Observations and projections of extreme events
Sonia I. Seneviratne, ETH Zurich, Switzerland
Overview of SREX: IPCC Working Group 1 Contribution
nature and severity of event
vulnerability
exposure
IPCC SREX: Contents & Chapter 3
1: Climate change: new dimensions in disaster risk, exposure,
vulnerability, and resilience
2: Determinants of risks: exposure and vulnerability
3: Changes
3
Ch
in
i climate
li t extremes
t
and
d their
th i iimpacts
t on th
the natural
t l
physical environment
4: Changes in impacts of climate extremes: human systems and
ecosystems
5: Managing the risks from climate extremes at the local level
6: National systems for managing the risk from climate extremes
7: Managing the risks: international level and integration across scales
8: Towards a resilient and sustainable future
9 Case
9:
C
studies
t di
Overview of SREX Chapter 3
• Authors: Sonia Seneviratne, Neville Nicholls, David Easterling,
Clare Goodess, Shinjiro Kanae, James Kossin, Yali Luo, Jose
Marengo Kathleen McInnes,
Marengo,
McInnes Mohammad Rahimi,
Rahimi Markus
Reichstein, Asgeir Sorteberg, Carolina Vera, Xuebin Zhang
• Complexities: variety of extremes,
extremes definitional issues
issues, different
measures, scale issues
• Applied new uncertainty guidance throughout.
throughout
– More than 50 assessments using uncertainty terms (e.g., “very likely”,
“medium confidence”) in Chapter 3 Executive Summary
– Most of these are consistent with AR4, but there are a few revisions;
one-to-one comparison is not possible (change in uncertainty guidance,
differences in aspects being assessed
assessed, …))
• Provided regional assessments of changes in extremes of
temperature,
p
, heavy
yp
precipitation,
p
, drought
g in tables and figures
g
• Tried to balance needs of policymakers for regional projections,
with the need for scientific credibility
• >5’000 comments on chapter 3 material; 6500 CLA-CLA emails…
SREX Chapter 3: Contents
Executive Summary
3.1. Weather and Climate Events Related to Disasters
3.2. Requirements and Methods for Analyzing Changes in Extremes
3.3. Observed and Projected Changes of Weather and Climate
Extremes
3.4. Observed and Projected Changes in Phenomena Related to
Weather and Climate Extremes
3.5. Observed and Projected Impacts on the Natural Physical
Environment
FAQ 3.1: Is the Climate Becoming More Extreme?
g Affected Individual Extreme Events?
FAQ 3.2: Has Climate Change
Progress regarding extremes since AR4
• More literature
~ 900 references in Chapter 3
~ 75%
% of these p
published since AR4
• More observations & further study of quality of
obser ations (tropical ccyclones,
observations
clones dro
drought
ght meas
measures)
res)
• New attribution studies
Floods; heat waves; heavy rainfall
• Closer study of model projections
• Extensive
E t
i study
t d off droughts
d
ht
More studies;; definition issues
SREX: Assessing uncertainty based on evidence & agreement
p1
Step
Assess confidence confidence
level
Low confidence
Medium confidence
Di ti
f
Direction of change only
Virtually certain (99‐
100%)
Very likely
Very likely (90‐100%)
High confidence
Likelihood assessment
Likely (66‐
Likely (66
100%)
Step 2
More likely than not (50‐
100%)
About as likely as not (33‐66%)
SREX: Regional assessments
Large-scale, land only, regions used for temperature &
precipitation
p
p
extremes:
SREX: Regional assessments
Large-scale, land only, regions used for temperature &
precipitation
p
p
extremes: Î More detail than AR4
SREX: Regional assessments
B1
A1B
A2
Projected ret
return
rn
period (of hot day
with late 20th
century return
period of 20 years)
SREX: Regional assessments, daily temperature extremes
Strong regional variations
SREX: Regional assessments, daily temperature extremes
Strong regional variations
SREX: Temperature extremes
A1B, A2:
A1B
A2 A (late
(l t 20th-century)
t ) 1-in-20
1 i 20 year h
hottest
tt t day
d iis likely
lik l to
t become
b
a 11
in-2 year event by the end of the 21st century in most regions, except in the
high
g latitudes of the Northern Hemisphere,
p
where it is likelyy to become a 1-in-5
year event
B1: likely to become a 1-in-5
1 in 5 year event (1
(1-in-10
in 10 in NH high latitudes)
SREX: Precipitation extremes
A (late
(l t 20th-century)
t ) 1-in-20
1 i 20 year annuall maximum
i
daily
d il precipitation
i it ti amountt iis
likely to become a 1-in-5 to 1-in-15 year event by the end of the 21st century in
many
y regions,
g
and in most regions
g
the higher
g
emissions scenarios ((A1B and
A2) lead to a stronger projected decrease in return period
SREX: Dryness assessments
Severall ttypes off measures can be
S
b used
d
to quantify changes in dryness / drought:
• Reflect different dimensions of dryness
(soil moisture drought, meteorological
drought hydrological drought)
drought,
SREX: Dryness assessments
Severall ttypes off measures can be
S
b used
d
to quantify changes in dryness / drought:
• Reflect different dimensions of dryness
(soil moisture drought, meteorological
drought hydrological drought)
drought,
• Some examples:
• Consecutive Dry Days (AR4)
• Soil moisture anomalies
• Standardized Precipitation Index
• Palmer-drought severity index
•…
SREX: Dryness assessments
T
Two
dryness
d
iindices
di
Gray shading: less than 66% model agreement on sign of change
Coloured shading: ≥ 66% model agreement on sign of change
Stippling: ≥ 90% model agreement on sign of change
SREX: Dryness assessments
Consistency between indices
Consistent projections of increased dryness for these (and other)
indices in the Mediterranean region, central Europe, central North
A
America,
i
C
Central
lA
America
i and
dM
Mexico,
i
northeast
h
B il and
Brazil,
d southern
h
Africa
SREX: Dryness assessments
Consistency between indices
Limited number of regions with agreement,
but including important agricultural regions
Î global
l b l implications
i li i
Consistent projections of increased dryness for these (and other)
indices in the Mediterranean region, central Europe, central North
A
America,
i
C
Central
lA
America
i and
dM
Mexico,
i
northeast
h
B il and
Brazil,
d southern
h
Africa
Key messages – projected changes
• Virtually
Vi t ll certain
t i that
th t increases
i
in
i the
th frequency
f
and
d
magnitude of warm daily temperature extremes and
decreases in cold extremes will occur
Key messages – projected changes
• Virtually
Vi t ll certain
t i that
th t increases
i
in
i the
th frequency
f
and
d
magnitude of warm daily temperature extremes and
decreases in cold extremes will occur
• Likely that the frequency of heavy precipitation or the
proportion of total rainfall from heavy falls will increase over
many areas
Key messages – projected changes
• Virtually
Vi t ll certain
t i that
th t increases
i
in
i the
th frequency
f
and
d
magnitude of warm daily temperature extremes and
decreases in cold extremes will occur
• Likely that the frequency of heavy precipitation or the
proportion of total rainfall from heavy falls will increase over
many areas
• Medium confidence that droughts will intensify in some
seasons and areas
Key messages – projected changes
• Virtually
Vi t ll certain
t i that
th t increases
i
in
i the
th frequency
f
and
d
magnitude of warm daily temperature extremes and
decreases in cold extremes will occur
• Likely that the frequency of heavy precipitation or the
proportion of total rainfall from heavy falls will increase over
many areas
• Medium confidence that droughts will intensify in some
seasons and areas
• Very likely that mean sea level rise will contribute to upward
trends in extreme coastal high water levels
Key messages – projected changes
• Virtually
Vi t ll certain
t i that
th t increases
i
in
i the
th frequency
f
and
d
magnitude of warm daily temperature extremes and
decreases in cold extremes will occur
• Likely that the frequency of heavy precipitation or the
proportion of total rainfall from heavy falls will increase over
many areas
• Medium confidence that droughts will intensify in some
seasons and areas
• Very likely that mean sea level rise will contribute to upward
trends in extreme coastal high water levels
• Average tropical cyclone maximum wind speed is likely to
increase, although increases may not occur in all ocean
basins It is likely that the global frequency of tropical
basins.
cyclones will either decrease or remain essentially
unchanged
Summary and conclusions
• SREX: Significantly expanded information compared to
AR4 in particular on regional scale
• Level of certainty
y in p
projection
j
strongly
g y depends
p
on the
considered extreme, region and season
• Both adaptation and mitigation are required to reduce
impacts: Need to be considered jointly
26
IPCC SRES Scenarios
27