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The 2°C climate target and COP in Paris 

Humans affect extreme weather 

Has global warming stopped? 

Much has been speculated about the reduced surface warming in the last 15 years and the implications for the future. Several papers quantify climate sensitivity and transient response from the most recent data and explain the causes of the warming hiatus, and a number of blog and press articles over several months provide a broader perspective.
Nature Geoscience: Natural variability, radiative forcing and climate response in the recent hiatus reconciled (PDF, 1.6 MB)
GRL: Estimating climate sensitivity and future temperature in the presence of natural variability (PDF, 931 KB)
Nature Geoscience: Energy budget constraints on climate response (PDF, 414 KB)
ETH News: Why global warming is taking a break
Klimablog: Der Klimawandel pausiert (nicht)
Klimablog: Keine Entwarnung beim Klimawandel
SRF Tagesschau
Tagesanzeiger: Die Klimapause (PDF, 770 KB)

IPCC AR5, and how to slice the global carbon pie 

The Working Group I summary of the Intergovernmental Panel on Climate Change Fifth Assessment Report is published. Some reactions of the media, with a focus on what I think is the most relevant topic: the global carbon budget for the 2°C target.
New York Times: How to Slice a Global Carbon Pie?
BAZ: Das CO2 Budget ist schon fast weg
Presentation of IPCC AR5 at ETH Zurich
Multimedia presentation, AURA Zurich
IPCC AR5 WG1 Summary and drafts of chapters
SRF: Wissenschaft und Politik sind sich einig; SRF Autorenbeitrag, September 2013

Ocean eddies influence weather 

On the way to four, not two degrees 

Several recent reports have highlighted the gap between a pathway to 2°C warming and the political reality. In the report “Klimaziele und Emissionsreduktion - Eine Analyse und politische Vision für die Schweiz“ we review the science and discuss the role that Switzerland could take.
OcCC: Klimaziele und Emissionsreduktion - Eine Analyse und politische Vision für die Schweiz
Interview Sonntagszeitung, November 2012 (PDF, 2 MB)
SF Tageschau
Rendez-vous SR DRS1
Bis zur Jahrhundertwende ohne Emissionen, ETH Life
Klimablog: Immer noch nicht auf dem Weg zum 2-Grad-Ziel
Proclim Climate Press: Ein Klimaziel für die Schweiz – Wieviel Ehrgeiz können wir uns leisten?

Climate models: useful or useless? 

In three new papers in Nature Climate we show that some climate projections are surprisingly robust, but overall the uncertainties in projections are not decreasing quickly. Some of the uncertainty is caused by internal climate variability that can be surprisingly large.
Robustness and uncertainties in the new CMIP5 climate model projections, Nature Climate Change 2012 (PDF, 4.9 MB)
Robust joint projections for humidity and temperature extremes, Nature Climate Change 2012 (PDF, 1.4 MB)
Communication of the role of natural variability in future North American climate, Nature Climate Change 2012 (PDF, 3.8 MB)
Klimablog: Hurrikan Sandy und der Nutzen von Klimamodellen

The others should do something first… 

In a joint report with INFRAS we consider the implications of different burden sharing approaches for different countries in a scenario where greenhouse gases are reduced globally to reach the 2°C target. The interpretation of “common but differentiated responsibility” of course varies in the different burden sharing proposals, but developed countries will have to reduce emissions quickly in all cases. 
Emission pathways to reach 2°C target (PDF, 988 KB)

At least three quarters of warming since 1950 manmade

Is two degrees warming still possible? 

Swiss climate change scenarios CH2011

Tropics feel the heat

Which climate model prediction should I trust? 

The 2008 Olympics as an aerosol field experiment 

New simulations with the a comprehensive high resolution model under strong mitigation scenarios show that about half of the climate change can be avoided by the end of the century. A two degree warming target preserves much of the permafrost and Arctic sea ice.
GRL paper: How much climate change can be avoided by mitigation (PDF, 1.5 MB)
Science editor’s choice: How low can we go? (PDF, 269 KB)
Nature Reports Climate Change Research Highlight: Cuts curb impacts (PDF, 335 KB)
News New York Times: Emissions Cuts Could Lessen Climate Change
News 20 Minuten: CO2 muss um 70 Prozent gesenkt werden
News Focus Online: Die Zukunft der Arktis

Irreversible climate change

Research interests

My research interests are the changes in the global climate system caused by the growing emissions of anthropogenic greenhouse gases like carbon dioxide. I use numerical models of different complexity, from simple energy balance to three-dimensional coupled climate models that resolve the atmosphere, ocean, land, sea ice and their interactions. In particular, I work on simulation of scenarios for future climate change, the quantification of uncertainties in the climate response, and the development of methods to constrain important feedback processes in the climate system by comparing observations with model results.

 
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28.03.2017
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