GEOG 2300:CHAPTER 11
25 Cards in this Set
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Climate: Past, Current, and Future
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-current: weather station data, remote sensing data, numerical modeling using GCM
-past (paleoclimatology): proxy indicators (ice-core data, sediments, coral reefs, ancient pollen, tree rings)
-future: numerical prediction using GCMs
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Methods for Long-Term Climate Reconstruction
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-paleoclimatic techniques (proxy methods) yield long term records that span 100,000s to millions of years ago (ocean bottom sediment cores; ice cores from thickest ice sheets)
-basis for long-term climate change reconstruction is isotope analysis
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isotope analysis
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-technique that uses the atomic structure of chemical elements, specifically the relative amounts of their isotopes, to identify chemical composition of past ocean & ice masses such as oxygen isotope analysis, ocean sediment cores & ice cores
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Oxygen isotope analysis
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-dating method, uses ratio of O-18 to O-16
-near the poles
-atmospheric water vapor is increasingly enriched in O-16
-heavy O-18 rich water vapor condenses over mid-latitudes
-water slightly enriched in O-16 evaporates from warm sub-tropical waters
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Methods for short-term climate reconstruction
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Techniques include:
–carbon dating
–lake cores
–growth rings
- trees
- speleothems
- corals
*short term=100s or 1000s of years
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Tree Rings
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-bands from trees of different ages can be correlated to build a longer record.
-WIDE BANDS = plenty of water; better growing conditions
-NARROW BANDS = tree was stressed (drought, extended cold periods)
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Speleothems
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- Dripstone features found in caverns
-rate of growth depends on: amount of rainwater percolating through the rocks that form the cave; its acidity, and the temp/humidity conditions of the cave
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Mechanisms of Natural Climate Fluctuation
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-Solar variability
-Earth's orbital cycles
-Continental position and topography
-atmospheric gases and aerosols
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milankovitch cyles
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eccentricity
obliquity
precession
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eccentricity
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-variations in the shape of Earth's orbit
-100,000 year cycle
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Obliquity
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-tilt of the earth's axis
-41,000 year cycle
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Precession
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-wobbling of the Earth's axis
-every 26,000 years
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Climate feedbacks
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-processes that respond to a distribution in earth's heat balance
-processes that either amplify or reduce climatic trends, towards either warming or cooling
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Earth's Carbon budget
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-Carbon moves through Earth system, including atmosphere, ocean, living things, sediments
-C sources release C
-C sinks store C
-Carbon budget describes relative balance between sources & sinks
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Water vapor feedback
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-function of the relationship between air temp and water vapor capacity
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carbon-climate feedback
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-temperature change induced by orbital factors affects atmospheric greenhouse gas concentrations
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CO2 weathering feedback
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-operates on extremely long time scales
-negative feedback affect chemical weathering of exposed rock
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Thawing Arctic Permafrost
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-natural carbon balance (in= plants photosynthesizing; out= plants respiring)
-more carbon in than out (in= plants growing faster; out= more old carbon respired)
-more carbon out than in (in=plants still growing faster; out=even more old carbon released)
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Evidence of Present Climate Change
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-atmospheric temp
-ocean temps
-melting ice (glaciers, permafrost, sea ice)
-sea level rise (happening more quickly than expected; melting land ice; thermal expansion of water)
-increasing humidity (temp, precipitation, storm intensity)
-extreme events (heatwaves, heavy rainfall even…
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Causes of Present Climate Change
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-contributions of anthropogenic greenhouse gases and effects on radiative forcing
-carbon dioxide
-methane
-nitrous oxide
-halogeneated gases
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Scientific Consensus
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-IPCC say 95-100% certain that human activities are the primary cause of the current climate change
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Climate models and future projections
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climate models: general circulation models, need to make assumptions, tested numerous times against knowing conditions (current climate, past climate, future climate)
future projections: 6 emission scenarios, temp, sea level, polar regions, weather patterns, plants and animals, already l…
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sea level rise
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-sea levels are rising faster now than in the previous two million years; the rise will continue to accelerate; regardless of emissions scenario, even w/ strong climate mitigation
-due to inertia in the system
-more likely frequent storm surges as a result of rise
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USGCRP
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-U.S. Global Change Research Program
-coordinates and integrates federal research on changes in the global environment and their implication for society.
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Mitigation Measures to Slow Rates on Climate Change
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-reduce carbon emissions
-plant trees and expand green spaces in urban areas
-alter agricultural practices to retain more carbon
-increase motor vehicle fuel-efficiency standards
-promote efficient water use
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GEOG 2300: CHAPTER 12