Disconcerting learning on climate sensitivity and the uncertain future of uncertainty

How will our estimates of climate uncertainty evolve in the coming years, as new learning is acquired and climate research makes further progress? As a tentative contribution to this question, we argue here that the future path of climate uncertainty may itself be quite uncertain, and that our uncertainty is actually prone to increase even though we learn more about the climate system. We term disconcerting learning this somewhat counter-intuitive process in which improved knowledge generates higher uncertainty. After recalling some definitions, this concept is connected with the related concept of negative learning that was introduced earlier by Oppenheimer et al. (Clim Change 89:155–172, 2008). We illustrate disconcerting learning on several real-life examples and characterize mathematically certain general conditions for its occurrence. We show next that these conditions are met in the current state of our knowledge on climate sensitivity, and illustrate this situation based on an energy balance model of climate. We finally discuss the implications of these results on the development of adaptation and mitigation policy.     

The capabilities of the EISCAT Svalbard Radar for inter-hemispheric coordinated studies

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A comparison of solar radiative flux above clouds from MODIS with BALTIMOS regional climate model simulations

A comparison study for the solar radiative flux above clouds is presented between the regional climate model system BALTEX integrated model system (BALTIMOS) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations. For MODIS, an algorithm has been developed to retrieve reflected shortwave fluxes over clouds. The study area is the Baltic Sea catchment area during an 11-month period from February to December 2002. The intercomparison focuses on the variations of the daily and seasonal cycle and the spatial distributions. We found good agreement between the observed and the simulated data with a bias of the temporal mean of 13.6 W/m² and a bias of the spatial mean of 35.5 W/m². For summer months, BALTIMOS overestimates the solar flux with up to 90 W/m² (20%). This might be explained by the insufficient representation of cirrus clouds in the regional climate model.     

SBAS orbit and satellite clock corrections for precise point positioning

The quality of real-time GPS positions based on the method of precise point positioning (PPP) heavily depends on the availability and accuracy of GPS satellite orbits and satellite clock corrections. Satellite-based augmentation systems (SBAS) provide such corrections but they are actually intended to be used for wide area differential GPS with positioning results on the 1-m accuracy level. Nevertheless, carrier phase-based PPP is able to achieve much more accurate results with the same correction values. We applied SBAS corrections for dual-frequency PPP and compared the results with PPP obtained using other real-time correction data streams, for example, the GPS broadcast message and precise corrections from the French Centre National d’Etudes Spatiales and the German Deutsches Zentrum für Luft- und Raumfahrt. Among the three existing SBAS, the best results were achieved for the North American wide area augmentation system (WAAS): horizontal and vertical position accuracies were considerably smaller than 10 cm for static 24-h observation data sets and smaller than 30 cm for epoch-by-epoch solutions with 2 h of continuous observations. The European geostationary navigation overlay service and the Japanese multi-functional satellite augmentation system yield positioning results with biases of several tens of centimeters and variations larger by factors of 2–4 as compared to WAAS.     

Trimlines as evidence for palaeo-tsunamis

As seen in many of the satellite images from the tsunami in the Indian Ocean which struck in 2004, there is a distinctive limit between an area with sand coverage, vegetation destruction, and soil erosion on the one hand, and the unaffected natural vegetation on the other. This distinction provides a good landmark to map the inundation width, delimited on the landward side by a trimline. In this study, older trimlines, dating back about 300?years, from tsunamis that occurred throughout the world were documented. We discuss the origin and chronology of trimline modification and extinction, both of which depend on local topography, rock type, and climate.     

Crater morphology in sandstone targets: The MEMIN impact parameter study

Abstract– Hypervelocity (2.5–7.8 km s^?1) impact experiments into sandstone were carried out to investigate the influence of projectile velocity and mass, target pore space saturation, target‐projectile density contrast, and target layer orientation on crater size and shape. Crater size increases with increasing projectile velocity and mass as well as with increasing target pore space saturation. Craters in water‐saturated porous targets are generally shallower and larger in volume and in diameter than craters from equivalent impacts into dry porous sandstone. Morphometric analyses of the resultant craters, 5–40 cm in diameter, reveal features that are characteristic of all of our experimental craters regardless of impact conditions (I) a large central depression within a fragile, light‐colored central part, and (II) an outer spallation zone with areas of incipient spallation. Two different mechanical processes, grain fragmentation and intergranular tensile fracturing, are recorded within these crater morphologies. Zone (I) approximates the shape of the transient crater formed by material compression, displacement, comminution, and excavation flow, whereas (II) is the result of intergranular tensile fracturing and spallation. The transient crater dimensions are reconstructed by fitting quadric parabolas to crater profiles from digital elevation models. The dimensions of this transient and of the final crater show the same trends: both increase in volume with increasing impact energy, and with increasing water saturation of the target pore space. The relative size of the transient crater (in percent of the final crater volume) decreases with increasing projectile mass and velocity, signifying a greater contribution of spallation on the final crater size when projectile mass and velocity are increased.     

Similar Adsorption Parameters for Trace Metals with Different Aquatic Particles

Conditional surface binding constants and complexation capacities for Zn, Pb, Cd, and Cu were determined from surface titration experiments of heterogeneous natural aquatic particulate matter of different origin and composition. Metals and particles were evaluated in naturally occurring concentration ranges in river water.The adsorption of trace metals can be adequately described with a single conditional binding constant over a wide range of metal : particle ratios. Binding constants for aquatic particles at pH 8.0 are remarkably independent from particle composition and are specific for each metal: log K^ads _Zn = 8.39, log K^ads _Pb = 9.67, log K^ads _Cd = 8.61, log ^ads _Cu = 9.84. From competition experiments with Ca and Pb we extracted a sorption coefficient for Ca of log K^ads _Ca = 2.5 (pH 8.0). Maximum surface binding capacities for all metal ions were found for particles containing high fractions of Mn-oxides which are associated with large specific surface areas. Generally, we found sorption capacities to decrease in the sequence Cu Pb, Zn > Cd.The experiments suggest that the conditional surface binding constants and complexation capacities are applicable to model trace metal adsorption in the concentration ranges of natural waters under conditions similar to the experiments. Results also imply that the chemical nature of particle surface sites is rather uniform in the intermediate concentration range or that the array of binding sites averages out differences in sorption strength over the prevailing concentration range of metal ions, respectively.     

Darss Sill as a biological border in the fossil record of the Baltic Sea: evidence from diatoms

Biostratigraphical and palaeoecological analyses of cores along a transect from Femer Belt to the Arkona Basin reveal that North Sea waters began to enter the western Baltic Sea between 8600 and 8400 calibrated years BP. Studies of diatoms indicate that Mecklenburg Bay was characterised by slightly brackish-water conditions between 8400 and 8000 cal. years BP. At around 8000 cal. years BP increasing salinity is indicated by a strong dominance of the diatoms Paralia sulcata and Dimeregramma minor. Some centuries later another diatom assemblage appeared and became dominant in Mecklenburg Bay. This assemblage includes Hyalinella lateripunctata and Pravifusus hyalinus species typical of shallow water areas along the Atlantic coast today. At this time the first marine molluscs made their appearance. The oldest shell of a marine mollusc found in our material is dated to 7600 cal. years BP. The associated assemblage that includes adult specimens of the gastropod Aporrhais pespelicani indicates higher salinities than today.During the Littorina Sea stage a marine diatom flora with P. sulcata, Catenula adhaerens and D. minor crossed the Darss Sill and became widely distributed in the Arkona Basin, Pomeranian Bay and the Baltic Sea proper. In contrast, taxa indicative of the Hyalinella lateripunctata/P. hyalinus assemblage are only found west of the Darss Sill in Femer Belt and Mecklenburg Bay. Apparently, the Darss Sill threshold has been acting as an important salinity border from around 7800 cal. years BP until today.     

A Statistical Analysis of the North Atlantic Oscillation and its Impact on European Temperature

In this study the behaviour of the North Atlantic Oscillation (NAO) and its impact on the surface air temperature in Europe 1891-1990 is analysed using statistical time series analysis techniques. For this purpose, both the NAO index (NAOI) and the surface air temperature time series from 41 European stations are split up into typical variation components. Various measures of correlation indicate that the NAOI-temperature relationships are approximately linear and most pronounced in winter. The spatial correlation patterns show a correlation decrease from North West to South East (winter) exceeding correlation coefficients of 0.6 in the Scotland-South Norwegian area. In summer, these correlations are very weak, in spring and autumn stronger but smaller than in winter. These correlations change significantly in time indicating increasing correlations in Central and North Europe and decreasing correlations in the North West. Low-frequent episodic components represented by related polynomials of different order are very outstanding in both NAO and temperatures showing up in all seasons, except summer, relative maxima roughly 1900 and in recent times, relative minima in the beginning ( ca . 1870) and roughly 1960-1970. Periodogramm analysis reveals a dominant cycle of 7.5 years (NAOI and a majority of temperature time series) whereas in case of the polynomial component one may speculate about a 80-90 year cycle.     

Climatic and limnological changes at Lake Karakul (Tajikistan) during the last ~29 cal ka

We present results of analyses on a sediment core from Lake Karakul, located in the eastern Pamir Mountains, Tajikistan. The core spans the last ~29 cal ka. We investigated and assessed processes internal and external to the lake to infer changes in past moisture availability. Among the variables used to infer lake-external processes, high values of grain-size end-member (EM) 3 (wide grain-size distribution that reflects fluvial input) and high Sr/Rb and Zr/Rb ratios (coinciding with coarse grain sizes), are indicative of moister conditions. High values in EM1, EM2 (peaks of small grain sizes that reflect long-distance dust transport or fine, glacially derived clastic input) and TiO₂ (terrigenous input) are thought to reflect greater influence of dry air masses, most likely of Westerly origin. High input of dust from distant sources, beginning before the Last Glacial Maximum (LGM) and continuing to the late glacial, reflects the influence of dry Westerlies, whereas peaks in fluvial input suggest increased moisture availability. The early to early-middle Holocene is characterised by coarse mean grain sizes, indicating constant, high fluvial input and moister conditions in the region. A steady increase in terrigenous dust and a decrease in fluvial input from 6.6 cal ka BP onwards points to the Westerlies as the predominant atmospheric circulation through to present, and marks a return to drier and even arid conditions in the area. Proxies for productivity (TOC, TOC/TN, TOC _Br ), redox potential (Fe/Mn) and changes in the endogenic carbonate precipitation (TIC, δ¹⁸O _Carb ) indicate changes within the lake. Low productivity characterised the lake from the late Pleistocene until 6.6 cal ka BP, and increased rapidly afterwards. Lake level remained low until the LGM, but water depth increased to a maximum during the late glacial and remained high into the early Holocene. Subsequently, the water level decreased to its present stage. Today the lake system is mainly climatically controlled, but the depositional regime is also driven by internal limnogeological processes.