted 4 sub-monsoon regions, viz. South Asian Summer Monsoon (SAS), the East Asian Summer Monsoon (EAS), the Western North Pacific Tropical Monsoon (WNP) and the Australian- Maritime Continent Monsoon (AUSMC). We found that the RCMs showed a reasonable performance to capture the extreme rainfall event in 1998. The RCMs simulated the seasonal mean, annual cycle and inter-annual variability acceptably. However, individual models exhibited significant biases in some sub-regions and seasons. Moreover, most of the RCMs significantly improved their performance in capturing precipitation climatology and monsoon characteristics over the Korean Peninsula, the Korea Strait and southern Japan. Based upon this performance study, we conclude that the present set of RCMs from CORDEX can be used to provide useful information on climate projections over East Asia

Seasonal prediction skill of East Asian summer monsoon in CMIP5 models

The East Asian summer monsoon (EASM) is an important part of the global climate system and plays a vital role in the Asian climate. Its seasonal predictability is a long-standing issue within the monsoon scientist community. In this study, we analyse the seasonal (the leading time is at least 6 months) prediction skill of the EASM rainfall and its associated general circulation in non-initialised and initialised simulations for the years 1979–2005, which are performed by six prediction systems (i.e. the BCC-CSM1-1, the CanCM4, the GFDL-CM2p1, the HadCM3, the MIROC5, and the MPI-ESM-LR) from the Coupled Model Intercomparison Project phase 5 (CMIP 5). We find that most prediction systems of simulated zonal wind over 850 and 200hPa are significantly improved in the initialised simulations compared to non-initialised simulations. Based on the knowledge that zonal wind indices can be used as potential predictors for the EASM, we select an EASM index based upon the zonal wind over 850hPa for further analysis. This assessment shows that the GFDL-CM2p1 and the MIROC5 added prediction skill in simulating the EASM index with initialisation, the BCC-CSM1-1, the CanCM4, and the MPI-ESM-LR changed the skill insignificantly, and the HadCM3 indicates a decreased skill score. The different responses to initialisation can be traced back to the ability of the models to capture the ENSO (El Niño–Southern Oscillation) and EASM coupled mode, particularly the Southern Oscillation–EASM coupled mode. As is known from observation studies, this mode links the oceanic circulation and the EASM rainfall. Overall, the GFDL-CM2p1 and the MIROC5 are capable of predicting the EASM on a seasonal timescale under the current initialisation strategy

Der derzeitige und der zukünftige Klimawandel in den historischen Parks Berlin-Brandenburgs

Um die Auswirkungen des Klimawandels auf historische Parkanlagen abzuschätzen, wurden beobachtete Klimadaten für die vier ausgewählte Parkanlagen in Berlin und Brandenburg ausgewertet und regionalen Modellsimulationen für zwei Zukunftsszenarien (RCP 4.5 und RCP 8.5) bis zum Jahr 2100 gegenüber gestellt. In der bodennahen Lufttemperatur erkennt man, dass im letzten Jahrhundert eine Erwärmung stattgefunden hat, die sich in der Zukunft fortsetzen wird (bis zum Jahr 2100 um ca. 1°C [RCP 4.5] bis 3°C [RCP 8.5]). Auch der Niederschlag hat in den letzten Jahrzehnten zugenommen, wobei der Winterniederschlag stärker anwuchs als der Sommerniederschlag. Dieser Trend setzt sich im RCP 8.5 Szenarium bis zum Jahr 2100 fort.In order to estimate the impact of climate change on historic parks, climate data for four selected parks in Berlin and Brandenburg were analysed and compared with regional model simulations for two future scenarios (RCP 4.5 and RCP 8.5) up to the year 2100. In ground-level air temperature one can see that warming has occurred during the last century that will continue in future (up to the year 2100 by approximately 1°C [RCP 4.5] up to 3°C [RCP 8.5]). Rainfall has likewise increased in recent decades whereby winter precipitation increased more than summer precipitation. This trend will continue up to 2100 in the RCP 8.5 scenario

Mechanisms of hydrological responses to volcanic eruptions in the Asian monsoon and westerlies-dominated subregions

Explosive volcanic eruptions affect surface climate, especially in monsoon regions, but responses vary in different regions and to volcanic aerosol injection (VAI) in different hemispheres. Here, we use six ensemble members from the last-millennium experiment of the Coupled Model Intercomparison Project Phase 5 to investigate the mechanisms of regional hydrological responses to different hemispheric VAIs in the Asian monsoon region (AMR). Northern hemispheric VAI (NHVAI) leads to an intensified aridity over the AMR after northern hemispheric VAI (NHVAI); spatially, a distinct inverse response pattern to the climatological conditions emerges, with an intensified aridity in the relatively wettest area (RWA) but a weakened aridity in the relatively driest area (RDA) of the AMR. Southern hemispheric VAI (SHVAI) shows a weakened aridity over the AMR, but the spatial response pattern is not that clear due to small aerosol magnitude. The mechanism of the hydrological impact relates to the indirect change of atmospheric circulation due to the direct radiative effect of volcanic aerosols. The decreased thermal contrast between the land and the ocean after NHVAI results in a weakened East Asian summer monsoon and South Asian summer monsoon. This changes the moisture transport and cloud formation in the monsoon and westerlies-dominated subregions. The subsequent radiative effect and physical feedbacks of local clouds lead to different hydrological effects in different areas. Results here indicate that future volcanic eruptions may temporarily alleviate the uneven distribution of precipitation in the AMR, which should be considered in the near-term climate predictions and future strategies of local adaptation to global warming. The local hydrological responses and mechanisms found here can also provide a reference for stratospheric aerosol engineering