Transcript The Atmosphere climate, climate change, and ozone depletion

The Atmosphere
climate, climate change, and
ozone depletion
Chapter 20
Hurricane Katrina
• August 29,2005 made landfall in the Gulf
Coast east of New Orleans.
• Day before was a category 5, by landfall
was a category 4 (131-155 mph winds).
• Costliest storm ever: $80 billion in
damage.
• 1300 deaths in four states.
• 1 of 27 named storms that year.
The cycle of storms
• 2005 part of a multi-decade cycle of ideal
conditions for spawning hurricanes.
– Abnormally warm surface temps.
– Low wind shear.
• Studies suggest there is a link between
global warming and hurricanes.
– Links: atmosphere, oceans, human activities,
and hurricanes.
Lesson 20.1
ATMOSPHERE AND WEATHER
The Troposphere:
• Area closest to Earth
– Where weather occurs.
– Moderates the flow of energy to Earth
– Involved in the biogeochemical cycling of
many elements and compounds.
• Capped by the tropopause.
The Stratosphere
• Above the tropopause
• Temperatures increase with altitude
• Little vertical mixing of air and no
precipitation from it
– Substances can remain there (trapped) for a
long time.
• Location of ozone layer
• Capped by the stratopause
Gases of the Atmosphere
• Most crucial gases
– Oxygen
– Nitrogen
– Carbon
– Sulfur
– Water
Weather vs. Climate
Weather
Climate
• Day-to-day variations in
• Result of long-term
temperature, air pressure,
weather conditions.
wind, humidity, and
precipitation.
• Mediated by the
atmosphere.
•The study of both weather and
climate (atmosphere) is called
meteorology.
Air currents
Vertical
• As heat is radiated back
toward the atmosphere
the gases near the Earth
become heated,
expanding and rising.
Horizontal
• Air that must flow in to
replace the rising air
causes horizontal airflow
(wind).
•Convection currents bring us the day to day changes in our
weather as they move in a general pattern from west to east.
•Rising air creates high pressure area in atmosphere and low
pressure on Earth.
•Winds tend to flow from high to low pressure regions.
Hadley Cell
• The ultimate source of the horizontal flow
is cooler air that is sinking and the
recombination produces the Hadley cell.
Jet Streams
• Earth’s rotation and air-pressure gradients
generate “rivers” of air.
Fronts
• Air masses of different temperatures and
pressures meet at boundaries called fronts.
Lesson 20.2
CLIMATE
Climate and biomes
• The different temperatures and moistures
in different parts of the world create the
different ecosystems (biomes).
– Tundra
– Desert
– Rainforest…
• These reflect the different adaptations of
plants, animals, and microbes that will be
present.
Humans and climate
• Humans can adjust to practically any
climate (short of the brutal conditions of
mountain tops or burning deserts)
• Other organisms in a region are adapted
to a particular climate and any major
changes present a major threat to the
structure and function of the existing
ecosystem.
Since 1880…
• Global average temperature has shown
periods of cooling and warming, but the
general pattern has increased 0.8˚C (1.4 ˚F)
Warming trends
• There have been two
warming trends in the 20th
century.
– 1910-1945
– 1976-present
Proxies
• Measurable records that can provide data
on factors such as temperature, ice cover,
and precipitation.
– Additional proxies include:
•
•
•
•
•
•
Tree rings
Pollen deposits
Changes in landscape
Marine sediments
Corals
Ice cores
Why warming then ice ages?
• The most likely explanation for the major
oscillations is the existence of known
variations in Earth’s orbit.
– Orbital configuration varies the amount of solar
radiation over different continents and latitudes
substantially.
• These intervals take place according to
several periodic time intervals called
Milankovitch cycles.
– 100,000 years, 41,000 yrs. And 23,000 yrs.
Younger Dryas
• Within the major oscillations of
Milankovitch cycles are rapid climate
fluctuations called Younger Dryas.
– 10,700 years ago the temperature in the arctic
region rose 7˚C in 50 years!
– Tremendous effect on living organisms
El Nino
• Occurs when a major shift in the atmospheric
pressure over the Central Equatorial Pacific Ocean
leads to a reversal of the trade winds that
normally blow from an easterly direction.
• Warm water spreads to the east, the jet stream
strengthen and shift from their normal courses,
patterns in precipitation and evaporation are
affected.
• Most severe El Nino occurred 1997-2000.
– 1998 shifted to a La Nina.
– Global damage approx. $36 billion, 22,000 deaths.
La Nina
• Reverse of El Nino:
• Easterly trade winds are reestablished
with even greater intensity, upwelling of
colder ocean water in the eastern Pacific
from the depths replaces surface water
blown westward, the jet streams are
weakened, and weather patterns are again
affected.
Thermohaline
• Refers to the effects that temperature and
salinity have on the density of water.
• Conveyer like system
– Salty water from the Gulf stream is carried
northward on the surface and is cooled by the
arctic air currents. Cooling increases density of
the water, which then sinks to depths of 4,000m
(the North Atlantic Deep Water NADW). This
deep water spreads southward where it is joined
by the northward Antarctic waters.
Thermohaline
Thermohaline
• When the conveyer is interrupted, climate
changes abruptly.
• North Atlantic marine sediments show
evidence of the periodic invasion of
icebergs from the polar ice cap that
supplied huge amounts of fresh water as
they melted-called Heinrich events.
Lesson 20.3
GLOBAL CLIMATE CHANGE
Factors affecting climate
Internal
• Oceans
• Atmosphere
• Snow cover
• Sea ice
External
• Solar radiation
• Earth’s rotation
• Slow changes in orbit
• Gaseous makeup of the
atmosphere
Greenhouse Effect
•The interior of a car heats up when the car is sitting in
the Sun with the windows closed. Sunlight comes
through the windows and is absorbed by the seats and
other interior objects thus converting light energy to heat
energy in the form of Infrared radiation. “IR” is trapped
by the glass and cannot leave the car, causing the
internal temperature to rise.
•Earth’s “glass” is the CO2, water vapor, and other gases
in the atmosphere.
Greenhouse gases
• Greenhouse effect was first recognized by
Jean-Baptiste Fourier in 1827.
• Without greenhouse gases the Earth
would be too cold to inhabit.
• Ozone in the troposphere has a positive
forcing effect (leads to warming).
– Negative forcing leads to a cooling effect.
IPCC
• Intergovernmental Panel on Climate Change.
• 1988, Established by the UN Environment Program and World
Meteorological Society.
• Established three working groups:
– One to assess scientific issues (working group I)
– One to evaluate the impact of global climate change and the prospects
for adapting to it (working group II)
– A third to investigate ways of mitigating the effects (working group III)
• Groups consist of more than 2000 experts in appropriate fields
from over 100 countries.
• The work of the IPCC has been guided by 2 basic questions:
– Risk assessment: Is the climate changing and what is the impact on
society and ecosystems?
– Risk management: How can we manage the system through adaptation
and mitigation?
IPCC findings:
• January 2001 third assessment released
– Bullets on pages 517-518
• February 2007 fourth assessment released
by group I
– Global climate change is now occurring, it is
an outcome of the rising levels of
anthropogenic greenhouse gases, and the
global impacts of the expected future changes
will be unprecedented and severe
Carbon Sinks
• Areas that absorb CO2 and keep it from
accumulating at a more rapid rate in the
atmosphere.
– Oceans (uptake of CO2 by phytoplankton)
– Terrestrial biota
– See figure 20-11 on page 520
The greenhouse gases
• Most abundant
– Water vapor
• Concentration in the atmosphere is quite variable
• Rapid turnover in the lower atmosphere
• Does not accumulate over time (unlike the other
gases)
• Other greenhouse gases
– Methane (CH4)
– Nitrous oxide (N2O)
– Chlorofluorocarbons
ACIA
• Arctic Climate Impact Assessment
• 300 scientists and elders from six
indigenous communities, funded by the
National Science Foundation and the
National Oceanic and Atmospheric
Administration
• Published in November 2004
• Key findings (bullets pages 528-529)
Lesson 20.4
RESPONSE TO CLIMATE CHANGE
Responses to climate change
1. Adaptation: we must anticipate some
harm to natural and human systems and
should plan adaptive responses to lesson
the vulnerability.
2. Mitigation: take action to reduce
emissions
• Skeptics base their arguments on the fact
that we don’t know much about the role
of oceans, clouds, biota, and the
chemistry of the atmosphere.
FCCC
• Framework Convention on Climate
Change
• Document signed by the heads of state at
the UNCED Earth Summit in Rio de
Janeiro in 1992
• Agreed to goal of stabilizing greenhouse
gases in the atmosphere starting by
reducing greenhouse gas emissions to
1990 levels by 2000.
FCCC
• Proposed three principle:
– Precautionary principle: though we may not
know for sure, we must take action just in
case.
– Polluter pays principle: polluters should pay
for the damage their pollution causes.
– Equity principle: The richest produce the
most CO2 and therefore should be the ones
taking the action for the consequences paid by
all.
Kyoto Protocol
• Third conference of parties to the FCCC
met in Kyoto, Japan in December 1997 to
create an agreement on reducing
greenhouse gases
• 38 nations agreed to reduce emissions of 6
GHG’s to 5% below 1990 levels by 2012.
– Signers have a lot of flexibility on deciding
how to meet the goals.
– Kyoto expires in 2012
UN climate Control Conference
• Agreed on two things:
– There will be future meetings to produce
new, tougher set of binding limits on GHG’s
that will take effect after 2012.
– Broader dialogue towards reaching
nonbinding accords addressing global climate
change.
• George W. Bush opposes Kyoto for two
reasons:
– It exempts the developing countries (unfair)
– Cause serious harm to US economy
GCCI
• February 2002
• Global Climate Change Initiative
• Reduction of 18% in emissions intensity
(ratio of GHG emissions to economic
output) over the next 10 years
CCSP
• July 2003, Bush administration report
• Climate Change Science Program
– Put sharper image on the government’s
approach to climate research.
– Seeks to address a number of issues in climate
science, such as the natural variability in
climate
NCCTI
• National Climate Change Technology
Initiative
• Provides support for research and analysis
of GHG’s and technologies to lower GHG
emissions.
Likely consequences
• Crop yields are likely to be reduced in
tropical and subtropical areas
• Water is likely to become more scarce in
many regions already suffering
• Increased heat and moisture in many
regions leading to increased infectious
disease and potentially lethal heat waves
• Increased intensity and frequency of storm
events (flooding)
Lesson 20.5
DEPLETION OF THE OZONE LAYER
Ozone Layer
• Protects Earth from harmful ultraviolet
radiation.
• Depletion mainly caused by human
technologies, specifically the CFC’s
• Read table 20-5 on page 534.
• Because the ozone layer blocks out more
than 99% of the UV radiation it is
commonly referred to as the Ozone Shield.
Formation of Ozone
• Formed in the stratosphere when UV
radiation acts on oxygen molecules. The
high-energy UV radiation first causes
some molecular oxygen (O2) to split apart
into free oxygen (O) atoms and these then
combine with molecular oxygen to form
ozone (O3)
CFC’s
• A type of halogenated hydrocarbon
• Nonreactive, nonflammable, nontoxic organic
molecules in which both chlorine and fluorine
atoms have replaced some hydrogen atoms.
• Under modest pressure, they liquefy giving off
heat in the process and becoming cold.
• Used as refrigerants, production of plastic
foams, electronic industry for cleaning
computer parts and as the pressurizing agent in
aerosol cans.
CFC’s Safe?
• CFC’s would be stable in the troposphere,
but in the stratosphere they would be
subject to intense UV radiation, which
would break them apart, releasing free
chlorine atoms via
CFCl2 + UV  Cl + CFCl2
– Chlorine acts as a catalyst to the break down
of ozone.
Ozone hole
• Fall 1985, British scientists working in
Antarctica reported a “hole” in the
stratospheric ozone layer.
– The hole was actually a serious thinning.
– Area the size of the US where ozone levels are
less than 50% (of normal)
– The hole was not discovered earlier by NASA
because the computers were set to reject data
showing a drop larger than 30%.
Polar Vortex
• Winter in the Antarctic (June).
• A whirlpool like vortex which confines
stratospheric gases within a ring of circulation
air.
• The cloud of particles provide surfaces on
which chemical reactions release molecular
Chlorine.
• When summer arrives, the sun’s warmth
breaks up clouds and UV radiation attacks the
molecular Chlorine initiating the Chlorine cycle
which rapidly destroys ozone.
Arctic Hole??
•
•
•
•
NO
Higher temperatures
Weaker vortex
Ozone depletion has occurred, but only at
25% loss in especially cold winters.
Ozone depletion
• Worldwide network on ozone measuring
stations
• Data sent to the World Ozone Data Center
in Toronto, Canada
• Depletion levels of 3% and 6% over the
period 2002-2005 in midlatitudes of the
Northern and Southern hemispheres
respectively.
Montreal Protocol
• 1987, UN convened in Montreal Canada
• Goal: address ozone depletion
• Members reached an agreement called the
Montreal Protocol
– Scale CFC production back 50% by 2000.
– To date 184 countries (including the US) have
signed
– Because Ozone losses were greater than expected,
an amendment was adopted in June 1990.
• Phase out major CFC chemicals by 2000 (developed and
2010 (developing)
– Another amendment November 1992
• Complete CFC phaseout by January 1, 1996