Transcript Peter Stott`s Presentation

Extreme weather and climate change
Dr Peter Stott, Met Office Hadley Centre
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Australia
January 2013
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Hobart, Tasmania, 4th January 2013
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Dunalley, 4th January 2013
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Dunalley, 4th January 2013
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Australia’s “angry summer”
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Britain’s washout Summer : 2012
Diamond Jubilee, 3rd June, Reading
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• Why is climate changing ?
• How is extreme weather changing ?
• Is it possible to link recent extreme
weather like the Australian heatwave or
the wet British summer to climate
change ?
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The climate is warming
Annual mean temperature (1901-2012)
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Concentrations of carbon dioxide and
other greenhouse gases are
increasing
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The greenhouse effect
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The oceans have warmed
and sea level has risen.
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The climate system has continued to accumulate
energy during the last 15 years
Box 3.1 Fig 1
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IPCC Fifth Assessment Report
Observed decadal mean warming
Fig SPM.5
Observed warming inconsistent with that expected
from natural factors
Fig SPM.5
Observed warming consistent with simulations that
include anthropogenic factors
Fig SPM.5
Observed
CO2, CH4, N2O
Anthropogenic
Aerosols
Solar, Volcanic
Internal Variability
Fig. TS.10
Global mean warming since 1951 (°C)
The observed warming 1951− 2010 is
approximately 0.6°C to 0.7°C.
Observed
CO2, CH4, N2O
Anthropogenic
Aerosols
Solar, Volcanic
Internal Variability
Fig. TS.10
Global mean warming since 1951 (°C)
The observed warming 1951− 2010 is
approximately 0.6°C to 0.7°C.
Observed
CO2, CH4, N2O
Anthropogenic
Aerosols
Solar, Volcanic
Internal Variability
Fig. TS.10
Global mean warming since 1951 (°C)
The observed warming 1951− 2010 is
approximately 0.6°C to 0.7°C.
Observed
CO2, CH4, N2O
Anthropogenic
Aerosols
Solar, Volcanic
Internal Variability
Fig. TS.10
Global mean warming since 1951 (°C)
The observed warming 1951− 2010 is
approximately 0.6°C to 0.7°C.
Observed
CO2, CH4, N2O
Anthropogenic
Aerosols
Solar, Volcanic
Internal Variability
Fig. TS.10
Global mean warming since 1951 (°C)
The observed warming 1951− 2010 is
approximately 0.6°C to 0.7°C.
Observed
CO2, CH4, N2O
Anthropogenic
Aerosols
Solar, Volcanic
Internal Variability
Fig. TS.10
Global mean warming since 1951 (°C)
It is extremely likely that human influence has
been the dominant cause of the observed
warming since the mid-20th century.
IPCC Summary for Policy Makers agreed line by line in
Stockholm, September 2013, by 110 governments
• Why is climate changing ?
• How is extreme weather changing ?
• Is it possible to link recent extreme
weather like the Australian heatwave or
the wet British summer to climate
change ?
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Was Australia’s “angry summer” due
to anthropogenic climate change ?
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It isn’t possible to say a particular extreme
season was or was not due to
anthropogenic climate change.
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But it is possible to evaluate how the
odds of such an event have changed.
Human influence has very likely at least doubled the
probability of European summer temperatures as hot
as 2003. Stott et al, Nature, 2004.
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Change in Extremes in
warming climate
in future
• Temperature now
New
average
Probability of
occurrence
More hot
extremes
Fewer
cold
extremes
Hot
temperature
extremes
Cold
temperature
extremes
Cold
threshold
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Average
More
record
hot
extremes
Hot
threshold
E. Palin
This has also now been done for the
Australian summer of 2012/13.
Such extreme summer temperatures as 2013 very
likely at least 2.5 times more probable due to human
influence. Lewis et al, GRL, 2013.
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Explaining extreme climate and weather events
of the previous year from a climate perspective
Tom Peterson, Martin Hoerling, Peter Stott,
Stephanie Herring.
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Extreme event
Evidence for anthropogenic
influence ?
US heatwave
YES
Hurricane Sandy storm surge
YES
September Arctic sea ice minimum
YES
February European cold spell
NO
Wet UK summer
NO
Iberian winter drought
YES
Rainfall deficitits in Eastern Kenya
and Southern Somaliia
NO
North China floods, July
NO
Heavy rainfall in Southwestern
Japan, July
NO
Extreme rainfall over Eastern
Australia, March
YES
Extreme rainfall, Goldan Bay, New
Zealand, December 2011
YES
US drought
NO
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Summer 2012
Wettest since
1912
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Summer 2012
• Long term natural cycle
• Atlantic sea surface temperature
• Shifts jet stream
% of 1981-2010 average - May to September
140
130
120
110
100
90
80
70
2010
2005
2000
1995
1990
1985
1980
1975
1970
1965
1960
1955
1950
1945
1940
1935
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1930
1925
1920
1915
1910
60
Iberian winter drought
Trigo et al, 2013
A tendency towards a drier Mediterranean driven by
anthropogenic emissions of greenhouse gases and aerosols,
although modulated by the North Atlantic oscillation
The North Atlantic Oscillation
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The North Atlantic Oscillation
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Winter 2009/2010
Rainfall patterns are projected to
continue to change leading to more
frequent droughts in some regions
and more floods in others.
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Arctic sea ice in September
could be gone by 2050
1950
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2000
2050
2100
Sea level rise will continue
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The extent of climate change
depends on future
greenhouse gas emissions
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Human influence on the
climate system is clear
• Better understanding of the changing risks of extreme
weather will help people cope with the effects of
anthropogenic climate change.
• Extreme weather and seasons result from the interplay of
natural climate variability and anthropogenic climate
change.
• At the Met Office we are developing an “operational
attribution” system to assess the risks of such extremes
on a regular basis.
• A new annual report provides puts extreme weather from
last year in different regions of the world into the context
of natural climate variability and anthropogenic climate
change.
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