Lecture 10:Lecture 10:

(1) an example of human (1) an example of human impacts on global climate: impacts on global climate:

the ozone holethe ozone hole

(2) end of oil: alternative (2) end of oil: alternative energy sourcesenergy sources

The atmospheric circulation above the South Pole The atmospheric circulation above the South Pole surf. temp, surf. temp, 1000mb1000mb, , 300mb300mb, , 30mb30mb dynamic heightdynamic height

‘polar vortex’

OZONE: good up high, bad nearbyOZONE: good up high, bad nearby

Ozone is a highly reactive gas that is a form of oxygen. Near Ozone is a highly reactive gas that is a form of oxygen. Near the the ground, it results primarily from the action of sunlight on hydrground, it results primarily from the action of sunlight on hydrocarbons ocarbons and nitrogen oxides emitted in fuel combustion. Ozone reacts and nitrogen oxides emitted in fuel combustion. Ozone reacts chemically ("oxidizes") with internal body tissues that it comeschemically ("oxidizes") with internal body tissues that it comes in in contact with, such as those in the lung. It also reacts with othcontact with, such as those in the lung. It also reacts with other er materials such as rubber compounds, breaking them down. materials such as rubber compounds, breaking them down.

Ozone (OOzone (O33) absorbs ultraviolet sunlight, protecting us (and the world’s ) absorbs ultraviolet sunlight, protecting us (and the world’s phytoplankton at the top of the ocean) from genetic damage to ouphytoplankton at the top of the ocean) from genetic damage to our r skin….yet ozone has been destroyed by CFC’s …spray cans and skin….yet ozone has been destroyed by CFC’s …spray cans and refridgeratorrefridgerator fluid.fluid.

The temperature high above Antarctica has been dropping,The temperature high above Antarctica has been dropping,in late winter, for the past 30 yearsin late winter, for the past 30 years

33

ICE!warmtropics

77

Northern hemisphere: more landNorthern hemisphere: more landthan the southern hemispherethan the southern hemisphere

Pressure field (winter 1993)Pressure field (winter 1993)at 3 levels: at 3 levels: 1000mb1000mb,,300mb300mb and 30 and 30 mbmb::

surface storms (blue, low surface storms (blue, low pressure); jet stream (red pressure); jet stream (red contours) andcontours) andstratospheric polar vortexstratospheric polar vortex(dark contours)(dark contours)

The jet stream/polar frontThe jet stream/polar fronthas great asymmetry abouthas great asymmetry aboutthe North Pole, which the North Pole, which communicates with thecommunicates with thestratospheric polar vortex,stratospheric polar vortex,the ‘rugby ball’ overhead:the ‘rugby ball’ overhead:

it stirs and mixes awayit stirs and mixes awaythe ozone hole of the Norththe ozone hole of the NorthThe origin of this The origin of this wigglinesswiggliness

of the Arctic circulation is the of the Arctic circulation is the vast mountain ranges: the Rockiesvast mountain ranges: the Rockiesand Tibetan Plateau, and alsoand Tibetan Plateau, and alsothe contrast between land and seathe contrast between land and sea

The polar and The polar and subpolarsubpolar ocean/atmosphere are a ‘tall’ ocean/atmosphere are a ‘tall’ dynamical system.dynamical system.

UpUp--down interactions follow from:down interactions follow from:--strong strong CoriolisCoriolis effectseffects--weak density stratification orweak density stratification or--thin layers of strong stratificationthin layers of strong stratification--high energy levels in both troposphere and high energy levels in both troposphere and

stratosphere: stratosphere: jetstreamjetstream, polar front, , polar front, storm tracksstorm tracks

--strong topographic control in both atmospherestrong topographic control in both atmosphereand ocean (in the north, Greenland ice and ocean (in the north, Greenland ice

cap, complex ocean basins and ridges) cap, complex ocean basins and ridges)

In high southern latitudes, In high southern latitudes, with weaker mountains, with weaker mountains, the atmosphere’s polar the atmosphere’s polar vortex is active and vortex is active and communicates from communicates from stratosphere to ground, stratosphere to ground, polar symmetry is still polar symmetry is still strong.

The atmospheric polar vortex The atmospheric polar vortex over Antarctica has strengthenedover Antarctica has strengthenedduring the past 30 years: during the past 30 years: a a striking humanstriking human--induced induced change in global climate change in global climate

Thompson + Solomon Science 2002Thompson + Solomon Science 2002

strong.dynamic heightanomaly overAntarctica inspring 2001indicates strongerpolar vortex, followinga 30-year upward trend

……and with it the surface and with it the surface westerly windswesterly winds

…and zonal circulation of …and zonal circulation of the Antarctic the Antarctic Circumpolar Current Circumpolar Current (the greatest of ocean (the greatest of ocean currents; currents; J. Richman, J. Richman, OSUOSU))

Antarctic Oscillation IndexAntarctic Oscillation Index

• A proxy for the variability of the winds over the Southern Ocean is the Antarctic Oscillation Index (AOI), which is defined Gong and Wang (1999) as

AOI= P*40°S - P*65°SWhere P*40°S and P*65°S are the zonally averaged sea level pressure (SLP) at 40°S and 65°S respectively.

1950 1960 1970 1980 1990 2000 2010−4

−3

−2

−1

0

1

2

3

4

Year

Sea Le

vel Pr

essure

Diffe

rence

Antarctic Oscillation Index

trend of −0.30 hPa/yr

Transport and Sea Level Difference Transport and Sea Level Difference across Drake Passageacross Drake Passage•• The sea level difference The sea level difference

across the Passage show across the Passage show a trend of a trend of --0.62 cm/year.0.62 cm/year.

•• Assuming that the Assuming that the transport fluctuations are transport fluctuations are barotropicbarotropic with a 2.25 with a 2.25 SvSv/cm and transport of /cm and transport of 123 123 SvSv in 1980, the in 1980, the modeled transport has a modeled transport has a trend of 1.4 trend of 1.4 SvSv/year /year increasing from 110 increasing from 110 SvSv in in 1970 to 150 1970 to 150 SvSv at presentat present

1970 1975 1980 1985 1990 1995 2000-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

Year

Sea L

evel

Diffe

rence

(m)

Trend of -0.62 cm/year

Sea Level Difference Across Drake Passage

1970 1975 1980 1985 1990 1995 200060

80

100

120

140

160

180

Year

Trans

port f

rom Se

a Lev

el Dif

feren

ce (S

v)

Transport through Drake Passage

Trend of 1.4 Sv/year

low ozone air over the Arctic…no ‘ozone hole’ because of intenselow ozone air over the Arctic…no ‘ozone hole’ because of intensepenetration of storms from low latitude replenishing high latitupenetration of storms from low latitude replenishing high latitude de ozone, but still there is depletion induced by CFC’sozone, but still there is depletion induced by CFC’s

SummarySummary

•• The winds over the Southern Ocean from the NCAR/NCEP The winds over the Southern Ocean from the NCAR/NCEP Reanalysis show a trend of 4.4 cm/s/yr increasing from a mean ofReanalysis show a trend of 4.4 cm/s/yr increasing from a mean of 7 7 m/sm/s to 9.2 to 9.2 m/sm/s over 53 years, representing a 50% increase in the over 53 years, representing a 50% increase in the wind stress.wind stress.

•• Satellite Satellite scatterometersscatterometers show a similar trend of 3.9 cm/s/yr in the show a similar trend of 3.9 cm/s/yr in the 1990s and the 3 months of SEASAT in 1979 are consistent with the1990s and the 3 months of SEASAT in 1979 are consistent with thelong term trendlong term trend

•• The modeled Drake Passage transport from sea level difference The modeled Drake Passage transport from sea level difference shows an increase of 1.4 shows an increase of 1.4 SvSv/yr corresponding to an increase from /yr corresponding to an increase from

123 123 SvSv in 1980 to 150 in 1980 to 150 SvSv in 2000in 2000..

• The chain of effects here is very long:our use of CFCs put chlorine atoms in the upper atmosphere where they react

with ozone, destroying it; a single chlorine atom can go on to remove many ozone molecules. Then:

⇒ air cools because not so much sunlight is absorbed by less ozone⇒ cooler air is dense, and drives a stronger ‘overturning’ circulation (up/down,

north/south)⇒ this drives stronger east-west winds…a more rapid polar vortex.⇒ the stronger westerly winds work their way down to the lower atmosphere.⇒ these blow on the ocean, possibly accelerating the circumpolar ocean

current, and changing the distribution of nutrients and phytoplankton at the surface. Of course the plankton are already worried by the increase in UV (ultraviolet) radiation due to ozone loss.

⇒ The Australians are having droughts that have developed over the past decade…possibly related to the change in the westerly winds.

The story is a long example of the intricacy of the climate system. On top of all this we saw a big fluctuation in the westerly winds in the 1960s, before there was an ozone problem. Natural variability is always present, in addition to human-induced effects.

Alternative energy sources: solar and windAlternative energy sources: solar and wind

•• solar 0.009%solar 0.009%•• wind 0.04%wind 0.04%•• biomass 0.4%biomass 0.4%•• geothermal 0.12%geothermal 0.12%•• traditionaltraditional--fuelwoodfuelwood 6.4%6.4%•• hydro 6.6% hydro 6.6% •• nuclear 6.0%nuclear 6.0%•• coal 21.8%coal 21.8%•• gas 21.1%gas 21.1%•• oil 37.5%oil 37.5%

These estimates are from These estimates are from Lomborg’sLomborg’sbook, who got them from book, who got them from EIAEIA 2000 2000 (US Dept of (US Dept of Energy Energy www.eia.doe.gob/pub/international/iea98www.eia.doe.gob/pub/international/iea98/)/) and and WRIWRI(World Resources (World Resources www.wri.org/facts/datawww.wri.org/facts/data--tables.htmltables.html).). The The numbers other people give can be greatly numbers other people give can be greatly different from thesedifferent from these

SOLARSOLAR

•• two kinds:two kinds:photovoltaic (PV) electric photovoltaic (PV) electric

cellscells••

solar hotsolar hot--water systems water systems (sun heats pipes directly, with (sun heats pipes directly, with water or more exotic fluid flowing water or more exotic fluid flowing slowly through them)slowly through them)

•••• PV cells have efficiency PV cells have efficiency

ranging from 6% to 30% ranging from 6% to 30% (percentage of incident solar (percentage of incident solar power that comes out as power that comes out as electricity). Cost of PV cells electricity). Cost of PV cells coming down rapidlycoming down rapidly

•• Growth of industry is strong. Growth of industry is strong. Government subsidies have Government subsidies have declined. declined.

•• Solar hot water is simply Solar hot water is simply black colored pipes in which black colored pipes in which water is warmed by the sun and water is warmed by the sun and circulates back into your hotcirculates back into your hot--water heater. Usually combined water heater. Usually combined with electric booster for dark with electric booster for dark days.days.

At solar noon on a clear March or September At solar noon on a clear March or September equinoxequinox day, the solar radiation day, the solar radiation at the equator is about 1000 W/m2. Hence, the "standard" solar rat the equator is about 1000 W/m2. Hence, the "standard" solar radiation adiation (known as the "air mass 1.5 spectrum") has a power density of 10(known as the "air mass 1.5 spectrum") has a power density of 1000 00 wattswatts per per square square metermeter. Thus, as 12% efficiency solar cell having 1 m. Thus, as 12% efficiency solar cell having 1 m22 of surface area in of surface area in full sunlight at solar noon at the equator during either the Marfull sunlight at solar noon at the equator during either the March or September ch or September equinoxequinox will produce approximately 120 watts of peak power.will produce approximately 120 watts of peak power.

•• Using the commercially available solar cells (as of 2005) Using the commercially available solar cells (as of 2005) and system technology leads to system efficiencies and system technology leads to system efficiencies between 5 and 15%. As of 2005, electricity generation between 5 and 15%. As of 2005, electricity generation costs ranged from ~ 50 eurocents/kWh (0.60 US$/kWh) costs ranged from ~ 50 eurocents/kWh (0.60 US$/kWh) (central Europe) down to ~ 25 eurocents/kWh (central Europe) down to ~ 25 eurocents/kWh (0.30 (0.30 US$/kWh) in regions of high solar irradiationUS$/kWh) in regions of high solar irradiation. This . This electricity is generally fed into the electrical grid on the electricity is generally fed into the electrical grid on the customer's side of the meter. The cost can be compared customer's side of the meter. The cost can be compared to prevailing retail electric pricing (as of 2005), which to prevailing retail electric pricing (as of 2005), which varied from between varied from between 0.04 and 0.50 US$/kWh worldwide.0.04 and 0.50 US$/kWh worldwide.

Wind powerWind power is estimated by our riveris estimated by our river--flowflow--power formula, ½ power formula, ½ CρvCρv33AA where A is the area swept out by the blades of the generating where A is the area swept out by the blades of the generating tower and v is the wind speed, ρ the density of air. I add a mutower and v is the wind speed, ρ the density of air. I add a multiplier C ltiplier C which is a smallish number expressing the inefficiency of capturwhich is a smallish number expressing the inefficiency of capturing the ing the full power of the wind; suppose C=0.1.full power of the wind; suppose C=0.1.…notes from …notes from en.wikipedia.orgen.wikipedia.org

Denmark’s coastReading England

•• The largest offshore wind turbines in the world The largest offshore wind turbines in the world are are 3.6MW3.6MW (peak power) rated machines that (peak power) rated machines that are installed in a small group of seven turbines are installed in a small group of seven turbines off the east coast of Ireland about off the east coast of Ireland about 60km60km south south of Dublin. The turbines are located on a of Dublin. The turbines are located on a sandbank approximately sandbank approximately 10km10km from the coast from the coast that has the potential for the installation of that has the potential for the installation of 500MW500MW of generation capacity. of generation capacity. As of 2006As of 2006, the , the largest offshore wind farm is Horns Rev which is largest offshore wind farm is Horns Rev which is located located 15km15km west off the West coast of west off the West coast of JutlandJutland, , DenmarkDenmark..[11[11]]

•• [3][3] Wind power is growing quickly, at about 38%,Wind power is growing quickly, at about 38%,[4][4] up from 25% up from 25% growth in 2002. In the United States, as of 2003, wind power wasgrowth in 2002. In the United States, as of 2003, wind power wasthe fastest growing form of electricity generation on a percentathe fastest growing form of electricity generation on a percentage ge basis.basis.[5[5]] In 2005, wind energy cost oneIn 2005, wind energy cost one--fifth as much as it did in fifth as much as it did in the late 1990s, the late 1990s,

Wind's long-term technical potential is believed 5 times current global energy consumption or 40 times current electricity demand. This requires 12.7% of all land area, or that land area with Class 3 or greater potential at a height of 80 meters. It assumes that the land is covered with 6 large wind turbines per square kilometer.Offshore resources experience mean wind speeds ~90% greater than that of land, so offshore resources could contribute ~7 times more energy than land.[24][25]

•• The ratio of actual productivity The ratio of actual productivity in a year to this theoretical in a year to this theoretical maximum is called the capacity maximum is called the capacity factor. A wellfactor. A well--sited wind sited wind generator will have a capacity generator will have a capacity

factor of as much as 35%.factor of as much as 35%.

darkest blue: 1000 watts/m2 (that is, m2 of swept out area by propellers); mid-blue (N Dakota) 225 watts/m2

lightest blue 125 watts/m2

•• There are many thousands of wind turbines operating, with a totaThere are many thousands of wind turbines operating, with a total l capacity of 58,982 MW of which capacity of 58,982 MW of which EuropeEurope accounts for 69% (2005). It accounts for 69% (2005). It was the most rapidlywas the most rapidly--growing means of alternative electricity growing means of alternative electricity generation at the turn of the century and provides a valuable generation at the turn of the century and provides a valuable complement to largecomplement to large--scale basescale base--load power stations. World wind load power stations. World wind generation capacity more than quadrupled between 1999 and 2005. generation capacity more than quadrupled between 1999 and 2005. 90% of wind power installations are in the US and Europe, but th90% of wind power installations are in the US and Europe, but the e share of the top five countries in terms of new installations feshare of the top five countries in terms of new installations fell from ll from 71 % in 2004 to 55 % in 2005. 71 % in 2004 to 55 % in 2005.

•• By 2010, World Wind Energy Association expects 120,000 MW to be By 2010, World Wind Energy Association expects 120,000 MW to be installed installed worldwide.worldwide.[12[12]] Wind accounts for 1% of the total Wind accounts for 1% of the total electricity production on a global scale (2005). Germany is the electricity production on a global scale (2005). Germany is the leading producer of wind power with 32% of the total world leading producer of wind power with 32% of the total world capacity in 2005 (6% of German electricity); the official targetcapacity in 2005 (6% of German electricity); the official target is is that by 2010, renewable energy will meet 12.5% of German that by 2010, renewable energy will meet 12.5% of German electricity need electricity need

•• Energy payback ratio (ratio of energy produced Energy payback ratio (ratio of energy produced compared to energy expended in construction and compared to energy expended in construction and operation)foroperation)for wind turbines is between 17 and 39 (i.e. wind turbines is between 17 and 39 (i.e. over it's lifeover it's life--time a wind turbine produces time a wind turbine produces 1717--3939 times as times as much energy as is needed for its manufacture, much energy as is needed for its manufacture, construction, operation and construction, operation and decomissioningdecomissioning). This is to ). This is to be compared with be compared with 1111 for coal power plants and for coal power plants and 1616 for for nuclear power nuclear power plants.plants.[28[28]]

•• The energy consumption for production, installation, The energy consumption for production, installation, operation and decommissioning of a wind turbine is operation and decommissioning of a wind turbine is usually earned back within usually earned back within 3 months3 months of of operation.operation.[[DanishDanish Wind Turbine Manufacturers Ass Wind Turbine Manufacturers Ass

Capacity (MW)

Rank Nation 03/2006 2005 2004

1 Germany 18,428 16,629

2 Spain 10,027 8,263

3 USA 9,549 9,149 6,725

4 India 5,200 4,430 3,000

5 Denmark 3,128 3,124

6 Italy 1,717 1,265

7 United Kingdom 1,598 1,353 888

8 China 1,260 764

9 Netherlands 1,219 1,078

10 Japan 1,040 896

•• Even Bjorn Even Bjorn LomborgLomborg waxes poetic about the value of these alternative waxes poetic about the value of these alternative energy sources. It is apparently now cheaper to build a unit of energy sources. It is apparently now cheaper to build a unit of electricity electricity generation from wind than from fossil fuel, and the hidden envirgeneration from wind than from fossil fuel, and the hidden environmental onmental costs of fossil fuel are not even factored in to that comparisoncosts of fossil fuel are not even factored in to that comparison..

•• An important issue (consult our first week’s list of ‘propertiesAn important issue (consult our first week’s list of ‘properties of energy’ that of energy’ that we studied) is we studied) is storage and transmissionstorage and transmission: the desert is a great place to make : the desert is a great place to make solar PV electricity but how do move it to where it is needed. Tsolar PV electricity but how do move it to where it is needed. The advent of he advent of power utilities willingness to buy excess electricity from consupower utilities willingness to buy excess electricity from consumers with mers with roofroof--top generation goes a long way toward promoting that source. Andtop generation goes a long way toward promoting that source. Anddecentralization decentralization of our power generation makes sense for other reasons: of our power generation makes sense for other reasons: stability, immunity from terrorism.stability, immunity from terrorism.

•• Energy has suffered the same push toward ‘Energy has suffered the same push toward ‘commodificationcommodification’…putting it all ’…putting it all in the hands of private commercial interests, which is also affein the hands of private commercial interests, which is also affecting fresh cting fresh water supplies. Enron’s collapse came after it had manipulated water supplies. Enron’s collapse came after it had manipulated energy energy markets, notably affecting the California electricity ‘crisis’. markets, notably affecting the California electricity ‘crisis’. There is an There is an ongoing debate over which of our natural resources should be fulongoing debate over which of our natural resources should be fully ly commercialized and which should have some degree of government acommercialized and which should have some degree of government and nd social protection…acknowledging that people have some right to hsocial protection…acknowledging that people have some right to harvest arvest energy that lies in the public domain.energy that lies in the public domain.