the challenge imposed by climate change...4 1880-1884 average global mean temperature relative to...

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TheChallengeImposedbyClimateChange

Francis Zwiers Pacific Climate Impacts Consortium

University of Victoria, Victoria, Canada Action Canada Vancouver, 2 April 2016

Phot

o: F

. Zw

iers

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Outline •  Observed changes •  Interpretation •  Projections •  Limiting future warming •  Key messages •  Impacts (if time permits) •  Questions

Photo: F. Zwiers

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Observed Changes

Photo: F. Zwiers

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1880-1884 average

Global mean temperature relative to 1951-1980 1.0

0.5

0.0

-0.5

°C

1880 1900 1920 1940 1960 1980 2000 2020

2011-2015 average

2

0

-2

°C

Courtesy NASA GISS (accessed 28 March 2016)

Warming is unequivocal Multiple lines of evidence including

•  Temperature •  Snow cover extent •  Arctic sea ice •  Ocean heat content •  Sea level rise

Associated changes in •  Precipitation • Ocean surface

salinity •  Temperature and

precipitation extremes

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Interpretation of the Evidence

Photo: F. Zwiers

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Global mean temperature anomaly

Jonesetal,2013

Krakatoa Santa Maria

Agung El Chichon

Pinatubo °C

See also Figure 10.1, IPCC WG1 AR5

7 Jonesetal,2013

Jonesetal,2013

Jonesetal,2013

All forcings Greenhouse gas forcing

Global mean temperature anomaly

Solar and volcanic forcing

See also Figure 10.1, IPCC WG1 AR5

It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.

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Impacts in BC •  Warming clearly evident •  Glaciers in retreat across the province •  Winter snowpack reductions •  Summer stream flow declining •  Large reduction in number of frost days each year •  Pine bark beetle infestation linked to less intense

winter cold extremes

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Annual frost days

Frost day change relative to 1986-2005

Historical 1900-2011 trend: 24 days (statistically significant)

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Projected climate change

Photo: F. Zwiers

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Summary for Policymakers

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Figure SPM.7 | CMIP5 multi-model simulated time series from 1950 to 2100 for (a) change in global annual mean surface temperature relative to 1986–2005, (b) Northern Hemisphere September sea ice extent (5-year running mean), and (c) global mean ocean surface pH. Time series of projections and a measure of uncertainty (shading) are shown for scenarios RCP2.6 (blue) and RCP8.5 (red). Black (grey shading) is the modelled historical evolution using historical reconstructed forcings. The mean and associated uncertainties averaged over 2081−2100 are given for all RCP scenarios as colored verti-cal bars. The numbers of CMIP5 models used to calculate the multi-model mean is indicated. For sea ice extent (b), the projected mean and uncertainty (minimum-maximum range) of the subset of models that most closely reproduce the climatological mean state and 1979 to 2012 trend of the Arctic sea ice is given (number of models given in brackets). For completeness, the CMIP5 multi-model mean is also indicated with dotted lines. The dashed line represents nearly ice-free conditions (i.e., when sea ice extent is less than 106 km2 for at least five consecutive years). For further technical details see the Technical Summary Supplementary Material {Figures 6.28, 12.5, and 12.28–12.31; Figures TS.15, TS.17, and TS.20}

6.0

4.0

2.0

−2.0

0.0

(o C)

4232

39

historicalRCP2.6RCP8.5

Global average surface temperature change(a)

RC

P2.6

R

CP4

.5

RC

P6.0

RC

P8.5

Mean over2081–2100

1950 2000 2050 2100

Northern Hemisphere September sea ice extent(b)R

CP2

.6

RC

P4.5

R

CP6

.0

RC

P8.5

1950 2000 2050 2100

10.0

8.0

6.0

4.0

2.0

0.0

(106 k

m2 )

29 (3)

37 (5)

39 (5)

1950 2000 2050 2100

8.2

8.0

7.8

7.6

(pH

uni

t)

12

9

10

Global ocean surface pH(c)

RC

P2.6

R

CP4

.5

RC

P6.0

R

CP8

.5

Year

SPM

We have a choice …

Figure SPM.7, IPCC WG1 AR5

Carbon emissions CO2 concentration

Van Vuuren et al. 2011

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Projected warming (mean climate)

RCP2.6

RCP8.5

Difference between 1986-2005 and 2081-2100


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Projected mean precip change

RCP2.6

RCP8.5

Difference between 1986-2005 and 2081-2100


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Limiting future warming

Photo: F. Zwiers

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Keeping warming below 2°C … •  Warming is essentially permanent (even if

emissions are completely curtailed) •  Global temperature change is proportional to the

total amount of carbon emissions accumulated over time.

•  To have decent odds of keeping global warming below 2°C (likely, i.e., ≥ 2 chances in 3), the total amount of carbon dioxide emissions (since the pre-industrial era) needs to be limited to less than 1000 GtC.

•  More than half of this amount has already been emitted.

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Cumulative emissions and warming Fi

gure

SP

M.1

0, IP

CC

WG

1 A

R5

RCP2.6 RCP4.5 RCP6.0 RCP8.5

Cumulative total anthropogenic CO2 emissions from 1870 (GtC)

Tem

pera

ture

ano

mal

y re

lativ

e to

186

1-18

80 (°

C)

~66%

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Some key messages

Photo: F. Zwiers

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•  Warming of the climate system is unequivocal •  Warming is essentially permanent •  Impacts are occurring •  Continued emissions will cause further warming and

exacerbate some types of extremes •  Adaptation will be required to reduce impacts and risks •  The magnitude of impacts, risks and adaptation costs

depends upon the level of warming •  Limiting warming will require deep emissions reductions •  Cumulative emissions largely determine the amount of

long-term warming •  Selecting a warming limit implies a fixed, global,

emissions budget

Some messages

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Impacts experienced via extremes

Photo: F. Zwiers (Gravelbourg Sunset)

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China’s Summer of 2013

Photo: F. Zwiers (Yangtze River)

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Eastern China is densely observed

• 1749 stations (1955 onwards) • JJA mean temperature increased

0.82°C over 1955-2013 •  records were broken at more

than 45% of stations in JJA 2013

JJA mean temperature in Eastern China

-1

-0.5

0

0.5

1

1.5

1955

19

57

1959

19

61

1963

19

65

1967

19

69

1971

19

73

1975

19

77

1979

19

81

1983

19

85

1987

19

89

1991

19

93

1995

19

97

1999

20

01

2003

20

05

2007

20

09

2011

20

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The 5 hottest summers have all occurred since 2000

(2013, 2007, 2000, 2010 and 2011)

1.1°C

Ano

mal

y re

lativ

e to

195

5-19

84 °C

Sun et al, Nature Climate Change, 2014

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The multi-model ensemble mean (ALL forcing) well simulates the observed temperature record.

Observed and simulated JJA mean temperature in Eastern China (1955-2012)

125 (26) 49 (12)

Anomalies relative to 1955-1984


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JJA mean temperature in Eastern China

-1

-0.5

0

0.5

1

1.5

1955

19

57

1959

19

61

1963

19

65

1967

19

69

1971

19

73

1975

19

77

1979

19

81

1983

19

85

1987

19

89

1991

19

93

1995

19

97

1999

20

01

2003

20

05

2007

20

09

2011

20

13

The 5 hottest summers have all occurred since 2000

(2013, 2007, 2000, 2010 and 2011)

1.1°C

Ano

mal

y re

lativ

e to

195

5-19

84 °C


•  How rare was this event? •  once in 270-years in control simulations •  once in 29-years in “reconstructed” observations •  once in 4.3 years relative to the climate of 2013

•  Fraction of Attributable Risk in 2013: (p1 – p0)/p1≈ 0.984

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Calgary flood, 2013

Looking towards downtown Calgary from Riverfront Avenue (June 21, 2013), courtesy Ryan L.C. Quan

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Calgary floods (Teufel et al, submitted)

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Figure 13. Return times of (a) average May-June evapotranspiration over the northern

Great Plains, (b) maximum 1-day and (c) 3-day May-June precipitation over southern

Alberta, in present-day (red) and pre-industrial ensembles (blue). Gray horizontal

lines show (a) average evapotranspiration during the 14-21 June period, (b) average

precipitation on 20 June and (c) average precipitation during the 19-21 June period,

for the members of the CRCM5_Ref ensemble. Black dashed lines show (b) average

precipitation across the region on 20 June and (c) average precipitation during the 19-

21 June period, as estimated from CaPA.

100 101 102 1030

10

20

30

40

50

60

70

1−da

y m

axim

um (m

m)

Return period (years)

IRPIRaPIRbPIRc

100 101 102 1030

20

40

60

80

100

120

3−da

y m

axim

um (m

m)


IRPIRaPIRbPIRc

(a)

(b) (c) Distribution of annual May-June maximum 1-day southern-Alberta precipitation in CRCM5 under factual and counter-factual conditions (conditional on prevailing global pattern of SST anomalies)

Frequency doubles (~25-yr à ~12 yr)

Magnitude increases ~10%

Southern Alberta MJ max 1-day precip

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Calgary floods (Teufel et al, submitted)

Distribution of annual May-June maximum 1-day Bow River Basin precipitation in CRCM5 under factual and counter-factual conditions (conditional on prevailing global pattern of SST anomalies)

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Figure 14. Return times of maximum 1-day (left) and 3-day (right) May-June

precipitation (top) and surface runoff (bottom) in present-day (red) and pre-industrial

ensembles (blue), over the western BRB. Gray horizontal lines show the average

precipitation (top) and average surface runoff (bottom) over this region on 20 June

(left) and during the 19-21 June period (right) for the members of the CRCM5_Ref

ensemble. Black dashed lines show the average precipitation over this region on 20

June (top left) and during the 19-21 June period (top right), as estimated from CaPA.

100 101 102 1030

20

40

60

80

100

120

1−da

y m

axim

um (m

m)


IRPIRaPIRbPIRc

100 101 102 1030

50

100

150

200

3−da

y m

axim

um (m

m)


IRPIRaPIRbPIRc

100 101 102 1030

10

20

30

40

50

1−da

y m

axim

um ru

noff


IRPIRaPIRbPIRc

100 101 102 1030

20

40

60

80

100

3−da

y m

axim

um ru

noff

(mm

)


IRPIRaPIRbPIRc

(a) (b)

(c) (d)

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www.PacificClimate.org

Thank You!

Photo: F. Zwiers

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