Outline post industrial climate change
- Global temp rises around 1 1900-2010
- Artic sea ice cover dropping rapidly
- Sea level rise since 19000 – 0.2m
- Hotter and wetter – esp. in higher latitudes
Describe sea level change
- Average level of ocean key source of information in global climatic trends
- Redrock rising and sinking
- Ocean basins sinking
- 17cm rise in sea level since 1880
- Caused by land ice melting and ocean warming and expanding
Outline changes in surface temp
- Temp warmed by about 0.8 over last century
- Problem of population growth around hot areas – urban heat
- Dramatic rises in temp over last few hundred years
Describe the recent warm summers
- Tree ring records to research temp for last 2100
- Summer temp during last 30 years have been high
- No evidence of any period in the last 2000 years being as warm
What is El Niño-southern oscillation (ENSO)?
- El Niño accompanies high pressure in western pacific and unusually warm oceans
- La Nina – opposite pattern
- Pattern of el Niño seasons/years
What is the North Atlantic Oscillation (NAO)?
The North Atlantic Oscillation is a weather phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level between the Icelandic Low and the Azores High
Outline positive NAO phase
- Strengthening of high-pressure cell over Azores
- Weakening of Icelandic low
- Accentuates pressure gradient between cells
- Warmer, wetter conditions in NW Europe and e USA
- Greenland, Canada and Med cooler and drier
Outline negative NAO phase
- Gradient between Azores high and Icelandic is reduced
- Situation reversed
- Warmer, wetter conditions in Med, Greenland and Canada
What caused the NAO?
- Driven by changes within the atmosphere
- No discernible periodicity
- Displays interdecadal and inter-annual variability
- NAO conditions can persist for many years
What is the Atlantic multi decadal oscillation?
- Identified in 1994
- Marked by variations in North Atlantic sea surface temp
- Linked to small changes in N Atlantic branch of thermohaline circulation
- Quasi cycle – 50-90 years
- Linked to variations in air temp and rainfall throughout the Atlantic region
What is the pacific decadal oscillation?
- Has spatial distribution similar to ENSO
- Positive phase
- Sea surface temp warmer in tropics
- Cooler in west-central north pacific
- Negative phase
- Can be deconstructed based on SST reconstructions
- Possible cycle 20-30-year cycle – linked to ENSO
What are the causes of post-industrial climate change?
- Solar component – changes in sun strength
- Volcanic eruptions – not cause of changes
- Internal variability – random and does not cause great changes
- Anthropogenic component – cause of change in temp
What are the potential natural causes of recent warming?
- Great el Niño periods
- Warmer periods expected
- Large volcanic eruptions cool temp – difficult to measure due to sulphur content
- Natural variations have small effect – cannot affect global trend of rising temp
- Cannot be considered responsible for changes
What are anthropogenic forcing factors?
- Carbon dioxide - went from 280 ppm to 400ppm
- Methane - half occurrent emissions are anthropogenic
- Nitrogen
How can you model the climate?
Models must use natural and humans forcings can reproduce t readings
How has the transition from nature to human caused environmental change?
- Balance between difference spheres changing
- Humans more dominate than natural forces
What are the three preferred candidate dates for the start of the anthropocene?
1) Early anthropogenic hypothesis at 5020 cal yr BP
2) Boundary at 1610 AD representing the collision of the old and new world, defined by the pronounced dip in atmospheric carbon dioxide
3) Bomb peak at 1664 AD characterised by the peak in atmospheric radiocarbon from annual tree-with atmospheric carbon dioxide from Hawaii, post 1958 and ice core records pre 1958 and global temp anomalies
What is the early anthropocene hypothesis?
- Global concentrations of Co2 and methane in ice cores rose from early Holocene
- 80% of anthropogenic GHGs emitted before ad 1750
- Slight warming through the Holocene buffered and natural solar insolation and stopped onset of glaciation
What are the cumulative global impacts of the anthropocene?
- Cumulative
- Local and regional impacts caused by human actions – deforestation
- But becoming global problems – land surface reflectance as they aggregate
What are the systematic global impacts of the anthropocene?
- Systematic
- Local and regional actions that affect global systems directly, (e.g. carbon emissions at atmosphere) which are now producing local and regional impacts (heatwaves, storminess)
How has climate change impacted the hydrosphere?
- Massive changes to both movement and storage of freshwater
- Implications of changing pH in oceanic waters
- How much carbon dioxide it can store?
How has climate change impacted the biosphere?
- Years of extensive land use
- Not many wild areas left
- Mega fauna extinctions at the start of the anthropocene
- Populations declined by 40%
How has climate changed impacted the lithosphere?
- Human made landscapes - takes material away
- Erosion causes sediment yields and influxes
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Earths Global Systems9
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Earth Surface Science and its Origins23
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Plate Tectonics27
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Oceans29
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Atmospheric Circulation28
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The Critical Zone25
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Soil29
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Water19
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Weathering14
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The Catchment System19
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Fluvial Systems15
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Drylands25
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Coastal Systems60
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Glacial Environments11
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Permafrost and Preglacial Environments24
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Climate Change42
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Future Environmental Change23
