Download A review of ENSO and Climate Change

yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

IPCC Fourth Assessment Report wikipedia, lookup

Climate change, industry and society wikipedia, lookup

Surveys of scientists' views on climate change wikipedia, lookup

Effects of global warming on humans wikipedia, lookup

Public opinion on global warming wikipedia, lookup

Scientific opinion on climate change wikipedia, lookup

Climate change feedback wikipedia, lookup

Solar radiation management wikipedia, lookup

Climate change and poverty wikipedia, lookup

Attribution of recent climate change wikipedia, lookup

Climate change in the United States wikipedia, lookup

Climate sensitivity wikipedia, lookup

Media coverage of global warming wikipedia, lookup

Climate change and agriculture wikipedia, lookup

Effects of global warming wikipedia, lookup

Global warming wikipedia, lookup

General circulation model wikipedia, lookup

Citizens' Climate Lobby wikipedia, lookup

Global warming hiatus wikipedia, lookup

Climate change in Tuvalu wikipedia, lookup

Instrumental temperature record wikipedia, lookup

Climate engineering wikipedia, lookup

Climate governance wikipedia, lookup

Climate change adaptation wikipedia, lookup

Economics of global warming wikipedia, lookup

Effects of global warming on Australia wikipedia, lookup

Atmospheric model wikipedia, lookup

Years of Living Dangerously wikipedia, lookup

Numerical weather prediction wikipedia, lookup

Climate change in Saskatchewan wikipedia, lookup

El Niño wikipedia, lookup

Motivation and Background
AR4 Chapter 10: In summary, all models show
continued ENSO interannual variability in the
future no matter what the change in average
background conditions, but changes in ENSO
interannual variability differ from model to model.
Based on various assessments of the current
multi-model archive, in which present-day El
Niño events are now much better simulated than
in the TAR, there is no consistent indication at
this time of discernible future changes in ENSO
amplitude or frequency.
Motivation and Background
• Largely a review of GCM
• Separate changes in
mean (i.e. background)
climate and ENSO
• Consider that there are
errors in models and
uncertainties in projections
Changes in
Robust Changes in the Hydrological Cycle in
Robust Changes in the Hydrological Cycle in
Normal Conditions
© Crown copyright Met Office
Climate Change
© Crown copyright Met Office
Climate Change
(SST Anomalies)
• Not “El Nino-like”
• Trade winds weaken
• SSTs warm more on
the equator than off
• The equatorial
thermocline shoals
and the stratification
• Upwelling weakens
© Crown copyright Met Office
El Niño Conditions
(SST Anomalies)
© Crown copyright Met Office
Changes in
ENSO Variability
Changes in ENSO variability 2050-2100 in CMIP3 A1B experiments
© Crown copyright Met Office
van Oldenborgh et al 2005
El Niño Features
and Processes
Walker Circulation
atmospheric damping
SST response to
thermocline anomalies
surface zonal current
SST response to wind
stress anomalies
zonal advective feedback
© Crown copyright Met Office
Balance of ENSO Processes in Each Model
van Oldenborgh et al 2005
ENSO Variability: Processes and
Impact on ENSO
Mean upwelling and advection
Thermocline feedback
SST/wind stress (Ekman) feedback
Surface zonal advective feedback
no change
Atmospheric damping
Atmospheric variability
Other processes e.g. TIW
Summary and Conclusions
Background Conditions
• The tropical easterly trade winds are likely to weaken
• Models show SSTs warm more on the equator than off
• The equatorial thermocline shoals and the stratification of the
thermocline increases
• Upwelling weakens
• ENSO variability is controlled by a delicate balance of amplifying
and damping feedbacks, and it is likely that one or more of the major
physical processes that are responsible for determining the
characteristics of ENSO will be modified by climate change
• While the possibility of large changes in ENSO cannot be ruled out,
research conducted to date does not yet enable us to say precisely
whether ENSO variability will be enhanced or damped, or if the
frequency of events will change (because of errors in models)
East-Pacific vs Central Pacific/Modoki
Lee and McPhaden 2010
Opportunities and Questions: I
• Finding statistically significant changes in ENSO under
high levels of greenhouse gases is a mitigation-relevant
scientific problem – what about ENSO characteristics in
the next 10-30 years?
• New project; Tom Russon, Sandy Tudhope, Mat Collins,
Gabi Hegerl, …
• Assess long-term natural variations in ENSO from coral
archives and model simulations
• CMIP5 and Isotope-enabled HadCM3, palaeo-corals
from the Galapagos from last 1000 years
Opportunities and Questions: II
• Are CMIP3 findings confirmed in CMIP5 models?
• Can we design and implement better metrics?
• We expect uncertainties, so how do we deal with them?
• Funding proposal; Mat Collins, Eric Guilyardi, Fei-Fei
Jin, Axel Timmermann, Will Roberts, Geert Jan van
Oldenborgh, …
• New CMIP5 models and simulations, new metrics
• Use ENSO models of intermediate complexity
“ENMICs” to map out a much larger region of possible
ENSO futures and constrain with
observations/(re)analysis products
Opportunities and Questions: III
• Detection and attribution of observed changes (signalto-noise issue)
• Deeper understanding of the role of the ocean
especially clouds
• Reconciling past background and variability changes
from palaeo-archives (Pliocene, mid-Holocene, LGM)
with model simulations
El Niño Conditions
© Crown copyright Met Office
HadCM3 Perturbed Physics
• 33 ensemble
• Anthro and
natural forcings
• Mean ENSO
strength and
frequency is
sensitive to
forcing in 20th
and 21st
Is El Niño Changing?
• Ensemble mean
change in NINO3 std.
dev. in Hadley Centre
models and
• Increase in ENSO
variability over 20th
Century is seen in
observations and
model simulations
forced by increasing
greenhouse gases
• Future projections
show larger, more
frequent ENSO events
Forced changes in ENSO
Natural internal variability
Mat Collins, Met Office Hadley Centre
How does ENSO change?
• Switch from
smaller El Nino
events which
propagate EastWest…
• …to larger
events which
develop insitu or
even propagate
• More frequent
events in the
El Niño Southern Oscillation, Climate
Models and Climate Change
• Climate models solve the
dynamical equations of the
atmosphere and ocean on a grid
• Because of restrictions in
computer power, the grid is
relatively coarse and sub-grid scale
processes need to be
• Climate models are imperfect
representations of the real world
• Nevertheless, the recent
generation of climate models can
simulate the basic physics and
characteristics of ENSO
Understanding El Niño In Ocean–atmosphere General Circulation Models: Progress And
Challenges Eric Guilyardi, Andrew Wittenberg, Alexey Fedorov, Mat Collins, Chunzai Wang,
Antonietta Capotondi, Geert Jan Van Oldenborgh, And Tim Stockdale, BAMS 2009.