Reducing the risk of Atlantic thermohaline circulation collapse: sensitivity analysis of emissions corridors

We present emissions corridors for the 21^st century reducing the risk of collapse of the Atlantic thermohaline circulation (THC) while considering expectations about the socio-economically acceptable pace of emissions reductions. Emissions corridors embrace the range of CO₂ emissions that are compatible with normatively defined policy goals or ‘guardrails’. They are calculated along the conceptual and methodological lines of the tolerable windows approach. We investigate the sensitivity of the emissions corridors to key uncertain physical quantities (i.e. climate sensitivity and North Atlantic hydrological sensitivity, emissions of non-CO₂ greenhouse gases and sulfate aerosols) as well as to the guardrails. Results indicate a large dependency of the width of the emissions corridor on climate and hydrological sensitivity: for low values of the climate and/or hydrological sensitivity, the corridor boundaries are far from being transgressed by business-as-usual emissions scenarios for the 21^st century. In contrast, for high values of both quantities already low non-intervention scenarios leave the corridor in the early decades of this century. The width of the CO₂ emissions corridor is also affected by the emissions pathway of non-CO₂ greenhouse gases and sulfate aerosols, but to a lesser extent. We further find that the choice of the policy goal strongly influences the shape of the emissions corridor. Pursuit of a more ambitious THC target, for instance, tightens the corridor considerably. More strict expectations concerning the socio-economically admissible pace of emissions reduction (expressed in terms of a maximum emissions reduction rate and a transition time towards a de-carbonizing economy) act in the same direction. This indicates that a trade-off between THC and socio-economic guardrails may be unavoidable in the case of very tight emissions corridors.     

Geomorphic Expression of Abrupt Climate Change in Southwestern North America at the Glacial Termination

Eolian and subaqueous landforms composed of gypsum sand provide geomorphic evidence for a wet episode at the termination of glacial climate in southwestern North America. Drying of pluvial Lake Estancia, central New Mexico, occurred after ca. 12,000 ¹⁴C yr B.P. Thereafter, eolian landforms on the old lake floor, constructed of gypsum sand, were overridden by rising lake water, modified by subaqueous processes, and organized into beach ridges along the lake's eastern shore. Preservation of preexisting eolian landforms in the shallow lake suggests abupt changes in lake level and climate. Available radiocarbon ages suggest that the final highstand recorded by beach ridges may have developed during the Younger Dryas (YD) stade. The beach ridges provide information about lake surface area, which was 45% of the lake area reached during the maximum highstands of the late Pleistocene. A similar proportional response has been reported for YD climate changes outside the North Atlantic region.     

Holocene Climate in the Northern Great Plains Inferred from Sediment Stratigraphy, Stable Isotopes, Carbonate Geochemistry, Diatoms, and Pollen at Moon Lake, North Dakota

Seismic stratigraphy, sedimentary facies, pollen stratigraphy, diatom-inferred salinity, stable isotope (δ¹⁸O and δ¹³C), and chemical composition (Sr/Ca and Mg/Ca) of authigenic carbonates from Moon Lake cores provide a congruent Holocene record of effective moisture for the eastern Northern Great Plains. Between 11,700 and 9500¹⁴C yr B.P., the climate was cool and moist. A gradual decrease in effective moisture occurred between 9500 and 7100¹⁴C yr B.P. A change at about 7100¹⁴C yr B.P. inaugurated the most arid period during the Holocene. Between 7100 and 4000¹⁴C yr B.P., three arid phases occurred at 6600–6200¹⁴C yr B.P., 5400–5200¹⁴C yr B.P., and 4800–4600¹⁴C yr B.P. Effective moisture generally increased after 4000¹⁴C yr B.P., but periods of low effective moisture occurred between 2900–2800¹⁴C yr B.P. and 1200–800¹⁴C yr B.P. The data also suggest high climatic variability during the last few centuries. Despite the overall congruence, the biological (diatom), sedimentological, isotopic, and chemical proxies were occassionally out of phase. At these times the evaporative process was not the only control of lake-water chemical and isotopic composition.     

Return to normal — Leipzig in search of its future position in Central Europe

Before World War II Leipzig was one of the most important cities in Germany. Leipzig was a metropole holding the primate position in international trade fairs and in publishing. It was also the seat of the Supreme Court of Germany (since late 19th century). Under socialist dictatorship following the partition of the country after WW II the outstanding ranking was lost.The famous modest demonstration of the people of Leipzig in the fall of 1989 proved to be the main impetus of the velvet revolution, the marvelous turnaround eventually leading to the reunification of Germany, the key event for the gradual unification of all-Europe. From this moment the city of Leipzig started to regain a truely prominent position in the central European urban hierarchy. While some traditional functions may lag behind furtheron, as for example industrial production, services in particular in transportation, commerce and communication promise lasting booming. Correspondingly, construction activities are in full swing to thoroughly modernize the city core, to establish large scale economic foci (several giant distribution centers, the new fair grounds, the substantially up-graded airport, for example), and to catch up with the sub-urbanization process in modern housing which has been interrupted for half a century. The vigorious development of present-day Leipzig stands for the spirit of new hope which now is characteristic for vast areas in East-Central Europe.     

The regional differentiation of the German Democratic Republic — Structure · dynamics · development

In this paper aspects of the regional differentiation within the German Democratic Republic are presented, and the structure, dynamics and development of this differentiation are shown. The GDR founded after World War II comprises a territory of 108,000 sq.km with 16.7 million inhabitants. At the initial stage, its territorial structure was marked by a polarization between the industrialized regions in the South and the backward agricultural regions of the North and the East. Under socialist condition, however, his regional differentiation has been changed during the last three decades due to various basic and sequent processes. The foundation and development of a nationally-owned sector, particularly in industry, and a cooperative sector in agriculture, the industrialization of former agrarian regions, demographic processes, and a changing settlement structure has contributed to this development. The present regional differentiation is analysed by a new probabilistic approach, and seven macro-regions of the GDR are described.     

Future extreme events in European climate: an exploration of regional climate model projections

This paper compares how well satellite versus weather station measurements of climate predict agricultural performance in Brazil, India, and the United States. Although weather stations give accurate measures of ground conditions, they entail sporadic observations that require interpolation where observations are missing. In contrast, satellites have trouble measuring some ground phenomenon such as precipitation but they provide complete spatial coverage of various parameters over a landscape. The satellite temperature measurements slightly outperform the interpolated ground station data but the precipitation ground measurements generally outperform the satellite surface wetness index. In India, the surface wetness index outperforms station precipitation but this may be reflecting irrigation, not climate. The results suggest that satellites provide promising measures of temperature but that ground station data may still be preferred for measuring precipitation in rural settings.