Presentation on theme: "Climate and Climate Change Chapter 11"— Presentation transcript:
1Climate and Climate Change Chapter 11 Natural Hazards, 2eClimate and Climate ChangeChapter 11
2Learning ObjectivesUnderstand the difference between climate and weather, and how their variability is related to natural hazardsKnow the basic concepts of atmospheric science such as structure, composition, and dynamics of the atmosphereUnderstand how climate has changed during the last million years, through glacial and interglacial conditions, and how human activity is altering our current climate
3Learning Objectives, cont. Understand the potential causes of climate changeKnow how climate change is related to natural hazardsKnow the ways we may mitigate climate change and associated hazards
4Climate and WeatherWeather refers to atmospheric conditions over short periods of time.Climate refers to characteristic atmospheric conditions over a long period of time.Climate zonesDefined using Koeppen SystemUses monthly average temperature and precipitation associated with different types of vegetation
5Koeppen’s Classification System A-tropical, temp>18oC (64oF) year roundB-Dry, evaporation > precipitationC- Mild Mid-latitude, 18oC (64oF)>coldest month> -3oC (27oF)D- Severe Mid-latitude, coldest month< -3oC (27oF)E – Polar, temp < -3oC (27oF) year roundH-Highland, Mountain areas
7Atmospheric Conditions Permanent gassesGasses whose proportions stay constantEx. NitrogenVariable gassesGasses whose proportions vary with time and spaceEx. Carbon dioxide
8Permanent Gasses Percentages in atmosphere remain essentially constant Nitrogen, oxygen, and argonCompose approx. 99% by volumeRelatively unimportant to atmospheric dynamics
9Variable Gasses – Carbon Dioxide (CO2) Extremely important, but small in percentage (approx %)Describe in parts per million (ppm) or billion (ppb)Released naturally by volcanic activity, plant and animal respiration, decay of organic materialRemoved through photosynthesis, chemical weathering in soil, and mixing of air and seawater
10Variable Gasses – Carbon Dioxide (CO2), cont. Anthropogenic sourcesBurning of fossil fuels increases CO2 .Deforestation decreases amount used by trees, increasing ppm in atmosphere.Natural processes that remove CO2 don’t work as rapidly as amounts are increasing.Levels increase by 2 ppm per year.
11Variable Gasses – Water Vapor Created from evaporation at Earth’s surface.Returns to surface through hydrologic cycle.Air temperature is primary control of water vapor content.
12Variable Gasses – Ozone O3 Forms when atomic oxygen (O) collides with oxygen molecule (O2)Mostly found in stratosphereActs as a shield for ultraviolet light and is essential to life on earthChlorofluorocarbons (CFCs) partially destroyed ozone shieldIncreases skin cancer, cataracts, caused local crop failuresCan also be found in smog
13Variable Gasses – Methane (CH4) Primary constituent of natural gasOccurs naturally from bacterial decay, intestinal tracks of termites, cows, and sheepAnthropogenic sources: coal mines, oil wells, leaking natural gas pipelines, rice cultivation, landfills, and livestockLevels have doubled since 1700 and is a significant contributor to warming
14Variable Gasses – Nitrous Oxide (N2O) Natural sources include microbiological processes in soil and ocean and wildfires.Anthropogenic sources include fertilizers and burning fossil fuels.Contributes to atmospheric warming.
15Variable Gasses – Halocarbons Chemical compounds containing halogen elements bonded with carbonInclude CFCs and are almost entirely anthropogenicUsed in industrial processes, fire fighting, and as fumigants, refrigerants, and propellantsContribute to warming in troposphere and ozone depletion in stratosphere
16AerosolsMicroscopic liquid or solid particle that acts as nuclei for water particles to condense to form cloudsAssociated with air pollutionNatural sources: desert dust, wildfires, sea spray, and volcanoesAnthropogenic sources: burning of forests and fossil fuelsEffects are complex
17Structure of Atmosphere, revisited Defined by changes in air temperatureTroposphere is where weather happensStratosphere dry, cold layerLittle weather occurs hereStrong winds circulate aerosolsFigure 8.7
18Atmospheric Circulation Responsible for location of climate zonesAt equator, warm air rises towards polesAs it rises, it cools and loses moisture as rainDry air descends between 15o and 30o North and SouthDescending air produces high pressure and low rainfallHigh pressures at North and South PolesPolar deserts
20Climate Change Currently, the climate is warming Based on 30 years of warming in atmosphereAlso, global increase in sea temp, widespread melting of snow, glaciers, ice sheets, and permafrost, and sea level riseReferred to as global warming90% probability that humans are responsibleEcosystems capable of adjusting, but changes are too fast for these to take placeStudies changes in atmosphere and linkages with lithosphere, cryosphere, hydrosphere, and biosphere
21Cryosphere Part of the hydrosphere where most of the water is frozen Includes permafrost, sea ice, ice caps, glaciers, and ice sheetsGlaciersFlow from high to low elevations under weight of accumulated iceHave budgets with input and outputPeriods of continental glaciation called glacial intervalsInterglacial intervals occur in between
22Glaciations Refer to multiple advances and retreats of glaciers. Rare during the earth’s 4.6 billion year history.Several in the last 1 billion years.We are now living during one of those events that began 2.5 million years ago.
23Pleistocene Epoch Multiple ice ages Glaciers covered 30% of Earth (today 10%)Maximum extent 21,000 years agoGlobal sea level >100 m (330 ft) lower than todayFigure 11.3
24Causes of Glaciation Mostly unknown Related to position of continents Changes in amount of solar radiation influence advance and retreatMilankovitch cyclesChanges in Earth’s orbit around Sun, tilt and wobble of Earth’s axis of rotationCorrelate well with minor changes in global temperaturesExplain the “Medeival Warming Period” and the “Little Ice Age”They are not the primary cause of glaciation or global temperature changes.
25Glacial Hazards Huge, actively flowing masses of ice and debris Hazards include: property damage, injuries, and deathsPeople can fall into deep crevasses.Can expand to overrun villages, etc.Produce an ice jam to cause flooding.Blocks of ice may fall.Calving produces icebergs in ocean.
26The Greenhouse EffectDiscovered by Joseph Fourier in 1824: the Sun’s energy passes through, but reradiated heat is absorbed by, Earth’s atmosphere.Fourier also described the planetary balance of heat gain and loss ( the “heat budget”)The greenhouse effect was first reliably experimented on by John Tyndall in the year 1858 and first reported quantitatively by Svante Arrhenius in his 1896 paper.The mathematics were first proposed by Jožef Stefan in 1879, based on experiments by John Tyndall.Thermodynamic formulas describing the effects of greenhouse gas concentrations of the heat balance of Earth were developed by Ludwig Boltzmann, 1884.
27The Greenhouse EffectIn 1896, Swedish scientist Svante Arrhenius was the first to claim that fossil fuel combustion may eventually result in enhanced global warming.He proposed a relation between atmospheric carbon dioxide concentrations and temperature.He found that the average surface temperature of the earth is about 15oC because of the infrared absorption capacity of water vapor and carbon dioxide.This is called the natural greenhouse effect.
28The Greenhouse EffectArrhenius suggested a doubling of the CO2 concentration would lead to a 5oC temperature rise.He and Thomas Chamberlin calculated that human activities could warm the earth by adding carbon dioxide to the atmosphere.This research was a by-product of research of whether carbon dioxide would explain the causes of the great Ice Ages.This was not actually verified until 1987.
29The Greenhouse EffectIn 1972, eminent atmospheric scientist J.S. Sawyer summarized what was known about the role of carbon dioxide in enhancing the natural greenhouse effect, and made a remarkable prediction of the warming expected at the end of the twentieth century. He concluded that the 25% increase in atmospheric carbon dioxide predicted to occur by 2000 corresponded to an increase of 0.6 °C in world temperature. (Nature 239, 23-26; 1972).In 1988, NASA scientist Jim Hansen gave congressional testimony showing model projections of continued global warming. In spite of being one of the earliest transient climate model experiments, there is an impressive match between the recently observed data and Hansen’s projections.
30Scientific AgreementBy the early 1990’s, climatologists generally agreed that humans were making significant contributions to climate change.In 1995, the National Academy of Sciences reported that the research strongly supported anthropogenic warming. By this time, the burden of proof had now shifted to scientists who disagreed with these findings.Since this time, the research has not provided evidence to refute the basic findings. On the contrary, thousands of papers have been published providing further evidence of anthropogenic warming.Since 2007, no scientific body of national or international standing has maintained a dissenting opinion.In a recent University of Illinois at Chicago survey sent to 10,257 Earth Scientists, 97.4% of the climatologists who responded answered "yes" when asked "do you think human activity is a significant contributing factor in changing mean global temperatures?"
31The Greenhouse Effect Earth’s temperature depends on three things: Amount of sunlight receivedMost is ultraviolet with short wavelengthAbout 2/3 is absorbed to warm the atmosphereAmount of sunlight reflectedMostly reflected as infrared radiationDegree to which the atmosphere retains heatWater vapor, carbon dioxide, methane, nitrous oxides, and halocarbons absorb IR radiationGasses act as “blanket” to retain heat in troposphere
33The Greenhouse Effect, cont. Greenhouse effect is a natural and necessary process.Earth would be 33o colder without it.All surface water would be frozen.Little life would exist.Natural effect is from water vapor.Absorption by greenhouse gasses (carbon dioxide, methane, nitrous oxide, halocarbons)Enhance the greenhouse effect
34Carbon Dioxide and The Greenhouse Effect Carbon dioxide accounts for most of the anthropogenic greenhouse effect.It is the most studied.Figure 11.6
35Air Temperature and Carbon Dioxide CO2 concentrations from air bubbles in glacial ice in Antarctic ice sheetFigure 11.7
36Atmospheric Carbon Dioxide Concentrations Since the burning of fossil fuels, CO2 concentration has increased exponentially.Measurements are from glacial ice and from Mauna Loa in Hawaii.Figure 11.8b
37Atmospheric Carbon Dioxide Concentrations, cont. Atmospheric concentrations continue to rise and are likely to continue.Data from Mauna Loa in Hawaii.Figure 11.8a
38Global Temperature Change–Last 800,000 Years Low temperatures coincide with major continental glaciations, high temperatures with interglacial periodsFigure 11.9a
39Global Temperature Change–Last 150,000 Years Last major interglacial period, Eemian, sea level was 4–6 ft higher than todayFigure 11.9b
40Global Temperature Change–Last 18,000 Years Cold interval, Younger Dryas, occurred 11,500 years ago, followed by warming to Holocene maximum.Recent cooling, called Little Ice Age, 15th–19th centuries.Figure 11.9c
41Global Temperature Change–Last 1000 Years Several warming and cooling trendsWarming in 11–1300 allowed Vikings into Iceland, Greenland, and North AmericaFigure 11.9d
42Global Temperature Change–Last 140 Years 1750, warming trend begins until 1940s.1910 to 1998, global temperatures rise.Temperatures in past 30 years are warmest since monitoring began.Figure 11.9e
43Why Does Climate Change? Milankovitch CyclesNatural changes in Earth’s Orbit, tilt, and precessionExplain some changes, but not the observed large-scale changesOcean conveyor beltCirculation of ocean water in oceansCan cause fast changes in climateKeeps Northern Europe warmer than without it
44Ocean Conveyor Belt –Atlantic Ocean West side, strong warm current flows northward to Arctic.At Greenland, it is cool and salty and sinks to bottom.Cold, dense water flows southward around Africa.
46United Nations Intergovernmental Panel on Climate Change UN report found that shutdown of conveyor belt current has occurred historically, but there is no evidence that it will occur again this century.There is sufficient evidence to state:There is widespread evidence of human influence on global climate.Warming is now occurring.Mean surface temperature of Earth will likely increase between 1.80 and 40 C (30 and 70 F) during this century.
47Solar ForcingThere is a relationship between changes in solar energy and climate change.Medieval Warm Period (A.D. 1000–1300) corresponds to increased solar radiation.Little Ice Age corresponds to decreased solar radiation.Partially explains climate change, but effect is very small.
48Volcanic ForcingAsh from eruptions becomes suspended in the atmosphere, reflects sunlight having a cooling effect.Mount Tambora, 1815 eruption contributed to cooling in North America and Europe.Mount Pinatubo in 1991 counterbalanced global warming during 1991 and 1992.
49Anthropogenic Forcing Mathematical models of climate can isolate human causes from solar and volcanic forcing of climate change.Models found that present warming greatly exceeds natural variability.Models agree with climate change predicted from greenhouse gas forcing.
52Climate Patterns Climate important to agriculture Rainfall patterns, soil moisture, etc.Northern Canada and Eastern Europe may be more productive.Lands closer to equator become more arid.Violent storms may intensifyWarmer oceans provide more energy.
53Changes in Hydrosphere Increased sea surface temperatureIncreased precipitation in polar and temperate regionsDecreased precipitation in tropical and subtropical regions
54Changes in Hydrosphere, cont. Rising sea levelThermal expansion of oceanMelting glaciersIncreases coastal erosionIncreases vulnerability of structures to wavesFlood low-lying Pacific and Indian Ocean islandsFlood coastal cities, New York, Boston, Tampa, Washington, D.C.
55Changes in Cryosphere Global warming effects occur more rapidly here. Shrinking permafrost.Decreased Arctic Ice cap, ice sheets, and glaciersAffects communities dependent on snowmelt for water supply
56Changes in Biosphere Shifts in range of plants and animals Changes in plant and animal habitatMosquitoes are moving to higher elevations.Northward movement of butterflies in Europe and birds in U.K.Expansion of sub-alpine forests in Cascades.Sea ice melting stresses seabirds, walruses, and polar bears.Warming in Florida Keys bleaching coral reefs.Seawater increasing in acidity, threatening coral animals and algae.These are areas of extreme animal diversity.
57Desertification and Drought Climate change increases human induced conversion of land to desertCauses soil and natural vegetation degradationLong-term loses for agriculture and grazingIncrease in drought events
58Wildfires Wildfire events will increase due to global warming. Both in in frequency and intensity
59Minimizing the Effects of Climate Change Focus on reduction of greenhouse gassesMost scientists believe that we have a decade to reduce gas emissions to avoid catastrophe.Reduction of gasses must be done on an individual, community, national, and international level.Carbon sequestrationNecessary as we make transition to new energies
62International Agreements Montreal Protocol1987 agreement to limit depletion of ozone layer by CFCsCFCs have declined since 1989Kyoto ProtocolUnited Nations Framework Convention on climate changeEstablishes targets to reduce greenhouse gas emissions by 2012CopenhagenNo binding agreement was achieved. The U.S. Congress did not pass new laws in advance, and President Obama attended without any real authority to take meaningful action.
63Carbon SequestrationCapture and store carbon dioxide before it enters atmosphereBiological sequestrationPlanting more treesOceanic sequestrationInjecting CO2 into oceansGeologic sequestrationPower plants capture CO2Inject it, under pressure into wells in the earth
64Fossil Fuels and Future Threat of Climate Change Two scenarios for global warming in which there is rapid economic growth with population peaking and decliningA1–More efficient energy technologies, but still fossil fuel intensiveB1 – Clean resource-efficient technologies, economic structures change
65A1–More efficient energy technologies, but still fossil fuel intensive B1 – Clean resource-efficient technologies, economic structures changeFigure 11.18aFigure 11.18b
66Climate and Climate Change EndClimate and Climate ChangeChapter 11You are now freeto walk about the cabin