In the Global Climate division, large-scale climate variability is studied, including the effects of climate change. The research activities in the group focus on quantifying decadal to centennial climate variability, studying feedbacks in the earth system, development of global climate scenario’s and development of monthly, seasonal and decadal predictions. The group maintains global climate models of intermediate complexity and develops a state-of-the-art earth system model (EC-EARTH) as research tool and as tool for developing climate scenario’s. The group is internationally recognized in the fields of climate extremes, thermohaline circulation, tropical variability, atmospheric dynamics and land processes.

03-04-2013: Important role for ocean warming and increased ice-shelf melt in Antarctic sea-ice expansion. R. Bintanja*, G. J. van Oldenborgh, S. S. Drijfhout, B.Wouters and C. A. Katsman. Nature Geoscience Letters, doi:10.1038/NGEO1767.

Changes in sea ice significantly modulate climate change because of its high reflective and strong insulating nature. In contrast to Arctic sea ice, sea ice surrounding Antarctica has expanded1, with record extent2 in 2010. This ice expansion has previously been attributed to dynamical atmospheric changes that induce atmospheric cooling3. Here we show that accelerated basal melting of Antarctic ice shelves is likely to have contributed significantly to sea-ice expansion.

Specifically, we present observations indicating that melt water from Antarctica’s ice shelves accumulates in a cool and fresh surface layer that shields the surface ocean from the warmer deeper waters that are melting the ice shelves.

02-04-2013: The changing seasonal climate in the Arctic. R. Bintanja, E.C. van der Linden. Nature, for the full article please go to: http://www.nature.com/srep/2013/130327/srep01556/full/srep01556.html

Ongoing and projected greenhouse warming clearly manifests itself in the Arctic regions, which warm faster than any other part of the world. One of the key features of amplified Arctic warming concerns Arctic winter warming (AWW), which exceeds summer warming by at least a factor of 4. Here we use observation-driven reanalyses and state-of-the-art climate models in a variety of standardised climate change simulations to show that AWW is strongly linked to winter sea ice retreat through the associated release of surplus ocean heat gained in summer through the ice-albedo feedback (,25%), and to infrared radiation feedbacks (,75%). Arctic summer warming is surprisingly modest, even after summer sea ice has completely disappeared. Quantifying the seasonally varying changes in Arctic temperature and sea ice and the associated feedbacks helps to more accurately quantify the likelihood of Arctic’s climate changes, and to assess their impact on local ecosystems and socio-economic activities.

21-03-2013: Zware herfststormen in Europa door orkanen in warmer klimaat / More hurricanes to hit Western Europe due to global warming. Haarsma, R., W. Hazeleger, C. Severijns, H. de Vries, A. Sterl, R. Bintanja, G.J. van Oldenborgh, H.W. van den Brink. Geophysical Research Letters, doi:10.1002/grl.50360.

Orkanen boven de Atlantische Oceaan kunnen aan het eind van deze eeuw voor meer zware herfststormen in West-Europa zorgen. In een warmer klimaat zullen orkanen makkelijker naar de straalstroom trekken dan nu het geval is. Boven een warmere en vochtigere oceaan kunnen ze weer krachtiger worden en transformeren tot een zware storm die met windkracht 11 of 12 Europa treft.

Simulation of Hurricanes in high resolution (~25 km) version of EC-EARTH :

• Comparison with low resolution
• Hurricane hitting Europe

06-12-2012: Complete synchronization of chaotic atmospheric models by connecting only a subset of state space. Hiemstra, P.H., N. Fujiwara, F.M. Selten en J. Kurths. Nonlin. Proc. Geophys., 2012, 19, 611-621, doi:10.5194/npg-19-611-2012.

Connected chaotic systems can, under some circumstances, synchronize their states with an exchange of matter and energy between the systems. In this study we perform synchronization experiments with two connected quasi-geostrophic (QG) models. The purpose is to determine whether connecting only a subset of the model state space can still lead to complete synchronization (CS). In addition, we evaluated whether empirical orthogonal functions (EOF) form efficient basis functions for synchronization in order to limit the number of connections. In this paper, we show that indeed only a subset needs to be connected for CS. Both the coupling timescale and the spatial subset are consistent with the baroclinic instabilities in the model. Using the Lorenz 63 model, we show that EOFs are nearly optimal basis functions for synchronization. The QG model results show that the minimum number of EOFs that need to be connected for CS is a factor of three smaller than when connecting the original state variables. Abstract (html)  Volledige tekst (pdf)