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Quantifying the sensitivity of the hydrological cycle to increasing temperature

Applicant Knutti Reto
Number 129921
Funding scheme Project funding
Research institution Institut für Atmosphäre und Klima ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Climatology. Atmospherical Chemistry, Aeronomy
Start/End 01.04.2010 - 31.12.2012
Approved amount 157'948.00
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Keywords (6)

precipitation; climate change; hydrological cycle; climate models; hydrological sensitivity; observations

Lay Summary (English)

Lay summary
Since the preindustrial period, the concentration of greenhouse gases in the atmosphere is increasing due to human activities. It is well understood that greenhouse gases such as carbon dioxide act to increase the temperature of the atmosphere. Warmer air can consequently hold more moisture, which again results in an increase in precipitation.Global climate models are currently the most powerful tool to investigate the future climate but interestingly, the simulated increase in precipitation is smaller by a factor of two compared to observations. Since changes in precipitation will affect numerous ecosystems as well as food and water security, it is important to understand the reasons for the discrepancy between climate models and observations.On one hand, observations might overestimate the precipitation increase because of too short available time series or inadequacies in measurement systems. On the other hand, climate models might fail at simulating important processes leading to the precipitation formation. In a first step, different observation datasets will be analysed and compared. Then, simulations will be performed with a global climate model in order to investigate the mechanisms leading to precipitation and these results will be compared to already existing model datasets. The proposed project will allow to understand the nature of the discrepancy between climate models and observations. Overall, the project will inform policy makers about the future climate and allow them to agree on adequate adaptation measures.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants



Analyzing precipitation projections: A comparison of different approaches to climate model evaluation
Schaller N, Mahlstein I, Cermak J, Knutti R (2011), Analyzing precipitation projections: A comparison of different approaches to climate model evaluation, in JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES, 116, 1-14.
Extended warming of the northern high latitudes due to an overshoot of the Atlantic meridional overturning circulation
Wu PL, Jackson L, Pardaens A, Schaller N, Extended warming of the northern high latitudes due to an overshoot of the Atlantic meridional overturning circulation, in GEOPHYSICAL RESEARCH LETTERS, 38, 1-5.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
AGU Fall Meeting 03.12.2012 San Francisco
11th International NCCR Climate Summer School 09.09.2012 Monte Verita
9th Swiss Geoscience Meeting 11.11.2011 Zürich
Chemistry & Climate Processes group meeting 01.11.2011 Boulder, USA
WCRP Open Science Conference 24.10.2011 Denver, USA
Climate seminar, Met Office Hadley Centre 01.08.2011 Exeter, UK


Title Year
Poster Award 2011

Associated projects

Number Title Start Funding scheme
119952 Quantifying climate change uncertainty from the CMIP3 ensemble of global coupled climate models 01.04.2008 Project funding


High-impact and long-term policy decisions are informed by climate model predictions. Despite its relevance for life on Earth, it is still unclear by how much precipitation will change as a result of the projected temperature increase resulting from rising atmospheric greenhouse gas concentrations. Observations show a precipitation increase of up to 6% per Kelvin of surface warming, while the rate found in climate models is between 1 and 3%/K, suggesting a discrepancy of at least a factor two on the global scale. The aim of the proposed research project is to analyze global observations of the hydrological cycle and climate model output to improve process understanding and explain the discrepancies between models and observations. Precipitation trends will first be analyzed in a wide range of observation data sets and in the results of the Coupled Models Intercomparison Program 3 (CMIP3) models as used in the AR4. Then simulations with different setups will be performed with the NCAR Community Climate System Model (CCSM) in order to analyze the response of the hydrological cycle to various factors and processes. Finally, seasonal and spatial differences in precipitation trends will be analysed. In contrast to many previous studies, this project will not only focus on temperature and precipitation but also include other mechanisms and parameters of the hydrological cycle. The results of the project will help to fill a gap in the current understanding of the hydrological cycle and will contribute to a better understanding of precipitation changes, which impact on water resources, ecosystems and global food security.