Land-atmosphere coupling and
climate change in Europe
SONIA I. SENEVIRATNE, DANIEL LÜTHI, ET
AL.
COREY GODINE, ATMOSPHERIC SCIENCES
PROGRAM
What is “coupling?”
 Studies use two different hypotheses:
 Surface processes & future changes in radiation budget
 Future summertime atmospheric circulation modification
 Models do not take into account increasing
greenhouse gases likely in the future
 Coupling = Atmospheric circulations (temperature
or precipitation) + Soil moisture
What is “coupling?”
 Increased atmospheric greenhouse gases change
coupling dynamics
 Projected large fluxes in climatic extremes
 Humans can’t cope with large variability
Extreme Summers in Europe
HOT
 2003 heatwave and
drought
COLD
 2002 and 2005 torrential
flooding
The Big Ideas
 Goal: Discover role of land-atmosphere coupling in
yearly summer temperature & precipitation
extremes in Europe
 Researchers used several different models
 Not a lot of math
Great Scot!
Models and Equations
 Four 30-year-long experiments (RCM)
 Two recent (CTL, CTLuncoupled), 1960-1989
 Two future (SCEN, SCENuncoupled), 2070-2099
 Uncoupled models remove surface influences
 Equations:
Models and Equations
 Future regional model greenhouse gas scenario
based on IPCC specifications

3 numerical global models
 Global scenarios from present and future
taken from 12 different IPCC
global models
Analysis
 How does land-atmosphere coupling affect the
future temperature/precipitation variability in
Europe in the future?
Data from each
individual model
Differences between each
model
External forcings only
(ie, atmospheric
circulations)
External forcings +
Land-atmosphere
coupling
Why such a large change in T?
 Large difference between GLACE (a present-climate
model) and the model runs on previous page
CTL
SCEN
Why such a large change in T?
The percentage of variation in summer
temperature due to land-atmosphere coupling
Why such a large change in T?
 Models show land-atmosphere coupling is correlated
with a higher temperature change
 SCEN predicts that land-atmosphere coupling will
shift to east and north
 Consistent with other recent model runs (IPCC,
PRUDENCE)
Evapotranspiration and Temperature
 Negative correlation = strong soil control over
evapotranspiration (ie, coupling)
 Positive correlation = strong atmospheric control
over evapotranspiration (ie, uncoupled)
What about precipitation?
 Models are less certain about the relationship
between land-atmosphere coupling and precipitation
variability
Conclusion
 Land-atmosphere coupling is strongly affected by an
increase in greenhouse gases
 Northward shift of European climate zones
 Strong positive correlation between land-atmosphere
coupling and temperature variability

Strong negative correlation between coupling and evapotranspiration
 Weak correlation between land-atmosphere coupling and
precipitation variability
Opinions
 Temperature correlations convincing
 Run CTL and SCEN against more coupling models to confirm
results
 Would like more information about relationship between
evapotranspiration and coupling
 Needs more development in precipitation correlation
 Teleconnection problems!
 Many other process could contribute to projected shift in
surface temperatures
 Would have liked more accurate/effective global models to
supplement regional models
Questions?
Thank you!