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SUMMARY:Climate Change: From the Greenhouse Effect to High-Resolution Clim
 ate Modeling
DTSTART:20180416T103000
DTEND:20180416T113000
DTSTAMP:20260527T230110Z
UID:f8d3982b6adfaa5797da7fee4d9dd1e7207d3caf47154130e14966d6
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Christoph Schär\, ETH-Zürich\, Atmospheric and Climate
  Science\n\nClimate change is one of the most pressing social and economic
  issues\, but also one of the most complex scientific challenges. The basi
 c concepts of anthropogenic climate change are very old\, and first estima
 tes of the climate effects of increased atmospheric carbon dioxide concent
 rations date back to the work of Svante Arrhenius in 1896. Despite this lo
 ng history\, uncertainties in climate change projections have remained ver
 y large. More specifically\, the key uncertainty is phrased in terms of th
 e equilibrium climate sensitivity (ECS)\, which is the equilibrium global-
 mean surface warming from a doubling of atmospheric CO2 concentrations. In
  the influential 1979 Charney report\, the ECS was estimated to be between
  1.5 and 4.5 K\, while estimates of current climate models are scattered b
 etween 2 and 5 K. Thus the wide range of ECS estimates has neither shifted
  nor narrowed substantially. Projections of sea-level rise and regional cl
 imate change typically have even larger uncertainties\, thereby challengin
 g appropriate response strategies for adaptation and mitigation purposes.\
 nThe main cause behind the slow progress is the representation of clouds i
 n climate models\, especially convective clouds (i.e. thunderstorms\, rain
  showers\, shallow convective cloud layers). If clouds reflect more sunlig
 ht as the climate warms they reduce the warming\, and vice versa. Convecti
 ve clouds challenge current modeling strategies. They are characterized by
  small horizontal scales of O(1 km)\, while global climate models operate 
 at horizontal resolutions of typically 50-150 km\, implying the use of sem
 i-empirical parameterizations. With the advent of high-resolution climate 
 models\, there are now promising prospects\, as it becomes feasible to bas
 e the models on a set of equations that is much closer to first principles
 .\nThe presentation will report about current approaches to increase the h
 orizontal resolutions of climate models to O(1 km). Examples from limited-
 area simulations demonstrate how some of the key biases can be overcome an
 d how the simulation of clouds may dramatically be improved. This developm
 ent raises a number of technical issues\, covering a wide range of areas i
 ncluding hardware and software design\, as well as the optimal choice of n
 umerical and analysis methodologies. The presentation will address simulat
 ions over Europe and the tropical Atlantic and discuss recent approaches t
 o better exploit next generation supercomputing and mass-storage systems.\
 n 
LOCATION:PPB 019 https://plan.epfl.ch/?room=PPB019
STATUS:CONFIRMED
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