Latest climate scienceImplications for Wales
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Vicky Pope
Sept 2013
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Latest climate scienceImplications for Wales
• Basics of climate – theory and observations
• Why has there been such extreme weather recently?
• Is this the sign of things to come? Impact on projections
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Heat energy re-emitted to warm Earth
Heat energy passes through atmosphere
Heat energy radiated from Earth
Sun’s energy absorbed by atmosphere
Sun’s energy reflected by Earth
Sun’s energy reflected by clouds
Incoming energy from the sun
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Water evaporates from rivers lakes and the ocean
Water condenses to form clouds
Loss of water from plants, soil, animals and people
Water returns to land as precipitation
Water carried downhill by rivers
Water seeps into ground and flows to sea
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Hadley cell
Ferrel cell
Polar cell
Trade winds
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Evidence: the Greenhouse effect
The average temperature of the Earth is 14 ºC. Without the blanket of greenhouse gases it would be –18 ºC.
The water vapour feedback enhances the warming due to man-made greenhouse gases
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INCREASING – Atmospheric carbon dioxide
1850 1900 1950 2000
380
360
340
320
Atmospheric carbon dioxideA
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arb
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CO2 has risen by 107ppm (38%) from pre-industrial levels of 280ppm.
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INCREASING – Land surface temperature
Global temperatures have increased decade on decade since the mid 20th century, consistent with the basic physics.
The water vapour feedback enhances the warming due to man-made greenhouse gases
1850 1900 1950 2000
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INCREASING – Sea surface temperature
1850 1900 1950 2000
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INCREASING – Tropospheric temperature
1850 1900 1950 2000
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INCREASING – Specific humidty
1850 1900 1950 2000
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INCREASING – Sea level
1850 1900 1950 2000
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DECREASING – September Arctic sea ice extent
1850 1900 1950 2000
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DECREASING – Glacier mass balance
1850 1900 1950 2000
Why has there been such extreme weather recently?
19
Christidis and Stott, Met OfficeMassey et al, University of Oxford, Met Office
• The odds of the cold December 2010 temperatures have halved as a result of human-induced climate change
• Unusual circulation patterns can still bring very cold winter months
UK cold winter December 2010 Coldest December on record in Wales -3.8 degCRecord minimum: -18.0 deg C at Llysdinam (Powys) 28 November 2010
Oct 2010 – March 2012 Rainfall% of 1971-2000 average
2 dry winters
Extreme weatherFrom drought...
Summer 2012 Rainfall% of 1971-2000 average
2 dry winters
Extreme weather...to flood
Wettest June on record (180% of average)
3rd wettest summer on record for Wales (240% of average)
Is this the sign of things to come? Impact on projections
Representative comparison between CMIP3 and 5
models (scaled using simple models)
Climate model projections CMIP5Global surface temperature (single study, AR5 will contain synthesised results)Knutti and Sedláček, 2013
Climate model projections CMIP5Preciptation (single study, AR5 will contain synthesised results)Knutti and Sedláček, 2013
December - February
June - August
Stippling – high robustnessHatching – no significant changeWhite – models inconsistent
Important processes for UK weather and climate
• North Atlantic weather – slow changes in ocean surface temperatures
• Tropical Pacific weather – El Nino• Arctic Sea ice retreat• Solar variability
Atlantic Multidecadal Oscillation
Video of the jet streamhttp://www.metoffice.gov.uk/learning/wind/what-is-the-jet-stream?rel=0
Low UV from the sun leads to easterly winds and cold conditions in Europe and the US
Global focus
Global average temperatures (including latest observations)
Hiatus in warming: Possible contributions Met Office Hiatus report (IPCC AR5 will contain synthesised results) http://www.metoffice.gov.uk/research/news/recent-pause-in-warming
• Natural variability: models have 10-15 year periods with no warming or even cooling
• Incoming radiation: reduction of 0.6 Wm-2 needed to explain pause. Maximum possible is 0.3 Wm-2
• Recent decrease in stratospheric water vapour: traps less heat: up to 0.1Wm-2
• Change in man-made aerosols: little net effect
• Volcanic eruptions: not enough during period
• Extended solar minimum: less than 0.2Wm-2
• Ocean changes: could be a major contributor • Ocean heat content, sea-level rise observations: Earth system continued
to absorbed heat
• Additional heat appears to have been absorbed in the ocean.
• Increased exchange to deep ocean appears to have caused at least part of the pause in surface warming,
• Observations indicate that Pacific Ocean may play a key role.
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The impact of a global temperature rise of 4 ºC
Change in temperature from pre-industrial climate
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Current City population • 3-10 million • 10-20 million
Meltingice
OceanAcidification
Rainforestloss
Reduced crops
Forestfire
Increased drought
Stronger tropical storms
Methane release
More heatwaves
Steadily increasing CO2 (similar to BAU scenario by 2100). Excludes deforestation and fire
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Represent the earth by a grid of squares, typically of length 100 km or smaller. Atmosphere and oceans are divided into vertical slices of varying depths. 3-dimensional picture of the state of the atmosphere and oceans. Integrate equations of motion and thermodynamics forward in time. Conserve heat, moisture, salinity and momentum
Fundamentals of weather and climate modelling
Best long-term climate models, UKCP09
State-of-art seasonal
model
Current global weather forecasting
Current UK weather
forecasting + ground-breaking
climate work
Mountains (130km grid)
Mountains (60km grid)
1.5km resolution climate modelResolution of Welsh terrain
Mountains (25km grid)
Mountains (1.5km grid)
Important processes
Rainfall Oct to March
Video of the jet streamhttp://www.metoffice.gov.uk/learning/wind/what-is-the-jet-stream?rel=0
Sea Ice
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EP2 Headline results
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