Download Future Changes in ENSO Discussion

Future Changes in ENSO Discussion
Mat Collins
College of Engineering, Mathematics and Physical Sciences,
University of Exeter, UK
© Yann Arthus-Bertrand / Altitude
Joint Met Office Chair in Climate Change
@mat_collins
Chapter 14: Climate Phenomena and their Relevance for
Future Regional Climate Change
•  El Niño-Southern Oscillation very likely remains as the dominant mode
of interannual variability in the future and due to increased moisture
availability, the associated precipitation variability on regional scales likely
intensifies….. natural modulations of the variance and spatial pattern of
El Niño-Southern Oscillation are so large in models that confidence in
any specific projected change in its variability in the 21st century remains
low.
Extreme
El Niños
Cai, Borlce, Lengaigne,
van Rensch, Collins,
Vecchi, Timmermann,
Santoso, McPhaden, Wu,
England, Guilyardi, Jin.
Increasing frequency of
extreme El Niño events
due to greenhouse
warming. Nature Climate
Change, 2014
Changing El Niño
Teleconnections
Chung, Power, Arblaster, Rashid,
Roff, Climate Dynamics, 2014
CMIP5
Atmosphere model simulations
Power, Delange, Chung, Kociuba,
Keay, Nature 2013
Relationship Between ENSO and Mean Precip
Uncertainty in the ENSO amplitude
change from the past
to the future
Masahiro Watanabe, Jong-Seong
Kug, Fei-Fei Jin,Mat Collins,
Masamichi Ohba,
and Andrew T. Wittenberg
Changes in Mean Rainfall
•  Rainfall change anchored to an equatorial peak in SST warming across
the Pacific
•  SST change related to the pattern of latent heat flux in present-day
simulations (Xie et al., 2010)
•  Although the models agree, there are common SST biases in this
region. Model agreement ≠ robustness
http://climexp.knmi.nl/plot_atlas_form.py
Tropical Precipitation Changes: Chadwick et al., 2013
circulation changes
moisture availability
RH changes
circulation weakening
Some Open Questions
•  To what extent do errors and biases in present-day mean climate
in models affect the pattern of SST formation under climate
change?
•  How do different patterns of SST change affect patterns of rainfall
change, specifically how far the rainfall extends into the east?
•  Are the ENSO rainfall response results of Power et al. model
dependent?
•  How much is the result of Power et al. dependent upon the spatial
pattern of mean SST change?
•  What are the physical mechanisms underlying the change in
ENSO rainfall patterns?
•  What about different type of ENSO events e.g. central vs east
Pacific events?
Discussion - Coordinated Experiments
(CMIP6)?
•  Use
Power et al./Chung et al. experimental setup.
Atmosphere model experiments:
•  Present day fixed SSTs
•  Future SST pattern specified from coupled models (like
CFMIP)
•  Future SSTs + ENSOs with different amplitudes
•  Additional diagnostics specific to ENSO
Open Questions
•  Uncertainties in mean SST changes?
•  Canonical vs central Pacific ENSOs?