Natural Causes of Climate ChangeNatural Causes of Climate Change

Factors primarily responsible for most past Factors primarily responsible for most past climate change:climate change: Variations in the Earth's orbital characteristics. Variations in the Earth's orbital characteristics. Atmospheric carbon dioxide variations. Atmospheric carbon dioxide variations. Volcanic eruptions Volcanic eruptions Variations in solar output.Variations in solar output.

Volcanoes and GasesVolcanoes and Gases

Volcanic gases significant impact on global Volcanic gases significant impact on global change change

Magma contains gasesMagma contains gases Concentrations vary between volcanoes Concentrations vary between volcanoes Water vapor most abundant then carbon dioxide & Water vapor most abundant then carbon dioxide &

sulfur dioxide. Others = hydrogen sulfide, hydrogen sulfur dioxide. Others = hydrogen sulfide, hydrogen chloride, and hydrogen fluoride. chloride, and hydrogen fluoride.

Volcanic gas, aerosol droplets, and ash injected into Volcanic gas, aerosol droplets, and ash injected into the stratosphere during major explosive eruptions. the stratosphere during major explosive eruptions.

Sulfur dioxide, can cause global cooling, ozone Sulfur dioxide, can cause global cooling, ozone destruction, and volcanic smog or "vog". destruction, and volcanic smog or "vog".

Sulfur dioxide and AerosolsSulfur dioxide and Aerosols

Major impact is conversion of sulfur dioxide to Major impact is conversion of sulfur dioxide to sulfuric acid (Hsulfuric acid (H22SOSO44), ), condenses sulfate aerosols. condenses sulfate aerosols. aerosols increase reflection of radiation to space; cool aerosols increase reflection of radiation to space; cool

the Earth's lower atmospherethe Earth's lower atmosphere however, absorb heat radiated up from the Earth, however, absorb heat radiated up from the Earth,

warming stratosphere. warming stratosphere. sulfate aerosols also help destroy ozonesulfate aerosols also help destroy ozone

Chemical reactions produce chlorine monoxide (ClO), which Chemical reactions produce chlorine monoxide (ClO), which destroys ozone (O3). destroys ozone (O3).

Volcano DistributionVolcano Distribution

Volcano TypesVolcano Types

Non-explosiveNon-explosive Fluid Basaltic LavaFluid Basaltic Lava Basalt is rich in iron & Basalt is rich in iron &

MagnesiumMagnesium Not rich in gasesNot rich in gases High temperature High temperature

eruptioneruption Broad VolcanoBroad Volcano Examples--HawaiianExamples--Hawaiian

Britannica

Explosive VolcanoExplosive Volcano

Rich in Silica Rich in Silica (SiO2)(SiO2)

Rich in GasesRich in Gases Very ViscousVery Viscous Lower Lower

Temperature Temperature EruptionsEruptions

California Explosive VolcanoesCalifornia Explosive Volcanoes

ShastaLassen

Sampling gasesSampling gases

Sulphur dioxide measurements with spectrometer. Mt San HelensCollecting Gas Samples at Mt.

San Helens

Types of volcanic gasesThe most abundant gas typically released into the atmosphere from volcanic systems is water vapor (H20), followed by carbon dioxide (C02) and sulfur dioxide (S02). Volcanoes

also release smaller amounts of others gases, including hydrogen sulfide (H2S),

hydrogen (H2), carbon monoxide (CO), hydrogen chloride (HCL), hydrogen fluoride (HF),

and helium (He).

VolcanoVolcanoTectonic StyleTectonic StyleTemperature Temperature

Kilauea Kilauea SummitSummitHot SpotHot Spot1170°C 1170°C

Erta` AleErta` AleDivergent Divergent

PlatePlate1130°C 1130°C

MomotomboMomotomboConvergent Convergent

PlatePlate820°C 820°C

HH2200 37.1 37.1 77.2 77.2 97.1 97.1

C0C022 48.9 48.9 11.3 11.3 1.44 1.44

S0S022 11.8 11.8 8.34 8.34 0.50 0.50

HH22 0.49 0.49 1.39 1.39 0.70 0.70

CO CO 1.51 1.51 0.44 0.44 0.01 0.01

HH22SS 0.04 0.04 0.68 0.68 0.23 0.23

HCl HCl 0.08 0.08 0.42 0.42 2.89 2.89

HF HF --- --- --- --- 0.26 0.26

 Examples of volcanic gas compositions, in volume percent concentrations(from Symonds et. al., 1994)

USGS

Mount PinatuboMount Pinatubo Mount Pinatubo eruption, on June 12, 1991. Mount Pinatubo eruption, on June 12, 1991.

one of largest eruptions of this century. one of largest eruptions of this century. erupted over a cubic mile of rock material. erupted over a cubic mile of rock material. 20- million ton sulfur dioxide cloud into stratosphere to 20 miles. 20- million ton sulfur dioxide cloud into stratosphere to 20 miles. largest sulfur dioxide cloud observed since satellites in 1978.largest sulfur dioxide cloud observed since satellites in 1978. Sulfate aerosol formed in stratosphere from sulfur dioxide; increased the Sulfate aerosol formed in stratosphere from sulfur dioxide; increased the

reflection of radiation into space. reflection of radiation into space. Earth's surface cooled in the three years following the eruption, by as Earth's surface cooled in the three years following the eruption, by as

much as 1.3 degrees ( Fahrenheit scale) much as 1.3 degrees ( Fahrenheit scale) sulfate aerosols accelerated destruction of ozone. sulfate aerosols accelerated destruction of ozone.

Some blamed Midwest floods and larger Antarctic ozone hole on Mt. Some blamed Midwest floods and larger Antarctic ozone hole on Mt. Pinatubo aerosols. Pinatubo aerosols.

some large historic eruptions followed temperature decreases. not some large historic eruptions followed temperature decreases. not all large eruptions followed by temperature decreases, all large eruptions followed by temperature decreases,

Sulfur Dioxide-Pinatubo & El ChichonSulfur Dioxide-Pinatubo & El Chichon

Mt. PinatuboMt. Pinatubo

www.geo.mtu.edu NOAA

El Chichon

Graphs of average temperatures 5 years before and 5 years after the listed various volcanic eruptions. Low temperatures always occur after an eruption (occurring at Month #0). Graph “e.” is a composite of the graphs a.–d. Graph “f.” is the response to the most recent Mt. Pinatubo eruption. (From: Climate Research Unit).

http://earthguide.ucsd.edu/

A list of years characterized by low tree-ring densities, with the name of the volcano eruption immediately preceding the tree-ring event indicated in parentheses (n.d. = not determined).

http://earthguide.ucsd.edu/

Tree Rings & EruptionsTree Rings & Eruptions High density wood = warm High density wood = warm

temperatures, and vice versa. temperatures, and vice versa. lowest tree-ring densities lowest tree-ring densities

follow major eruptions follow major eruptions

Largest eruption, Peru 1601, Largest eruption, Peru 1601, caused severe economic caused severe economic damage in Peru and its damage in Peru and its neighbors took 150 years to neighbors took 150 years to recoverrecover

Severe winters, late frost, and Severe winters, late frost, and cool summers follow major cool summers follow major eruptions. Lead to poor eruptions. Lead to poor harvest harvest

Tambora eruptions = Europe Tambora eruptions = Europe spent summer around the spent summer around the fireplace in 1816, with frost in fireplace in 1816, with frost in July, followed by famine.July, followed by famine.

Deccan TrapDeccan Trap formed between 60 and formed between 60 and

68 68 million years ago,,[2] eruptions may have eruptions may have

lasted fewer than 30,000 lasted fewer than 30,000 years. years.

gases released may have gases released may have played a role in the played a role in the Cretaceous–Tertiary extinction event,.,.

the original area covered the original area covered by the by the lava flows was as was as large as 1.5 million km², large as 1.5 million km², approximately half the approximately half the size of modern India. size of modern India.

release of release of volcanic gases "contributed to an "contributed to an apparently massive apparently massive global warming. Some . Some data point to an average data point to an average rise in temperature of 8 °C rise in temperature of 8 °C (14 °F) in the last half (14 °F) in the last half million years before the million years before the impact at Chicxulub."."[3]

Naggs & Raheem

Deccan TrapDeccan Trap Cretaceous, associated with Dinosaur extinctionCretaceous, associated with Dinosaur extinction Much gas in atmosphere, warmed planetMuch gas in atmosphere, warmed planet More gas than by meteor impact thought to cause More gas than by meteor impact thought to cause

extinctionextinction

The basalt layers in India's Deccan Traps could be used to store huge amounts of carbon dioxide. DINODIA IMAGES/ALAMY

Tathagata 'Ted' Dasgupta

Siberian Trap - PermianSiberian Trap - Permian Permian about 250 mya-greatest extinctionPermian about 250 mya-greatest extinction Scant evidence for meteor impactScant evidence for meteor impact Gases from impact not enough for extinctionGases from impact not enough for extinction Gases from magma led to extinction?Gases from magma led to extinction?

Milankovitch TheoryMilankovitch Theory Climate change due to variations Climate change due to variations

in the earth's orbit - Milankovitch in the earth's orbit - Milankovitch TheoryTheory

1) eccentricity cycle - the earth's 1) eccentricity cycle - the earth's orbit around the sun is elliptical. orbit around the sun is elliptical. the shape of the ellipse the shape of the ellipse

(eccentricity) varies from less (eccentricity) varies from less elliptical to more elliptical back to elliptical to more elliptical back to less elliptical and take about less elliptical and take about 100,000 years to complete this 100,000 years to complete this cycle.cycle.

currently, we are in an orbit of currently, we are in an orbit of low eccentricity (near circular).low eccentricity (near circular).

review - when are we closest to review - when are we closest to the sun?the sun?

Data analysis for the last 800,000 Data analysis for the last 800,000 years of deep-ocean sediments years of deep-ocean sediments show that ice coverage is a show that ice coverage is a maxima every 100,000 yearsmaxima every 100,000 years

this matches the Eccentricity this matches the Eccentricity cycle periodcycle period

http://www.wwnorton.com/college/geo/egeo/flash/18_2.swf

Precession cycle - Precession cycle - The earth wobbles The earth wobbles

about it's axis of about it's axis of rotation like a rotation like a spinning topspinning top

one cycle = about one cycle = about 23,000 years23,000 years

in 11,000 years, in 11,000 years, seasons will switch seasons will switch times during year times during year and will be more and will be more severe...., why?severe...., why?

http://www.wwnorton.com/college/geo/egeo/flash/18_2.swf

ObliquityObliquity Tilt Cycle - ObliquityTilt Cycle - Obliquity

axis of earth’s rotation is tilted axis of earth’s rotation is tilted 23.5°23.5°

However, value changes from However, value changes from 22.5° to a maximum of 24.5° 22.5° to a maximum of 24.5° and takes 41,000 years to and takes 41,000 years to completecomplete

at 22.5° the seasonal variation at 22.5° the seasonal variation will be greater/less?will be greater/less?

at 24.5° the seasonal variation at 24.5° the seasonal variation will be greater/less than will be greater/less than current?current?

http://www.wwnorton.com/college/geo/egeo/flash/18_2.swf

100K cycles evident 100K cycles evident for climate changefor climate change

SunspotsSunspots huge magnetic storms that huge magnetic storms that

show up as dark (cool) areas show up as dark (cool) areas on the suns surfaceon the suns surface

more sunspots = more energy, more sunspots = more energy, = more energy on earth = more energy on earth

warmer climate during a sun warmer climate during a sun spot maximum; cooler climate spot maximum; cooler climate during minimum.during minimum.

what does a sun spot look what does a sun spot look like?like?

sun spot period is about 11 sun spot period is about 11 yearsyears

Sunspot CyclesSunspot Cycles

Sunspot minimum Sunspot minimum 1645-17151645-1715

Period called “Little Period called “Little Ice Age”Ice Age”

Images from Nasa

The solar disk seen by the Yohkoh soft-X-Ray imager, over the time period 1991-1995 (left to right), spanning the descending phase of cycle 23.

Source: http://www.heasarc.gsfc.nasa.gov

Solar irradiation is the amount of energy from solar radiation hitting earth’s surface.