Transcript Weather and Climate - Madison Area Technical College

Global Climate Change
Pollution
Lecture 15:
Weather and Climate online
The Iron Hypothesis
Vast stretches of ocean are barren
• Plenty of Nitrogen
• Plenty of Phosphorus
• Plenty of sun
– What’s Missing?
• IRON
• Add iron to water, phytoplankton
bloom will consume plenty of
carbon
The experiment was
vigorously opposed
• It was a testable hypothesis
• ‘Geritol’ solution
– Hazardous manipulation of the environment
– Removes carbon from environment, trapping it
in the ocean; this idea was embraced by
corporations and some countries to meet Kyoto
protocols
– Might cause algal blooms and methane release
Ironex I & II
• Ironex I: 445 kg of iron dumped into ocean
near the Galapos (64 km2 clear blue ocean)
– Phytoplankton levels tripled
• Ironex II spinkled iron into same ocean area
several times over a period of three days.
– Phytoplankton increased 30x
– Produced same biomass as 30 redwood trees
– Sequestered 2500 tons of carbon
Thermohaline Circulation
• A global conveyor belt in the ocean, by
which water moves great distances
horizontally and vertically
• Driven by density changes caused by
cooling water (which makes water denser)
and evaporating (which makes water saltier
and denser)
Dense water in the ocean is...
• Very cold
• Very salty -- rain makes
seawater lighter (fresher)
Thermohaline Circulation
• Warm water flows north in Gulf Stream,
and experiences strong evaporation and
cooling (makes water saltier and colder)
• Dense water sinks near Greenland, flows
south through Atlantic towards Antarctica
• Water also sinks near Antarctica
– There are just two sources of deep water!
Thermohaline circulation
• Deep water has lots of oxygen near
Labrador Sea, and near Antarctica
• Deep water has less oxygen in the Pacific -biological activity consumes oxygen as the
water moves along
Thermohaline circulation
• Why no sinking in N. Pacific?
– Pacific Ocean waters are fresher (less salty)
than the Atlantic, therefore less dense! Harder
to sink
• The deep water slowly warms and rises
(over years!) and then returns to the north
Atlantic to sink again
How to shut off Thermohaline?
• Warm up North Atlantic/Arctic Ocean
• Make a cheesy Jake Gyllenhaal movie
• Put fresh water over the North Atlantic
– Lots of Precipitation
– Lots of Glacial melt
Ozone
• Beneficial molecule in the stratosphere
• Absorbs harmful UV radiation
• Responsible for stratospheric temperature
inversion
hv is energy
• How is ozone formed?
from the sun
•
•
•
•
•
O2 + hv -> O + O (1)
O + O2 -> O3
(2)
O3 + hv -> O2 + O (3)
O + O2 -> O3
O + O3 -> O2 + O2 (4)
Ozone eventually
returns to ‘regular’
oxygen molecule
Stratospheric Inversion
• Helps put a ‘cap’ on
top of tropospheric
mixing
• Unique to Earth
Stratospheric Ozone Hole
• First noticed in 1970s by surface based and
space-based monitors, centered on South
Pole
– British Antarctic Survey
– TOMS [TOTAL OZONE MAPPING SPECTROMETER]
satellite -- measures ozone data from
back-scattered UV sunlight (no data
available during Antarctic winter)
– Readings initially thought erroneous
Big changes as time evolves!
What caused Ozone destruction?
• Catalytic reaction with Chloroflourocarbons
-- especially in the presence of ice.
• During Antarctic night, no sunlight to
produce ozone
• Over Antarctica, air is isolated during
winter because of circular vortex centered
over the South Pole -- rare to replenish with
ozone-rich air from lower latitudes. That’s
not the case in the northern Hemisphere –
air from mid-latitudes periodically
penetrates to the Poles.
CFCs
• Refrigerants
• Were popular because they were thought to be
chemically inert
– CFCs slowly diffuse upwards and reach stratosphere
– UV light in stratosphere breaks down CFCs
– Chlorine atoms react with Ozone molecules
Chlorine in the stratosphere
• During polar night, chlorine atoms are
liberated from HCl and ClONO2 on cold
clouds. (Converted to more active forms: Cl2
– Heterogeneous reaction that occurs on a surface - and it happens rapidly!
– Originally thought there were no surfaces in the
stratosphere for this to occur on, but because it’s so
cold, ice clouds will form
What happens when the sun rises?
• Cl2 split apart by sunlight to two Cl atoms
• Then
– ClO + ClO + M -> Cl2O2 + M
M is a surface on which
– Cl2O2 + hv -> Cl + ClO2
the reaction occurs
– ClO2 + M -> Cl + O2 + M
– then: 2 x (Cl + O3) -> 2 x (ClO + O2)
– net: 2 O3 -> 3 O2 -- and the ClO can then
react with more ozone
Summary
•
•
•
•
•
The polar winter leads to the formation of the polar vortex which
isolates the air within it.
Cold temperatures form inside the vortex; cold enough for the formation
of Polar Stratospheric Clouds (PSCs). As the vortex air is isolated, the
cold temperatures and the PSCs persist. PSCs are ice clouds.
Once the PSCs form, heterogeneous reactions (that means the
reaction takes place on a surface) take place and convert the inactive
chlorine and bromine reservoirs to more active forms of chlorine and
bromine.
No ozone loss occurs until sunlight returns to the air inside the polar
vortex and allows the production of active chlorine and initiates the
catalytic ozone destruction cycles. Ozone loss is rapid. The ozone hole
currently covers a geographic region a little bigger than Antarctica and
extends nearly 10km in altitude in the lower stratosphere.
Ozone gradually decreases in the winter – there is no sunlight to create
it – and then rapidly decreases in Spring.
Montreal Protocols 1987
• Reduce/eliminate CFCs by 2010, replace with
more chemically inert species, or more
chemically reactive species so they rain out in
troposphere
– CFC accumulation is declining – concentrations are
increasing but the rate of increase is less than it was –
but it takes up to 100 years to remove Cl atoms from
stratosphere
– [CFCs are also a powerful greenhouse gas]
Carbon Dioxide in the atmosphere
• Concentrations are rising because of fossil
fuel use
• Important greenhouse gas
• Vital for plant growth
Steady increase
CO2 drops in Spring/Summer as plants grow
CO2 rises in Fall/Winter as plants decay
How do we know CO2 is from fuel?
• Radiocarbon dating -- carbon in fossil fuels
lacks radioactive carbon because it is so old
- Roger Revelle
– 1957: First publication
– 1965: Presidential Advisory Panel
– 1977: National Academy of Sciences Panel
found 40% of anthropogenic carbon stayed in
the atmosphere
Where does the rest of CO2 go?
• Ocean absorbs much of it, but more slowly
than emitted on land -- takes about a decade
to absorb the typical molecule (and it stays
there for about 1000 years, which is how
long it takes the ocean to overturn)
Why is CO2 important
• Top Line: CO2 concentration
• Bottom Line: temperature inferred from deuterium
concentration
• Source: Vostok Ice core (to 150000 years BP)
What controls a locale’s climate?
• Short answer: the weather
–
–
–
–
Latitude
Altitude
Position relative to water
Prevailing wind direction (where does the place
sit with respect to the General Circulation?)
Note
change
in
climate
with
height
Koeppen Climate Classification
East side of Continents
• Humid, warm: Affected by circulation
around subtropical High, which
circulation moves warm, moist air
poleward
–
–
–
–
China
eastern US
eastern South America
eastern Australia
West side of Continents
• Humid, cool: Affected by west-east
motion of airmasses off upstream
ocean … unless the motion is blocked
by mountains
–
–
–
–
Europe
coastal Pacific Northwest
coastal western South America
southwestern Australia
San Francisco,
Wichita, and
Norfolk are all
at the same
latitude, and
about
the same
altitude.
Do they enjoy
the
same climate?
Cities far from
the moderating
effects of the
ocean show
greater
temperature
swings during
the year!
They have
higher
Continentality
This is also true of Extreme
Temperatures
• Which states have
record highs
exceeding 120 F?
–
–
–
–
–
California (134)
Arizona (127)
Nevada (122)
Kansas (121)
North Dakota (121)
• Which states have
record highs below
110 F?
– All border the ocean
(except Vermont)
– Only 109 F in FL!
Which places are HOT
• Low altitudes (Death Valley)
• Away from ocean (North Dakota)
• Sunny (downward motion in General
Circulation)
• Dry regions -- not a lot of precipitation, so
no need for a lot of evaporation
Which places are COLD
•
•
•
•
•
High altitudes
Away from ocean (North Dakota)
Clear (allow radiational cooling)
Dry regions -- not a lot of heat content
Far from equator (more energy input into
Earth system at the Equator)
Which places are DRY
• Very cold regions (saturation vapor pressure
will be very low)
• Away from ocean
• Leeward side of mountains
• Downwelling branch of General Circulation
(Hadley Cell)
Which places are WET
• In the ITCZ -- plenty of moisture, upward
motion
• Near the Polar Front
• Windward side of mountains
• Downwind of moisture sources (ocean)
What are ways WI climate could
be altered?
• Build an east-west Rockies-type mountain
range from North Carolina to Colorado
–
–
–
–
No more moisture from Gulf of Mexico
South winds: downslope/warming
Cold air couldn’t sweep south
North winds moving up into mountains would
deposit any moisture they had
What are ways WI climate could
be altered?
• Build an east-west Rockies-type mountain
range along the US-Canada border
– Still get moisture from Gulf of Mexico
– Much warmer in winter -- cold airmasses would
be unable to move over the mountains
– North wind: downslope wind with warming
What are ways WI climate could
be altered?
• Gulf of Mexico moves north, flooding
TX/OK/KS
– More moisture/warmth available year round
with a south wind
– More plentiful snows
– Increased threat from hurricanes in summer
What are ways WI climate could
be altered?
• Remove Rocky Mountains
– Mild, moist air from Pacific could
penetrate farther inland in winter
– More difficult to generate cP air in winter
because mountains would not block flow
– Mountains help lock in flow patterns
How is Earth affected by
Mountains?
• Higher altitudes are colder
– Plentiful snows will increase the albedo
– Temperature decreases with height
• Mountains divert west-east flow
– Air can ‘stagnate’ and become very cold
– Warm/Wet on windward side
– Cold/dry on leeward side
• A flat Earth is a warmer Earth
What kind of cloud?
What kind of cloud?
Air Pollution
• Not all pollution is anthropogenic (i.e.,
man-made). Choking gases can also come
from volcanoes and sea vents. Lightning
can start a forest fire that puts immense
amounts of pollutants into the atmosphere.
• Air pollution effects are magnified when
areas
– have light winds (little or no horizontal mixing)
– under inversions (little or no vertical mixing)
What kind of feature has light winds and inversions?
Smog
• Term coined by London physician Harold
Des Voeux in ~1911 -- a combination fog
and smoke.
The solution to
pollution is dilution
[That is, the short-term solution to an immediate problem]
There are some very famous
pollution episodes
• Donora, Pennsylvania in October 1948
• London, England in December 1952
– Both events had similar meteorology: Stagnant
high pressure prevented mixing so pollutants
slowly accumulated in the boundary layer,
leading to a killer noxious smog
How did Fog kill?
• Bronchitis/asthma suffers: suffocated as they
wheeze to death
• Congestive heart failure -- lack of oxygen makes
heart work harder -- leads to cardiac arrest
• ozone causes permanent lung damage -- other
contaminants damage respiratory cells, cause
lung inflammation
• Week before: 2000 died.
• Week of fog: 4000 died
Fog as a Killer
Death rates rose most
for 45-64 year-olds;
2/3rd s of those who
died were > 65.
Other famous pollution problems:
Houston, Texas
Causes: Automobiles, Petrochemical plants
Aggravations: Sea breeze/land breeze circulation
Stagnant weather for much of summer -- no change
in airmass
Houston pollution from satellite
Convert difference in downward looks and fore/aft
looks to particulate density (optical depth)
Denver’s “Brown Cloud”
Sources: Automobiles,
wood-burning stoves ;
big improvements since
early 1980s
Periodic inversions
trap air below mountain
tops
Los Angeles
• Sited in a basin
• Downstream of Pacific High (downward
motion, and an inversion)
• Difficult to ventilate -- pollutants get
trapped in sea/land breeze circulation
• Lots of cars!
Mexico City
7500’ above sea level
24,000,000 people
View From
Space Shuttle
Beijing
New Delhi
The persistent haze is a pungent mixture of
wood, coal, and cow-dung smoke, with
generous contributions from diesel auto,
bus, and truck exhaust, and from the
ubiquitous gas/oil-burning scooters and
rickshaws
Why do inversions promote pollution?
Temperature inversion
Pollution distribution in vertical
controlled by the stability
Difficult for particles to move in the vertical
Particles easily move in the vertical
Particles easily move to the surface, but don’t move aloft
Pollution Mitigation
• Make smoke stacks very tall!
– Stack output into inversion layer, above the unstable
boundary layer
• Site smokestack in a region where drainage winds
will remove pollution -- or where you’re far from
population
– Put your powerplants somewhere besides downtown!
Other effects of pollution
• Adds cloud condensation nuclei to air
– Fox River Valley cloudiness from extra CCN from
paper plants (more fog?) -- ditto Tyrone PA in the
1960s
• Heat source at smokestack, so cumulus cloud at
the top of smoke plume
• If you live on a lake, pollutants can get trapped in
Lake Breeze and “never” ventilate.
Main pollution sources
• Mercury and sulfur: from coal-burning
power plants
• Smoke from forest fires can cause pollution
over very large areas
• Carbon Monoxide, Nitrous Oxides: from
vehicles
Alaska had many fires in 2004
Visible from space
In the infrared channels too!
Dark Pixels are
very warm (fire)
Acid Rain
Acid Rain is mostly caused by SO2 and NOx
– 2/3 of SO2 from coal-fired power plants
– 1/4 of NOx from coal-fired power plants
– “Pure” rainwater has pH of 5.5
• pure water: pH of 7
• Acid rain: pH of 4.3
• pH down to 2.5 observed (Mt Tsukuba, 1984)
Effects of Acid Rain
• Increased mortality in
aquatic
species…chart at
right shows that some
are more tolerant of
acid than others
• Effects tempered by
local geography,
especially limestone
Effects of Acid Rain
• Increased nitrogen
deposition in water
leads to algal blooms
• Damages leaves, and
weakens trees
• Weakens paint on cars
• Erodes marble in
buildings
Pollution Modeling
• Use numerical models to tell where the
pollutants from a stack will end up
• Employs many meteorologists!
• “Fundamentals of Stack Gas Dispersion”
–
–
–
–
–
buoyant smoke plume rise
Gaussian modeling theory
Local meteorological observations
very realistic topography
interaction between microscale and mesoscale
Changing the Climate
• Climate naturally changes due to changes in
solar forcing (Milankovitch Cycles).
• Feedbacks can amplify any change
Other trace gases impact the climate
• Dimethyl sulfide (DMS)
–
–
–
–
Gas produced by phytoplankton
Acts as a cloud condensation nucleus
Enhanced production as temperature increases
More CCN with warmer temperatures, more
clouds and albedo increases, Earth temperature
drops
– Puts the brakes on warming
Snow Affects the climate!
Snow-Albedo feedbacks
Snow Affects the climate!
Snow-Albedo feedbacks
View from GOES West
Snow-Albedo feedbacks
View from GOES West
Snow-Albedo feedbacks
Did this affect the temperature?
Temperatures
2.5” snow in MKE
Degrees (F)
50
40
30
20
10
0
1
2
3
4
5
6
Milwaukee High
41
39
38
37
36
31
Milwaukee Low
32
29
25
24
26
21
Madison High
41
40
33
40
40
34
Madison Low
29
22
19
26
25
18
Milwaukee High
Day (28Nov-3 Dec)
Milwaukee Low
Madison High
Madison Low
Same Thing Every Winter
• Clear, calm night,
• Clear, calm night,
temperature falls to the
temperature falls to
dewpoint
below the dewpoint
How does snow cool?
[Remember these?]
• Incoming solar radiation reflected back to space
• Insulate bottom of atmosphere from warm
underlying surface
• Cool down more rapidly at night: snow is a
great emitter!
– Also, fresh snowcover has a HUGE surface area –
so a LOT of energy can leave
Why is snow darker over a city?
• Note that Chicago is
not as white
• Urban Heat Island -maybe less snow fell
• City is a very dirty
place -- snow rapidly
gets sooty
• Snow Removal
• Albedo effects
reduced over the city
• More shadows?
Today’s Topic: Global Warming
Is the Earth getting warmer?
YES! (or maybe)
How to tell what temperature was?
• Examine sediments and soil deposits
– ‘Heavy’ water more common when glaciation
preferentially removes ‘light’ water from the
ocean/lakes.
• Pollen in ice cores, sediments
• Deuterium in ice cores
– ‘Heavy’ hydrogen more common when it’s cold
• Tree Rings
• Need to know what T was if you’re trying to figure out
how it’s changing
Today:
385 ppmv
Extract dissolved CO2 from ice cores,
compare to heavy water
Note on the previous slide
• Temperature increases, then CO2 increases
– Likely cause: warmed ocean releases CO2
• CO2 has increased before temperature in the
past 200 years – this behavior is different
than in the past
• The historical record shows that
temperature increases, then the CO2
increases, then the temperature drops
What does past T record tell us?
• Earth is now warmer than it’s been -- we’re
emerging from a Glacial period
• Warming started about 18K years ago
• Period of cooling between 14K and 10K
years ago, then renewed warming
Younger-Dryas
Younger-Dryas
• Melting Glacier flooded North Atlantic,
capping the ocean with fresh water, shutting
off the Thermohaline circulation
Feedbacks can amplify change
• Remove snow: albedo drops, Earth warms
• Add vapor, Greenhouse forcing increases,
warms Earth so more water evaporates …
• Plants die from drought, air is drier because
of reduced evapotranspiration
Feedback can damp change
• Add vapor, more clouds will form, shading
Earth and causing cooling
• Warm the Earth, and it emits more energy,
causing cooling (and the amount emitted
varies as T4)
From Last time: Mountains
• Cause preferred flow regimes
• Block mild air from penetrating to center of
Continents…cP air can form unimpeded
• Also, if land at poles, more likely to have
glaciers there, which increases the Earth’s
albedo
Politics of Global Warming
• Some entities have a vested interest in the
status quo -- government-mandated
restrictions related to Global Warming
reduce profitability
• Politicization of science does little to
advance true understanding
Model Studies of Global Warming
• Most studies suggest that warming is
concentrated at the Poles
• Can model, if run backwards, ‘predict’ the
past climate? (Usually, no; is that a reason
to ignore model results?)
Climate Change is natural
The little hiccup in the
line is the Younger-Dryas
This time series suggests the Earth should be cooling!
What causes the regular pulses in temperature?
• Milankovitch forcing
• Changes in orbital parameters -- three
different effects
– Change in time of perihelion/aphelion
(‘Precession of the Equinox’)
– Change in ellipticity of orbit
– Change in Inclination (‘Obliquity’)
Precession of the Equinox
• Perihelion occurs about 5 January.
– Changes with time -- regresses 1 day every 58 years.
– Period is 21000 years
• In 21000 years, perihelion will be 5 January
• in 10500 year, perihelion will be 5 July
• Snowier in northern Hemisphere when it’s
warmer in winter, cooler in summer -- more
likely that snow will persist through the summer
(and become a glacier)
– More snow reduces Earth’s temperature through
albedo affect
– Effects in Northern Hemisphere dominate because
there’s more land in the northern Hemisphere
Changes in ellipticity
• Varies from nearly circular to 3x as elliptic as
now with a period of 100,000 years
• Eccentricity varies between 0 and 0.05 (right
now: 0.018)
• Modulates the effects of precession of the
equinox -- greater effects with very elliptic orbit
when perihelion is during NH winter
– Much cooler in NH summer -- support Glaciation
because winter snows won’t melt
Obliquity
• Axis tilt now is about 23.5 degrees -- in the
middle of the range of tilts.
• Tilt varies with a period of 41,000 years
between 22 and 24.5 degrees
• Larger tilt favors glaciation -- if NH winters are
warm
– Note that even warm winters are cold enough for
snow….you want warmth because that means more
moisture is available, and because summers are
cooler so glaciers won’t melt
What is not ‘natural’ ?
(to the extent that you consider anthropogenic changes unnatural, although
man is a part of the ecosystem!)
• Large increase in CO2 to atmosphere due to
burning of fossil fuels
– Increases ‘greenhouse effect’ [warming]
– CO2 values now very high (not as high as when
dinosaurs roamed)
• Lots of particulate matter from burning
fossil fuels
– Increases shading of Earth [cooling]
One Aspect of more CO2
• Increased plant growth
• When there’s more CO2 in the atmosphere, all
plants grow more vigorously
– Carbon dioxide + water yields sugars and oxygen (this
is how plants remove CO2 from the atmosphere -- they
convert it to sugar).
• Plants use carbon dioxide in different ways.
Response to enhanced CO2 varies by species -some ‘good’ plants grow faster, some weeds grow
faster
What are some effects of warming?
• Longer summers
– Would the number of cold frontal passages decrease?
That will increase the length of pollution events over
the US
– Longer growing season for some plants
– Some plants require a specific amount of cool weather
• Warmer oceans mean more hurricanes?
– Reality: Only the Atlantic Basin shows hurricane
activity trending upwards in the past 23 years
Does Global Warming = Warming
everywhere on the Globe?
• NO!
– Studies show strongest warming at Poles
– Relatively less warming at Equator
– Local effects (shut down of
Thermohaline circulation, for example)
could cause dramatic cooling in one
location even though the Globe as a
whole warms
Warming = Flooding
• Glacier meltwater increases ocean levels
– 6.5 m if Greenland ice cap melts
– 8 m and 65 m if west Antarctic and east Antarctic ice
caps melt
– Prediction of 5 to 15-inch rise by 2100
– 1-meter rise: Half of Bangladesh is underwater
• Thermal expansion of sea water as it warms
raises ocean levels [and warmer water cannot
hold as much CO2 in solution]
• Stronger hurricanes over warmer waters have
higher storm surges.
Glaciers are sensitive to
temperature and precipitation
• Most Glaciers retreated in 1900s
• 80% of the glaciers on Kilimanjaro have melted
• Most glaciers in Glacier National Park have
retreated
• Also examples in the Andes and Antarctica
• Is this from warmth or dryness? Not known for
sure
Blue: Retreating Glaciers
Red: Advancing Glaciers
Drake Peninsula,
Antarctica
Example From Alaska
From The Alps
Glacier National Park
1993
Mt. Kilimanjaro
2000
What happens when Glaciers melt?
• Albedo drops
• Earth warms up
• Glaciers melt some more
• Sea levels rise
• Are glaciers melting or evaporating?
Collapse of
Larsen Ice shelf
in Antarctica,
summer 2002
Lake Ice Seasons are shorter
• Canada, Europe, USA, Japan : Lake Ice
records are centuries long
– Ice appears 8.7 days later than 150 years ago
– Ice melts 9.8 days earlier than 150 years ago
Some Climate Features confound the
record in the short term
Great Lake
Ice Coverage
Other Lakes:
Other Lakes:
Other Lakes:
Sea Ice over Arctic Ocean
• Decreasing, consistent with predictions
– Each year shows more of a decrease
• Decreases albedo, which causes further
warming/melting
• Open Arctic Ocean: source of plenty of moisture
(to yield heavy snows and glaciation?)
• Model studies stress the importance of wind in ice
formation/melting over the Arctic, yet how the
wind changes with warming is not well
understood
Where will most change occur
• From Computer Simulations:
– AT THE POLES
– Snow-albedo feedbacks?
How is change manifest?
Temperature Anomalies at the Pole
Arctic is getting cloudier with time
Shorter time when roads on ice are open
Permafrost is warming!
Siberian Permafrost is warming, too [again!]
New species (in this case, birds) are colonizing the Arctic,
Moving north from warmer latitudes
Other species,
[Black
Guillemots]
are declining
Problems for migratory birds
• When birds leave might be tuned to the Sun
(amount of daylight)
• When prey emerges might be tuned to
temperature
– Time of departure for birds stays constant
– Time when food is available gets earlier and
earlier
Bering Sea is warming up!
Number of days with ice after 15 March 56-58 N/ 163-165 W
Shrimp catch way up…cod catch way down!
Sea Ice in Arctic is decreasing
Here is 2005
Glaciers are in retreat
Glacier Volumes in NH are dropping
Eurasian
Arctic
Russian
Arctic
Total
N. American
Arctic
For More Information:
http://www.arctic.noaa.gov/detect
The big question
• Is the increase linear, or part of an
oscillation of unknown cause?
• Hard to tell if you’re in a linear increase or
wave as it’s occurring