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CFCC CONFERENCE – PARIS
Climate indicators of the pace of changes
over the twenty-first century
Yann Chavaillaz LSCE/IPSL - France
July 8th, 2015
in collaboration with
S. Joussaume, S. Bony, P. Braconnot and R. Vautard
1 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH
Most studies about climate change: • fixed current baseline
• absolute future changes
• decision-making linked to absolute changes
1 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH
Most studies about climate change: • fixed current baseline
• absolute future changes
• decision-making linked to absolute changes
Relevance of the pace of climate change:
• need for continuous adaptation planning and implementation
• threat to biodiversity and ecosystem function
• often referred as an average trend
1 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH
Most studies about climate change: • fixed current baseline
• absolute future changes
• decision-making linked to absolute changes
Relevance of the pace of climate change:
Our study: • evolution relative to a running
baseline over periods of 20 years
• multi-model analysis with 18 GCMs
2020 2030 2040 2050 2060 2070 2080 2090
running
baseline
• need for continuous adaptation planning and implementation
• threat to biodiversity and ecosystem function
• often referred as an average trend
1 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH
Most studies about climate change: • fixed current baseline
• absolute future changes
• decision-making linked to absolute changes
Relevance of the pace of climate change:
Our study: • evolution relative to a running
baseline over periods of 20 years
• multi-model analysis with 18 GCMs
2020 2030 2040 2050 2060 2070 2080 2090
running
baseline
RISK
hazards
exposure
vulnerability
• need for continuous adaptation planning and implementation
• threat to biodiversity and ecosystem function
• often referred as an average trend
2 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH WARMING RATE
global evolution
RCP8.5 RCP6.0 RCP4.5 RCP2.6
2 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH WARMING RATE
global evolution
RCP8.5 RCP6.0 RCP4.5 RCP2.6
strong increase
since the 1960s
currently (i.e. 1995),
~0.5K / two-decade
2 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH WARMING RATE
global evolution
RCP8.5 RCP6.0 RCP4.5 RCP2.6
strong increase
since the 1960s
currently (i.e. 1995),
~0.5K / two-decade
2042: all models go out of
the current ±σ-interval
doubling by the 2nd
half of the century
2 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH WARMING RATE
global evolution
RCP8.5 RCP6.0 RCP4.5 RCP2.6
strong increase
since the 1960s
currently (i.e. 1995),
~0.5K / two-decade
2042: all models go out of
the current ±σ-interval
doubling by the 2nd
half of the century
2043: all models go
out of the current
±σ-interval
2076: all models go back to
the PiControl ±σ-interval
3 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH WARMING RATE EFFECTS ON TEMPERATURE DISTRIBUTIONS
• important shift in the distribution
• update of the definition of an extremely
warm year
3 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH WARMING RATE EFFECTS ON TEMPERATURE DISTRIBUTIONS
• important shift in the distribution
• update of the definition of an extremely
warm year
Land extent of these important shifts:
RCP8.5 RCP4.5
2σ-shifts
3 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH WARMING RATE EFFECTS ON TEMPERATURE DISTRIBUTIONS
• important shift in the distribution
• update of the definition of an extremely
warm year
Land extent of these important shifts:
RCP8.5 RCP4.5
<2%
9%
41%!
3 Yann Chavaillaz
CFCC Conference – July 8th, 2015
AN ALTERNATIVE APPROACH WARMING RATE EFFECTS ON TEMPERATURE DISTRIBUTIONS
• important shift in the distribution
• update of the definition of an extremely
warm year
Land extent of these important shifts:
RCP8.5 RCP4.5
41%!
60°N
0°
60°S
4
0
1
2
3
[-]
180°E90°E0°90°W180°W
Where?
4 Yann Chavaillaz
CFCC Conference – July 8th, 2015
WARMING RATE EFFECTS ON TEMPERATURE DISTRIBUTIONS POPULATION EXPOSURE
Fraction of population exposed to 2σ-shifts
average population
growth scenario
from the United
Nations extrapolation
4 Yann Chavaillaz
CFCC Conference – July 8th, 2015
WARMING RATE EFFECTS ON TEMPERATURE DISTRIBUTIONS POPULATION EXPOSURE
Fraction of population exposed to 2σ-shifts
RCP8.5 RCP6.0 RCP4.5 RCP2.6
currently, 8% of the
population exposed
4 Yann Chavaillaz
CFCC Conference – July 8th, 2015
WARMING RATE EFFECTS ON TEMPERATURE DISTRIBUTIONS POPULATION EXPOSURE
Fraction of population exposed to 2σ-shifts
RCP8.5 RCP6.0 RCP4.5 RCP2.6
currently, 8% of the
population exposed
2 billions
4 billions
6 billions, i.e. 61% of the population
4 Yann Chavaillaz
CFCC Conference – July 8th, 2015
WARMING RATE EFFECTS ON TEMPERATURE DISTRIBUTIONS POPULATION EXPOSURE
Fraction of population exposed to 2σ-shifts
RCP8.5 RCP6.0 RCP4.5 RCP2.6
currently, 8% of the
population exposed
2 billions
4 billions
6 billions, i.e. 61% of the population
significant gap
between RCP8.5 and
others
2037
2072
all models go under 0.5%
5 Yann Chavaillaz
CFCC Conference – July 8th, 2015
EFFECTS ON TEMPERATURE DISTRIBUTIONS POPULATION EXPOSURE EFFECTS ON PRECIPITATION
1950 20702010 1890 1890 1950 207020101950 20702010
rate of precip change drying rate moistening rate
RCP8.5 RCP2.6
5 Yann Chavaillaz
CFCC Conference – July 8th, 2015
EFFECTS ON TEMPERATURE DISTRIBUTIONS POPULATION EXPOSURE EFFECTS ON PRECIPITATION
1950 20702010 1890 1890 1950 207020101950 20702010
rate of precip change drying rate moistening rate
RCP8.5 RCP2.6
• the rate of precipitation change follows the warming rate
• strong increase without saturation under RCP8.5
• back to historical values by the end of the 21st century under RCP2.6
Do drying and moistening regions change over time?
6 Yann Chavaillaz
CFCC Conference – July 8th, 2015
POPULATION EXPOSURE EFFECTS ON PRECIPITATION STABILIZATION EFFECTS ON TEMPERATURE DISTRIBUTIONS
1995 2040 2080
1975 2015 2020 2060 2100
hatched areas = switching regions
6 Yann Chavaillaz
CFCC Conference – July 8th, 2015
POPULATION EXPOSURE EFFECTS ON PRECIPITATION STABILIZATION EFFECTS ON TEMPERATURE DISTRIBUTIONS
1995 2040 2080
1975 2015 2020 2060 2100
70
60
50
40
1890 1950 2010 2070
[%]
Fraction of switching regions
RCP8.5 RCP2.6
- some moistening and drying regions change
over time
- BUT large decrease of the extent of
switching regions
- SO more and more regions with persisting
trends
Under RCP8.5:
7 Yann Chavaillaz
CFCC Conference – July 8th, 2015
POPULATION EXPOSURE EFFECTS ON PRECIPITATION STABILIZATION MAIN CONCLUSIONS
RCP8.5 looks bleaker with this approach…
• warming occurring twice faster
• ~41% of land surfaces / ~60% of the total population exposed to
significant temperature shifts
• strong stabilization of drying and moistening regions
7 Yann Chavaillaz
CFCC Conference – July 8th, 2015
POPULATION EXPOSURE EFFECTS ON PRECIPITATION STABILIZATION MAIN CONCLUSIONS
RCP8.5 looks bleaker with this approach…
• warming occurring twice faster
• ~41% of land surfaces / ~60% of the total population exposed to
significant temperature shifts
• strong stabilization of drying and moistening regions
…BUT other RCPs are encouraging!
• future rates of change not worse than in the current period
• little population exposed
• in most cases, back to historical values
8 Yann Chavaillaz
CFCC Conference – July 8th, 2015
Thank you for your attention!
Related papers
- Chavaillaz, Y., S. Joussaume, A. Dehecq, P. Braconnot and R. Vautard: The pace of temperature
change and its effects on temperature distributions over the twenty-first century, Climatic
Change, in prep.
- Chavaillaz, Y., S. Joussaume, S. Bony and P. Braconnot: Spatial stabilization and intensification
of moistening and drying rate patterns under future climate change, Climate Dynamics,
submitted.
Web page: http://www.ulinks.fr/ychavaillaz
Twitter: @YChavaillaz