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Global Climate Change 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale 1 day – diurnal cycle Weather occurs on an hourly or daily basis Primary cause: Rotation of the Earth on it’s axis Yesterday’s weather was: 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale 1 year – yearly cycles Equinoxes and solstices. 23.5 degree tilt of the Earth’s axis Last year: Earth-Sun Relations 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale 10 years – decadal scale Longer-term variabilities begin to appear El Niño & La Niña Rapid climatic shifts can occur Last 10 years: El Niño & La Niña Summary of 10 Year Time Scale (National Climate Data Center) 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale What is El Niño? Basically, it's a giant puddle (or pod) of heated water that sloshes across the Pacific Ocean Similar to an iceberg Bulge on the surface Most of “pod” beneath the surface Due to difference in density National Geographic’s Model 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale What is El Niño? Normal conditions in the tropical Pacific Ocean Surface winds move from east to west From high pressure in S. America to low pressure in Australia Drags water westward Warm water pools in the western Pacific 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale What is El Niño? Every 3 – 8 years, system reverses Called the Southern Oscillation Trade winds weaken or reverse Warm water migrates from Australia to S. America Arrives in time for Christmas – Corriente del Niño El Niño and La Niña 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale ENSO - El Niño-Southern Oscillation Typically lasts 1 year May last up to 3 In multi-year events, first year not as affected Affects both hemispheres 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale Recognizing an El Niño Sea Surface Temperatures (SST) Normal: 6-8° C warmer in the western tropical Pacific than in the eastern tropical Pacific Check SST to see if in “normal” range 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale La Niña Return to “normal” conditions from an El Niño strong Produces: Strong currents Powerful upwelling Chilly and stormy conditions along S. American coast Eastern Pacific cools rapidly, Western Pacific warms rapidly Renewed Trade Wind activity spreads the cooler eastern Pacific waters westward El Niño & La Niña Regional Impacts Does ENSO Impact Hurricane Frequency? 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale 100 years – Centennial scale Paleoclimatic data to track solar and ocean variability Large scale climatic changes and variability Pacific Decadal Oscillation (PDO) & North Atlantic Oscillation (NAO) 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale 100 years – Centennial scale Last 100 years: Human population and CO2 levels rose exponentially Climate related events severely impacts human populations Summary of 100 Year Time Scale Occurs every 15 – 20 and 50 – 70 years Coincides with ENSO The Past 100 Years: The 20th Century's Human Climate Conundrum 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale 1,000 years Variability in Carbon cycles on land and sea Thermohaline current Last 1,000 years Europe’s “Little Ice Age” Large Volcanic Eruptions Multi-decadal droughts Thermohaline Circulation Millennial Temperature Reconstruction National Ice Core Laboratory (http://nicl.usgs.gov/proc.htm ) 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale 10,000 years Natural cycles begin to appear Those not influenced by humans Use Paleoclimatic data 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale 10,000 years Last 10,000 years End of last Ice Age Melting of polar ice caps and glaciers Rising sea level Formation of the Black Sea, Pleistocene Lakes in Western U.S. Did the influx of freshwater 8,200 years ago from large lakes in what is now northern Canada help trigger the coldest climate event in the Earth's climate system in the past 10,000 years? 24 hours 1 year 10 years 100 years 1000 years 10,000 years 100,000 years Introduction - Climate scale 100,000 years Extreme long term trends Milankovitch cycles Last 100,000 years Last Ice Age cycle 60,000 to 20,000 ybp Ice Age Cycles began ~2.6 myo to present Decline of the Neanderthal, rise of Homo sapiens Causes of Global Climate Change Global Cooling Volcanic Eruptions Tambora, Indonesia – 1815 “year without a summer” Mount Toba, present day Sumatra - 73,000 years ago accelerated glaciation Causes of Global Climate Change Milankovitch cycles Eccentricity – 100,000 to 400,000 year periods Obliquity – every 41,000 years Processional of equinoxes – every 23,000 years Eccentricity: The Shape of the Earth’s Orbit Shape of Earth’s orbit changes from circular to elliptical over 100,000 years. More circular: stable climate More elliptical: strong climate variations Eccentricity t warmer cooler Obliquity: Tilt of Earth’s Axis The degree to which the axis tilts varies from 21.5͍° to 23.5° over 41,000 years More tilt: poles receive more sunlight Less tilt: poles receive less sunlight Obliquity Precession of the equinoxes As the Earth spins, it wobbles a bit N Pole currently points towards Polaris (the North Star) but shifts to point towards Vega over 23,000 years Precession of the equinoxes Causes of Global Climate Change Global Cooling Changes in ocean circulation Changes to Thermohaline current Position of the continents THE GLOBAL OCEAN CONVEYOR—The global ocean circulation system, often called the Ocean Conveyor, transports heat throughout the planet. White sections represent warm surface currents. Purple sections represent deep cold currents. (Illustration by Jayne Doucette, WHOI) DRAMATIC CHANGES IN THE NORTH ATLANTIC—Subpolar seas bordering the North Atlantic have become noticeably less salty since the mid-1960s, especially in the last decade. This is the largest and most dramatic oceanic change ever measured in the era of modern instruments. This has resulted in a freshening of the deep ocean in the North Atlantic, which in the past disrupted the Ocean Conveyor and caused abrupt climate changes. (B. Dickson, et. al., in Nature, April 2002) DRAMATIC CHANGES IN THE NORTH ATLANTIC—Subpolar seas bordering the North Atlantic (top) have become noticeably less salty since the mid-1960s, especially in the last decade (bottom). This is the largest and most dramatic oceanic change ever measured in the era of modern instruments. This has resulted in a freshening of the deep ocean in the North Atlantic, which in the past disrupted the Ocean Conveyor and caused abrupt climate changes. (B. Dickson, et. al., in Nature, April 2002) A LONG RECORD OF ABRUPT CLIMATE CHANGES The Younger Dryas about 12,700 years ago, average temperatures in the North Atlantic region abruptly plummeted nearly 5°C and remained that way for 1,300 years before rapidly warming again. A LONG RECORD OF ABRUPT CLIMATE CHANGES The 8,200-Year Event A similar abrupt cooling occurred 8,200 years ago. It was not so severe and lasted only about a century. But if a similar cooling event occurred today, it would be catastrophic. A LONG RECORD OF ABRUPT CLIMATE CHANGES The Medieval Period An abrupt warming took place about 1,000 years ago. It was not nearly so dramatic as past events, but it nevertheless allowed the Norse to establish settlements in Greenland. A LONG RECORD OF ABRUPT CLIMATE CHANGES The Little Ice Age The Norse abandoned their Greenland settlements when the climate turned abruptly colder 700 years ago. Between 1300 and 1850, severe winters had profound agricultural, economic, and political impacts in Europe. What Happens if the Conveyor Shuts Down? Scenario 1: Conveyor slows down within next two decades. Such a scenario could quickly and markedly cool the North Atlantic region, causing disruptions in global economic activity. These disruptions may be exacerbated because the climate changes occur in a direction opposite to what is commonly expected, and they occur at a pace that makes adaptation difficult. Source: Abrupt Climate Change: Should We Be Worried? By Robert B. Gagosian <http://www.whoi.edu/institutes/occi/viewArticle.do?id=9986> What Happens if the Conveyor Shuts Down? Scenario 2: Conveyor slows down a century from now. In such a scenario, cooling of the North Atlantic region may partially or totally offset the major effects of global warming in this region. Thus, the climate of the North Atlantic region may rapidly return to one that more resembles today’s—even as other parts of the world, particularly less-developed regions, experience the unmitigated brunt of global warming. If the Conveyor subsequently turns on again, the “deferred” warming may be delivered in a decade Source: Abrupt Climate Change: Should We Be Worried? By Robert B. Gagosian <http://www.whoi.edu/institutes/occi/viewArticle.do?id=9986> Effects of Global Cooling Temperatures Europe and North America ~20°C colder than present Tropical regions ~ 2°C colder than present Development of ice caps Lowers sea levels Causes land bridges to form Changes to flora and fauna Effects of Changes in Sea Level Across Beringia Sea Level at LGM ~10,000 ybp ~12,000 ybp Present Last Glacial Maximum Today Causes of Global Climate Change Global Warming Sunlight received by the Earth may be reflected by either the atmosphere or the surface. Some of the light is absorbed by the Earth and re-emitted as infrared energy (heat). Gases prevent some of this heat from escaping to space thereby causing the Earth to grow warmer. Global temperatures are 0.6ºC higher than 100 years ago Temperatures of the northern hemisphere for the past 1000 years. Globally-averaged surface temperatures Causes of Global Climate Change Global Warming Gases that cause the global warming (greenhouse effect) Carbon dioxide (CO2) Methane Chlorofluorocarbons Effects of Global Warming The impact on the Earth is uncertain Scientists are unable to precisely model the nature of this process General atmospheric warming due to human pollution is highly probable Polar ice caps may partially melt raising sea level Some parts of the land may receive less rain while others receive more Lands Vulnerable to Sea Level Rise On the Gulf Coast Table 3 AMOUNTS OF LOW LAND IMPLIED BY VARIOUS MAP DATA SETS 1 (square kilometers) State Elevation between 0 and 1.5 meters Elevation between 1.5 and 3.5 meters District of Columbia 1.5 4 Pennsylvania 2.5 2.5 New Hampshire 42.4 20 Connecticut 63 48.6 Rhode Island 121.9 61.7 Mississippi 173.2 824.1 Alabama 194.7 354.6 New York 239.9 265.8 Massachusetts 364.7 375 Maine 382.9 176.1 Delaware 387.8 172 Virginia 968.5 1,041.40 New Jersey 1,083.00 637.8 Maryland 1,547.10 806.1 Georgia 1,742.60 1,078.30 South Carolina 2,333.70 2,401.70 Texas 5,177.70 4,213.20 North Carolina 5,835.90 3,864.60 Florida 12,250.80 12,742.90 Louisiana 24,724.70 4,345.20 Total 57,638.60 33,435.70 Effects of Global Warming Some Solutions To The Global Warming Problem Use Energy More Efficiently Develop Alternate Energy Sources Effects of Global Warming Some Solutions To The Global Warming Problem Other Strategies Improve public transit to reduce automobile use Reverse deforestation Rapidly terminate the world-wide use of chlorofluorocarbons Modify your life style so as to minimize impact on the environment Effects of Global Warming Serious Concerns The developed countries achieved their wealth on fossil fuels. How can we deny developing nations these same benefits? Deforestation is a short-term benefit to the logging industry and farmers around the world. How can we prevent them from making a living? Effects of Global Warming Serious Concerns Many poor coastal countries will suffer greatly from a sea level rise and yet they produce very little carbon pollution. What obligations do the rich countries have to those who will suffer because of the pollution of others? Past Civilizations & Climate Change Maya Three time periods Preclassic Period from 2000 BC to 250 A.D., Classic Period from 250 A.D. to 900 A.D., Postclassic Period from 900 A.D. to the time of Spanish Conquest beginning in 1524 A.D.. Source: http://www.ncdc.noaa.gov/paleo/slides/slideset/12/ Past Civilizations & Climate Change Maya Classic Period from 250 A.D. to 900 A.D., Culture flourished 600 – 800 A.D. Collapse occurred between 800 and 900 A.D.. Past Civilizations & Climate Change Maya Symptoms of the collapse included: rapid depopulation of the countryside and ceremonial centers in 50 to 100 years abandonment of administrative and residential structures cessation of: – building construction, carving of sculptured monuments, manufacture of pottery, stonework, jade carvings, Classic calendrical (long count) and writing systems. Past Civilizations & Climate Change Maya Proposed causes of the Collapse (Natural): soil exhaustion due to slash-and-burn agriculture water loss and erosion of topsoil evident by increased sedimentation in lakes natural disasters (earthquakes, hurricanes) climatic change disease insect infestations overpopulation Past Civilizations & Climate Change Maya Proposed causes of the Collapse (sociopolitical): peasant revolts resulting in the overthrowing of the elite class inter-site warfare between Maya city-states invasions by peoples from outside the Maya civilization failure of centralized political authority. Past Civilizations & Climate Change Mesopotamia Akkadian empire established between the Tigris & Euphrates Rivers around 2300 B.C. Society collapsed +/- 150 years later Abandonment of agricultural plains in the north Mass migration to more arid lands to the south Source: http://www.ldeo.columbia.edu/res/pi/arch/examples.shtml Past Civilizations & Climate Change Mesopotamia World climate records abrupt climate change around the same time Cool & drought conditions for next 200 – 300 years Source: http://www.ldeo.columbia.edu/res/pi/arch/examples.shtml Map of the Akkadian empire (source: http://research.yale.edu/leilan/akkadian/) Past Civilizations & Climate Change Others Akkadian empire (Mesopotamia) Teotihuacán Roanoke Modern Civilizations & Climate Change Where will the people go if . . . Sea level rises? Climate regimes shift? Animals/fish/etc. become extinct or migrate elsewhere? “Whatever befalls the Earth befalls the sons of the Earth. Man did not weave the web of life; he is merely a strand in it. Whatever he does to the web, he does to himself. Contaminate your bed, and you will one night suffocate in your own waste.” Chief Seattle 1785 - 1866 ~ End ~