Exam 4

The Ozone Layer and Chlorofluorocarbons (CFCs)

-How do humans change this natural ozone equilibrium? -A thick ozone layer is beneficial to life on earth -Periodically, an ozone hole forms over either pole. -CFCs attack ozone and can destroy, or thin, the ozone layer -Cl •+ O3 -> ClO •+ O2 Eq-1 ClO• + O -> Cl •+ O2 Eq-2 Life of Cl atom in atmosphere is 1-2 years. In 1-2 years, one Cl atom will repeat Eq-1 100,000times. One Cl atom destroys ~ 100,000 the # of O3 atoms. It is a very efficient reaction mechanism! -CFCs build up their concentration in the upper atmosphere, have a residence time of about 100 years

How does O3 interacts with UV radiation?

-O3 is being consistently produced and destructed via interacting with UV radiation, which achieves an equilibrium for O3 concentration -UVC absorbed by O2: UVC splits O2 into two oxygen atoms - these combine with another O2 to form O3 (O3production) O2-> O + O O + O2-> O3 -UVB absorbed by O3 ( O3 destruction) UVB splits O3 into O2 plus a free oxygen atom (which combines with another to form O2) O3-> O2 +O O+O->O2

Causes of global climate changes

1. changes in solar output 2. Changes in Earth's orbit (via Milankovitch Cycles) 3. Plate tectonics and continent configuration. 4. Changes in the concentration of "Greenhouse Gases" in the atmosphere. - note the mechanisms operate over different timescales.

Rainwater that has a PH less than ( ) is considered acid rain.

5.3

Which of the following is a correct statement of the Suess Effect? Adding large quantities of fossil fuel carbon to the atmosphere will decrease the concentration of 14C in the atmosphere Adding large quantities of fossil fuel carbon to the atmosphere will not change the concentration of 14C in the atmosphere Adding large quantities of fossil fuel carbon to the atmosphere will increase the concentration of 14C in the atmosphere None of the above

Adding large quantities of fossil fuel carbon to the atmosphere will decrease the concentration of 14C in the atmosphere

Possible causes of modern period climate change

Anthropogenic: chemical fertilizers, deforestation, increase vehicles, emissions of GHG, Industries, Emission of Co2. Natural: Sunspot and solar cycle, Ocean Currents, Forest Fire, Volcanic Eruptions, Meteorites, Methane emissions form animals.

Please observe the figure below and think why the pH of precipitation is overall lower in the east than in the west?

Because pedofer soil has lower neutralizing capacity than pedocal soil (review the soil topic as needed)

Ozone

Concentrations below even 1 ppm can be hazardous Lung irritant- "It can cause headaches, eye, nose and throat irritations. It may cause the lung function impaired, coughing." Inhibits photosynthesis- "It can damage plants, leading to the loss of crops and damage plants" It can cause rubbers and fabrics to deteriorate.

eccentricity

Earth's distance to Sun; seasonal changes.

Milankovitch Cycles : eccentricity

Eccentricity: describing the changes in the shape of the Earth's orbit (eccentricity) as the Earth rotates about the Sun. Eccentricity influences the distance between the earth and the sun The cycle is ~100,000 years High eccentricity = the more elliptical (less round) the orbital shape Eccentric influences seasonality High eccentricity= wilder fluctuations between perihelion and aphelion= more changes among seasons Presently, we are in a period of low eccentricity (~3%) and this gives us a seasonal change in solar energy of ~7%. When the eccentricity is at its peak (~9%), the "seasonality" reaches ~20%.

EPA clean air act

Emissions of sulfur dioxide: effectively reduced by the EPA clean air act

Why are nitrogen oxide (NOx) gases air pollutants?

First, NOx also contributes to acid rain •2NO2 + H2O + ½ O2 = 2HNO3 (nitric acid, acid rain)

Stable isotopic evidences

Fossil Fuel has lower δ13C values compared to many other CO2sources (e.g. oceans, weathering) However, this same principle applies to 13C vs. 12C: plants preferentially take up 12C over 13C; lighter isotopic ratios are typical of photosynthesis-filtered carbon populations. So when isotopically light fossil fuels are burned, once again, the overall isotopic ratio of the atmosphere becomes "seasoned" with lightweight CO2. The measure of the ratio of 13C to 12C is usually expressed as a value called δ13C. Higher δ13C = more 13C than 12C. Lower δ13C = more 12C than 13C. Here's data from Mauna Loa (Hawaii) and the South Pole (Antarctica), showing variations in atmospheric δ13C over the past ~30 years:

slide 14

From this figure: 1) the rate of ice shelve loss is spatially uneven in Antarctica; 2) the loss rate is high in the west; 3) ice shelve in the north show slight gain; 4) The total mass of ice shelves showed net loss in 18 years

Good versus Bad Ozone (O3)

Good Ozone in Stratosphere, which is beneficial and crucial for life- Stratospheric ozone Bad Ozone in Troposphere related to photochemical smog- Tropospheric ozone

Here is an example that acid rain accelerates chemical weathering

Granite obelisk - in Egypt (left): 1600BC, well defined for 3500yrs; but became elusive after 75yrs in central park in NY (right)

Antarctic Mass Variation

Gravity data collected from space using NASA's Grace satellite show that Antarctica has been losing more than a hundred cubic kilometers of ice each year since 2002

Storm Surge

Hurricane season July -November, peak between August-October 90% death in Hurricane is due to storm surge A storm surge is an abrupt bulge of water driven ashore by hurricanes or storms Offshore rise of water > 15ft High winds pushing on ocean's surface

Sulfur Gases

Less than 50 million tons of sulfur dioxide (SO2) are emitted worldwide. - ~2/3 from coal combustion. - Remainder from refining and burning of petroleum. •SO2 sulfur dioxide forms acid rain -very short residence time (days or hours) -Reacts with rain (SO2 + H2O + ½ O2 = H2SO4) to produce •Lowers pH of rain - acid rain (pH < 5.3) •Can cause lung and eye irritation •Increase soil leaching (think about the chemical weathering in the topic of soil), harm vegetation, kill aquatic organisms (think about the acid mine drainage)

Why are some cities developing photochemical smog more often than others?

Local topography - mountains, basins, valleys, and local wind patterns amplify the pollution The two figures below show that pollutants can be trapped locally due to temperature inversion (cool air below warm air, as opposed to the normal condition where cool air is above warm air)

Loss of ecological habitats-example: the Chesapeake Bay

Loss of biological habitats of ecological importance Also the loss of protection from wetlands & islands from the storms

Why is there an Ozone hole over Antarctic and Arctic?

Low temperature- formation of polar stratospheric clouds (PSC), which provides a surface for reaction ClO + NO2à ClONO2 ; ClONO2 + HCl à Cl2 + HNO3; Cl2 +hvà 2Cl•

Among the following, which one is not greenhouse gas? - CO2 - CH4 - CFC-12 - O2

O2

Milankovitch Cycles

Obliquity Cycle: 41,000 years Describes changes in the tilt of the Earth's axis The current tilt is 23.5º, the range of tilt over one cycle is from 22 to 24.5º Smaller obliquity= smaller tilt=less seasonal variation between summer and winter (mild winter and cool summer= glaciation) Precession Cycle: 23,000 years Describes the "wobble" of the spin axis Presently the Earth is closest to the Sun in winter and farther away in summer (mild winter and cool summer in N Hemisphere) After ~11,000 years, the opposite would be true (server, harsh winter and hot summer in N Hemisphere)

All of the following cause rainwater to be acidic except?

Ozone

smog

Photochemical Smog is the interaction of electromagnetic radiation from the Sun and Primary Pollutants to form photochemical smog. Photochemical smog is a mixture of pollutants which includes particulates, nitrogen oxides, ozone, aldehydes, peroxyethanoyl nitrate (PAN), unreacted hydrocarbons, etc. Photochemical smog appears as Brown haze due to the presence of nitrogen dioxide—Los Angeles and Denver--- vehicles It is different from Grey smog (traditional) --- ashes, soot, and sulfur compounds --- London and NYC---coal and fuel oil

Long-term Sea Level Rise

Satellite Altimetry has not been used until recently Sea level rise over a longer term can be also reconstructed using paleoclimate proxies and numerical modeling The data show a steady rise in the sea level after 1920

Sea Level Rise

Satellite Altimetry shows that the sea level increases at ~3mm per year since 1994.

Why are nitrogen oxide gases air pollutants?

Second, NOx contributes to the production of photochemical smog and the formation of bad ozone (troposphere ozone) NOx + VOC (volatile organic compound) + Sunlight -> Ozone Three Key ingredients of photochemical smog: UV light, hydrocarbons, nitrogen oxide What does bad ozone do? (see the next slide) More details about photochemical smog? (see the slide after the next slide)

All of the following cause rainwater be acidic

Sulfur dioxide, nitrogen oxide, carbon dioxide( this does not lead to acid rain but does make rainwater acidic ref. CO2)

Flood and loss of land- example: southern Louisiana

The region highlighted in red is only 8 meters or less above the sea level With the current rising rate of 3mm/year, it takes ~267 years or less for the region to be underwater Note this also applies to some areas in Mobile, AL

Temperature anomaly in the past 2k yr

This figure shows temperature data collected using three different methods: 1) Instrumental record (smallest error); 2) Paleotemperature reconstruction; and 3) Numerical model simulationsThis figure also shows: 1) uncertainties are large in reconstructed temperature records; 2) temperature rises at a unprecedently high rate since after ~1950

Global Climate Network Temperature Stations

This map shows that we have started accumulating long-term instrumental temperature data However, most of the records are less than 150 years; many are <100 years Also, the spatial distribution is uneven; the highest density in the US

Volume loss from Antarctic ice shelves is accelerating

This paper shows that Antarctic ice shelf volume loss is accelerating The data are collected using satellite altimetry Unlike gravity satellite that measures the mass of glaciers, satellite radar altimeter measures the thickness of glaciers See notes below on how satellite altimetry works Altimetry satellites basically determine the distance from the satellite to a target surface by measuring the satellite-to-surface round-trip time of a radar pulse. However, this is not the only measurement made in the process, and a lot of other information can be extracted from altimetry. The principle is that the altimeter emits a radar wave and analyses the return signal that bounces off the surface. Surface height is the difference between the satellite's position on orbit with respect to an arbitrary reference surface (the Earth's centre or a rough approximation of the Earth's surface: the reference ellipsoid) and the satellite-to-surface range (calculated by measuring the time taken for the signal to make the round trip). Besides surface height, by looking at the return signal's amplitude and waveform, we can also measure wave height and wind speed over the oceans, and more generally, backscatter coefficient and surface roughness for most surfaces off which the signal is reflected.If the altimeter emits in two frequencies, the comparison between the signals, with respect to the frequencies used, can also generate interesting results (rain rate over the oceans, detection of crevasses over ice shelves, etc).

Ozone in the upper atmosphere can protect our skin because it efficiently absorbs______________ -UVA - UVB - Visible light - Infrared light

UVB

*note this question is not exactly the same with a similar question on the slide. True or False: TrueThe ozone layer in the Stratosphere is considered pollutant.

false

Brown haze we observe in large cities such as Los Angeles and Beijing is due to the presence of sulfur compounds from coal combustion.

false

True or False: When a chlorine atom destroys an ozone molecule, that chlorine atom is taken out of circulation and locked in the product molecule (ClO) so that it can do no more harm.

false

UVC is the most hazardous UV to humans and has longer wavelength than UVA and UVB.

false

For the Milankovitch Cycle, higher eccentricity means_________________________ - greater deviation from a perfect round shape for the orbital of the Earth rotating about the sun. - lower deviation from a perfect round shape for the orbital of the Earth rotating about the sun. - a greater tilt of the Earth's axis. - a lower tilt of the Earth's axis.

greater deviation from a perfect round shape for the orbital of the Earth rotating about the sun.

Large obliquity will lead to ______. mild winter and cool summer harsh winter and hot summer Mild winter and hot summer Harsh winter and cool summer

harsh winter and hot summer.

Most likely, acid rain will _______ leaching in soils.

increase

weather

is the ever-changing combination of winds, clouds, temperature, and pressure at a particular location and time.

climate

is the long-term average of weather (usually 30 years or longer for Earth climate); likely in very large area.

Indirect evidence of climate change

observations indicating a rising temperature. - glacier meltdown - sea level rise.

The ingredients necessary for the formation of photochemical smog include all of the following EXCEPT__________ - sunlight - volatile organic compounds - nitrogen oxides (NOx) - Ozone

ozone

ozone hole" over Antarctica September,2006

ozone hole: ozone is depleted.

PH

pH reflects the hydrogen ion concentrations in a solution High hydrogen ion concentration=low pH=acidic Low hydrogen ion concentration=high pH=alkaline pH=-log[H+] Observe the figure on the left: Neutral pH=7 Normal precipitation: pH ~5.3 to 6 Acid rain: pH<5.3 Normal range of stream of pH: 6-8 Seawater pH: ~8.1 Think: 1) why is normal precipitation slightly acidic? 2) Why is the pH of stream water higher than the pH of normal precipitation?

The long-term (100s millions of years) climate change is linked to __________________________

plate tectonics

obliquity

strength of season

Air Pollution

sulfur and nitrogen gases and CFCs.

Interpret this figure: 0= the mean of the temperature record of AD 1000-1980 Note that the 1998 instrument value (black dashed line) shows an anomaly of +0.7 oC Also note the quick rise of temperature since 1900

t

direct evidence of climate change?

temperature increase.

precession

timing of season.

Acid rain was a severe issue in the eastern part of the U.S. in 1980s It has been significantly improved due to the reduction of SO2 emission and NOx emission

true

Greenhouse gases act like glass in a gardener's greenhouse. Light enters the greenhouse, changes to heat, and is trapped inside by the glass. Likewise, sunlight enters the atmosphere, is changed to heat, and is trapped by greenhouse gases.

true

Medium-term climate change (1 million year): Milankovitch Cycles There are three types of orbital changes: eccentricity, obliquity, and precession The three orbital parameters co-regulate climate changes The climatic records reflect accumulative effects of the three cycles

true

Sea Level Rise threatens coastal regions

true

This figures shows long-term climate changes (100s million years) During the last 2 billion years the Earth's climate has alternated between a "Ice House", like today's world, and a "Hot House", like the world of the dinosaurs. Long-term changes have been attributed to plate tectonics

true

•SO2 emission has been effectively reduced to below the level of the National standard

true

Note that the EPA Clean Air Act did not effectively reduce the NOx emissionNitrogen-gas emissions - hard to reduce as they are an inevitable by-product of combustion: reduce temperature?

true •Although NO2 emission is below the level of National standard, one of the products O3 is still above the national standard

In the Troposphere, is ozone considered a pollutant?

yes

Air Pollution Control

•Automobile Emissions - -Goal to reduce automobile emissions -Catalytic converters (platinum group) •Enhances combustion or oxidation of hydrocarbons and CO to produce CO2 and water, which is good for reducing hydrocarbon and CO pollution •Meanwhile it enhances production of sulfuric acid and nitrogen oxide, which is not so good •Control Methods -Air filters - very efficient (99.9%), but typically combustible - not good for hot gases -Scrubbers - high voltage charges particulates - caught on charged plates - 98-99.5% efficient •Costly •Used at coal fired power stations -Wet scrubber - passed through mist or stream of water •Dissolves gases, removes particulates -Wet chemical scrubber - passed through slurry of lime (CaO) or limestone (CaCO3) •Reacts with sulfur gases -Lower combustion temperatures, which can reduce the emission of nitrogen oxides -Afterburners to complete combustion process Converts carbon monoxide to carbon dioxide

•Why is the pH of stream water higher than the pH of normal precipitation?

•Because stream water comes mostly from surface runoff and groundwater; precipitation can be neutralized to some extent via reacting with minerals For example: CaCO3+ 2H+= Ca2+ + H2O+CO2

How do we know this is anthropogenic CO2?

•CO2 rises agree with fossil fuel burning data •Geochemical evidences: Global alteration in carbon isotopes---"Suess" effect (14C (radiogenic carbon) is produced continuously in the upper atmosphere 1n + 14N --> 14C + 1H The half life of 14Carbon is 5730 years 14C becomes undetectable 10 half livers- dead carbon Large quantities of "dead" carbon have been added to the atmosphere--- dilute the 14C pool) •Climate modeling evidences

What is the difference between hydrogen containing (H)CFCs and halogen saturated CFCs?

•Change in CFC formula: current substitute---- Hydrohaloalkanes (containing at least one hydrogen atoms) •Hydrogen containing CFCs only last a relatively short time and probably never make it to the Stratosphere. CH3CCl3 and CHClF2 only last 6-7 years. Short lifetime: lower O3 destruction ability •Method of destruction in Troposphere. CHClF2 + OH• àH2O + CClF2• The hydroxyl radical is the natural air cleanser of the Troposphere and can work on (H)CFCs (not CFCs).

climate change

•Direct evidence, Temperature: the global temperature has been rapidly increasing since 1900s •Indirect evidence, glacier melting and sea-level rising: agreeing with the temperature change and supporting global warming over the last century

Glacier Meltdown

•How do we estimate glacier mass? •One way is to use satellite •Grace Twin Satellite (Gravity Recovery and Climate Experiment): Tom and Jerry, launched in 2002 •They measure changes in glacier mass by measuring the gravity exerted by the ice sheet •The principle is that mass and gravity are positively correlated- an increase in mass corresponds to an increase in the gravitation force exerted •Loss of glacier mass is thus reflected in the loss of gravity of a scoped region Check the note below on how the twin satellites measure gravity field fluctuations GRACE, twin satellites launched in March 2002, are making detailed measurements of Earth's gravity field which will lead to discoveries about gravity and Earth's natural systems GRACE will obtain a gravity field map by looking at how the Earth's mass varies from place to place on the surface as the twin satellites pass over. Mass and gravity are positively correlated - that is to say an increase in mass relates to an increase in the gravitational force exerted. Mass is also related to the density and amount of materials located in any one place. For example rock is more dense (i.e., more mass per unit of volume) than water, and water in its liquid form is generally more dense than in its solid form. Also, a very large amount of rock, such as would be found in a large mountain, has more mass than a small amount of rock, such as might be found in a coastal area . Since the Earth has varied topographic features such as mountains, valleys, and underground caverns, the mass is not evenly distributed around the globe and different physical features can be distinguished. The lumps observed in the Earth's gravity field result from this uneven distribution of mass on the Earth's surface and GRACE will map these perturbations with unprecedented accuracy. As the GRACE-twins fly in formation over the Earth the precise speed of each satellite and the distance between them is constantly communicated via a microwave K-band ranging instrument. As the gravitational field changes beneath the satellites - correlating to changes in mass (topography) of the surface beneath - the orbital motion of each satellite is changed. This change in orbital motion causes the distance between the satellites to expand or contract and can be measured using the K-band instrument. From this, the fluctuations in the Earth's gravitational field can be determined. Here's an example of how it works. The two GRACE satellites are traveling in space, both 500 kilometers above the earth. As the front satellite approaches an area of higher gravity, it will be pulled toward the area of higher gravity and speed up. This increases the distance between the two satellites. As the satellites straddle the area of higher gravity, the front satellite will slow down and the trailing satellite will speed up. As the trailing satellite passes the area of higher gravity, it will slow down and the lead satellite will not be affected. As the satellites move around the Earth, the speeding up and slowing down of the satellites will allow scientists to measure the distance between the two satellites, and, therefore, map the earth's gravity field. . The GRACE satellites house microwave ranging systems that measure the change in the distance between the satellites over time, enabling them to essentially "weigh" the changes in Gulf of Alaska glaciers. Credit: NASA

Extreme Climatic Events: Hurricane and tropical storms

•Increase the frequency and intensity of Hurricane and tropical storms •The first step of Hurricane formation is warm ocean surface temperature (>80F) that provides energy and evaporation •Increases in the global temperature and sea surface temperature lead to increases in tropic storms •Catastrophic damages are seen around the world •Category 4 hurricanes have increases from 0.26 per year from 1851-1900 to 1.4 per year from 2001-2020 •Some examples: Hurricane Katrina (2005): category 5; Hurricane Delta and Eta (2020): category 4

why is normal precipitation slightly acidic?

•It is due to the presence of CO2. CO2 reacts with water and produces hydrogen ions •CO2+H2O= H+ + HCO3-

Nitrogen Gases

•Nitrogen gases have complex geochemistry -oxygen and nitrogen are very abundant in the atmosphere (O2: 21%, N2: 78%) -However, N2 and O2 require high temperatures tocause nitrogen and oxygen to form nitrogen oxide compounds (engine) (NOx) -Nitrogen oxides (NOx) include: NO, NO2, etc. -Anthropogenic sources are related to combustion; the pollution is concentrated in urban areas, mostly from transportation

Food security- example: Bangladesh

•Saltwater intrusion •Salinity increases in groundwater and surface water •Disastrous effects in rice farms

Why is stratospheric O3 beneficial?

•Stratospheric ozone layer absorbs harmful ultraviolet (UV) radiation •UV radiation causes skin cancer: 1% reduction in stratospheric ozone might result in 3% increase in skin cancer cases •UVA -longest wavelength, least harmful (aging of skin, tanning, some cancer, moles) - zinc and titanium oxide •UVB - intermediate wavelength, absorbed by ozone (main cancer risk) •UVC - shortest wavelength, most damaging, but absorbed by oxygen and water vapor in the atmosphere •Note the energy E is negatively proportional to wavelength. So, the longer the wavelength, the less energy and less harmful •Observe the figure below to check the wavelength of different lights

Modern period climate changes (centuries): The Greenhouse Effect

•The Greenhouse Effect involves sun light (energy) entering the atmosphere and a component of the atmosphere (CO2) trapping radiant heat (infrared energy) •The result is warming of the atmosphere and Global Warming •Increases, or decreases, in the concentration of CO2 in the atmosphere will show a respective increase, or decrease, in global warming

Long-term climate change vs. Plate tectonics

•The continents (plates) "drift" on top of a fluid substrate over geologic time. • •At the edge of plates, plates collide or move apart, leading to increased volcanism. •Volcanism releases greenhouse gas "CO2" to the atmosphere • •CO2 can be removed from the atmosphere by dissolving into the ocean and reacting with rocks and minerals • •Ice House: low volcanism, low CO2 Warm House: high volcanism, high CO2

Sea level change

•Tools: satellite radar altimetry the Ocean ToPography EXperiment (TOPEX/Poseidon): a joint U.S./French satellite that uses radar to map the precise features of the oceans' surface Jason: measures ocean height and monitors ocean circulation Ice, Cloud and Land Elevation Satellite (ICESat): to study the mass of polar ice sheets and their contributions to global sea level change. Altimeter received waveforms in sea to land transition illustration (COASTALT portal); http://www.altimetry.info/radar-altimetry-tutorial/how-altimetry-works/

Loss of land, country, culture-Tuvalu is Disappearing

•Tuvalu is a Polynesian island nation in the Pacific Ocean •It has a population of ~13k •4.5 meter above sea level •Tuvalu is the strongest critics for the lack of adequate joint efforts in mitigating climate changes •Check this video to learn the consequences of Climate Change in Tuvalu

CFC Sources

•Uses of CFCs: Coolants in air conditioning and refrigerating; Cleaning of electrical parts; Fumigants for granaries and cargo holds; Bubbles in polystyrene plastic foam packaging & insulation; Propellants in aerosol spray cans Industrialized countries use 84% of CFCs •US is 25% of global consumption of CFCs: Vehicle air conditioners account for about 3/4 of US CFC emission. •Demographics: By year 2000, 75 countries phased out all CFC use, banned in US since 1978 •Current substitute---- HCFC, containing at least one hydrogen atoms shorter residence time: 6-7yrs Beginning of phase-out HCFCs

Is Global Warming happening?

•Weather vs. climate •If this is true, what types of evidence you need to see? As such, we must examine long-term weather records across a large spatial area to examine climate change