Humboldt-Universität zu Berlin - Mathematisch-Naturwissen­schaft­liche Fakultät - International Research Training Group 1740


Project C5: Interaction of tipping elements in the climate system

Research Team: H.M.J. Barbosa (USP), J. Kurths (PIK, HUB), G. Obregón (INPE), G. Sampaio (INPE), R. Winkelmann (PIK)

Outline: Several tipping elements are known to exist in the climate system, with profound environmental and societal impacts. Feedbacks between these elements, and even the potential for nonlinear domino effects have been suggested but have yet to be quantified. In the proposed project, we will investigate a sub-network of potential tipping elements in the climate system (See Fig. 10). Under unmitigated climate change, the Atlantic meridional overturning circulation (AMOC) is likely to weaken. An AMOC shutdown could cause a shift of the Intertropical Convergence Zone (ITCZ) which in turn would significantly impact the seasonal cycle over Amazonia and increase the risk of drought. A shift of the ITCZ would also have severe consequences for North-East Brazil, a region which is far more populated and already in the process of desertification. In addition to these direct impacts, a change in the Atlantic overturning circulation could indirectly lead to drying over much of the Amazon basin through strengthening of the El Niño Southern Oscillation (ENSO) variability. The fate of each of the tipping elements is thus determined by a complex interplay of reinforcing and dampening effects. Here, we aim at analyzing these effects and the resulting change in tipping potential.

Research Topic: Tipping events are low probability – high impact events. It is therefore essential to derive probability distributions for each of the tipping elements on its own and within the network, and it is especially important to take the long tail of the distributions into account. For the AMOC, a probability density function has been derived for different levels of global warming. However, the effects of freshwater influx through Greenland melting or ice loss from Antarctica for instance are missing from this analysis. Based on output from comprehensive climate models, we will derive probability estimates of overturning changes including these and other feedbacks. Response theory can be used to combine the results with possible future temperature pathways in order to quantify the effective tipping potential.