Max Planck Institutes and Experts

The global climate system and its anthropogenic influences are key issues of earth system science. Currently new components, like terrestrial vegetation or marine biosphere are added to earth system models to improve climate predictions. Reconstructions of the palaeoclimate are essential to evaluate the model simulations and estimate the quality of the model predictions. Most promising are reconstructions of the terrestrial climate, as continental climate variability is much larger than marine variability. Unfortunately, in terrestrial records often suitable climate proxies are missing. Here we investigate if aquatic and terrestrial biomarkers, e.g. chemical fossils, from the terrestrial record can be used for direct climate reconstruction. Results of this project suggest that compound specific hydrogen isotope ratios of alkanes are emerging as a new palaeoclimate proxy.

Since begin of the industrial revolution levels of the greenhouse gases carbon dioxide, methane and nitrous oxide have risen dramatically. Fossil fuel combustion, increasingly intensive agriculture and an expanding global human population have been the primary causes for this rapid increase. The same increases in fossil fuel burning and biofuel use have also led to an increase in the emissions of sulphur dioxide, soot and particulate organic matter which form aerosol (=suspended particulate matter) in the atmosphere. Most aerosols cool the atmosphere by increasing Earth's reflectivity, but aerosols containing soot warm it by absorbing sunlight. Cleaner fuel technologies are today leading to a reduction in sulphate emissions. Unlike carbon dioxide and sulphur dioxide emissions, soot emissions are largest in developing countries and are still increasing. According to future emission scenarios, the most polluted regions in the first part of the 21th century will be found at lower latitudes whilst aerosol emissions have decreased in North America and Europe. The most notable climate response as calculated by the MPI Earth-System Model to this latitudinal shift in atmospheric aerosol load is a mitigated surface warming and a wetter soil in highly polluted regions and a pronounced warming and drying in regions where the aerosol load is decreasing.

Our long-term goal is the understanding of the genetic differences between Arabidopsis accessions affecting important adaptive traits such as seed dormancy and plant growth. We expect that understanding this genetic variation will help explaining why specific variants are adapted to specific environments and that knowledge of the genetic basis of these traits will help breeding crop plants.

While there is ample experimental evidence for a role of species diversity in ecosystem performance, the functional significance of genetic diversity is less clear. In fact, many aquatic plant communities are highly productive although they consist of only a few or a single dominant species. In order to shed light on this apparent contradiction, scientists at the MPI of Limnology manipulated the genotypic diversity in the field in the seagrass species Zostera marina. The experiment took place in the Baltic Sea in 2003. During that year, a heat wave caused surface water temperatures to rise above 25°C, leading to widespread heat stress related mortality among shallow water animals and plants. Such conditions may serve as a model for predicted increases in climatic extremes. After the heat wave, genotypically diverse seagrass areas recovered faster, had more shoots and biomass and harboured more associated invertebrates at the end of the experimental period. Positive effects of genotypic diversity were due to true biodiversity effects (complementarity) and not due to the dominance of particularly resistant genotypes. These results provide experimental evidence that not only species diversity but also genetic diversity should be preserved. Genotypic diversity had a similar function as species diversity. This way, the level of genetic diversity can be incorporated into existing ecological theory on biodiversity at the level of species.

With the missions Cluster and Double Star, coordinated measurements in Earth’s magnetosphere with up to 6 spacecraft are now becoming available for the first time. Cluster, with its 4 spacecraft in tetraeder-configuration provides data for variable distances in the range ~100 to 20000 km. These are complimented by the measurements of the Two Double Star spacecraft in polar and equatorial orbit.