Chapter 2 Gateway 2

What is happening to

the Earth’s climate?

Global Climate Change

• The variation in global climate• Changes in the climatic patterns in the long

term• General trend has been an irregular but

significant increase in global temperature.

Global Warming• Process where

global temperatures increase over a long period of time.

Global Cooling

• Process where global temperature decrease over a long period of time.

Changes since 1880• Drastic fluctuations on annual basis.• 5-year mean still fluctuates.• Over 120 years, mean has risen significantly.• Increase in temperature is more obvious in

Africa, Parts of Asia and the Arctic.

Natural Causes of Climate Change

• There are some natural phenomena that will cause climate change.1. Variations in Solar Output2. Volcanic Eruptions

Variations in Solar Output

• Solar radiation changes as the magnetic field of the sun changes.

• Increase in magnetic activity will lead to increase in solar radiation.

• Sunspot activity leads to more solar radiation emitted.

• Solar activity cycle is linked with earth’s cycle of high and low global temperature. – High activity leads to spikes in temperature.

What are Sunspots?

Volcanic Eruptions

• During eruptions, cabon dioxide, water vapour, sulphur dioxide, dust and ash are released into the environment.

• Sulphur dioxide reacts with water to form sulphur-based particles in the atmosphere.

• These work with the dust and ash to reflect solar energy back into space, causing global dimming.

Global Dimming

• The gradual reduction in the amount of sunlight reaching the earth’s surface.

• Causes temporary cooling of the earth.• Eruption of Mt Pinatubo, 1991, lead to

lowering of temperatures in the northern hemisphere by as much as 0.6°C.

• Effect can last several years.

Greenhouse Effect

What is greenhouse effect?

• Process that sustains habitable temperature on earth.

• Shortwave radiation from the sun reaches earth as visible light.

• Longwave radiation is heat from the heated surface of the earth.– Earth’s surface is heated by the shortwave

radiation from the sun.

Process of greenhouse effect• Shortwave radiation comes from the sun.• Some of it is reflected and trapped in the

atmosphere by greenhouse gases.• Some of it passes through and heats up the earth’s

surface.• The earth’s heated surface emits (gives off) longwave

radiation.• Some longwave radiation is reflected back by the

atmosphere layer while some escapes.• The reflected radiation continues to heat up the

earth’s surface. • This maintains the optimal temperatures on earth for

life to exist.

What is enhanced greenhouse effect?

• When greenhouse gases in the atmosphere increase, the amount of radiation trapped increases.

• This causes the heat on Earth’s surface to increase.

• Key greenhouse gases are nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4).

Who causes this spike?Burning of Fossil Fuels• Industries and modern fossil-fuel burning

machines have accounted for the spike in greenhouse gases.

• Intense spike in all 3 tracked gases since 1500 to date (due to the onset of the Industrial Revolution and rapid human population growth)

Deforestation• Loss of forests due to removal and clearance

of tress.• Commercial value of timber• Enhance need for agricultural / residential /

commercial land• Loss of carbon lungs of the earth. • South America and Southeast Asia are the 2

highest areas of forest loss.

Reforestation

• Process where trees are planted to replace lost forest areas.

• China, India, Vietnam, USA has large scale reforestation programs.– When you need to reforest it means that you had

previously done deforestation.– Reforestation levels often fall short of deforestation

levels.– Reforestation also tends to be of lesser variety

compared to the original lost species.

Changing land use

Agriculture• Global increase in meat consumption leads to

increased livestocks reared.• Argentina is one of the world’s largest beef

producers.• Methane gas emitted from lifestock account for

30% of Argentina’s total greenhouse gas emissions.• Widespread use of machines in agriculture release

additional CO2 into the atmosphere.

Our new cow doesn’t release

any methane gas.