Due to anthropogenic emissions, the climate is changing, with urban areas responsible for 67-72 % of global greenhouse gas emissions. The European Green Deal sets the objective for the European Union to become climate neutral by 2050. The city of Berlin (Germany) aims to reduce its CO2 emissions by 95 % by 2025 and wants to become climate neutral by 2050. This report examines how realistic these targets are. For this purpose, a case study for the Charlottenburg-Wilmersdorf district was conducted, guided by the research question: Is it possible for a city to become carbon neutral? A sampling campaign across four urban systems, including park, forest, construction site, and street trees, was implemented to analyse the carbon storage of water, soil, lake sediments, and trees. The carbon uptake and emissions of these systems were determined with a literature review. These values were upscaled for the entire district and provided the basis for three possible future scenarios: (1) Business as usual, assuming anthropogenic emissions follow the current trend, whereas the carbon uptake and emissions from vegetation remain constant; (2) Emissions Reduction without Additional Carbon Uptake, assuming a decrease in anthropogenic emissions (on basis of the Energy and Climate Protection Program of Berlin) while carbon uptake and emissions from vegetation remains constant; (3) Emissions Reduction with Additional Carbon Uptake, assuming the same emission reduction pathway as scenario 2 but includes an increase in carbon uptake and emissions from vegetation. Currently, Charlottenburg-Wilmersdorf has anthropogenic (heating and traffic) and natural emissions in the amount of approximately 1,559,861 t C a-1, whereas forests, street trees, parks, and lakes only take up around 268,146 t C a-1. Based on current conditions, the district is not carbon neutral. It has been determined that none of the three scenarios achieved carbon neutrality. Various measures for reducing carbon emissions and increasing carbon uptake and storage were examined in detail, such as photovoltaic systems on rooftops, heating with wastewater heat and heat pumps, timber constructions, and expansion of blue-green infrastructure. However, it should be noted that the challenge is not in the lack of possible measures, but rather in their implementation. In urban areas, this often results in conflicting priorities, and the absence of strong political will further hinders progress. The implementation of sustainable climate policy is not possible without broad participation, transparent decision-making, and long-term communication strategies. These elements are often neglected in research and practice. Our results show that, under the current conditions, reaching climate neutrality is not realistic for the district of Charlottenburg-Wilmersdorf. It can be hypothesized that a similar situation exists in Berlin. However, this cannot be concluded with certainty based on the findings of this study. Nevertheless, taking decisive action towards becoming a carbon neutral city remains essential for meeting EU climate neutrality targets and mitigating climate change.
Müller et al. (Wed,) studied this question.