Climate change – Natural Climate change – Natural CausesCauses

CATASTROPHICCATASTROPHICVolcanic EruptionsVolcanic EruptionsMeteorite ImpactsMeteorite Impacts

REGULARREGULAROrbital Variation, Orbital Variation,

Solar Cycles & Cosmic raysSolar Cycles & Cosmic raysTectonic ShiftTectonic Shift

Volcanic Explosivity IndexVolcanic Explosivity Index

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• Volcanoes have the Volcanoes have the capability of throwing capability of throwing cubic kilometers of ash cubic kilometers of ash and debris into the and debris into the atmosphere which can atmosphere which can significantly alter the significantly alter the climate for years at a climate for years at a time– this is measured time– this is measured by the by the Volcanic Volcanic Explosivity IndexExplosivity Index ((VEIVEI))

Source: US Geological Survey: http://volcanoes.usgs.gov/images/pglossary/vei.php

Volcanic EruptionsVolcanic Eruptions• Short eruptions can influence climate patterns for years Short eruptions can influence climate patterns for years

due to the outpouring of gases and ash due to the outpouring of gases and ash • Droplets containing about 75 percent sulfuric acid can Droplets containing about 75 percent sulfuric acid can

linger as long as three to four years in the stratosphere. linger as long as three to four years in the stratosphere. • Major eruptions alter the Earth's radiative balance Major eruptions alter the Earth's radiative balance

because volcanic aerosol clouds absorb terrestrial because volcanic aerosol clouds absorb terrestrial radiation, and scatter a significant amount of the radiation, and scatter a significant amount of the incoming solar radiation, an effect known as "radiative incoming solar radiation, an effect known as "radiative forcing" that can last from two to three years following forcing" that can last from two to three years following a volcanic eruption.a volcanic eruption.

• Source: NASA: http://earthobservatory.nasa.gov/Features/Volcano/Source: NASA: http://earthobservatory.nasa.gov/Features/Volcano/

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The Year Without a SummerThe Year Without a Summer• Mount Tambora, Indonesia erupted in April 1815 with a rating of Mount Tambora, Indonesia erupted in April 1815 with a rating of

seven on the Volcanic Explosivity Indexseven on the Volcanic Explosivity Index• The 1815 eruption of Tambora was the largest volcanic eruption in The 1815 eruption of Tambora was the largest volcanic eruption in

recorded history. The explosion was heard 2,600 kilometres away, recorded history. The explosion was heard 2,600 kilometres away, and ash fell at least 1,300 kilometres awayand ash fell at least 1,300 kilometres away

• An aerosol of sulphuric acid circled the globe and blocked a large An aerosol of sulphuric acid circled the globe and blocked a large proportion of the sun’s energy from reaching the earth. This was proportion of the sun’s energy from reaching the earth. This was called the called the sulfate aerosol veil.sulfate aerosol veil.

• In 1816, global temperatures fell dramatically:In 1816, global temperatures fell dramatically:– in June – 30 cm of snow fall was recorded in Quebec Cityin June – 30 cm of snow fall was recorded in Quebec City– Drought conditions were reported in July and August as rainfall patterns changed.Drought conditions were reported in July and August as rainfall patterns changed.– Widespread crop failure due to lack of direct sunlight in Europe and North America Widespread crop failure due to lack of direct sunlight in Europe and North America

created famine.created famine.– Early frosts in August and September damaged the few crops which did growEarly frosts in August and September damaged the few crops which did grow– Significant livestock deaths were recorded in North America in the winter of 1816-Significant livestock deaths were recorded in North America in the winter of 1816-

17 due to lack of food for the animals.17 due to lack of food for the animals.

• Source: Wikipedia: Source: Wikipedia: http://en.wikipedia.org/wiki/Year_Without_a_Summerhttp://en.wikipedia.org/wiki/Year_Without_a_Summer 44

Volcanic ActivityVolcanic Activity• Mount Pinatubo, Philippines - 1991Mount Pinatubo, Philippines - 1991• The powerful eruption of such an enormous volume of lava and ash The powerful eruption of such an enormous volume of lava and ash

injected significant quantities of aerosols and dust into the injected significant quantities of aerosols and dust into the stratosphere. stratosphere.

• Sulfur dioxide oxidized in the atmosphere to produce a haze of Sulfur dioxide oxidized in the atmosphere to produce a haze of sulfuric acid droplets, which gradually spread throughout the sulfuric acid droplets, which gradually spread throughout the stratosphere over the year following the eruption. The total mass stratosphere over the year following the eruption. The total mass of SOof SO22 of about 17 million tons being ejected. of about 17 million tons being ejected.

• This very large stratospheric injection resulted in a reduction in the This very large stratospheric injection resulted in a reduction in the normal amount of sunlight reaching the Earth's surface by roughly normal amount of sunlight reaching the Earth's surface by roughly 10%. This led to a decrease in northern hemisphere average 10%. This led to a decrease in northern hemisphere average temperatures of 0.5–0.6 °C and a global fall of about 0.4 °C temperatures of 0.5–0.6 °C and a global fall of about 0.4 °C

• At the same time, the temperature in the stratosphere rose to At the same time, the temperature in the stratosphere rose to several degrees higher than normal, due to absorption of radiation several degrees higher than normal, due to absorption of radiation by the aerosols. The stratospheric cloud from the eruption by the aerosols. The stratospheric cloud from the eruption persisted in the atmosphere for three years after the eruption.persisted in the atmosphere for three years after the eruption.

• Source: US Geological Survey: http://pubs.usgs.gov/fs/1997/fs113-97/Source: US Geological Survey: http://pubs.usgs.gov/fs/1997/fs113-97/55

MeteoritesMeteorites• Large meteorite impacts have been noted in the geological recordsLarge meteorite impacts have been noted in the geological records• Depending on their size, their impacts on climate can be larger Depending on their size, their impacts on climate can be larger

than volcanoesthan volcanoes– An example of one huge impact is located in the Yucatan An example of one huge impact is located in the Yucatan

peninsuala in Mexico called the peninsuala in Mexico called the Chicxulub craterChicxulub crater – thought to – thought to have been formed 65 Million years agohave been formed 65 Million years ago

– The crater is more than 180 kilometers in diameter, the The crater is more than 180 kilometers in diameter, the impacting meteor that formed the crater was at least 10 km in impacting meteor that formed the crater was at least 10 km in diameter.diameter.

– The meteor triggered an extinction level event as debris would The meteor triggered an extinction level event as debris would have been thrown into the atmosphere and blocking sunlight have been thrown into the atmosphere and blocking sunlight from reaching the surface. Almost all plant and animal life was from reaching the surface. Almost all plant and animal life was thought to have been extinguished by this event.thought to have been extinguished by this event.

– A layer of Iridium rich sediment is seen in the geologic record A layer of Iridium rich sediment is seen in the geologic record around the world confirming the impact. around the world confirming the impact. http://www.metacafe.com/watch/2070635/video_of_meteor_crashing_in_canadahttp://www.metacafe.com/watch/2070635/video_of_meteor_crashing_in_canada_meteorite_impact_reformulated_earths_crust/_meteorite_impact_reformulated_earths_crust/

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Milankovitch CyclesMilankovitch Cycles• Milutin Milankovitch (1920) first proposed that Milutin Milankovitch (1920) first proposed that

glacial-interglacial cycles were controlled by the glacial-interglacial cycles were controlled by the amount and distribution of radiation received amount and distribution of radiation received from sun. from sun.

• Milankovitch argued that different periods of Milankovitch argued that different periods of major glaciations were initiated by changes in major glaciations were initiated by changes in Earth's orbital parameters of: Earth's orbital parameters of: – Eccentricity -100 000 year cycleEccentricity -100 000 year cycle– Axial Tilt (obliquity) – 41 000 year cycleAxial Tilt (obliquity) – 41 000 year cycle– Precession or Wobble – 21 000 year cyclePrecession or Wobble – 21 000 year cycle

EccentricityEccentricity• Eccentricity is the change in the shape of the Earth's Eccentricity is the change in the shape of the Earth's

orbit around the sun. orbit around the sun. • There is only about a 3% difference in distance There is only about a 3% difference in distance

between the time when we're closest to the sun between the time when we're closest to the sun (perihelion) and the time when we're farthest from (perihelion) and the time when we're farthest from the sun (aphelion). the sun (aphelion). – Perihelion occurs on January 3 and at that point, Perihelion occurs on January 3 and at that point,

the earth is 146 million km away from the sun. the earth is 146 million km away from the sun. – At Aphelion, July 4, the earth is 156 million km At Aphelion, July 4, the earth is 156 million km

from the sun.from the sun.• Over a 100,000 year cycle, the earth's orbit around Over a 100,000 year cycle, the earth's orbit around

the sun changes from a thin ellipse (oval) to a circle the sun changes from a thin ellipse (oval) to a circle and back again.and back again.

http://oceanworld.tamu.edu/students/iceage/iceage2.htmhttp://oceanworld.tamu.edu/students/iceage/iceage2.htm

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ObliquityObliquity• The angle of the Earth's axial tilt, or obliquity,The angle of the Earth's axial tilt, or obliquity, varies with respect to the plane of the Earth's varies with respect to the plane of the Earth's orbit. orbit. • These slow 2.4° obliquity variations take approximately These slow 2.4° obliquity variations take approximately

41,000 years to shift between a tilt of 22.1° and 24.5° and 41,000 years to shift between a tilt of 22.1° and 24.5° and back again.back again.

• Less of an angle than our current 23.45° means less Less of an angle than our current 23.45° means less seasonal differences between the Northern and Southern seasonal differences between the Northern and Southern Hemispheres while a greater angle means greater Hemispheres while a greater angle means greater seasonal differences (i.e. a warmer summer and cooler seasonal differences (i.e. a warmer summer and cooler winter). winter).

• The tilt is in the decreasing phase of its cycle, and will The tilt is in the decreasing phase of its cycle, and will reach its minimum value around the year 10,000 reach its minimum value around the year 10,000 – This trend would tend to make winters warmer and summers This trend would tend to make winters warmer and summers

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PrecessionPrecession• Precession operates on a 21 000 Precession operates on a 21 000 year cycle; also referred to as year cycle; also referred to as wobble.wobble.• 12,000 years from now the Northern Hemisphere will 12,000 years from now the Northern Hemisphere will

experience summer in December and winter in June experience summer in December and winter in June because the axis of the earth will be pointing at the star because the axis of the earth will be pointing at the star Vega instead of it's current alignment with the North Star Vega instead of it's current alignment with the North Star or Polaris. or Polaris.

• This seasonal reversal won't happen suddenly but the This seasonal reversal won't happen suddenly but the seasons will gradually shift over thousands of years. seasons will gradually shift over thousands of years.

• Precession occurs due to the tidal forces generated by the Precession occurs due to the tidal forces generated by the gravitational attraction of the moon and sun combined on gravitational attraction of the moon and sun combined on the Earth.the Earth.

1010

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Schwabe CycleSchwabe Cycle• Cosmic rays cause high level clouds to Cosmic rays cause high level clouds to

form => coolingform => cooling• ““active” sun produces more solar wind active” sun produces more solar wind

that deflects cosmic rays => warmingthat deflects cosmic rays => warming• cycles see combinations of solar cycles see combinations of solar

intensity overlaid with changes in intensity overlaid with changes in cosmic ray concentration as we move cosmic ray concentration as we move around the galaxyaround the galaxy

Sunspot ObservationsSunspot Observations

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The Maunder and Dalton Minimum resulted in a cool period in global temperature

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Schwabe CycleSchwabe Cycle

• Sun has direct relationship to temperature Sun has direct relationship to temperature on both long term and short term scaleson both long term and short term scales

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Solar Activity CycleSolar Activity Cycle

1515

Tectonic ShiftTectonic Shift• The continental land masses have moved The continental land masses have moved throughout time. At one time, all of the throughout time. At one time, all of the continents were together in a single land mass, continents were together in a single land mass, named Pangea, that fractured, forming oceans named Pangea, that fractured, forming oceans between them. between them.

• As continents changed position based on As continents changed position based on latitude, their individual climates would latitude, their individual climates would obviously change accordingly. The relative obviously change accordingly. The relative longitudinal positions of the continents also has longitudinal positions of the continents also has an impact on global climate however. As Africa an impact on global climate however. As Africa moved north into Europe, it forced ocean moved north into Europe, it forced ocean currents to divert around it, driving these warm currents to divert around it, driving these warm bodies into the cooler polar regionsbodies into the cooler polar regions

• Youtube video: Youtube video: http://www.http://www.youtubeyoutube.com/watch#!v=NYbTNFN3NBo&feature=relate.com/watch#!v=NYbTNFN3NBo&feature=relatedd

1616

Tectonic ShiftTectonic Shift• Continents had been Continents had been

arranged so warm arranged so warm equatorial currents equatorial currents flow freely. flow freely.

• Equatorial current is Equatorial current is heated more as it heated more as it circumnavigates the circumnavigates the Earth more than once. Earth more than once.

• North & South flowing North & South flowing currents diverging currents diverging from it are warmer.from it are warmer.

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Tectonic ShiftTectonic Shift• Fossil forests similar to Fossil forests similar to

those found in the those found in the Georgia today have Georgia today have been found in the been found in the Eocene sediments of Eocene sediments of Axel Heiberg Island.Axel Heiberg Island.

1818

Tectonic ShiftTectonic Shift• Present ConditionsPresent Conditions• Equatorial current Equatorial current

closed off 3 myaclosed off 3 mya• Gateways at high Gateways at high

latitude allow latitude allow circumpolar currents to circumpolar currents to pass. pass.

• Circumpolar currents Circumpolar currents insulate polar insulate polar continents from continents from warmer seas & cause warmer seas & cause polar temps to drop.polar temps to drop.

1919

Tectonics also cause mountain formation Present Monsoons are a geologically NEW

addition to climate there Mountains cause rain, plateaus dry conditions N.A. forests and prairies result

OrogenesisOrogenesis