"GEOG 1100 Earth’s Climate and Climate ChangeThe Sun • Almost all of the energysupplied to Earth’s surfacecomes from the sun • Exoatmospheric solarirradiance – Energy reaching averagedistance of Earth’s orbit – 1361 Watts per square meter-2 (Wm ) – This value varies due toEarth’s elliptical orbit aroundthe sun, sun’s 11-yearsunspot cycle – Very stable in long term – ~50% of energy is in visiblewavelengths Thierry LegaultThierry LegaultISS and Atlantis, 22 May 2010 (Thierry Legault)Lambert’s Cosine Law • When light strikes a surface atan angle, the energy is spreadover a larger area – The light received by anyindividual point is reduced • Since the Earth is curved, theEarth only receives the fullamount of exoatmosphericsolar irradiance where the sunis directly overhead • Tropical latitudes receive 2-3times as much energy peryear compared to polarlatitudesEarth’s Axial TiltLight Interactions With Matter • When electromagnetic radiation (light)interacts with matter (gas, liquid, or solid),three things can happen: – Light can be transmitted – Light can be absorbed – Light can be reflectedEarth’s Energy Balance • Energy balance is a balance between incomingand outgoing energy • For the Earth system, energy can only be gainedor lost through electromagnetic radiation • Incoming shortwave radiation – Ultraviolet, visible, near infrared, & shortwave infrared • Outgoing longwave radiation – Thermal infrared, microwave • More incoming than outgoing warms the Earthup • More outgoing than incoming cools the EarthdownIncoming Shortwave Radiation • Earth absorbs 69% ofincoming shortwaveradiation • Earth reflects 31% ofincoming shortwaveradiation • Total percent of reflectedradiation across allwavelengths is calledalbedo Apollo 17 “Blue Marble” (NASA)Earth’s Global, Annual Average Energy Balance Kiehl and Trenberth, 1997 Net Radiation • Net radiation = absorbed incomingshortwave – outgoing longwave • How could a sensor onboard a satellitemeasure net radiation? CERES Net Radiation (NASA)Energy Transport • Differences in net radiation mean thatenergy must be transported from tropicallatitudes to polar latitudes • Air – Moves rapidly – Low heat capacity • Water – Moves slowly – High heat capacity (4x heat capacity of air)Global Atmospheric Circulation • Highest irradiance is near Earth’s equator • Heating causes a broad band of rising air • Rising air sets the Hadley Cell in motion – Air rises near equator, flows north or south,and then sinks near 25-35° N and 25-35° S • Band of rising air is the IntertropicalConvergence Zone (ITCZ)GOES (NOAA)Intertropical Convergence Zone GOES (with artificial background), NOAANASA JPLCoriolis Effect • If the Earth wasn’t rotating, air would flowin a north-south direction from warmerregions to colder regions • Coriolis Effect causes air currents to turnto an east-west directionCoriolis Force North Pole (0 km per hour) Equator (1675 km per hour)Coriolis Force North Pole (0 km per hour) Equator (1675 km per hour)Coriolis Force North Pole (0 km per hour) Equator (1675 km per hour)Coriolis Effect • North-south movement in the northernhemisphere deflects to the right • North-south movement in the southernhemisphere deflects to the left • Tradewinds moving towards equatordeflect to the west • Westerlies moving away from the equatordeflect to the eastOcean Currents • Ocean currents are produced by: – Wind patterns• Trade winds and westerlies • Winds are primary control on surface currents – Coriolis effect • Deflects to the right in northern hemisphere and to the left insouthern hemisphere – Differences in temperature and salinity• Causes differences in density of water, can cause verticalmovement – Shape of the continents • Determines where currents can flowSurface Currents Christopherson, 2005Ocean Currents • Surface currents have major impacts onlocal climate – Europe and Eastern U.S. are warmer andwetter because of warm water broughtnorthward by the Gulf Stream – California is cooler and drier because of coolwater brought southward by the CaliforniacurrentThermohaline Circulation • Surface currents are part of a largervertical circulation called the thermohaline circulation • This circulation is caused by thecombination of winds and variations in thetemperature and salinity of water– Decreasing the temperature of waterincreases its density – Increasing the salinity of water increases itsdensityThermohaline Circulation • The thermohaline circulation is powered bysinking water in the North Atlantic Ocean – Water moving north in the Atlantic is exposed to highsolar irradiance in the region near the equator – Water evaporates, leaving behind denser, moresaline water – As the water moves into the north Atlantic, watercools, becoming even denser – In the North Atlantic, the denser water sinks • The resulting deep current travels around theworld, resurfacing in many locations wherewater is upwellingIPCCWhat is Climate? • Long-term patterns of temperature andprecipitation– Includes annual averages, seasonalaverages, and extreme events • How is climate different from weather? – Weather is short-term – Climate is long-termWeather NationalWeatherServiceRadarClimateTemperature • Four factors that control long-term spatialvariation in temperature: 1. Latitude 2. Water bodies 3. Elevation 4. Cloud coverLatitude • Tropical latitudes havemore absorbed incomingshortwave radiation,higher temperatures • Polar latitude have lessabsorbed incomingshortwave radiation,lower temperatures • Range in temperatures ishigher at polar latitudesthan tropical latitudesAnnual Temperature Range (°C) Christopherson, 2009Water Bodies • Water has a higher heat capacity than air • Large bodies of water moderate daily andannual temperature ranges • Cold and warm currents in oceans candecrease or increase regionaltemperaturesSalt Lake City Climograph National Drought Mitigation Center, UNLEureka, CA Climograph National Drought Mitigation Center, UNLElevation • Temperaturedecreases withincreasing elevation • At higher elevation,less dense air causescooler temperaturesand a wider rangebetween daytime andnighttimetemperaturesCloud Cover • Clouds reflect incoming shortwaveradiation, resulting in cooler daytimetemperatures • Clouds absorb outgoing longwaveradiation, resulting in warmer nighttimetemperaturesClimateWizard.orgPrecipitation • Four factors that control long-term spatialvariation in precipitation: 1. Air temperature 2. Latitude 3. Water bodies 4. TopographyAir Temperature • Warm air can hold larger quantities ofwater vapor than cold airAir Temperature • Warmed air can cause convectiveprecipitation – Warmed air is more buoyant – Air rises, then cools at higher altitude – Cooling causes condensation, precipitation • Often occurs during or after the warmestpart of the dayLatitude • Latitude partially controls temperature • Latitude also controls broad patterns ofatmospheric circulation – Rising air near the equator (ITCZ) causesclouds and precipitation – Falling air near 30° N and S inhibits cloudsand precipitationWater Bodies • Large bodies of water add water vapor toair through evaporation • Air that has passed over a body of waterwill have higher humidity than air that hasnot passed over a body of water • Warm water promotes convectiveprecipitation • Cold water inhibits convective precipitationTopography • Topographic features can block air currents• Air is forced to rise over topographic features – Increase in altitude cools the air – Cooling the air causes clouds to form, precipitation • Orographic precipitation occurs on the windward side of mountain ranges • A rain shadow occurs on the leeward side ofmountain rangesOrographic Precipitation Christopherson, 2009Global Average Annual Precipitation Christopherson, 2005Precipitation Seasonality • Timing of precipitation is very important • Areas of rising and falling air shift northand south depending on the season – ITCZ moves north and south as the area ofhighest incoming shortwave radiation shiftswith the seasons – Subtropical high pressures that are broadzones of falling area shift to the north andsouth with the ITCZTRMM June and DecemberAverage Precipitation (mm/day)Los Angeles (34° N) • Undersubtropical highin the summer(falling air, lowprecipitation) • Subtropical highshifts to thesouth in winter • Moreprecipitation inwinter thansummer National Drought Mitigation Center, UNLAcapulco, Mexico (17° N) • Undersubtropical highin the winter(falling air, lowprecipitation) • Subtropical highand ITCZ shift tothe north insummer • Moreprecipitation insummer thanwinter National Drought Mitigation Center, UNLPrecipitation Seasonality • Precipitation is water “supply” • We also need to consider water “demand” • Evaporation: movement of water from a liquid to a gas • Transpiration: also movement of water from a liquid to agas, but through a plant’s leaves • Potential evapotranspiration is the maximum amount ofwater that can be evaporated and transpired – Potential evapotranspiration is higher in warmer temperatures • Deserts are defined based on low precipitation relative toevapotranspirationKöppen Climate Zones • Different climate zones are based ontemperature and precipitation – Tropical – Mesothermal (“moderate temperature”) – Microthermal (“low temperature”) – Polar – Highland – DesertKöppen Climate Zones Christopherson, 2005Temperature Profile of Earth’s Atmosphere • Troposphere – Lowest part of the atmosphere – Declining temperature with altitude, up toapproximately 18 km (11 miles) – Region of atmosphere where all weather occurs • Tropopause – Upper boundary of the troposphere, beginning of thestratosphere • Stratosphere – Increasing temperature with altitude – 1-10% of air pressure at sea levelChristoperson, 2005The Ozone Layer • Through its creation and destruction, ozone absorbsultraviolet radiation • Ozone absorption of ultraviolet radiation causes thetemperature of the stratosphere to increase with altitude • Ultraviolet radiation splits oxygen molecules O-O + UV? O + O • Atomic oxygen (O) combines with another oxygenmolecule (O ) to form ozone (O ) 2 3 O + O-O? O-O-O • Ultraviolet radiation can also split the ozone molecule O-O-O + UV ? O-O + OThe Ozone Layer • The ozone layer absorbs most UV radiationbetween 240 nm and 320 nm • Absorbs between 90 and 99% of this UVradiation • There isn’t very much ozone in the stratosphere – Maximum concentration is approximately 12 parts permillion • Ozone concentration is measured in “DobsonUnits” – 1 Dobson unit is equivalent to a layer of ozone 0.01mm thick at sea level pressureearthobservatory.nasa.govOzone Destruction • Ozone is split apart by chlorine O-O-O + Cl ? O-O + Cl-O • Sunlight can split up chlorine monoxide Cl-O + Cl-O + visible light ? 2Cl + O 2 • In the presence of sunlight, chlorine actsas a catalyst for destroying ozone – 1 chlorine atom can break up 100,000 ozonemoleculesHow Does Chlorine Get Into theStratosphere? • Chlorofluorocarbons (CFCs) – Lighter than air, easily rises into thestratosphere – Used for refrigerant or solvent – About 5 billion kg have been released into theatmosphereDiscovery of the Ozone Hole • 1970s, theorized that chlorine could destroy ozone in thestratosphere, decreasing concentration of stratosphericozone • 1984/85, British scientists in Antarctica that measuredozone concentrations from the ground noticed decreasein stratosphere over Antarctica• At the same time, a satellite sensor called TOMS wasmapping a decreased concentration of ozone in thestratosphere over AntarcticaOzone Concentration over HalleyBay, Antarctica (ground) (satellite) (satellite) Looking back at TOMS data, scientists determined that decreasein stratospheric ozone has been occurring since late 1970s NASAWhy Antarctica? 1. Circumpolar vortex – Belt of wind around Antarctica forms during dark winter months – Keeps air trapped in area over Antarctica – Doesn’t allow fresh ozone to come in a replace ozone that is destroyed 2. Stratospheric clouds – It gets so cold during Antarctic winter that clouds can form instratosphere – Ice crystals help break up chlorine compounds into atomic chlorine,which destroys the ozone 3. Once sun comes up in mid-September, chemical reactions begin,and ozone is rapidly depleted • Minimum ozone concentrations occur in October • In November and December, circumpolar vortex breaks down, letsin fresh ozoneSciamachy TEMIS Ozone Map, http://www.temis.nlNASA GSFCMontreal Protocol • Signed in 1987, banned most uses ofozone depleting chemicals • No quick fixes – CFCs can take decadesto rise into the stratosphere and breakdown • The ozone hole should start to shrink by2025 and reach 1980 levels by 2050Net Radiation • Incoming shortwave radiation – outgoinglongwave radiation • Absorbed incoming shortwave radiationadds energy to the Earth system • Outgoing longwave radiation subtractsenergy from the Earth systemAbsorbed Incoming Shortwave • Controlled by two factors: 1. Solar irradiance 2. Earth’s albedoSolar Irradiance 2 • Earth system receives on average 342 W/m • This varies by about 7% due to the ellipticalorbit of the Earth – Highest in January when Earth is closest to the sun – Lowest in July when Earth is furthest away from thesun • After accounting for the Earth’s elliptical orbit,solar irradiance has been very stable sincesatellite measurements began – Long term variation has +/- 0.1% since 1978Solar Irradiance • Although irradiance from the sun is stable,seasonal variability in irradiance iscontrolled by the Milankovitch cycles onscales of thousands to millions of years– Eccentricity – Axial Tilt – PrecessionUCAR COMET Programearthobservatory.nasa.govSolar Irradiance • Changes in the seasonal timing of solarirradiance have affected climate on longtime scales (thousands to millions ofyears) • Lower solar irradiance in the summerproduces cooler summer temperatures inthe northern hemisphere, allowing snow toaccumulate and ice sheets to growAlbedo • Earth reflects 31% of incoming shortwaveradiation • Decreasing albedo warms Earth up (moreenergy is absorbed) • Increasing albedo cools Earth down (lessenergy is absorbed)Albedo • Factors controlling albedo: – Clouds – Snow and ice – Aerosols – Land coverNet Radiation • Net radiation = incoming shortwave – outgoing longwaveEarth’s Global, Annual Average Energy Balance Kiehl and Trenberth, 1997 The Greenhouse Effect • Certain gasses strongly absorb outgoinglongwave radiationGreenhouse Gasses • 3 primary greenhouse gasses – Water vapor (1-4% of atmosphere) – Carbon dioxide (399 ppm) – Methane (1.8 ppm) • Others: nitrous oxide, ozone, CFCsHow can the Earth cool? • Increase albedo • Decrease greenhouse gasses • Decrease solar irradianceHow can the Earth warm? • Decrease albedo • Increase greenhouse gasses • Increase solar irradianceFeedbacks • Changing Earth’s temperature can createpositive and negative feedbacks • Positive feedbacks reinforce change: – Increasing temperature decreases albedo orincreases greenhouse gasses – Decreasing temperature increases albedo ordecreases greenhouse gasses • Negative feedbacks cancel out change: – Increasing temperature increases albedo ordecreases greenhouse gasses – Decreasing temperature decreases albedo orincreases greenhouse gassesGlobal Climate Change • Is the Earth warming? 0.74 °C (1.33 °F) warming over the past 100 yrsWarmest Years on Record, 1880-2013 Global Top 10Anomaly °C Anomaly °F Warmest Years (Jan-Dec) 2010 0.66 1.19 2005 0.65 1.17 1998 0.63 1.13 2013 0.62 1.12 2003 0.62 1.12 2002 0.61 1.10 0.60 1.08 2006 2009 0.59 1.07 2007 0.59 1.06 2004 0.57 1.04 2012 0.57 1.03 Anomaly is based on 1901-2000 average temperature. NOAABiological Evidence • Earlier spring migrations • Earlier spring green-up • Poleward movement of plant and animalspecies • Changes in timing of events like mating,floweringHydrological Evidence • Glaciers are melting around the world • Earlier runoff from snow melt • Sea level is increasing – Currently 3 mm per year – Thermal expansion (~60%) – Increased melting (~40%)Qori Kalis Glacier, Peru, 1978 (L. Thompson)Qori Kalis Glacier, Peru, 2000 (L. Thompson) Proglacial lake ~ 80m deepQori Kalis Glacier, Peru, 2010 (L. Thompson) Glacier calved into lake in 2006 causing flooding in valley belowCarbon Dioxide • Carbon dioxide in the atmosphere isincreasing due to human activity – What are the major sources of anthropogenicCO ? 2 • Preindustrial level: 280 ppm • 2014: 399 ppm • Ice cores tell us this is likely the highestlevel of CO in the atmosphere in 420,0002 yearsIPCC AR4Carbon Dioxide • Seasonal fluctuation: – Carbon dioxide increases in fall and wintermonths due to decay of organic matter innorthern hemisphere – Carbon dioxide decreases in spring andsummer months as plants take up carbondioxide in northern hemisphere – Signal is dominate by northern hemispherebecause of greater land massEquatorCarbon Dioxide • How do we know the increase in atmosphericCO is coming from human activity? 2 12 13 • Carbon has three isotopes: C (stable), C14 (stable), and C (radioactive) 12 • Plants prefer to take up the lighter C isotopefrom the atmosphere – Plants and all fossil fuels have higher percentage of12 C relative to the atmosphere • As we burn fossil fuels, we can measure the13 decrease in C in the atmosphere over timeMethane • Lower concentration in the atmosphere,but 20 times as effective as a greenhousegas • Naturally emitted by wetlands • Anthropogenic emissions from agricultureand petroleum production • Pre-industrial level: 700 ppb • 2010: 1825 ppbNOAA IPCC AR4Anthropogenic Greenhouse GasEmissions • Carbon dioxide is approximately 75% ofanthropogenic greenhouse gas emissions • Carbon dioxide emissions have grown by80% over the last 35 years • Largest source of carbon dioxide is fossilfuel combustion9000 Total 8000 Natural Gas Petroleum 7000 Coal Cement 6000 5000 4000 3000 2000 1000 0 1850 1870 1890 1910 1930 1950 1970 1990 2010 Year CDIAC Millions of Metric Tons of Carbonbased on data from CDIAC, EPA, USGS and DOE2011 Greenhouse Gas Emissions Excluding Land-Use Change and Forestry 2011 % of Metric tons Country Rank Rank MtCO2e World Total CO2e Per Person (1) (48) China 10,552.6 24.1% 6.7 (2) (11) United States 6,550.1 14.9% 17.1 (3) (39) European Union 4,540.9 10.4% 7.3 (4) (114) India 2,486.2 5.7% 1.5 (5) (20) Russian Federation 2,374.3 5.4% 12.0 (6) (25) Japan 1,307.4 3.0% 9.5 (7) (98) Brazil 1,131.1 2.6% 2.3 (8) (26) Germany 882.9 2.0% 9.4 (9) (105) Indonesia 834.6 1.9% 1.8 (10) (12) Canada 716.2 1.6% 15.7 World Resources Institute, based on data from CDIAC, EPA, USGS and DOEClimate Modeling • Global Climate Models (GCMs) are usedto predict changes in climate in responseto: – Increases in greenhouse gasses – Feedbacks • GCMs are calibrated using past data – Increase in atmospheric greenhouse gassesover the past 50 years is required toreproduce present day temperaturesModeling the Future • Population – Even if per capita emissions stay stable, increasingpopulation with increase greenhouse gas emissions – When and at what level will global populationstabilize? • Economic development – US per capita GDP: $52,800 – World per capita GDP: $13,100 • Cumulative emissions – Carbon dioxide has a lifetime in the atmosphere of100-200 years – Future warming is “built in” from today’s emissionsIPCC AR4IPCC AR4Impacts • Changing temperature and precipitation patterns • Sea level rise – 20-60 cm due to thermal expansion by end of century(barring a “tipping point” in ice cap melting) – More frequent flooding of coastal areas • Earlier snow melt • Arctic will likely be ice-free during summer bymid century • Major loss of species and ecosystems – 20-30% of species will be in danger of extinctionwithout intervention by end of century Local Effects • 2007 Governor’s Report • Utah will warm more than average • Precipitation trends are unclear, but lesssnow pack and earlier snow melt arecertain – Big impact on water supplies and storage • Increased wildfire intensity, more insectoutbreaks in forestsUncertainty • Precipitation – Globally precipitation will increase – Climate models do not agree on regionalchanges in precipitation • Local effects – Climate models run at coarse spatialresolutions, so local effects (especially thosedependent on topography) are not wellresolvedUncertainty • Role of aerosols – Aerosols are tiny particle suspended in theatmosphere – Some aerosols have a cooling effect(sulfates) – Other aerosols have a warming effect (soot) – Aerosols act as condensation nuclei forcloudsUncertainty • Continuation of sinks – Since the industrial revolution, we have produced 500billion metric tons of CO , enough to raise2 atmospheric CO above 500 ppm 2 – Ocean and terrestrial vegetation have absorbed someof this CO and kept levels below 400 ppm 2 – The saturation of these sinks is likely, but timing ofsaturation is unknown • Unanticipated feedbacks – Increased ice melting in polar regions – Increased methane emissionsUncertainty Also Applies to Impacts • Climate change impacts – Ecosystems – Agriculture and food resources – Human adaptationReducing Emissions • To maintain present day climate, we needan atmospheric carbon dioxideconcentration at 350 ppm • To limit temperature increase to 2 °C, weneed an 80% cut of emissions by 2050 – We have to do this while population increasesby another 2 billion peopleRegulating Carbon Emissions • Kyoto Protocol had goal to reduce emissions by5% below 1990 levels by 2012 • Treaty required this reduction from developedcountries, not from developing countries • In countries that committed to emissions, targetswill likely be met • US emissions up 16% since 1990 • Globally emissions are up 41% since 1990 dueto increased emissions from developingcountriesHow can we reduce greenhousegas emissions? • Major direct emissions for Utah: – Electricity generation (37%) – Transportation (25%) • Reducing energy intensity • Making smart choices as a consumerHow can we reduce greenhousegas emissions? • Major direct emissions for Utah: – Electricity generation (37%) – Transportation (25%) • Reducing energy intensity • Making smart choices as a consumerScenarios • A1: Rapid economic growth, global population peaksmid-century and declines afterward, rapid introduction ofmore efficient technologies – A1FI: fossil fuel intensive – A1T: non-fossil fuel energy sources – A1B: balanced fossil fuel and non-fossil fuel energy sources • A2: High population growth, slow economic developmentand technological change • B1: Same population trends as A1, but more rapideconomic changes • B2: Intermediate population and economic growthPredictions for Future Warming • Global temperature will increase 1-6 °C (2- 11 °F) by the end of the century – Middle range is 2-4 °C (4-7 °F) • Regional changes will be higherUncertainty • Where is there legitimate uncertainty inclimate models?IPCC AR4"