Global Climate ChangePollution

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• How is ozone formed?

• O2 + hv -> O + O (1)

• O + O2 -> O3 (2)

• O3 + hv -> O2 + O (3)

• O + O2 -> O3

• O + O3 -> O2 + O2 (4)

Ozone eventuallyreturns to ‘regular’oxygen molecule

hv is energy from the sun

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  

– Cl2O2 + hv -> Cl + ClO2  

– 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

M is a surface on which the reaction occurs

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 increaseCO2 drops in Spring/Summer as plants growCO2 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 allat the same latitude, and

aboutthe same altitude.

Do they enjoy the

same climate?

Cities far fromthe moderatingeffects of the ocean show

greater temperature

swings duringthe year!

They havehigher

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 mostfor 45-64 year-olds;2/3rd s of those whodied were > 65.

Other famous pollution problems:

Houston, Texas

Causes: Automobiles, Petrochemical plantsAggravations: Sea breeze/land breeze circulationStagnant weather for much of summer -- no changein 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 mountaintops

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 arevery 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 WestSnow-Albedo feedbacks

View from GOES WestSnow-Albedo feedbacks

Did this affect the temperature?Temperatures

0

10

20

30

40

50

Day (28Nov-3 Dec)

Deg

rees

(F

)

Milwaukee High Milwaukee Low Madison High Madison Low

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

1 2 3 4 5 6

2.5” snow in MKE

Same Thing Every Winter

• Clear, calm night, temperature falls to the dewpoint

• Clear, calm night, temperature falls to 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

Extract dissolved CO2 from ice cores, compare to heavy water

Today:385 ppmv

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

This time series suggests the Earth should be cooling!

The little hiccup in the line is the Younger-Dryas

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 GlaciersRed: Advancing Glaciers

Drake Peninsula,Antarctica

Example From Alaska

From The Alps

Glacier National Park

Mt. Kilimanjaro

1993

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 LakeIce 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

RussianArctic

EurasianArctic

N. AmericanArctic

Total

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