This preview shows page 1. Sign up to view the full content.
Unformatted text preview: Chemical Cycles: •Greenhouse Effect: Cause and effect
•Chemical Cycles: CO2 and O2
•Chemical Fluxes: CO2 and O2
•Proxies for climate change: Isotopes Greenhouse Effect & Global Warming • Global Warming
• World wide increase in avg. Temp.
Cause = greenhouse effect What is climate change 1 Greenhouse Effect: Greenhouse Effect: Simply put …
• Anomalous heating of atmosphere
• • E from surface absorbed by GH gas
GH gas re-radiate the E, heating atm. & surface Natural process! W/out it, 30 ºC cooler Goldie Locks Effect • • If Earth was 17% closer to sun, then liquid water would not
form on surface. Thus no CO 2 dissolved in oceans and E would
be hot enough to melt Lead … .Like Venus is.
If Earth was further from sun, then solar radiation would be
lower and E would be and ice house like Mars. Observed increase in GH gases
Mona Loa Ice core data 2 Observed Effects of GH Global Warming by 0.3-0.6 ºC!
Receading Glaciers & Ice caps - past 100 yr
Rising Sealevel - 18 cm in 100 yrs (greatest rate in E history)!
• Some would argue the Global Warming trend is
natural - not forced by human activity.
• Some argue that solar activity is
linked to global warming.
In the geologic past this is true:
Global trends in temperature
proxies sometimes correlate
with solar activity and
cosmogenic nuclide abundances
• • • E.g.
E.g. Midieval Warm period
(900-1400 A.D.) and the Little
Ice Age (1500-1800 A.D.)
However, this is not true of
today ’s warming trend: there is
no measurable increase in 36 Cl
abundance over the past
Measurable variability in solar
activity after 1978 accounts for
~0.01% of total irradiance. 3 Some would argue the Global Warming trend is
natural - not forced by human activity. • Long-term trends in temperature proxies sometimes correlate with Earth orbital cycles
called Milankovitch cycles (e.g. the last ice age) • The cause of today ’s climate change is the greenhouse effect! However, this is not true of today ’s warming trend - it is much to rapid to correlate with
variations in Earth ’s orbit • • This is the overwhelming consensus of the scientific community. AGU ’s position Observed Results of GH
• Global Warming by 0.3-0.6 ºC (avg surface T)!
Receding Glaciers & Ice caps - past 100 yr
Rising Sea level - >20 cm in 100 yrs (greatest rate in
• Averaging ~1.8 mm/y from 1950 to 2000
Rising faster today
Mostly from thermal expansion of ocean, not added
melt water Observed results of GH: Loss of Sea Ice • Effects polar bears: 2006 study showed predation and cannibalism within Beaufort
Sea population. In past 5 years, 43% of cubs survive compared to 65% between 19801990
•Barnes Ice Cap on Baffin Island is thinning (0.12 m/y ‘70-’84) accelerating (1.0 m/y
‘04- ’06). Correlates with increases in number of positive degree days (warming). 4 Observed results of GH: Increased hydrologic cycle Cyclone activity • Increase in number of category 4 and 5 cyclones over past 35 yrs.
Increase in the duration of cyclones over past 35 yrs.
Extreme rain events during Indian Monsoon between 1951-2001
• 10% Increase in frequency of intense rain events (>10 cm/day)
• Increasing magnitude of intense rain events
• Total amount of precipitation not increasing
• • Global Dimming - may have muted global warming
• Aerosols in atmosphere
increase Earth ’s albedo
• • Carbon aerosol Particles reflect sunlight Between 1960 and
~1985, increase in
‘dimming ’ of ~3 to 6% S-dioxide aerosol •~1985 to early ‘90s Earth began to brighten again
~1985 Total aerosol –Decreasing aerosol emissions
–Improved air-quality regulations
–Reduced Pinatubo (volcanic) aerosols - 1991 eruption Brightening and Global Warming • ~1985 to early ‘90s Earth began to brighten again
Decreasing aerosol emissions
Improved air-quality regulations
• Reduced Pinatubo (volcanic) aerosols - 1991 eruption
• • This correlates with the rapid increase in
temperature during the 1990s 5 Predicted Effects of Global Warming
• Increasing Global
climate will require
GH gasses remain in
atm for centuries
• Must stop emissions
to prevent warming
beyond today ’s
• Not possible given
energy needs and
• Predicted Effects: Shifts in climate zones Predicted Effects: Continued rise in sea level •
• Consider how this will effect coastal communities.
Bangladesh: 1000 people/km 2 6 Predicted Effects: Extreme Weather Heightened hydrologic cycle (greater rainfall and snowfall)
Recall Current Observations of Cyclones and Monsoon events above. •
• Predicted Effects: Negative impact on marine ecosystems
Increasing CO 2atm increases
amount of CO 2 in oceans.
This decreases pH of oceans
(making them more acidic)
Harmful to Plankton and
• • These form the base of the
marine food web! Prediction - Harmful
conditions will develop first
in southern ocean within
decades. • Nature, 2005 Predicted Effects: Negative impact on marine ecosystems • Measured decline in
productivity in all oceans
Area of low productivity
(<0.07 mg chlorophyll/m 3).
Area is expanding in all
• Area expanding fastest in
• 7 Predicted Effects: Negative impact on marine ecosystems • Observed change in phytoplankton productivity with latitude in
both N. Atlantic and E. Pacific
• Productivity migrating to high latitude. Direct effect on food webs,
especially large mammals and fish who feed on zooplankton Predicted Effects: Negative impact on marine ecosystems
• Global warming and resulting changes
in ocean chemistry (increasing acidity)
lead to negative effects on Coral
Coral is a symbiotic relationship
between the coral polyp and algae
Coral Bleaching - coral expel their algae
due to change in environment.
This negatively impacts the vitality of
the reef community.
Recent results suggest this may not lead
to the ‘death’ of coral. It is suggested
that this, in-fact, opens a niche for
another algae more capable of
surviving. Predicted Effects: Negative impact on terrestrial ecosystems •
• Alpine Frogs - as climate warms, they must migrate up-mountain to reach cooler climate.
Thus, the available habitat is decreasing.
Tropical frogs - fungus growing on skin is killing them. Increased humidity is favoring the
growth of fungus.
Polar Bears in competition with Grizzly Bears around Hudson Bay - Polar Bears don’t
hibernate. Will they eat sleeping grizzly cubs? Polar bears eat seals, will they adapt?
These are just a few examples of many - we are currently experiencing the greatest rate of
extinction on Earth (i.e., we are in the midst of the most rapid mass extinction in Earth
history). 8 9 Negative feedback
- Hot-house increases weathering
(of silicates) consumption of CO2
- Hot-house causes anoxic bottom
water & inhibits decomposition CO2 (from proxies) over Time
1. High CO 2 in Early Phanerozoic
•few primary producers
•(no forest beyond coasts, few
•Was it hot? Likely not
•low solar output. So warm
not hot. 2. CO2 Decline in Devonian
•Land plants evolve to
forest higher elevation
•more plants - less CO 2 3. Carboniferous: CO2
from increased mountain
building during assembly
•ICE HOUSE 10 4. CO2 rise in Mesozoic
•mountain building slows
•weathering rates slow
•Evolution of coccolithophores and
•increased calcareous ooze
•increased CO 2 flux from
subduction as these sediments
subduct Infer Oxygen rich Carboniferous from Heavy C isotopes 11 Moderate Temp. vs . Warm Poles - no deep circulation 12 ...
View Full Document
- Spring '11