New Core CurriculumNew Core Curriculum

Foundations of Scientific ProcessFoundations of Scientific Process

Factors that govern Global & Local ClimateFactors that govern Global & Local Climate

Life – Atmospheric Conditions – ClimateLife – Atmospheric Conditions – Climate

Proxies- needed to infer past climate-related changes

Time before present (billions of years)

Atmospheric CO2

Atmospheric O2

Development of the Habitable Conditions on Earth

The History of Life on Earth

Elements of Habitability

• Stability• Chemical Composition• Temperature

Temperature of a planet is determined from an energy balance:

Energy IN = Energy OUT

Star’s Luminosity Distance planet-star Tilt of planet’s axis,

eccentricity of planet's orbit

Reflectivity of planet, Albedo (cloud cover, surface ice, vegetation, aerosols)

Star’s Luminosity Distance planet-star Tilt of planet’s axis,

eccentricity of planet's orbit

Reflectivity of planet, Albedo (cloud cover, surface ice, vegetation, aerosols)

Planet’s atmosphere– Water vapor– Carbon dioxide– Methane– Nitrous oxides– Sulfur dioxide– Aerosols

Planet’s atmosphere– Water vapor– Carbon dioxide– Methane– Nitrous oxides– Sulfur dioxide– Aerosols

Elements of Habitability

• Stability• Chemical Composition• Temperature

Energy input = Earth output

1) Ein (from the Sun)

Eout

2) Reflectivity (Albedo)3) Greenhouse Concentration

How do we determine the energy into the climate system?

Distance from Sun

B = L/4πd2

Solar Max2001

Solar Min2006

Solar Max2011

Sunspots!

More sunspots = “brighter” sun

Small effect: 1-2 W/m2 of 1360 W/m2

Sunspot cycles occur over decades to hundreds of years

significant climate responses to sun spots

1 - 2

W/m2

Year

Precession is the change in the direction of the Earth's axis of rotation relative to the fixed star.

The angle of the Earth's axial tilt varies with respect to the plane of the Earth's orbit.

The eccentricity is a measure of the departure of this ellipse from circularity.

100,000

41,000 23,000

Milankovitch cycles

years years years

Green house gasesHow do we determine the energy out of the climate system?

Albedo

Clouds, ice, white aerosols reflect about 30% of incoming sunlight back to space

Albedo = Reflectivity fraction of incoming radiation that is not absorbed, yet just bounces back in space

Sample albedos

Surface Albedo

Fresh asphalt

0.04[1]

Conifer forest(Summer)

0.08[2]

Worn asphalt

0.12[1]

Bare soil 0.17[3]

Green grass

0.25[3]

Desert sand

0.40[4]

New concrete

0.55[3]

Fresh snow

0.80–0.90[3]

Venus ~ 0.65

Mars ~ 0.15Earth ~ 0.3Moon ~ 0.12Jupiter ~ 0.52

Europa ~ 0.67

Venus ~ 0.65

Mars ~ 0.15Earth ~ 0.3Moon ~ 0.12Jupiter ~ 0.52

Europa ~ 0.67

Volcanoes cool climate, briefly

Mt. Pinatubo - 1994

Big eruptions inject aerosols into the upper atmosphere.Earth becomes more reflective for 2-3 years

Natural effects that Increases

Earth’s Albedo

Greenhouse Effect:Greenhouse Effect: gases (H gases (H22O, COO, CO22,..) trap heat in the atmosphere,..) trap heat in the atmosphere

Greenhouse gases Greenhouse gases are highly influentialare highly influential

HH22O vapor constitutes the largest % of the O vapor constitutes the largest % of the

greenhouse effect (absorbs terrestrial radiation)greenhouse effect (absorbs terrestrial radiation)

How do we determine the energy out of the climate system?

Heat & TemperatureHeat & Temperature

• Heat: energy of atomic and molecular motion

• Temperature: measure of average kinetic energy of moving atoms and molecules

vavg 140(m /s)T

m

T (in Kelvin) m (atomic mass

unit, # protons + # neutrons)

T (in Kelvin) m (atomic mass

unit, # protons + # neutrons)

Ex: Room temperature

T = 293 K Air particles as

N2

(m = 2 x 14 g/mol)

vavg ~ 450 m/s

Ex: Room temperature

T = 293 K Air particles as

N2

(m = 2 x 14 g/mol)

vavg ~ 450 m/s

Climate: Climate: average weather (average temperature) for average weather (average temperature) for the whole planet that prevails over certain the whole planet that prevails over certain time-span; time-span;

it is variable with time;it is variable with time;

it is a sensitive system;it is a sensitive system;

3 factors 3 factors determining determining the global the global climate:climate:

1) Ein (from the Sun)2) Reflectivity (Albedo)3) Greenhouse Concentration

Complicated Feedback Complicated Feedback Loops “in-play”Loops “in-play”

What controls local climate?

differential heating What causes Seasons?

Temperature of a planet is determined from an energy balance:

Energy IN = Energy OUT

Star’s Luminosity Distance planet-star Tilt of planet’s axis,

eccentricity of planet's orbit

Reflectivity of planet = Albedo (cloud cover, surface ice, vegetation, aerosols)

Star’s Luminosity Distance planet-star Tilt of planet’s axis,

eccentricity of planet's orbit

Reflectivity of planet = Albedo (cloud cover, surface ice, vegetation, aerosols)

Planet’s atmosphere– Water vapor– Carbon dioxide– Methane– Nitrous oxides– Sulfur dioxide– Aerosols

Planet’s atmosphere– Water vapor– Carbon dioxide– Methane– Nitrous oxides– Sulfur dioxide– Aerosols

Elements of Habitability

• Stability• Chemical Composition• Temperature

Global TrendsGlobal Trends

Climate Change(global worming, sea-level rise, coastal flooding, extreme weather)

HOW DO WE KNOW?

The Earth’s Past (evidence from the geologic record)The Earth’s Past (evidence from the geologic record)

Proxies- needed to infer past climate-related changes

Time before present (billions of years)

Atmospheric CO2

Atmospheric O2

Natural Recorders of Temperature Natural Recorders of Temperature Paleo-climate ProxiesPaleo-climate Proxies

Ice Core

Glacial features

Tree Rings

Sedimentary Layers

Fossils

Retreating glaciers – Proxy for past climatic conditionsRetreating glaciers – Proxy for past climatic conditions

TODAY

Full extent was in ~1850 AD

Glaciers “clean” rock surfaceLeave hills or mounds of sediments (moraines) and discoloration

But this is with reference to Greenland. Is it applicable on the global

scale?

Retreating glacier in Greenland

Examine retreat of glaciers elsewhere on Earth

Franz Josef Glacier in New ZealandCompare size in 1880 AD and now

Retreat of glacier Climate much colder in the past

Retreating glaciers in the Southern hemisphere

Historical records of past conditions

Ref : IPCC Report 2001

Retreating glaciers worldwide

Glacial grooves and striations at the base of the Matterhorn

Glaciers as Proxies

Like in our backyard of Central Park!

Evidence that glaciers extended here in the past over 20,000 years ago

Ice Core Archiveshttp://www.pbs.org/saf/1505/video/watchonline.htm

movie of ocean sample

How glaciers trap bubbles samples of atmosphere

Snow falls Ice becomes closer packed Eventually pores are isolated and gas is trapped Gas is record of the atmosphere in the past and the content of various gases – CO2, CH4 etc. in it

2-5 km length

Data: CO2 content of air trapped in ice core

Earth’s paleoclimate

How was an estimate of temperature obtained?

How was an estimate of CO2 obtained?

Air bubbles trapped in the ice core

Ratio of Oxygen isotopes (atoms with different number of neutrons)

Calibration Curve

Homo Sapiens about 200 thousand years ago

Nature, June 2003 20,000 YEARS AGO

300

400

500

600

Mauna Loa

700

600

500

400

300

200

Mauna Loa

IPCCA1B scenario

1950 2000 2050 2100

Time (years)

CO2 concentrations (ppm)

IPCCA1B

300

400

500

600

Mauna Loa

Factors responsible for Climate Factors responsible for Climate Variation:Variation:

A) Natural A) Natural Causes Causes B) Anthropogenic Causes B) Anthropogenic Causes

Global Warming of Climate: Global Warming of Climate:

Who is responsible for the change? Who is responsible for the change?

Natural Natural Causes Causes

AnthropogeniAnthropogenic Causes c Causes

• addition of CO2

burn burning of coal/fossil fuels;

deforestation (vegetation decay);

• generation of Aerosols

• variations in Earth’s orbit

eccentricity, obliquity, precession

• movement of landmasses

• volcanic activity

So global climate is warming….So global climate is warming….

How can we distinguish between How can we distinguish between variations due to natural causes variations due to natural causes and those that are induced by and those that are induced by human activity?human activity?

Natural Natural Causes Causes

AnthropogeniAnthropogenic Causes c Causes

Climate Models as Climate Models as Evidence: used to Evidence: used to determine the amount of determine the amount of change anticipated by change anticipated by accounting for certain accounting for certain factorsfactors

Modern Climate Changes dominated by Human Influence

Climate Models as Evidence:Climate Models as Evidence:

Modern Climate Changes dominated by Human

Influence

Testing models against past climate: The last ~ 100 years

“Natural”

Influences

Human Influenc

es