Atmospheres & Global Warming Earth and the Other Terrestrial Worlds
Weather and Climate Weather – short-term changes in wind, clouds, temperature, and pressure in an atmosphere at a given location Climate – long-term average of the weather at a given location § These are Earth’s global wind patterns or circulation • local weather systems move along with them • weather moves from W to E at midlatitudes in N hemisphere § Two factors cause these patterns • atmospheric heating • planetary rotation
Global Wind Patterns § Air heated more at equator • Warm air rises at equator; Pressure pushes to poles • Cold air moves from poles to equator along the surface § Two circulation cells are created in each hemisphere § Cells of air do not go directly from pole to equator; air circulation is diverted by… § Coriolis effect • moving objects veer right on a surface rotating counterclockwise • moving objects veer left on a surface rotating clockwise
Global Wind Patterns § On Earth, the Coriolis effect breaks each circulation cell into three separate cells • winds move either W to E or E to W • Coriolis effect not strong on Mars & Venus • Mars is too small • Venus rotates too slowly • In thick Venusian atmosphere, the pole-to-equator circulation cells distribute heat efficiently • surface temperature is uniform all over the planet
Earth’s Atmosphere
Structure of Earth’s Atmosphere § Pressure & density of decrease with altitude § Temperature both increases and decreases with altitude • Temperature domains define the major atmospheric layers § exosphere • low density; fades into space § thermosphere • temp begins to rise at the top (mesosphere) § stratosphere • UV light heats air (ozone absorbs it. ) § troposphere • layer closest to surface • Convection heats air (rising hot air) • temp drops with altitude Stratosphere Ozone Layer (absorbs UV) Troposphere
Structure of Terrestrial Planet Atmospheres § Mars, Venus, Earth all • have warm tropospheres (and greenhouse gases) • have warm thermospheres which absorb Solar X rays § Only Earth has • a warm stratosphere • an UV-absorbing gas (O 3) § All three planets have warmer surface temps due to greenhouse effect
CFCs Attack Ozone (O 3) The stratospheric ozone is an environmental success story. Scientists detected the declining ozone in the atmosphere, collecting the evidence that convinced governments around the world to take regulatory action.
Climate History of Venus § Venus should have outgassed as much H 2 O as Earth. • Early on, when the Sun was dimmer, Venus may have had oceans of water § Venus’ proximity to the Sun caused all H 2 O to evaporate. • • H 2 O caused runaway greenhouse effect surface heated to extreme temperature CO 2 released from rocks: Adds to greenhouse effect UV photons from Sun dissociate H 2 O; H 2 escapes, O is stripped If Earth moved to Venus’ Orbit
Venusian Weather Today • Venus has no seasons to speak of. • rotation axis is nearly 90º to the ecliptic plane • Venus has little wind at its surface • rotates very slowly, so there is no Coriolis effect • The surface temperature stays constant all over Venus. • thick atmosphere distributes heat via two large circulation cells § There is no rain on the surface. • it is too hot and Venus has almost no H 2 O § Venusian clouds contain sulfuric acid! • implies recent volcanic outgassing?
Mars’ Thin Atmosphere § Martian sunset illustrates just how thin the Martian atmosphere is.
Martian Weather: N Polar Ice Cap & Dust Storm
Martian Weather Today • Seasons on Mars are more extreme than on Earth • Mars’ orbit is more elliptical • CO 2 condenses & vaporizes at opposite poles • changes in atmospheric pressure drive pole-to-pole winds • sometimes cause huge dust storms
§ The last decade of the 20 th Century was the warmest in the entire global instrumental temperature record, starting in the mid-1800’s. § All 10 years rank among the 15 warmest, and include the 6 warmest years on record. § Through the reconstruction of past climate we can evaluate the rarity and magnitude of this warming.
4. 6 Billion Years Ago. . . SUN Venus 0. 7 AU Earth 1 AU (150 million km from Sun) Mars 1. 5 AU
Temperature: Top of Atmosphere decreases with distance from Sun Temperature (Celsius) 500 Earth -18 o. C (0 o. F) 300 100 Venus Mars 0 0 AU -100 5500 o. C Distance From Sun 1 AU
EARTH: EARTH Surface 15 o. C (60 o. F) Top of Atm: -18 o. C (0 o. F) Temperature (Celsius) 500 300 Surface All three phases of water 100 0 No Greenhouse -100 Surface warmer than top of atm Greenhouse Effect Clue: atm composition
Vibrational Modes for CO 2 n 1 symmetric n 2 bending 15 mm n 2 asymmetric 4. 3 mm O C O Greenhouse effect: Radiation at specific wavelengths excite CO 2 into higher energy states. Light energy is absorbed by the CO 2 molecules
Other Greenhouse Gases O H O O ozone water H N O N H C H H nitrous oxide methane
Absorption by different molecules l = 0 -15 µm Absorption CO 2 Bending Mode Transmission Peak terrestrial emission at ~300 K
How Greenhouse Gases Warm the Troposphere CO 2
Energy Balance
Carbon Dioxide: in our atmosphere is Increasing rapidly Worldwide CO 2 Emission By fuel type: 1970 - 2020 Burning coal gasoline CO 2 Causes Global Warming: Stay tuned. . . Natural gas
Increase in Temperature tracks Increase in Greenhouse Gases Since 1850: Atmospheric CO 2 has increased by 30% Temperature vs Time 1850 Year 2000
CO 2 Since the Year 1000 AD CO 2 in atmosphere, measured in thick arctic ice.
FAQ 2. 1, Figure 1
Heat Content: Increase in Atmosphere and Ocean since 1945.
CO 2 Deuterium (hydrogen with a neutron) Time (thousands of years before present) Variations of deuterium (δD) in antarctic ice, which is a proxy for local temperature, and the atmospheric concentrations of the greenhouse gases carbon dioxide (CO 2), methane (CH 4), and nitrous oxide (N 2 O) in air trapped within the ice cores and from recent atmospheric measurements. Data cover 650, 000 years and the shaded bands indicate current and previous interglacial warm periods.
Figure TS. 6 Patterns of linear global temperature trends over the period 1979 to 2005 estimated at the surface (left), and for the troposphere from satellite records (right). Grey indicates areas with incomplete data. (Bottom) Annual global mean temperatures (black dots) with linear fits to the data. The left hand axis shows temperature anomalies relative to the 1961 to 1990 average and the right hand axis shows estimated actual temperatures, both in °C. Linear trends are shown for the last 25 (yellow), 50 (orange), 100 (magenta) and 150 years (red). The smooth blue curve shows decadal variations (see Appendix 3. A), with the decadal 90% error range shown as a pale blue band about that line. The total temperature increase from the period 1850 to 1899 to the period 2001 to 2005 is 0. 76°C ± 0. 19°C.
Retreat of Glaciers 1948 2002 2006 Trift Glacier, Gadmental, Berner, Oberland Switzerland
Easton Glacier A 2003 photograph of the ~2. 9 square kilometer Easton Glacier on Mount Baker in Washington State. Between ~1890 and 1950, this glacier retreated ~2400 meters. It subsequently expanded 600 meters during a locally cold period between 1950 and 1979. Since then, it has again retreated 315 meters (as of 2002) with 150 meters lost solely between 1997 and 2002. [1]. The extent of the glacier in 1985 is indicated in the
§ Franz Josef Glacier In Retreat 1939 1951 1964 1960
All survey regions except Scandinavia show a net thinning. This widespread glacier retreat is generally regarded as a sign of global warming. During this period, 83% of surveyed glaciers showed thinning with an average loss across all glaciers of 0. 31 m/yr.
Receding Glaciers Glacier Length (km) South Cascade Glacier in Washington. The yellow line indicates the location of the terminus in 1958. The red line shows the position of the terminus in 1998. 1500 2000
Is the Sun to Blame ? No. Luminosity has been constant. (Solar max) Percentage change in monthly values of the total solar irradiance composites of Willson and Mordvinov (2003; WM 2003, violet symbols and line) and Fröhlich and Lean (2004; FL 2004, green solid line). Sunlight hitting Earth: • 11 year Sunspot cycle • Offsets among instruments • No trend
Global Warming § Made a political issue by certain people. Three Facts are Absolute: 1. 2. 3. Earth has warmed by 0. 5 C in past 50 years. Temperature rise greatest in past 10 years. Humans are increasing by 30 -50% the CO 2 in the atmosphere. Rising CO 2 will cause rising temperatures Only Question: Not Whether, but by how much are humans contributing to Global Warming ?
Feedback Proceses: Positive and Negative Suppose Temp rises ==> Evaporation of ocean water. Feedback: § H 2 O is a greenhouse gas ==> Earth gets even Warmer ! § But clouds may form, increasing albedo. ==> Earth cools.
The Arctic: Positive Feedback Process § Temp rise causes polar cap ice to melt. § Artic ground exposed: dirt absorbs more sunlight (lower albedo). § Ground warms up more: Earth gets hotter. § More polar cap ice melts. Earth gets even hotter.
Consequences of Global Warming 1. More evaporation of oceans: More storms, and more severe storms. 2. Water in oceans expand with rising Temp. Sea level has already risen 20 cm in past 100 years. Coastal regions and islands flood. 3. Polar caps and Glaciers melt: Causes rising ocean levels. 4. Change in ocean current patterns. Desserts may get rain; Farmland may get none.
Consequences of Global Warming According to UN report: the world will be a much hotter place by 2100. +2. 4｡: Coral reefs almost extinct In North America, a new dust-bowl brings deserts to life in the high states, centeredd on Nebraska, but also wipes out agriculture and ranching as sand dunes appear across five US states, from Texas south to Montana in the north. Rising sea levels accelerate as the Greenland ice sheet tips into irreversible melt, submerging atoll na and low-lying deltas. In Peru, disappearing Andean glaciers mean million people face water shortages. Warming seas wipe out the G Barrier Reef and make coral reefs virtually extinct throughout the t
Predictions of temperatures next 100 years DEPENDS ON MAGNITUDE OF FEEDBACK AND RATE OF INCREASE OF GHG. IN 100 YEARS, FORCED CLIMATE CHANGE WILL MOST LIKELY EXCEED NATURAL VARIABILITY
The Kyoto Agreement The Kyoto Protocol, negotiated by more than 160 nations in 1997, will reduce emissions of certain greenhouse gases (primarily CO 2). Each of the participating developed countries must decide how to meet its respective reduction goal. Signed by every country in the European Union, by Japan, and by Russia.
Kyoto Agreement: The United States Won’t Sign § In March 2001, President Bush announced that the United States would not sign the Kyoto Protocol on Global Climate Change. § The Protocol requires signatories to cut carbon dioxide emissions an average of 5 percent below 1990 levels between 2008 and 2012. Developing nations are exempt from emission reductions. § “President Bush strongly opposes any treaty or policy that would cause the loss of a single American job, let alone the nearly 5 million jobs Kyoto would have cost. ” - James Connaughton, chairman of the White House council on Environmental Quality.
Stop Here. Show: An Inconvenient Truth § Get DVD somewhere. § Interesting Chapters: § 5 -9, 11, 16 -17, 20, § 21 -28, 30 -32 (or 5 -9, 16 -28) Takes 30 min.
Three Perspectives on Global Warming § Kyoto Protocol: unfccc. int/resource/convkp. html § White House Council on Environmental Quality: www. whitehouse. gov/ceq § Pew Center on Global Climate Change: www. pewclimate. org
http: //www. eia. doe. gov/oiaf/1605/vrrpt/summary/longform. html
United States Policy on CO 2 “Voluntary Reductions”
Three Perspectives on Global Warming § Kyoto Protocol: unfccc. int/resource/convkp. html § White House Council on Environmental Quality: www. whitehouse. gov/ceq § Pew Center on Global Climate Change: www. pewclimate. org
Ozone formation - ultra-violet radiation from the sun (shown in yellow) splits oxygen molecules into oxygen atoms which then react with more O 2 to form ozone. Another molecule (M) is needed to absorb some of the huge amount of energy involved in the reaction. § Formation of ozone: § Without ozone in the sttratosphere, life would not be possible on Earth. § Ozone prevents harmful ultraviolet radiation from the Sun (light with wavelengths less than 320 nm) reaching the ground. § If allowed to reach Earth, this radiation would severly damage the cells that plants and animals are made up of. § Ozone was first formed in the Earth's atmosphere after the release of oxygen, between 2000 and 600 million years before the first humans appeared.
The Ozone Hole § Ozone also plays a very important, natural role in the upper atmosphere (the stratosphere). Ozone absorbs harmful ultraviolet (UV) radiation from the sun. § Reductions in ozone results in the increase of harmful UV radiation reaching the Earth's surface. § The biggest destroyer of the ozone in the stratosphere is human produced chemical compounds: (chlorofluorocarbons - CFC's), Oct 1998
Earth radiance in the near ultraviolet spectrum. § More solar UV light is reaching the Earth over polar regions. March 14, 2006
Ozone Layer: Damage and Recovery In 1985 over 60 countries pledged to phased out a group of chemicals called CFC's. These very stable chemicals were once widely used in aerosols and refrigerators. It was thought that their release into the atmosphere produced chlorine radicals which reacted with O 3 to produce O 2. The emission of CFC's into the environment is now greatly reduced.
Human Activity Changes Our Planet § Ozone “hole” forming in the ozone layer over the Antarctic. § CFC (chlorofluorocarbons) Cl-O § International Treaties and policies: Montreal protocol: phase out of production of CFC and methyl bromide. § Ozone hole will take decades to recover: 100 year lifetimes of CFCs in the atmosphere. Recovery will be slow.
Habitat Destruction and Pollution § Chemicals, such as pesticides, damage reproduction of many species. § Habitat is lost, such as wetlands and migration paths over hundreds of miles. § Extinctions occurring at high rates, compared to historic averages.
Clouds, Rain and Snow § Clouds strongly affect the surface conditions of a planet • they increase its albedo, thus reflecting away more sunlight • they provide rain and snow, which causes erosion § Formation of rain and snow:
Four Major Factors that affect Long-term Climate Change
Gain/Loss Processes of Atmospheric Gas § Unlike the Jovian planets, the terrestrials were too small to capture significant gas from the Solar nebula. • what gas they did capture was H & He, and it escaped • present-day atmospheres must have formed at a later time § Sources of atmospheric gas: • outgassing – release of gas trapped in interior rock by volcanism • evaporation/sublimation – surface liquids or ices turn to gas when heated • bombardment – micrometeorites, Solar wind particles, or highenergy photons blast atoms/molecules out of surface rock § occurs only if the planet has no substantial atmosphere already
Gain/Loss Processes of Atmospheric Gas § Ways to lose atmospheric gas: • condensation – gas turns into liquids or ices on the surface when cooled • chemical reactions – gas is bound into surface rocks or liquids • stripping – gas is knocked out of the upper atmosphere by Solar wind particles • impacts – a comet/asteroid collision with a planet can blast atmospheric gas into space • thermal escape – lightweight gas molecules are lost to space when they achieve escape velocity gas is lost forever!
Origin of the Terrestrial Atmospheres § Lack of magnetospheres on Venus & Mars made stripping by the Solar wind significant. • further loss of atmosphere on Mars • dissociation of H 2 O, H 2 thermally escapes on Venus § Gas and liquid/ice exchange occurs through condensation and evaporation/sublimation: • on Earth with H 2 O • on Mars with CO 2 § Since Mercury & the Moon have no substantial atmosphere, fast particles and high-energy photons reach their surfaces • bombardment creates a rarified exosphere
Climate History of Mars • More than 3 billion years ago, Mars must have had a thick CO 2 atmosphere and a strong greenhouse effect. • the so-called “warm and wet period” • Eventually CO 2 was lost to space. • • • some gas was lost to impacts cooling interior meant loss of magnetic field Solar wind stripping removed gas § Greenhouse effect weakened until Mars froze.
Rock cycle
Rock cycle
Water cycle
Residence time § Average amount of time spent in a reservoir Amount in/time Amount in reservoir Amount out/time § Residence time = amount in reservoir/amount added (removed) per unit time
Residence time at Berkeley § 20, 000 students § 5, 000 enter (leave)/year § Residence time? Residence time = 20, 000 students/5, 000 students/year = 4 years
Residence time of water in the ocean § Volume in ocean: 1. 3 x 109 km 3 § Discharge from rivers: 3. 5 x 104 km 3/yr § Residence time: volume/discharge = 1. 3 x 109 km 3/ 3. 5 x 104 km 3/yr = 30 x 103 years
Carbon cycle
Long term Carbon cycle
Carbon cycle: volumes
Magnetospheres § The Sun ejects a stream of charged particles, called the solar wind. • it is mostly electrons, protons, and Helium nuclei § Earth’s magnetic field attracts and diverts these charged particles to its magnetic poles. • • • the particles spiral along magnetic field lines and emit light this causes the aurora (aka northern & southern lights) this protective “bubble” is called the magnetosphere § Other terrestrial worlds have no strong magnetic fields • solar wind particles impact the exospheres of Venus & Mars • solar wind particles impact the surfaces of Mercury & Moon
Earth’s Magnetosphere Solar Wind: Electrons, protons, helium nuclei
How Molecules Absorb Light § X rays • • • ionize atoms & molecules dissociate molecules absorbed by almost all gases § Ultraviolet (UV) • dissociate some molecules • absorbed well by O 3 & H 2 O § Visible (V) • passes right through gases • some photons are scattered § Infrared (IR) • absorbed by greenhouse gases
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