@article{PradhanKriewaldCostaetal.2020, author = {Pradhan, Prajal and Kriewald, Steffen and Costa, Lu{\´i}s F{\´i}l{\´i}pe Carvalho da and Rybski, Diego and Benton, Tim G. and Fischer, G{\"u}nther and Kropp, J{\"u}rgen}, title = {Urban food systems: how regionalization can contribute to climate change mitigation}, series = {Environmental science \& technology}, volume = {54}, journal = {Environmental science \& technology}, number = {17}, publisher = {American Chemical Society}, address = {Washington}, issn = {0013-936X}, doi = {10.1021/acs.est.0c02739}, pages = {10551 -- 10560}, year = {2020}, abstract = {Cities will play a key role in the grand challenge of nourishing a growing global population, because, due to their population density, they set the demand. To ensure that food systems are sustainable, as well as nourishing, one solution often suggested is to shorten their supply chains toward a regional rather than a global basis. While such regional systems may have a range of costs and benefits, we investigate the mitigation potential of regionalized urban food systems by examining the greenhouse gas emissions associated with food transport. Using data on food consumption for 7108 urban administrative units (UAUs), we simulate total transport emissions for both regionalized and globalized supply chains. In regionalized systems, the UAUs' demands are fulfilled by peripheral food production, whereas to simulate global supply chains, food demand is met from an international pool (where the origin can be any location globally). We estimate that regionalized systems could reduce current emissions from food transport. However, because longer supply chains benefit from maximizing comparative advantage, this emission reduction would require closing yield gaps, reducing food waste, shifting toward diversified farming, and consuming seasonal produce. Regionalization of food systems will be an essential component to limit global warming to well below 2 degrees C in the future.}, language = {en} } @misc{GudipudiRybskiLuedekeetal.2019, author = {Gudipudi, Venkata Ramana and Rybski, Diego and L{\"u}deke, Matthias K. B. and Kropp, J{\"u}rgen}, title = {Urban emission scaling - Research insights and a way forward}, series = {Environment and Planning B: Urban Analytics and City Science}, volume = {46}, journal = {Environment and Planning B: Urban Analytics and City Science}, number = {9}, publisher = {Sage Publ.}, address = {London}, issn = {2399-8083}, doi = {10.1177/2399808319825867}, pages = {1678 -- 1683}, year = {2019}, language = {en} } @article{FluschnikKriewaldRosetal.2016, author = {Fluschnik, Till and Kriewald, Steffen and Ros, Anselmo Garcia Cantu and Zhou, Bin and Reusser, Dominik Edwin and Kropp, J{\"u}rgen and Rybski, Diego}, title = {The Size Distribution, Scaling Properties and Spatial Organization of Urban Clusters: A Global and Regional Percolation Perspective}, series = {ISPRS International Journal of Geo-Information}, volume = {5}, journal = {ISPRS International Journal of Geo-Information}, publisher = {MDPI}, address = {Basel}, issn = {2220-9964}, doi = {10.3390/ijgi5070110}, pages = {1543 -- 1559}, year = {2016}, abstract = {Human development has far-reaching impacts on the surface of the globe. The transformation of natural land cover occurs in different forms, and urban growth is one of the most eminent transformative processes. We analyze global land cover data and extract cities as defined by maximally connected urban clusters. The analysis of the city size distribution for all cities on the globe confirms Zipf's law. Moreover, by investigating the percolation properties of the clustering of urban areas we assess the closeness to criticality for various countries. At the critical thresholds, the urban land cover of the countries undergoes a transition from separated clusters to a gigantic component on the country scale. We study the Zipf-exponents as a function of the closeness to percolation and find a systematic dependence, which could be the reason for deviating exponents reported in the literature. Moreover, we investigate the average size of the clusters as a function of the proximity to percolation and find country specific behavior. By relating the standard deviation and the average of cluster sizes—analogous to Taylor's law—we suggest an alternative way to identify the percolation transition. We calculate spatial correlations of the urban land cover and find long-range correlations. Finally, by relating the areas of cities with population figures we address the global aspect of the allometry of cities, finding an exponent \&\#948; \&\#8776; 0.85, i.e., large cities have lower densities.}, language = {en} } @misc{FluschnikKriewaldRosetal.2017, author = {Fluschnik, Till and Kriewald, Steffen and Ros, Anselmo Garc{\´i}a Cant{\´u} and Zhou, Bin and Reusser, Dominik Edwin and Kropp, J{\"u}rgen and Rybski, Diego}, title = {The size distribution, scaling properties and spatial organization of urban clusters}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-400486}, pages = {14}, year = {2017}, abstract = {Human development has far-reaching impacts on the surface of the globe. The transformation of natural land cover occurs in different forms, and urban growth is one of the most eminent transformative processes. We analyze global land cover data and extract cities as defined by maximally connected urban clusters. The analysis of the city size distribution for all cities on the globe confirms Zipf's law. Moreover, by investigating the percolation properties of the clustering of urban areas we assess the closeness to criticality for various countries. At the critical thresholds, the urban land cover of the countries undergoes a transition from separated clusters to a gigantic component on the country scale. We study the Zipf-exponents as a function of the closeness to percolation and find a systematic dependence, which could be the reason for deviating exponents reported in the literature. Moreover, we investigate the average size of the clusters as a function of the proximity to percolation and find country specific behavior. By relating the standard deviation and the average of cluster sizes—analogous to Taylor's law—we suggest an alternative way to identify the percolation transition. We calculate spatial correlations of the urban land cover and find long-range correlations. Finally, by relating the areas of cities with population figures we address the global aspect of the allometry of cities, finding an exponent δ ≈ 0.85, i.e., large cities have lower densities.}, language = {en} } @article{ZhouRybskiKropp2017, author = {Zhou, Bin and Rybski, Diego and Kropp, J{\"u}rgen}, title = {The role of city size and urban form in the surface urban heat island}, series = {Scientific reports}, volume = {7}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-017-04242-2}, pages = {9}, year = {2017}, abstract = {Urban climate is determined by a variety of factors, whose knowledge can help to attenuate heat stress in the context of ongoing urbanization and climate change. We study the influence of city size and urban form on the Urban Heat Island (UHI) phenomenon in Europe and find a complex interplay between UHI intensity and city size, fractality, and anisometry. Due to correlations among these urban factors, interactions in the multi-linear regression need to be taken into account. We find that among the largest 5,000 cities, the UHI intensity increases with the logarithm of the city size and with the fractal dimension, but decreases with the logarithm of the anisometry. Typically, the size has the strongest influence, followed by the compactness, and the smallest is the influence of the degree to which the cities stretch. Accordingly, from the point of view of UHI alleviation, small, disperse, and stretched cities are preferable. However, such recommendations need to be balanced against e.g. positive agglomeration effects of large cities. Therefore, trade-offs must be made regarding local and global aims.}, language = {en} } @article{GudipudiRybskiLuedekeetal.2018, author = {Gudipudi, Venkata Ramana and Rybski, Diego and L{\"u}deke, Matthias K. B. and Zhou, Bin and Liu, Zhu and Kropp, J{\"u}rgen}, title = {The efficient, the intensive, and the productive}, series = {Applied Energy}, volume = {236}, journal = {Applied Energy}, publisher = {Elsevier}, address = {Oxford}, issn = {0306-2619}, doi = {10.1016/j.apenergy.2018.11.054}, pages = {155 -- 162}, year = {2018}, abstract = {Urban areas play an unprecedented role in potentially mitigating climate change and supporting sustainable development. In light of the rapid urbanisation in many parts on the globe, it is crucial to understand the relationship between settlement size and CO2 emission efficiency of cities. Recent literature on urban scaling properties of emissions as a function of population size has led to contradictory results and more importantly, lacked an in-depth investigation of the essential factors and causes explaining such scaling properties. Therefore, in analogy to the well-established Kaya Identity, we develop a relation combining the involved exponents. We demonstrate that application of this Urban Kaya Relation will enable a comprehensive understanding about the intrinsic factors determining emission efficiencies in large cities by applying it to a global dataset of 61 cities. Contrary to traditional urban scaling studies which use Ordinary Least Squares (OLS) regression, we show that the Reduced Major Axis (RMA) is necessary when complex relations among scaling exponents are to be investigated. RMA is given by the geometric mean of the two OLS slopes obtained by interchanging the dependent and independent variable. We discuss the potential of the Urban Kaya Relation in mainstreaming local actions for climate change mitigation.}, language = {en} } @article{LiRybskiKropp2021, author = {Li, Yunfei and Rybski, Diego and Kropp, J{\"u}rgen}, title = {Singularity cities}, series = {Environment and planning. B, Urban analytics and city science}, volume = {48}, journal = {Environment and planning. B, Urban analytics and city science}, number = {1}, publisher = {Sage Publ.}, address = {London}, issn = {2399-8083}, doi = {10.1177/2399808319843534}, pages = {43 -- 59}, year = {2021}, abstract = {We propose an upgraded gravitational model which provides population counts beyond the binary (urban/non-urban) city simulations. Numerically studying the model output, we find that the radial population density gradients follow power-laws where the exponent is related to the preset gravity exponent gamma. Similarly, the urban fraction decays exponentially, again determined by gamma. The population density gradient can be related to radial fractality and it turns out that the typical exponents imply that cities are basically zero-dimensional. Increasing the gravity exponent leads to extreme compactness and the loss of radial symmetry. We study the shape of the major central cluster by means of another three fractal dimensions and find that overall its fractality is dominated by the size and the influence of gamma is minor. The fundamental allometry, between population and area of the major central cluster, is related to the gravity exponent but restricted to the case of higher densities in large cities. We argue that cities are shaped by power-law proximity. We complement the numerical analysis by economics arguments employing travel costs as well as housing rent determined by supply and demand. Our work contributes to the understanding of gravitational effects, radial gradients, and urban morphology. The model allows to generate and investigate city structures under laboratory conditions.}, language = {en} } @article{BoettleRybskiKropp2016, author = {Boettle, Markus and Rybski, Diego and Kropp, J{\"u}rgen}, title = {Quantifying the effect of sea level rise and flood defence-a point process perspective on coastal flood damage}, series = {Natural hazards and earth system sciences}, volume = {16}, journal = {Natural hazards and earth system sciences}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1561-8633}, doi = {10.5194/nhess-16-559-2016}, pages = {559 -- 576}, year = {2016}, abstract = {In contrast to recent advances in projecting sea levels, estimations about the economic impact of sea level rise are vague. Nonetheless, they are of great importance for policy making with regard to adaptation and greenhouse-gas mitigation. Since the damage is mainly caused by extreme events, we propose a stochastic framework to estimate the monetary losses from coastal floods in a confined region. For this purpose, we follow a Peak-over-Threshold approach employing a Poisson point process and the Generalised Pareto Distribution. By considering the effect of sea level rise as well as potential adaptation scenarios on the involved parameters, we are able to study the development of the annual damage. An application to the city of Copenhagen shows that a doubling of losses can be expected from a mean sea level increase of only 11 cm. In general, we find that for varying parameters the expected losses can be well approximated by one of three analytical expressions depending on the extreme value parameters. These findings reveal the complex interplay of the involved parameters and allow conclusions of fundamental relevance. For instance, we show that the damage typically increases faster than the sea level rise itself. This in turn can be of great importance for the assessment of sea level rise impacts on the global scale. Our results are accompanied by an assessment of uncertainty, which reflects the stochastic nature of extreme events. While the absolute value of uncertainty about the flood damage increases with rising mean sea levels, we find that it decreases in relation to the expected damage.}, language = {en} } @misc{BoettleRybskiKropp2016, author = {Boettle, Markus and Rybski, Diego and Kropp, J{\"u}rgen}, title = {Quantifying the effect of sea level rise and flood defence}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {559}, issn = {1866-8372}, doi = {10.25932/publishup-41240}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-412405}, pages = {18}, year = {2016}, abstract = {In contrast to recent advances in projecting sea levels, estimations about the economic impact of sea level rise are vague. Nonetheless, they are of great importance for policy making with regard to adaptation and greenhouse-gas mitigation. Since the damage is mainly caused by extreme events, we propose a stochastic framework to estimate the monetary losses from coastal floods in a confined region. For this purpose, we follow a Peak-over-Threshold approach employing a Poisson point process and the Generalised Pareto Distribution. By considering the effect of sea level rise as well as potential adaptation scenarios on the involved parameters, we are able to study the development of the annual damage. An application to the city of Copenhagen shows that a doubling of losses can be expected from a mean sea level increase of only 11 cm. In general, we find that for varying parameters the expected losses can be well approximated by one of three analytical expressions depending on the extreme value parameters. These findings reveal the complex interplay of the involved parameters and allow conclusions of fundamental relevance. For instance, we show that the damage typically increases faster than the sea level rise itself. This in turn can be of great importance for the assessment of sea level rise impacts on the global scale. Our results are accompanied by an assessment of uncertainty, which reflects the stochastic nature of extreme events. While the absolute value of uncertainty about the flood damage increases with rising mean sea levels, we find that it decreases in relation to the expected damage.}, language = {en} } @article{ZhouRybskiKropp2013, author = {Zhou, Bin and Rybski, Diego and Kropp, J{\"u}rgen}, title = {On the statistics of urban heat island intensity}, series = {Geophysical research letters}, volume = {40}, journal = {Geophysical research letters}, number = {20}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0094-8276}, doi = {10.1002/2013GL057320}, pages = {5486 -- 5491}, year = {2013}, abstract = {We perform a systematic study of all cities in Europe to assess the Urban Heat Island (UHI) intensity by means of remotely sensed land surface temperature data. Defining cities as spatial clusters of urban land cover, we investigate the relationships of the UHI intensity, with the cluster size and the temperature of the surroundings. Our results show that in Europe, the UHI intensity in summer has a strong correlation with the cluster size, which can be well fitted by an empirical sigmoid model. Furthermore, we find a novel seasonality of the UHI intensity for individual clusters in the form of hysteresis-like curves. We characterize the shape and identify apparent regional patterns.}, language = {en} }