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?

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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%

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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

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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?

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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

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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

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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