Transcript What are the Different Types of Seaweeds, and How Do They

How Does Heat Transfer Affect Climate?
– The Horse Latitudes and The Intertropical Convergence Zone
• Dry air sinks at about 30⁰N and 30⁰S latitudes  locations of deserts; great
evaporation from ocean; often lack winds  “Horse Latitudes”
• The Intertropical Convergence Zone: ~ equator; trade winds converge, warm air
rises; often lack winds  “Doldrums”
– Ocean Currents Affect Regional Climates
• Example: San Francisco cooled by California Current, while Washington D.C.
warmed by Gulf Stream (both cities at same latitude)
– Monsoons and Cyclones
• Monsoons: seasonal wind patterns caused by heating and cooling of continents;
in summer, warm air rises over land, draws in moist warm air from ocean,
which rises and cools  heavy rainfall; common in India, Southeast Asia
• Cyclones: rotating storm systems around low-pressure center (eye of storm);
tropical cyclones (typhoons in Pacific, hurricanes in Atlantic) fueled by
warm water, draw in moist tropical air; extratropical cyclones form where
polar winds meet the westerlies (lead to unstable air, thunderstorms);
cyclones rotate counterclockwise in the Northern Hemisphere, clockwise in
the Southern Hemisphere
– Clouds and the Hydrologic Cycle
• The Water (Hydrologic) Cycle: includes evaporation, condensation, precipitation
• Clouds (condensed water vapor) trap heat but also reflect energy (white)
Figure 8-20
Figure 7-9
Figures 8-21 and 8-22
Figure 7-16
Figure 8-4
Figure 8-5
Is the Ozone Layer Still Threatened?
• Stratospheric Ozone Depletion
– Ozone a component of smog in lower atmosphere; in
upper atmosphere, shields Earth from UVB radiation
– Chlorofluorocarbons (CFC’s) lighter than air, rise to
upper atmosphere, where they stick to ice crystals;
each molecule able to destroy many ozone molecules
(most during summer); Antarctic ozone hole detected in
1985, Arctic ozone hole detected in early 1990’s; global
ozone declining (ex. Toronto, UV increased 5.3% per
year from 1989-1993)
– Effects of UV: skin cancers, stress immune systems,
coral bleaching, reduces productivity of phytoplankton
– International Response: Montreal Protocol (1987) phased
out production of CFC’s, but existing CFC’s stable
(long-lived; ex. freon)
Figure 8-2
Figure 8-3
What Evidence Supports the Theory of
Global Warming?
• A theory, supported by multiple lines of evidence (that
current observed warming trend is due largely to
human-caused influences)
– Greenhouse Effect: greenhouse gases trap warm air in lower
atmosphere (esp. carbon dioxide, methane, and carbon
monoxide)
– Combustion of fossil fuels adds CO2 to atmosphere; deforestation
is often via burning (combustion) and loss of trees reduces
uptake of carbon dioxide; more cattle  more methane
(proposal for effort to measure this effect laughed out of U.S.
Congress as “cow-fart study”)
– Observed: rise in atmospheric CO2; global atmospheric and
oceanic warming; rising sea levels (Tuvalu, Kiribati, other
Pacific islands flooding); retreat of mountain glaciers, Arctic ice
thinned, Antarctic ice shelves apparently breaking up;
tropical diseases and insects spreading; regional climates
shifting, affecting species ranges and causing extinctions;
widespread coral bleaching; lower heating costs on the
“bright side”
Figures 16-2 and 16-3
What are the Predicted Effects of Global
Warming and the International Response?
– Predicted: approx. 6°C rise by 2100; warming of tundra releases more
CO2, melting of polar ice reduces reflection of energy by white ice and
accelerates melting (vicious cycles); melting of West Antarctic ice sheet
would raise sea level by 20 feet, flooding London, New York, Florida,
New Orleans (among others); cooling of Northern Europe due to likely
disruption of Gulf Stream current by melting Arctic (more icebergs will
also endanger ships); rise in intensity of tropical cyclones due to
warmer water temperature
– Debate among specialists is mainly regarding the ocean’s role in the
absorption of CO2 (but note that levels steadily rising in atmosphere,
corresponding to steady rise in combustion/emissions)
– Public debate mainly regarding Earth’s natural cycles of warming/cooling
and lack of “definite proof”; also regarding economic costs of reducing
carbon emissions
– International Response: Rio Earth Summit (1992) – agreed that Global
Warming is serious problem and response needed by year 2000
(George Bush Sr. signed); Kyoto Accord (1998) – signed by nearly all
nations; Copenhagen (Dec. 2009); Adapt (?): sea walls planned in
Thailand and Bangladesh