German Climate Research Articles

The German Climate Forecast System: GCFS

AbstractSeasonal prediction is one important element in a seamless prediction chain between weather forecasts and climate projections. After several years of development in collaboration with Universität Hamburg and Max Planck Institute for Meteorology, the Deutscher Wetterdienst performs operational seasonal forecasts since 2016 with the German Climate Forecast System, now in Version 2 (GCFS2.0). Here, the configuration of the previous system GCFS1.0 and the current GCFS2.0 are described and the performance of the two systems is compared over the common hindcast period of 1990–2014. In GCFS2.0, the forecast skill is improved compared to GCFS1.0 during boreal winter, especially for the Northern Hemisphere where the Pearson correlation has increased for the North Atlantic Oscillation index. Overall, a similar performance of GCFS2.0 in comparison to GCFS1.0 is assessed during the boreal summer. Future developments for climate forecasts need a stronger focus on the performance of interannual variability in a model system.

Stimulating E-Mobility Diffusion in Germany (EMOSIM): An Agent-Based Simulation Approach

The German Climate Action Plan targets an electric vehicle fleet of 6 million by 2030. However, from today’s perspective, we are far away from a path that is steep enough to reach this goal. In order to identify how different policy instruments can stimulate e-mobility diffusion in Germany, we build and calibrate an agent-based simulation model (ABM). The model allows for the consideration of the rich dynamics of social influence as well as the heterogeneity of actors and is flexible enough to be applied with other technologies. We simulate different policy scenarios against a business as usual (BAU) scenario. We show that with the currently implemented set of policies (BAU scenario), it is very unlikely that the envisaged goals in terms of e-mobility diffusion can be reached. Moreover, we suggest additional measures such as a carbon tax on fuel, more charging points, and higher direct subsidies, which are as a combined package likely to have a significantly positive effect on the diffusion of electric cars.

Heat stored in the Earth system: where does the energy go?

Abstract. Human-induced atmospheric composition changes cause a radiative imbalance at the top of the atmosphere which is driving global warming. This Earth energy imbalance (EEI) is the most critical number defining the prospects for continued global warming and climate change. Understanding the heat gain of the Earth system – and particularly how much and where the heat is distributed – is fundamental to understanding how this affects warming ocean, atmosphere and land; rising surface temperature; sea level; and loss of grounded and floating ice, which are fundamental concerns for society. This study is a Global Climate Observing System (GCOS) concerted international effort to update the Earth heat inventory and presents an updated assessment of ocean warming estimates as well as new and updated estimates of heat gain in the atmosphere, cryosphere and land over the period 1960–2018. The study obtains a consistent long-term Earth system heat gain over the period 1971–2018, with a total heat gain of 358±37 ZJ, which is equivalent to a global heating rate of 0.47±0.1 W m−2. Over the period 1971–2018 (2010–2018), the majority of heat gain is reported for the global ocean with 89 % (90 %), with 52 % for both periods in the upper 700 m depth, 28 % (30 %) for the 700–2000 m depth layer and 9 % (8 %) below 2000 m depth. Heat gain over land amounts to 6 % (5 %) over these periods, 4 % (3 %) is available for the melting of grounded and floating ice, and 1 % (2 %) is available for atmospheric warming. Our results also show that EEI is not only continuing, but also increasing: the EEI amounts to 0.87±0.12 W m−2 during 2010–2018. Stabilization of climate, the goal of the universally agreed United Nations Framework Convention on Climate Change (UNFCCC) in 1992 and the Paris Agreement in 2015, requires that EEI be reduced to approximately zero to achieve Earth's system quasi-equilibrium. The amount of CO2 in the atmosphere would need to be reduced from 410 to 353 ppm to increase heat radiation to space by 0.87 W m−2, bringing Earth back towards energy balance. This simple number, EEI, is the most fundamental metric that the scientific community and public must be aware of as the measure of how well the world is doing in the task of bringing climate change under control, and we call for an implementation of the EEI into the global stocktake based on best available science. Continued quantification and reduced uncertainties in the Earth heat inventory can be best achieved through the maintenance of the current global climate observing system, its extension into areas of gaps in the sampling, and the establishment of an international framework for concerted multidisciplinary research of the Earth heat inventory as presented in this study. This Earth heat inventory is published at the German Climate Computing Centre (DKRZ, https://www.dkrz.de/, last access: 7 August 2020) under the DOI https://doi.org/10.26050/WDCC/GCOS_EHI_EXP_v2 (von Schuckmann et al., 2020).

The first German climate case

This article explains the first German climate case filed against the Federal Government in the Berlin Administrative Court in 2018 and decided in October 2019. The article identifies and examines the key elements of the decision of the Berlin Court and it places the legal issues of the case within the relevant framework of German administrative court procedure law, administrative law and constitutional law. The case evolved around the legally binding force of a cabinet decision of the Federal Government which laid down the German greenhouse gas emissons reduction target for 2020. Despite the fact that the application was dismissed for lack of standing, some important legal developments can be derived from the judgment, especially in relation to justiciability of the case and the state’s duty to protect fundamental rights under the German Basic Law (Grundgesetz) in the climate change context. Just after the judgment was delivered, the German Federal Parliament (Bundestag) adopted the first Federal Climate Protection Act in November 2019 and thus defined the state’s new climate targets in statutory form. This changed the legal landscape and claimants consequently abstained from appealing the judgment. However, the German Constitutional Court now has the opportunity to clarify further some of the legal issues that arose in this first German climate case from applying ‘traditional’ legal concepts to the challenge of climate change, if it decides to hear the constitutional complaint which was filed in 2020 against the Federal Climate Protection Act.

Rezo and German Climate Change Policy: The Influence of Networked Expertise on YouTube and Beyond

Just before the European election in May 2019 a YouTube video titled <em>The Destruction of the CDU</em> (Rezo, 2019a) caused political controversy in Germany. The video by the popular German YouTuber Rezo attacked the conservative Government party CDU (<em>Christlich Demokratische Union Deutschlands</em>) mainly for climate inaction. As a reaction to the subsequent attacks on Rezo and his video from the political establishment an alliance of popular German YouTubers formed to release a second video. In this video, the YouTubers asked their followers not to vote for the Government or the far-right parties, because they would ignore the expertise of scientists and the scientific consensus on anthropogenic climate change and therefore be unable to provide sustainable solutions for the future. This debate started as a YouTube phenomenon but quickly evolved into a national public discussion that took place across various social media channels, blogs, newspapers, and TV news, but also e.g., in discussions in schools, churches, as well as arts and cultural events. The focus of this contribution is on the formation of the heterogeneous coalition that emerged to defend and support the YouTubers. It prominently involved scientists and scientific expertise, but other forms of expertise and ‘worlds of relevance’ were also part of this coalition. The conceptual tools of ‘networked expertise’ and ‘ethno-epistemic assemblages’ are employed to explore expertise and credibility as well as the associations and networks of actors involved which illuminate how a single YouTuber was able to contribute to the unleashing of a national debate on climate change policy.

Future Renewable Fuel Mixes in Transport in Germany under RED II and Climate Protection Targets

With the Renewable Energy Directive 2018/2001 (RED II), adopted in December 2018, the EU is continuing the political framework for the use of renewable energy sources in the transport sector for the period from 2021 to 2030. At the same time, the German federal government has set a target of reducing greenhouse gas (GHG) emissions in the transport sector by at least 40% to 42% by 2030 compared to the 1990 GHG level. To investigate the possible effects of the European and national requirements on the German GHG quota, cost-optimal fuel mixes were modelled to achieve the GHG targets of 26 fuel options in each of the nine different scenarios. The results show clear differences between the scenarios that implement the RED II targets (including 14% renewables in transport by 2030) and those that implement the climate protection target (40–42% GHG reduction compared to 1990 by 2030). If only the minimum requirements of RED II are met, the German climate protection target is clearly missed without further measures. In order to achieve the climate protection target, a significant reduction in the final energy consumption in transport is required, as well as a very high GHG quota of 34.5%, meaning a high proportion of renewables of ca. 40% and using almost all the fuel options considered.

The German Climate Forecast System: GCFS

The German Climate Forecast System: GCFS

Methodology for Determining Charging Strategies for Urban Private Vehicles based on Traffic Simulation Results

A major part of urban private vehicles needs to be electrified in order to meet the German climate protection goals in the transport sector. Therefore, charging strategies must be developed and the geographical distribution of infrastructure has to be planned accordingly. We propose a new method to combine a multi agent traffic simulation (MATSim) with real-world vehicle distribution and measured charging behavior. The results of our simulation were analyzed for the exemplary use case of Berlin’s private passenger cars. Three different charging strategies were developed and analyzed: charging at home, at work and during leisure activities. Charging at home was suitable to serve all agents’ charging demand with low charging power (7.4 kW). Charging at work only served 56.23 % of the agents with a charging power of 11 kW, but required fewer charging points. Charging during leisure activities served from 46.36 % to 81.92 % of the agents, depending on the chosen charging power and user behavior.

Time to change course on climate

Summary The 25th annual climate conference marks a quarter of a century of humanity failing to do enough to avert a climate catastrophe. Although a wave of climate strikes and Extinction Rebellion protests has brought the issues to the forefront, experts warn that the pledged reductions are insufficient. A backlash from short-term corporate interests and populist politics could threaten even what little progress has been secured so far. Michael Gross reports.

Climate policy, stranded assets, and investors’ expectations

Climate policies to keep global warming below 2°C might render some of the world's fossil fuels and related infrastructure worthless prior to the end of their economic life time. Therefore, some energy-sector assets are at risk of becoming stranded. This paper investigates whether and how investors price in this risk of asset stranding. We exploit the gradual development of a German climate policy proposal aimed at reducing electricity production from coal and analyze its effect on the valuation of energy utilities. We find that investors take stranded asset risk into consideration, but that they also expect a financial compensation for their stranded assets.

Comparison of manual and automatic daily sunshine duration measurements at German climate reference stations

Abstract. Precise quantification of climate change depends on long time series of meteorological variables. Such time series should be as homogeneous as possible but some changes of measurement conditions cannot be prevented. At German climate reference stations, parallel measurements are used to analyze the effects of changes in measurement systems for example for the transition from manual to automatic instruments. These parallel measurements aim to identify measurement uncertainties and to analyze the comparability of measurement systems to investigate the homogeneity. In this study, we investigate daily sunshine duration. Traditionally, manual measurements of daily sunshine duration are taken with Campbell-Stokes sunshine recorders. For automatic measurements the SONIe or SCAPP instrument is used. The different measurement principles (glass sphere and photodiode) cause systematic differences between the observations. During summer, values for manual observations are larger especially in case of frequent alternations between sunny and cloudy conditions. Furthermore, the standard deviation of the differences between the two measurement systems is larger during summer because of the greater day length. To adjust the automatic measurements a linear regression model is suggested based on parallel measurements from 13 climate reference stations in Germany. To validate the regression coefficients, a leave-one-out cross validation was performed (by leaving out data of individual stations). The regression coefficients (derived from different sets of stations) are similar, thereby indicating a robust data set for the estimation of the linear model. With this method we want to prevent breaks in long time series of daily sunshine duration caused by the transition from manual to automatic instruments.

Interference of billing and scheduling strategies for energy and cost savings in modern data centers

The high energy consumption of HPC systems is an obstacle for ever-growing systems. Unfortunately, energy consumption does not decrease linearly with reduced workload; therefore, energy conservation techniques have been deployed on various levels which steer the overall system. While the overall saving of energy is useful, the price of energy is not necessarily proportional to the consumption. Particularly with renewable energies, there are occasions in which the price is significantly lower. The potential of saving energy costs when using smart contracts with energy providers is lacking research. In this paper, we conduct an analysis of the potential savings when applying cost-aware schedulers to data center workloads while considering power contracts that allow for dynamic (hourly) pricing.The contributions of this paper are twofold: (1) the theoretic assessment of cost savings; (2) the development of a simulator to replay batch scheduler traces which supports flexible energy cost models and various cost-aware scheduling algorithms. This allows to approximate the energy costs savings of data centers for various scenarios including off-peak and hourly budgeted energy prices as provided by the energy spot market. An evaluation is conducted with four annual job traces from the German Climate Computing Center (DKRZ) and Leibniz Supercomputing Centre (LRZ).The theoretic analysis indicates a cost savings for 4–8% when shutting down unused client nodes, and 6–20% with hourly cost models and optimal scheduling. The experimental validation of a practicable scheduler increases the accuracy against the theoretical best case analysis. As expected, a cost-efficient scheduling algorithm that is fed with the information about future energy costs shifts the jobs to the timeslots where the job execution is cheaper and reduces the energy expenditure, yet increases the waiting times of pending jobs. However, the expected savings for this effort are not justifiable compared to the simple strategy of turning off the unused nodes. Additionally, we compare the cost savings to the total costs of ownership showing that smaller systems with on-demand provisioning yield better cost efficiency.

Climate Policy, Stranded Assets, and Investors' Expectations

Climate policies to keep global warming below 2℃ might render some of the world’s fossil fuels and related infrastructure worthless prior to the end of their economic life time. Therefore, some energy-sector assets are at risk of becoming stranded. This paper investigates whether and how investors price in this risk of asset stranding. We exploit the gradual development of a German climate policy proposal aimed at reducing electricity production from coal and analyze its effect on the valuation of energy utilities. We find that investors take stranded asset risk into consideration, but that they also expect a financial compensation for their stranded assets.

Politicized Science Communication: Predicting Scientists’ Acceptance of Overstatements by Their Knowledge Certainty, Media Perceptions, and Presumed Media Effects

Partisans in mediated conflicts usually perceive hostile news media, anticipate undesired media effects, and intend to engage discursively. It is hypothesized that hostile media perceptions also encourage polarizing communication. This is tested for scientists involved in a politicized science dispute. German climate scientists ( n = 131) firmly believe in anthropogenic global warming (AGW). Yet not all dismiss alternative hypotheses altogether. Results indicate that the more certain climate scientists are of AGW, the more they perceive that the news media downplay AGW and presume that the media nourish politicians’ doubts about it. This explains their justifications of overstatements of scientific findings in public.

Evaluation of 20CR reanalysis data and model results based on historical (1930–1940) observations from Franz Josef Land

This study was financially supported by the Helmholtz Climate Initiative REKLIM. Collecting, digitizing and analyzes of observational data were financially supported by the National Science Centre, Poland (Decision No. DEC--2012/07/B/ST10/04002). A work of Rajmund Przybylak was supported by the grant No. 2015/19/B/ST10/02933 funded by the National Science Centre, Poland. Klaus Dethloff and Annette Rinke acknowledge the support by the project Quantifying rapid climate change in the Arctic: Regional feedbacks and large-scale impacts (QUARCCS) funded by the German Federal Ministry of Education and Research (BMBF). We thank for the 20th Century Reanalysis v2 and v2c data, available at http://www.esrl.noaa.gov/psd/, provided by the NOAA/OAR/ESRL PSD, Boulder, Colorado, USA. Also, we are grateful for the provision of the PANGAEA archive, available at https://doi.pangaea.de/10.1594/PANGAEA.823609. The HIRHAM5 model simulation was conducted on the high performance computer “blizzard” of the German Climate Computing Center (DKRZ) and model data can be provided in case of request.

Investigation of indoor thermal comfort in warm-humid conditions at a German climate test facility

As a result of climate change outdoor temperature and humidity are predicted to increase within the next decades in Germany, especially in the Upper Rhine area. As indoor summer conditions will be affected by this change, responses of 136 subjects to warm-humid conditions have been investigated in a test-facility at the Karlsruhe Institute of Technology (KIT). Nine experimental conditions with high operative temperature (to) and different relative humidity (RH) levels (26 °C, 28 °C or 30 °C combined with 50%, 65% or 80%) were scheduled, with each participant experiencing two of the possible combinations. In contradiction to the German addendum of the European standard EN 15251, where a single upper limit for humidity ratio (HR) of 11.5 g/kg is recommended in summer, results indicate that human responses are additionally dependent on current temperature and other factors like thermal history. A linear regression model using operative temperature and humidity ratio is shown to describe the percentage of acceptability and is used to derive an extended comfort zone for seated activity in summer conditions (met = 1.1 and clo = 0.5). Thermal acceptance is compared to other studies (using effective temperature) and proves to be significantly lower with the German subjects than with participants who are adapted to a hot-humid climate. PMV shows underestimation of thermal sensation at elevated air humidity, up to 0.5 scale points under certain conditions.

Heating up the debate? Measuring fragmentation and polarisation in a German climate change hyperlink network

Research into polarisation on the internet has so far primarily focused on contentious issues and yielded contradictory results. Shifting the focus to a non-contentious setting, this article combines community detection with brokerage analysis and exponential random graph models to assess the degree of polarisation at different levels of a German hyperlink network on climate change. Although homophily accounts for a moderate degree of polarisation at the top level of the network, the communities reveal that other factors prove more decisive in shaping its structure and the article thus contributes to a more refined understanding of the nature of online polarisation.

Demonstration of a 100-mJ OPO/OPA for future lidar applications and laser-induced damage threshold testing of optical components for MERLIN

In the field of atmospheric research, lidar is a powerful technology that can measure gas or aerosol concentrations, wind speed, or temperature profiles remotely. To conduct such measurements globally, spaceborne systems are advantageous. Pulse energies in the 100-mJ range are required to achieve highly accurate, longitudinal resolved measurements. Measuring concentrations of specific gases, such as CH4 or CO2, requires output wavelengths in the IR-B, which can be addressed by optical-parametric frequency conversion. An OPO/OPA frequency conversion setup was designed and built as a demonstration module to address the 1.6-μm range. The pump laser is an Nd:YAG-MOPA system, consisting of a stable oscillator and two subsequent Innoslab-based amplifier stages that deliver up to 500 mJ of output pulse energy at 100 Hz repetition frequency. The OPO is inherited from the OPO design for the CH4 lidar instrument on the French–German climate satellite methane remote-sensing lidar mission (MERLIN). To address the 100-mJ regime, the OPO output beam is amplified in a subsequent multistage OPA. With potassium titanyl phosphate as nonlinear medium, the OPO/OPA delivered more than 100 mJ of output energy at 1645 nm from 450 mJ of the pump energy and a pump pulse duration of 30 ns. This corresponds to a quantum conversion efficiency of about 25%. In addition to demonstrating optical performance for future lidar systems, this laser will be part of a laser-induced damage thresholds test facility, which will be used to qualify optical components especially for the MERLIN.

Alliance of antagonism: Counterpublics and polarization in online climate change communication

Debates around climate change are a prominent example of polarized online communication. We examine the German climate hyperlink network and evaluate the degree to which it is shaped by mainstream and skeptical views. By combining the theoretical frameworks of the networked public sphere and counterpublics, we describe the relation between publics and counterpublics and discuss the role of hyperlinks in delineating communities. Our analysis of blogrolls and link lists shows the debate’s structures to be polarized along factional lines with political and scientific institutions supporting the mainstream “climate-friendly” position. We find that skeptics form a counterpublic that is only loosely connected to the mainstream as neither skeptics nor the mainstream want to be affiliated with each other. Skeptics, thus, are mostly excluded within the German online climate network. However, skeptics are part of an “alliance of antagonism” with other groups, such as conspiracy theorists, men’s right groups, and right-wing sites.

Approaches to enhance the energy performance of a zero-energy building integrated with a commercial-scale hydrogen fueled zero-energy vehicle under Finnish and German conditions

The building and transportation sectors in the EU are progressing towards the zero-energy/emission levels according to the EU 2050 roadmap while the H2 vehicles have recently started to be commercialized. Based on these backgrounds, this paper focuses on the investigation of a hybrid zero-energy system which consists of a zero-energy building and a H2 vehicle integrated H2 system. The focused aspects in this paper are the impact of the ground source heat pump (GSHP), the Finnish and German climate conditions, and the on-site PV and wind turbine capacities and their mix on system performance. The parametric analyses based on these aspects are conducted in the TRNSYS simulation environment. The results show that the use of a GSHP helps realize the net zero-energy balance with less local generation, while improving the overall matching capability with marginal influence on the utilization of the cogenerated heat. Moreover, the Finnish condition has a clear preference on the wind based net zero-energy system, whereas the German condition has a preference on the solar based system. Correspondingly, the optimal mix of PV and wind turbine for the net zero-energy cases occurs when the PV generation percentage reaches 20% and 60% under Finnish and German conditions, respectively.