Transcript Climate Climate Change Ozone Depletion

Weather…Climate…
Climate Change…
Ozone Depletion…
…what does it all MEAN?
Question: What’s in the atmosphere?
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N2 (78%)
O2 (21%)
Ar (0.9%)
WV (greenhouse gas)
CO2 (greenhouse gas)
O3
Particulates
Thermosphere
TROPOSPHERE
• Gases here moderate flow of energy to E.
• 10 mi thick @ tropics; 5 mi thick @ higher
lats.
• Contains all the WV & clouds.
• Weather occurs here!
• Temp ↓ as altitude ↑.
• Pollutants can rise to top within days...
• TROPOPAUSE caps it...temp stops
decreasing.
(higher...)
STRATOSPHERE
• Temp ↑ as altitude ↑...
• Contains O3 (it absorbs radiation).
• Persistent substances
What happens to TEMP
as you go farther away
from E?
Why does it warm up in
the stratosphere?
What happens to the TEMP as
you move farther from E?
Good to know...
• Weather: day-to-day variations in temp,
precip, wind, pressure, & humidity.
• Climate: long-term regional weather
patterns.
• Factors affecting climate:
• Latitude
• Atmospheric circulation
• Oceanic circulation
• Topography
• Solar activity
• Volcanic activity
Latitude
Latitude
•
latitudes close to equator receive
more direct (vertical) rays; more
concentrated E per surface area.
LOW
• No winter…no summer…all hot.
•
HIGH
latitudes receive less direct
(oblique) rays; less concentrated E per
surface area.
• Wider temp range, seasons!
Atmospheric
Circulation
(wind…)
Warm air rises (low pressure...)
Cold air sinks (high pressure...)
Pressure flows from HIGH to low
Latent Heat
• Warm air holds more WV than cool air
• Warm air rises (less dense)
• As moist/warm air rises, it cools & WV
condenses to liquid…clouds form…
– Latent heat (“trapped” in WV) is released
– Energy source for t-storms, tornadoes,
hurricanes.
– QUESTION: will increased temps lead to
more WV…more latent heat…resulting in
more intense severe weather?
How OCEANS affect temp...
• HEAT CAPACITY: water stores heat
more effectively than solid earth
(heats up & cools more slowly than land).
• HEAT TRANSFER: ocean currents
carry warm equatorial water
towards poles.
• SOURCE for WV: when wv
condenses in the atmosphere it
releases latent heat.
Surface Currents
One cycle: 1,000
years
El Nino-Southern Oscillation
(ENSO)
Solar Maximum
- Increased UV
- Increased O3
- Increased temps
- SO2 gas reaches
upper atmosphere.
- SO2 & dust & WV
form haze.
- Haze reflects sunlight, global temps
decrease.
And finally…
…the seasons!
Greenhouse Effect
• Analogy: sunlight pours into your car
& heats up the interior (gets
absorbed by seats, dash, etc) as it’s
converted from light energy to heat
energy (IR).
– The light energy escapes back out
through the glass...but the heat energy
is blocked by the glass and so cannot
leave the car.
– Much like a “greenhouse.”
Greenhouse Effect
• The Greenhouse Gases - WV,
CO2,CH4,& N2O are analogous to the
glass in a greenhouse.
• Light energy from Sun passes through
them, strikes E and is converted to heat
energy (IR)...the converted IR is
absorbed and re-radiated back into the
troposphere by the GHGs.
Your diagram goes here!
ABSORBED: 70%
REFLECTED: 30%
An important 70%...
• The solar energy not reflected back
into space (70%) gets transferred
to the atmosphere as IR energy...
• This warmed-up air becomes less
dense, rises, and creates air
currents called convection cells.
...it’s actually a good thing...
• The greenhouse
effect moderates
the temp and
makes it warm
enough for many
( a word that
often leaves you
guessing) life
forms to exist...
...a force to be reckoned with.
• HOWEVER... If
the concentration
of these GHGs
changes, their
insulating effect
changes
also...and so will
our climate.
Enhanced Greenhouse Effect
• 1958: Charles Keeling begins measuring CO2
levels on Mauna Loa
Anthropogenic warming
• Warming of the Earth derived from
human activity
...climate change is such an
important issue today
because we depend on those
orgs for vital goods &
services we need to survive...
If the global climate changes,
can these ecosystems
change with it - so those vital
goods & services continue?
CLIMATES
• ...remember how ecosystems & biomes
result from different combo’s of temp &
precip?
• ...and the orgs that inhabit a particular
biome are adapted to those limits?
• HUMANS can live anywhere (we don’t
have to adapt – we control the
environment...)
Past Climates
• Global surface temps
fluctuate!
• This chart is
modern... stats
come from actual
weather stations.
...but what about long ago?
• Proxies are used to provide info about
ancient climate conditions.
• Pollen deposits...marine
sediments...coral...ice cores...
historical data…
Pollen!
Marine sediments
• Biological
– Changes in
fossilized orgs (type
& amount)
– Oxygen isotope
concentrations in
shelled remains
• Inorganic
– Clay mineralogy
– Aeolian dust
Coral
• “Greer and Swart were investigating the
relationship between non-radioactive or
stable isotopes of oxygen in the calcium
carbonate of the coral. The ratio of normal to
heavier oxygen depends on the temperature
of the water the coral grew in and its salinity.
In warmer water, the coral incorporates more
of the normal oxygen into its structure, but if
the water is cooler, the coral will incorporate
a higher percentage of the heavier oxygen
isotope.”
Medieval Warming Period
Little Ice Age
What does it MEAN?
• E’s climate has oscillated between ice
ages and warm periods.
• Milankovich cycles : Earth rotational &
revolutionary movements combine to
affect global climate.
• Theory: Ice ages are caused by 100,000
year coincidences of these cycles.
...during the ice ages, major
amounts of water were “tied
up’ in glaciers & ice
sheets...sea levels dropped
hundreds of feet below
current levels.
Rapid changes...
• Younger-Dryas Event: at the end of
the last ice age, E warmed up 7o C
in just 50 years!
• Scientists scratch heads: most
likely due to atmosphere / ocean /
global temp combo... kind of an El
Nino gone bad...
THERMOHALINE Circulation
• What’s THAT mean?
• Thermo: heat......Haline: salty...
• Cold water is more dense than
warm water ; Saltier water is more
dense than fresher water.
• Warm salty water cools; sinks @
poles...flows along ocean bottom
towards equator where it warms &
rises.
One cycle: 1,000
years
...could the conveyor belt be STOPPED?
• Recent evidence shows that it has been
interrupted in the past...six times.
• Large quantities of fresh water in the North
Atlantic (glacier/ice pack melting...) would
lower the salinity (density) of the water up
there... water would stop sinking...
• The northward flow of warm water would
be blocked and the belt shifts south.
• Results in ABRUPT global cooling.
• Scientists are monitoring salinity in the
northern ocean...
Climate Change: the DATA.
#1: CO2
• Released by burning of fossil fuels!
• Annual oscillations are due to seasonal
changes in NH terrestrial ecosystems
photosynthesis: Apr-Sep: CO2 ↓
respiration: Oct-Mar: CO2↑
• As of 2012, CO2 levels @ 399ppm (40%
higher than before the Industrial
Revolution)...higher than they’ve been
in 400,000 years!
Sources & Sinks
• 1 kg combusted fossil fuel = 3kg CO2
• 6.6 GtC (gigaton: billion metric tons) per
year of fossil fuel carbon.
• 1.6 GtC per year from burning forests.
• Sinks: carbon sequestration.
– Oceans: uptake by phytoplankton @ 2
GtC/year
– Forests: @ 3 GtC/year
#2: WV
• Absorbs IR...the most abundant GHG!
Atmospheric concentration variable...
• Major factor in “Supergreenhouse
effect”: in South Pacific, wv
traps/reradiates heat over ocean,
resulting in MORE evaporation, thus
more wv, thus more greenhouse
effect...positive feedback.
#3: Methane (CH4)
• Sources: microbial fermentation
(swamps, livestock, landfills, coal
mines, natgas production, rice
cultivation, manure).
• Atmospheric methane has doubled
since Industrial Revolution; is leveling
off!
#4: Nitrous Oxide (N2O)
• Sources: agriculture & biomass
burning; fossil fuel combustion
• 15% increase in past 200 years.
• Particularly unwelcome because it’s
so persistent: residence time 114
YEARS!
• Also bad for O3...
#5: O3
• Sources: motor
vehicle exhaust,
biomass burning.
• Short-lived, but
potent.
#6: CFC’s & Halocarbons, et al
• Entirely anthropogenic.
• Sources: refrigerants, fire retardants,
solvents.
• Extraordinary capability for IR absorption
(x10,000 CO2’s rate)
• Long residence time (100+ years)
• Double whammy: GHG AND O3 destroyers!
• Good news: manufacture & use has been
curtailed.
IPCC
• Intergovernmental Panel on Climate
Change.
• est. 1988 by UN and World Meteorological
Society to provide accurate, relevant
information on anthropogenic climate
change.
• Three working groups:
– I: Assessment of scientific issues
– II: Impact of climate change & possible adaptations
– III: Mitigation of effects
IPCC
• More than 2,000 experts from
over a hundred countries.
• Unpaid...recoup only the cost
of their research & associated
professional activities.
Most recent report:
Sep 2013
The report finds that it is “very
likely” that emissions of heattrapping gases from human
activities have caused “most of
the observed increase in globally
averaged temperatures since the
mid-20th century...”
”...evidence that human
activities are the major cause
of recent climate change is
even stronger than in prior
assessments...”
“It is unequivocal that
Earth’s climate is
warming...”
“...as is now evident from
observations of increases in
global average air and ocean
temperatures, widespread
melting of snow and ice, and
rising global mean sea
level...”
“...atmospheric
concentrations of CO2 and
methane exceed by far the
natural range over the last
650,000 years.”
Further findings/evidence
• 11 of last 12 years rank among top 12
hottest years on record since 1850.
• Tropical storms, precipitation, and
severe drought incidence have all
increased.
• Mountain glaciers and snow fields are
in world-wide decline.
• Summer Arctic sea ice has decreased
20% since 1978.
• Global mean sea level is rising.
What’s been done...
• Rio ’92: Earth Summit calls for voluntary
reduction of GHGs.
– Failure: all increased...
• Kyoto ’97: binding agreement to reduce
emissions.
– Failure: major players non-participants.
• Copenhagen ‘09: ill-will…mistrust
between developed/developing nations.
– Details of the “accord:”
Latest IPCC Report (Sep 2013)
•
•
•
•
•
The warming is unequivocal.
Humans caused the majority of it.
The warming is largely irreversible.
Most of the heat is going into the oceans.
Current rates of ocean acidification are
unprecedented.
• We have to choose which future we want very soon.
• To stay below 2°C of warming, the world must
become carbon negative.
• To stay below 2°C of warming, most fossil fuels must
stay buried in the ground.
Carbon Credit Trading
• Countries (both developed & developing)
receive an allowance of carbon
production.
• Developing countries can initiate cleaner
technologies using less carbon.
– They can trade unused carbon credits to
other countries and use the profit to grow.
• Developed countries will either pay or
change…
• Market based.
The future...?
• Confidence in computer
models to predict future
scenarios has increased...
• Human influences will continue
to change atmospheric
composition throughout the
21st century.
B1 scenario
pop↑ then↓, economies &
governments cooperate to achieve
sustainability
A1T scenario
pop↑ then↓, global shift to non-fossil
fuel energy sources
B2 scenario
pop↑, significant efforts to achieve
sustainability
A1B scenario
pop↑ then↓, balance of all energy
sources
A2 scenario
pop↑ then↓, countries act
independently with varied
economic/technological change
A1F1 scenario
pop↑ then↓, fossil fuel intensive
society
Projected Surface Temp./Sea-Level Rise at Year 2090
Temp. Change
(oF @ yr 2090)
Case
Best
Estimate
Likely Range
Sea-Level Rise
(“ @ yr 2090)
Model-based range
(excluding future
rapid dynamical
changes in ice flow)
Constant Year 2000
concentrations
1.1
0.5 - 1.6
NA
B1 scenario
3.2
4.3
4.3
2.0 – 5.2
2.5 - 6.8
2.5 - 6.8
7.1 - 15.0
7.9 - 17.7
7.9 - 16.9
A2 scenario
5.0
6.1
3.1 - 7.9
3.6 - 9.7
8.3 - 18.9
9.1 - 20.1
A1F1 scenario
7.2
4.3 - 11.5
10.2 - 23.2
A1T scenario
B2 scenario
A1B scenario
Projected Surface Temp./Sea-Level Rise @ Year 2090
Temp. Change
(oF @ yr 2090)
Case
Best
Estimate
Likely Range
Sea-Level Rise
(“ @ yr 2090)
Model-based range
(excluding future
rapid dynamical
changes in ice flow)
Constant Year 2000
concentrations
1.1
0.5 - 1.6
NA
B1 scenario
3.2
4.3
4.3
2.0 – 5.2
2.5 - 6.8
2.5 - 6.8
7.1 - 15.0
7.9 - 17.7
7.9 - 16.9
A2 scenario
5.0
6.1
3.1 - 7.9
3.6 - 9.7
8.3 - 18.9
9.1 - 20.1
A1F1 scenario
7.2
4.3 - 11.5
10.2 - 23.2
A1T scenario
B2 scenario
A1B scenario
What Must Be Done.
• World-wide cap on GHG emissions.
• Investment in, & deployment of renewable
energy technologies.
• Removal of fossil-fuel subsidies.
– &10 billion/yr in Europe...$15-35 billion/yr
U.S.A.
• Develop nuclear power.
– Cost-effective, reliable, waste, spent fuel...
• More stringent energy conservation
measures.
What Must Be Done.
• Stop TRF loss; plant more trees.
• Reduce the amount of fuels used in
transportation.
• Sequester CO2 emissions.
• Slow HPG.
Depletion of the
Ozone Layer
UV that penetrates the
atmosphere may be absorbed
by biological tissues, where it
damages proteins and DNA
molecules.
If the full amount of UV from
the sun reached E’s surface
(without being absorbed by
the atmosphere), it is
doubtful that any life forms
could survive.
Fortunately, over 99% of UV is
absorbed by ozone in the
stratosphere...
...the small amount that does
reach E is responsible for more
than 700,000 cases of skin
cancer/precancerous conditions
per year, just in North America.
Formation and Destruction
of Stratospheric O3
•
•
•
•
O2 + UVB → O + O
O + O2 → O3
O + O3 → O2 + O2
O3 + UVB → O + O2
Seasonal changes in
distribution of solar
radiation cause ozone
concentrations to vary...
(High in summer, low in winter)
Ozone concentrations are
higher near the equator, and
diminish as latitude
increases...also a function of
distribution of solar radiation.
CFC (chlorofluorocarbon)
• Nonreactive, nontoxic, nonflammable
organic molecules in which Cl & Fl have
replaced hydrogens; gases @ normal
temp & pressure...
• ...they liquefy at modest pressure, giving
off heat in the process, becoming cold...
• ...used in refrigerators, heat pumps,
production of foam plastic, & as
propellants in aerosol cans.
CFCs break down O3
in stratosphere
• CFCI3 +UV → Cl + CFCI2
• CI + O3 → ClO + O2
• CIO + ClO→ 2 Cl + O2
Chlorine acts as a catalyst: a
chemical that promotes a
chemical reaction without itself
being used up in the reaction.
...each chlorine can last from
40 to 100 years in the
stratosphere...it has the
potential to break down
100,000 molecules of ozone.
...it’s not really so much a
hole...
...it’s more like a bald spot.
Rowland & Molina
• Called it in 1974...published a paper
that concluded CFCs would damage
the stratospheric ozone layer,
increasing UV radiation on E’s
surface, resulting in more skin
cancer.
• Won Nobel Prize for their work
(1995).
1985
• British researchers in Antarctica report
a “hole” over the South Pole (about the
size of the United States) in the fall of
’85...levels were 50% lower than
normal.
• NASA satellites would have discovered
it first; but they were programmed to
reject anything over a 30% drop as an
instrument failure!
Surprise...
• Scientists thought that ozone loss
would be gradual & uniform all
over the planet – not a “hole!”
• The “hole” came as a surprise...if it
had happened anywhere other than
South Pole, UV damage to life
would have been extensive.
Why it happens where it happens:
• Summertime creates chlorine reservoirs (Cl
gets “locked up” in methane & nitrogen
compounds)
• Wintertime’s extreme cold traps stratospheric
gases within a ring of air circulating around the
Antarctic...clouds form...clouds provide
surfaces on which Cl2 gets “unlocked” from its
reservoir.
• When sunlight returns in spring, UV attacks the
Cl2, releasing free Cl – which begins the ozone
destruction cycle.
Sad days in the Outback, mate...
• Ozone-poor air shifts over the
Southern Hemisphere...
• UV radiation increases up to 20% above
normal in Australia...
• Three out of four in Queensland
(thinnest layer) are expected to develop
skin cancer.
Montreal Protocol
• 184 participating nations must phase out
ozone-destroying chemicals by 2000
(developed countries) and 2010
(developing countries).
• ..in most industrialized countries, CFCs
are no longer produced or used.
• Prediction: the ozone shield will reach full
recovery by 2050.