Climate Review

Climate• Long term average conditions of a region

(occurs over many years)– Usually described in terms of average

temperatures, precipitation, humidity, weather patterns etc.

• Global warming is not the same a climate change (common misconception)– Refers to the recent increases in average global

temperature (temp. is just one aspect of climate)

Physical features of the Earth that affect climate:

• Axial tilt affects the length of seasons and day length (related to amount of radiation received)

• Precision affects how the Earth is oriented towards the Sun

• Shape of the Earth’s orbit– Varies from circular (more even heat) to

elliptical (more seasonal variation in heat.

Physical features of the Earth that affect climate:

• The curved surface of the Earth also has an effect on climate– More solar radiation is received at the equator

than latitudes north and south

• Location on a continent plays a role in climate– Wind patterns, mountains etc.

Physical features of the Earth that affect climate:

• Ocean currents have an effect on climate– Changes to the Pacific Ocean during El Niños

affects the Pacific coast of South America and other countries as well

– Great Ocean conveyor transfers heat around the planet

Physical features of the Earth that affect climate:

• Volcanic eruptions can send particulate matter into the air that affects solar radiation for years

• Earth’s albedo– How much solar energy it reflects

Particulate matter from Mt. Pinatubo eruption 1991

Solar energy

• About 20% is absorbed by the atmosphere• About 50% of the sun’s energy is either

absorbed by the earth’s surface or reflected back into space– For example, snow can reflect as much as 95%

while dark coloured soils absorb as much as 95%

Solar energy

• After 911 airplanes didn’t fly for 3 days so no contrails were created and the Earth’s temperature rose over those three days

• Indicating that if we stopped putting anymore particulate matter in the air overnight – the greenhouse effect would be more immediate and global temperatures would rise abruptly

Natural Greenhouse effect

• Natural greenhouse gases include water vapour, CO2, methane and nitrous oxide and have moderated our planet’s temperature for millions on years.– Some heat is absorbed by the atmosphere– Some heat is absorbed by the Earth and re-

radiated into the atmosphere where greenhouse gases trap reflected radiation

Natural Greenhouse effect

• The more greenhouse gases in the atmosphere the greater the temperature– When temperatures increase the oceans absorb

excess CO2 to decrease global temperatures, when the Earth is cooler CO2 is release to bring the temperature back up

– The average temperature of the Earth has not historically changed very much year to year

Greenhouse effect

Anthropogenic Greenhouse Effect

• Antarctic ice cores over thousands of years old show the temperature has been pretty constant within certain limits

• However, since the burning of fossil fuels (CO2) in the mid 1800s, the average global temperature has been steadily increasing– The “10 hottest years” in Earth’s history have

been in the past 10 years - for the last 20 years!

Average global temp. since 1978

Anthropogenic Greenhouse Effect

• The effect that increasing average global temperature will have depends in the latitude – less effect at the equator and greater effect at the poles

• Proximity to large bodies of water and prevailing winds etc. will also mitigate the effect of average temperature increases

Concerns with the Anthropogenic Greenhouse Effect

• Increase in extreme weather– More hurricanes and typhoons– Stronger monsoons– Tornados stronger and the

season lasting longer– Droughts increase or occur in

new areas, desertification– Flooding in new areas, or

rainfall patterns changing

Weather

• Weather is the Earth’s attempt to equalize solar radiation and global atmospheric pressure.

• Heated air rises and cooler air sinks – The attempt to equalize the pressure difference this

creates results in global winds– This helps moderate global temperatures by

redistributing heat

convection

Concerns with the Anthropogenic Greenhouse Effect

• Tropical diseases and pests moving into previously resistant areas as temperatures increase (e.g. malaria increasing)

• Glaciers melting, ice caps melting– Rising global sea levels, changing the albedo

• Acidification of the oceans– Coral bleaching

• Species extinction (Golden Toad)

Historical evidence for climate change

• Plate tectonics ensure that global temperature will change as continents move– Hotter when the global land mass is clustered at

the equator

• Ice ages (precision, orbit, albedo, axial tilt) are cyclical

• “medieval warming period”

Historical evidence for climate change

• However, these changes happened over long periods of time

https://www.youtube.com/watch?v=-JIuKjaY3r4