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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 mid-latitudes 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 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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 stratosphere • UV light heats air (ozone absorbs it.) troposphere • layer closest to surface • Convection heats air (rising hot air) • temp drops with altitude (mesosphere) 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 (O3) All three planets have warmer surface temps due to greenhouse effect CFCs Attack Ozone (O3) 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. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Climate History of Venus Venus should have outgassed as much H2O as Earth. • Early on, when the Sun was dimmer, Venus may have had oceans of water Venus’ proximity to the Sun caused all H2O to evaporate. • • • • H2O caused runaway greenhouse effect surface heated to extreme temperature CO2 released from rocks: Adds to greenhouse effect UV photons from Sun dissociate H2O; H2 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 H2O Venusian clouds contain sulfuric acid! • implies recent volcanic outgassing? Mars’ Thin Atmosphere Martian sunset illustrates just how thin the Martian atmosphere is. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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 • CO2 condenses & vaporizes at opposite poles • changes in atmospheric pressure drive pole-to-pole winds • sometimes cause huge dust storms QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. The last decade of the 20th 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 ... Venus Earth Mars SUN 0.7 AU 1 AU (150 million km from Sun) 1.5 AU Temperature: Top of Atmosphere decreases with distance from Sun 500 Temperature (Celsius) 500 400 Earth -18oC (0oF) 300 300 200 100 Venus 100 0 Mars 0 0 0 AU -100 -100 -100 5500 oC 0.2 0.4 0.6 0.8 Distance From Sun 1 1 AU 1.2 1.4 1.6 EARTH: Surface 15oC (60oF) Top of Atm: -18oC (0oF) Temperature (Celsius) 500 500 400 300 300 Surface 200 All three phases of water 100 100 0 0 0.5 No Greenhouse1 1.5 2 -100 -100 Surface warmer than top of atm Greenhouse Effect Clue: atm composition Vibrational Modes for CO2 n1 symmetric n2 bending 15 mm n2 asymmetric 4.3 mm O C O O C O O C O Greenhouse effect: Radiation at specific wavelengths excite CO2 into higher energy states. Light energy is absorbed by the CO2 molecules Other Greenhouse Gases O H 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 CO2 Bending Mode Transmission Peak terrestrial emission at ~300K How Greenhouse Gases Warm the Troposphere CO2 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Energy Balance Carbon Dioxide: in our atmosphere is Increasing rapidly Worldwide CO2 Emission By fuel type: 1970 - 2020 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Burning coal QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Quic kTime™ and a TIFF (Unc ompres sed) dec ompres sor are needed to see this pic ture. CO2 Causes Global Warming: Stay tuned . . . gasoline Natural gas Increase in Temperature tracks Increase in Greenhouse Gases Since 1850: Atmospheric CO2 has increased by 30% Temperature vs Time QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 1850 Year 2000 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. CO2 Since the Year 1000 AD CO2 in atmosphere, measured in thick arctic ice. FAQ 2.1, Figure 1 Heat Content: Increase in Atmosphere and Ocean since 1945. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. CO2 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 (CO2), methane (CH4), and nitrous oxide (N2O) 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. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Retreat of Glaciers QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 1948 2002 2006 Trift Glacier, Gadmental, Berner, Oberland Switzerland Easton Glacier QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 1964 1960 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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 ? QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. No. Luminosity has been constant. (Solar max) Percentage change in monthly values of the total solar irradiance composites of Willson and Mordvinov (2003; WM2003, violet symbols and line) and Fröhlich and Lean (2004; FL2004, 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 CO2 in the atmosphere. Rising CO2 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: H2O 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 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 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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 CO2). 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 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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 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 H2O, H2 thermally escapes on Venus Gas and liquid/ice exchange occurs through condensation and evaporation/sublimation: • on Earth with H2O • on Mars with CO2 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 CO2 atmosphere and a strong greenhouse effect. • the so-called “warm and wet period” • Eventually CO2 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 QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Rock cycle QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Water cycle QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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: 1.3x109 km3 Discharge from rivers: 3.5x104 km3/yr Residence time: volume/discharge = 1.3x109 km3/ 3.5x104 km3/yr = 30 x 103 years Carbon cycle QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Long term Carbon cycle QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Carbon cycle: volumes QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. 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 O3 & H2O Visible (V) • passes right through gases • some photons are scattered Infrared (IR) • absorbed by greenhouse gases