LONG AND SHORT TERM CHANGES IN CLIMATE

LONG TERM CHANGES

• Continental Drift• When continents move, ocean currents and

wind patterns change which affects heat transfer• Also affects the distribution of land• More ocean south of equator – more moderate climate

• New mountain ranges, weathering of old mountain rangers

CLIMATE CYCLES• Earth’s climate cycles between freezing ice ages

and warmer interglacial periods• Earth’s last ice age was 20 000 years ago• Average temp was 10 degrees less• Ice sheets 3km thick covered most of Canada

WHY CLIMATE CYCLES?

• Earth’s orbit!• Eccentricity: shape of the orbit varies from

being circular to elliptical (cycles every 100,000 years)• Tilt: rangers from 22.1 -24.5 degrees (cycle is

every 41,000 years)• Wobble: As Earth spins it wobbles on it’s axis,

angle remains the same but direction changes

SHORT TERM VARIATIONS IN CLIMATE

• Volcanic Eruptions• clouds cause shading and cool Earth

• Changes in Air and Ocean Currents• El Nino – Air/Water in pacific ocean changes direction every

3-7 years• https://www.youtube.com/watch?v=7FVZrw7bk1w

• Changes in Sun’s Radiation• Small changes make a big difference in Earth’s temperature

FEEDBACK LOOPS AND CLIMATE (8.10)

FEEDBACK LOOP

• Positive Feedback Loop: the effect increases the original cause• A small change can have a big effect!

• Negative Feedback Loop: the effect decreases the original cause

THE WATER VAPOUR FEEDBACK LOOP

• Heat increase water vapour increase heat (greenhouse gas)• Cool less water vapour Earth cools down even

more

THE ALBEDO EFFECT

• Albedo: the amount of radiation reflected by a surface• Different surfaces have different albedos• Ex:• Ice and snow have high albedos• grass and trees have low albedos

• Albedo Effect: Positive feedback loop between ice on Earth’s surface and Earth’s temperature• Colder more ice more reflection cools more• Warmer less ice less reflection heats up more

• Earth shifts from ice age to warm period fairly quickly because of this effect

HOMEWORK!

• Read pg. 348-357• Questions• Pg. 353 #1, 4• Pg. 357 #1-4, 6, 7

How do we know what Past Climates Were Like??

• Ice Cores – test air bubbles to determine make up of atmosphere, can also help determine temperature• Tree Rings – the thicker the rings, the better the

conditions (warm, wet)• Coral Reefs – Add layers of growth each year,

determine water temperature• Rock – layers contain pollen or fossils• Ocean Sediment – layers contain fossils• Caves – dripping minerals solidify, grow faster in

rainy weather