11.1 Natural Causes of Climate 11.1 Natural Causes of Climate

ChangeChange

ClimateClimate

�� Describes the average conditions of the Describes the average conditions of the atmatm in in

large regions over time (>30 years)large regions over time (>30 years)

�� Ex) precipitation, temperature, Ex) precipitation, temperature, atmatm pressure, pressure,

radiation, windradiation, wind

Climate ZonesClimate Zones

BiogeoclimaticBiogeoclimatic ZoneZone

�� Region with a certain type of plant life, soil, Region with a certain type of plant life, soil,

geography, and climategeography, and climate

�� BC has 14 zonesBC has 14 zones

Penticton, BCPenticton, BC

Studying the PastStudying the Past�� PaleoclimatologistsPaleoclimatologists study past climatesstudy past climates

�� Look for long term patternsLook for long term patterns

Ex) 21,000 years ago Canada was buried under a glacierEx) 21,000 years ago Canada was buried under a glacier

�� Examine fossils, sediment, ice cores (CO2)Examine fossils, sediment, ice cores (CO2)

Historic Concentrations of COHistoric Concentrations of CO22 in in

the Atmospherethe Atmosphere

Reading CheckReading Check

�� What does “climate” describe?What does “climate” describe?

�� What is a What is a biogeoclimaticbiogeoclimatic zone?zone?

�� How has the climate changed in Canada since How has the climate changed in Canada since

21,000 years ago?21,000 years ago?

�� What is a method to determine how much What is a method to determine how much

carbon dioxide was in the atmosphere in the carbon dioxide was in the atmosphere in the

past?past?

Greenhouse GasesGreenhouse Gases

�� Gases in the Gases in the atmatm that absorb that absorb

and emit radiation as and emit radiation as

thermal energythermal energy

�� Without these gases, the Without these gases, the

earth’s average temp would earth’s average temp would

be 34ºC lowerbe 34ºC lower

�� Too many = Greenhouse Too many = Greenhouse

EffectEffect

Earth’s movement affects climateEarth’s movement affects climate

1) 1) Earth’s TiltEarth’s Tilt

�� Earth’s tilt is responsible for seasonsEarth’s tilt is responsible for seasons

••In summer, we are tilted towards the Sun, decreasing the angle oIn summer, we are tilted towards the Sun, decreasing the angle of incidence.f incidence.

••In winter, tilted away from the Sun, solar radiation has a largeIn winter, tilted away from the Sun, solar radiation has a large angle of angle of

incidenceincidence

--Earth tilts between 22.3º and 24.5º Earth tilts between 22.3º and 24.5º

(currently 23.5º) in 41 000 year cycles.(currently 23.5º) in 41 000 year cycles.

--When tilt is largest, climate should When tilt is largest, climate should

experience the largest extremes.experience the largest extremes.

Earth’s movement affects climateEarth’s movement affects climate

2) Earth’s Wobble2) Earth’s Wobble

�� Earth also “wobbles” as it rotates Earth also “wobbles” as it rotates

on its axis.on its axis.

�� Because axis changes on a 23 000 year Because axis changes on a 23 000 year

cycle, cycle, the angle of incidence on solar the angle of incidence on solar

radiation also changes this wayradiation also changes this way..

Earth’s movement affects climateEarth’s movement affects climate

3 ) 3 ) Earth’s Earth’s RevolutionRevolution

�� Earth’s revolution around Earth’s revolution around the Sun is elliptical, not the Sun is elliptical, not circular.circular.

�� On a 100 000 year cycle, On a 100 000 year cycle, Earth’s elliptical orbit Earth’s elliptical orbit becomes more or less becomes more or less circular.circular.

�� When most elliptical, Earth When most elliptical, Earth will be farther away from will be farther away from the Sun than usual.the Sun than usual.

The Water CycleThe Water Cycle�� HH22O= most abundant greenhouse gasO= most abundant greenhouse gas

�� Warmer air can hold more waterWarmer air can hold more water

�� Increases temp on surfaceIncreases temp on surface

Ocean CurrentsOcean Currents

�� Convection currents transport large amount of Convection currents transport large amount of

heat around globeheat around globe

�� ThermoclineThermocline=separates cold, deep H=separates cold, deep H22O from warm O from warm

surface Hsurface H22O O

El NiñoEl Niño

�� Surface water off the coast of Ecuador and Peru Surface water off the coast of Ecuador and Peru

get warmerget warmer

�� Results in unusually mild weather along BC Results in unusually mild weather along BC

coast and E Canadacoast and E Canada

La NiñaLa Niña

�� Upwelling brings cooler waters to surface in E Upwelling brings cooler waters to surface in E

Pacific oceanPacific ocean

�� BC gets really coldBC gets really cold

El NiEl Niñoño--Southern Oscillation Southern Oscillation

(ENSO)(ENSO)

�� Variation in winds due to El NiVariation in winds due to El Niñoño and La Niña and La Niña

eventsevents

The Carbon CycleThe Carbon Cycle

�� Carbon dioxideCarbon dioxide-- important greenhouse gasimportant greenhouse gas

�� Carbon sinks remove Carbon from Carbon sinks remove Carbon from atmatm (deep (deep

ocean, forests)ocean, forests)

Catastrophic EventsCatastrophic Events

�� LargeLarge--scale disastersscale disasters

�� Ex) Ex) Meteorite ImpactMeteorite Impact, , volcanoesvolcanoes