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.

Evaluation of the agreement between the first global remotely sensed soil moisture data with model and precipitation data

Abstract: [1] The lack of global soil moisture data has spurred research in the field of microwave remote sensing. Both passive (radiometers) and active (scatterometer) microwave data are very sensitive to the moisture content of the surface soil layer. To retrieve soil moisture, the effects of vegetation, surface roughness, and heterogeneous land cover must be taken into account. Field experiments have shown that passive microwave data at long wavelengths (L-band) are best suited for soil moisture retrieval. Nevertheless, the first global, multiannual soil moisture data set (1992–2000) has been derived from active microwave data acquired by the European Remote Sensing Satellites (ERS) ERS-1 and ERS-2 scatterometer (C-band). The retrieval algorithm is based on a change detection approach that naturally accounts for surface roughness and heterogeneous land cover. In this paper the scatterometer-derived soil moisture data are compared to gridded precipitation data and soil moisture modeled by a global vegetation and water balance model. The correlation between soil moisture and rainfall anomalies is observed to be best over areas with a dense rainfall gauge network. Also, the scatterometer-derived and modeled soil moisture agree reasonably well over tropical and temperate climates. The fact that the algorithm performs equally well for regions with summer rain and Mediterranean areas indicates that dynamic vegetation effects are correctly represented in the retrieval. More research is needed to better understand the backscattering behavior over dry (steppe, deserts) and cold (boreal zone, tundra) climatic regions. The scatterometer-derived soil moisture data are available to other research groups at http://www.ipf.tuwien.ac.at/radar/ers-scat/home.htm.

Multimodel projections and uncertainties of irrigation water demand under climate change

Abstract: Crop irrigation is responsible for 70% of humanity’swater demand. Since the late 1990s, the expansion ofirrigated areas has been tapering off, and this trend isexpected to continue in the future. Future irrigation waterdemand (IWD) is, however, subject to large uncertaintiesdue to anticipated climate change. Here, we use a set ofseven global hydrological models (GHMs) to quantify theimpact of projected global climate change on IWD oncurrently irrigated areas by the end of this century, and toassess the resulting uncertainties arising from both theGHMs and climate projections. The resulting ensembleprojections generally show an increasing trend in futureIWD, but the increase varies substantially depending onthe degree of global warming and associated regionalprecipitation changes. Under the highest greenhouse gasemission scenario (RCP8.5), IWD will considerably increaseduring the summer in the Northern Hemisphere (>20% by2100), and the present peak IWD is projected to shift onemonth or more over regions where ≥80% of the globalirrigated areas exist and 4 billion people currently live.Uncertaint ies arising from GHMs and global climatemodels (GCMs) are large, with GHM uncertainty dominatingthroughout the century and with GCM uncertaintysubstantially increasing from the midcentury, indicating thechoice of GHM outweighing by far the uncertainty arisingfrom the choi ce of GCM and associated emission scenario.

The Financial Crisis and the Systemic Failure of Academic Economics

Abstract: The economics profession appears to have been unaware of the long build-up to the current worldwide financial crisis and to have significantly underestimated its dimensions once it started to unfold. In our view, this lack of understanding is due to a misallocation of research efforts in economics. We trace the deeper roots of this failure to the profession's focus on models that, by design, disregard key elements driving outcomes in real-world markets. The economics profession has failed in communicating the limitations, weaknesses, and even dangers of its preferred models to the public. This state of affairs makes clear the need for a major reorientation of focus in the research economists undertake, as well as for the establishment of an ethical code that would ask economists to understand and communicate the limitations and potential misuses of their models.

Carbon cycle, vegetation, and climate dynamics in the Holocene: Experiments with the CLIMBER-2 model

Abstract: Holocene was accompanied by significant changes in vegetation cover and an increase inatmosphericCO2concentration.Theessentialquestioniswhetheritispossibletoexplain thesechangesinaconsistentway,accounting fortheorbitalparametersasthemainexternal forcing for the climate system. We investigate this problem using the computationally efficient model of climate system, CLIMBER-2, which includes models for oceanic and terrestrial biogeochemistry. We found that changes in climate and vegetation cover in the northern subtropical and circumpolar regions can be attributed to the changes in the orbital forcing. Explanation of the atmospheric CO2 record requires an additional assumption of excessive CaCO3sedimentation in the ocean. The modeled decrease in the carbonate ion concentration in the deep ocean is similar to that inferred from CaCO3 sediment data [Broecker et al., 1999]. For 8 kyr B.P., the model estimates the terrestrial carbon pool ca. 90 Pg higher than its preindustrial value. Simulated atmospheric d 13 C declines during the

Climate change and Arctic ecosystems: 1. Vegetation changes north of 55°N between the last glacial maximum, mid‐Holocene, and present

Abstract: A unified scheme to assign pollen samples to vegetation types was used to reconstruct vegetation patterns north of 55°N at the last glacial maximum (LGM) and mid-Holocene (6000 years B.P.). The pollen data set assembled for this purpose represents a comprehensive compilation based on the work of many projects and research groups. Five tundra types (cushion forb tundra, graminoid and forb tundra, prostrate dwarf-shrub tundra, erect dwarf-shrub tundra, and low- and high-shrub tundra) were distinguished and mapped on the basis of modern pollen surface samples. The tundra-forest boundary and the distributions of boreal and temperate forest types today were realistically reconstructed. During the mid-Holocene the tundra-forest boundary was north of its present position in some regions, but the pattern of this shift was strongly asymmetrical around the pole, with the largest northward shift in central Siberia (∼200 km), little change in Beringia, and a southward shift in Keewatin and Labrador (∼200 km). Low- and high-shrub tundra extended farther north than today. At the LGM, forests were absent from high latitudes. Graminoid and forb tundra abutted on temperate steppe in northwestern Eurasia while prostrate dwarf-shrub, erect dwarf-shrub, and graminoid and forb tundra formed a mosaic in Beringia. Graminoid and forb tundra is restricted today and does not form a large continuous biome, but the pollen data show that it was far more extensive at the LGM, while low- and high-shrub tundra were greatly reduced, illustrating the potential for climate change to dramatically alter the relative areas occupied by different vegetation types.