Potsdam Institute for Climate Impact Research

About: Potsdam Institute for Climate Impact Research is a facility organization based out in Potsdam, Germany. It is known for research contribution in the topics: Climate change & Global warming. The organization has 1519 authors who have published 5098 publications receiving 367023 citations.

A new color image encryption scheme based on DNA sequences and multiple improved 1D chaotic maps

Abstract: A DNA-based color image encryption method is proposed by using three 1D chaotic systems with excellent performance and easy implementation.The key streams used for encryption are related to both the secret keys and the plain-image.To improve the security and sensitivity, a division-shuffling process is introduced.Transforming the plain-image and the key streams into the DNA matrices randomly can further enhance the security of the cryptosystem.The presented scheme has a good robustness for some common image processing operations and geometric attack. This paper proposes a new encryption scheme for color images based on Deoxyribonucleic acid (DNA) sequence operations and multiple improved one-dimensional (1D) chaotic systems with excellent performance. Firstly, the key streams are generated from three improved 1D chaotic systems by using the secret keys and the plain-image. Transform randomly the key streams and the plain-image into the DNA matrices by the DNA encoding rules, respectively. Secondly, perform the DNA complementary and XOR operations on the DNA matrices to get the scrambled DNA matrices. Thirdly, decompose equally the scrambled DNA matrices into blocks and shuffle these blocks randomly. Finally, implement the DNA XOR and addition operations on the DNA matrices obtained from the previous step and the key streams, and then convert the encrypted DNA matrices into the cipher-image by the DNA decoding rules. Experimental results and security analysis show that the proposed encryption scheme has a good encryption effect and high security. Moreover, it has a strong robustness for the common image processing operations and geometric attack.

Life‐history traits of lake plankton species may govern their phenological response to climate warming

Abstract: A prominent response of temperate aquatic ecosystems to climate warming is changes in phenology – advancements or delays in annually reoccurring events in an organism's life cycle. The exact seasonal timing of warming, in conjunction with species-specific life-history events such as emergence from resting stages, timing of spawning, generation times, or stage-specific prey requirements, may determine the nature of a species' response. We demonstrate that recent climate-induced shifts in the phenology of lake phytoplankton and zooplankton species in a temperate eutrophic lake (Muggelsee, Germany) differed according to differences in their characteristic life cycles. Fast-growing plankton in spring (diatoms, Daphnia) showed significant and synchronous forward movements by about 1 month, induced by concurrent earlier ice break-up dates (diatoms) and higher spring water temperature (Daphnia). No such synchrony was observed for slow-growing summer zooplankton species with longer and more complex life cycles (copepods, larvae of the mussel Dreissena polymorpha). Although coexisting, the summer plankton responded species specifically to seasonal warming trends, depending on whether the timing of warming matched their individual thermal requirements at decisive developmental stages such as emergence from diapause (copepods), or spawning (Dreissena). Others did not change their phenology significantly, but nevertheless, increased in abundances. We show that the detailed seasonal pattern of warming influences the response of phyto- and zooplankton species to climate change, and point to the diverse nature of responses for species exhibiting complex life-history traits.

Water savings potentials of irrigation systems:: global simulation of processes and linkages

Abstract: . Global agricultural production is heavily sustained by irrigation, but irrigation system efficiencies are often surprisingly low. However, our knowledge of irrigation efficiencies is mostly confined to rough indicative estimates for countries or regions that do not account for spatiotemporal heterogeneity due to climate and other biophysical dependencies. To allow for refined estimates of global agricultural water use, and of water saving and water productivity potentials constrained by biophysical processes and also non-trivial downstream effects, we incorporated a process-based representation of the three major irrigation systems (surface, sprinkler, and drip) into a bio- and agrosphere model, LPJmL. Based on this enhanced model we provide a gridded world map of irrigation efficiencies that are calculated in direct linkage to differences in system types, crop types, climatic and hydrologic conditions, and overall crop management. We find pronounced regional patterns in beneficial irrigation efficiency (a refined irrigation efficiency indicator accounting for crop-productive water consumption only), due to differences in these features, with the lowest values ( 60 %) in Europe and North America. We arrive at an estimate of global irrigation water withdrawal of 2469 km3 (2004–2009 average); irrigation water consumption is calculated to be 1257 km3, of which 608 km3 are non-beneficially consumed, i.e., lost through evaporation, interception, and conveyance. Replacing surface systems by sprinkler or drip systems could, on average across the world's river basins, reduce the non-beneficial consumption at river basin level by 54 and 76 %, respectively, while maintaining the current level of crop yields. Accordingly, crop water productivity would increase by 9 and 15 %, respectively, and by much more in specific regions such as in the Indus basin. This study significantly advances the global quantification of irrigation systems while providing a framework for assessing potential future transitions in these systems. In this paper, presented opportunities associated with irrigation improvements are significant and suggest that they should be considered an important means on the way to sustainable food security.