Global Climate ChangePollution Lecture 15: Weather and Climate online
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) hv is energy from the sun 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 [TOTALOZONEMAPPINGSPECTROMETER] satellite -- measures ozone data from back-scattered UV sunlight (no data available during Antarctic winter) • Readings initially thought erroneous
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 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?)
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
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! This is also true of Extreme Temperatures
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
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