GATEWAY 2: CHANGING EARTH’S CLIMATE

http://tinyurl.com/qyy26vu

Today’s objectives:

-we will be able to define key terms in Gateway 2-we will be able to explain the various causes of climate change

Buzzfeed

What comes to mind when you hear the term climate change?

Temperature Anomaly

It is a departure from a reference value

or a long term average.

A positive anomaly indicates that the

observed temperature was warmer than the

reference value, while a negative anomaly indicates that the observed

temperature was cooler than the reference value.

How has global climate changed?

Source: http://climate.nasa.gov/news/index.cfm?NewsID=249

Global Warming

The increase in global

temperatures over a long period of time

Global Cooling

The decrease in global

temperatures over a long period of time

Global dimming

The gradual reduction in the

amount of sunlight reaching earth

Hence, climate change is not

just about global warming.

Global Climate Change

Variation in global climate in the long term

Increase

Decrease

Certain years higher

increase in temperature

Global Climate Change

Increase in global temperatures over a long period of time GLOBAL

WARMING

Decrease in global temperatures over

a long period of time GLOBAL

COOLING

Is global climate change natural?

Or caused by humans???

Climate change in the past 150 years

Significant but irregular temperature rise of 0.3 to 0.6 since 1881

Global cooling recorded after WWII for several decades because of industrial pollution and volcanic activity Amount of sunlight that reaches earth’s surface is

reduced because of large amount of particles in the atmosphere low temperature

Also known as global dimming

Global warming over last century: world warming on an average of 0.74 especially since 1970s

Watch the video below to find out more about climate change

https://www.youtube.com/watch?v=8YQIaOldDU8

WHY?

Climate change

Natural causes

Variation in solar output

Volcanic eruptions

Human causes

Burning fossil fuels

Deforestation

Changing land use

Watch the video below to find out about the causes of climate change

You have to fill in the handout based on what you watched. You can also use the following slides below to help you with your handout.

You can also look at your textbook 103-108 for the answers. (But it might be more boring for you)’

https://www.youtube.com/watch?v=RHrFBOUl6-8

Natural causes (1) Volcanic Activity

Produces large volumes of carbon dioxide, water vapour, ash and dust

Sulphur dioxide + water sulphur-based particles in atmosphere that reflect solar energy back into space

Results in a reduction in amount of sunlight that reaches earth’s surface: also known as global dimming

E.g. When Mount Pinatubo in Philippines erupted in 1991, 17 million tonnes of sulphur dioxide was released into atmosphere. The sulphur-based particles reflected solar energy back into space & lowered temperature in northern hemisphere by 0.6

Natural causes (1) Volcanic Activity

Usually have few long-term effects on climate

Because temporary global cooling effect will cease once the volcanic dust & ash settle

E.g. Global climate returned to original state 2 years after Mount Pinatubo eruption. The large volume of carbon dioxide released by volcanoes was still 100 times lesser than those by human activities.

Natural causes (2) Variations in solar output

Sun emits solar radiation at different rates due to changes in magnetic field An increase in magnetic activity increase in

solar radiation. Magnetic activity of the sun has a cycle that

lasts about 11 years. Through the study of sunspots, the solar

activity cycle was discovered Many sunspots indicates high solar activity

& higher temperature

Greenhouse Effect

Incoming shortwave radiation from the sun passes through the greenhouse gases found in atmosphere

Some shortwave radiation is reflected back to space

Most shortwave radiation is absorbed by the earth’s surface which then heats up as a result

The warmed surface of earth emits longwave radiation to the atmosphere

Greenhouse gases absorb longwave radiation, warming the atmosphere

ENHANCED Greenhouse Effect Increase in the concentration of greenhouse

gases in atmosphere rise in global temperatures

Happens when human activity causes greenhouse gases to be released at a far greater rate than natural emission of greenhouse gases

Increase in concentration of carbon dioxide usually the greatest amongst the greenhouse gases

Human (1) Burning fossil fuels Fossil fuels: coal, oil, natural gas

Large amount of fossil fuel burnt for industries, transportation, electricity etc. gives out large amount of greenhouse gases, esp. carbon dioxide

Greater amount of greenhouse gases traps more heat temperature increase

Human (2) Deforestation

Forests cleared for development, agricultural and commercial activities like cattle ranching, commercial logging etc.

Forests absorb billions of tonnes of carbon dioxide each year via photosynthesis, absorbing a significant amount of global greenhouse gas emission. With deforestation lesser trees to absorb

carbon dioxide larger concentration of CO2 in atmosphere

Human (2) Deforestation

Soil: very large source of carbon because carbon is accumulated through decay of organic matter like dead leave and animals Exposes soil to sunlight Increases soil temperature and rate of

carbon oxidation Causes carbon dioxide to be released from

soil into atmosphere

Human (3) Changing land useAgriculture Population increases need for more

food More land used for agriculture (practice

of cultivating land, producing crops & raising livestock)

But such activities release a lot of greenhouse gases into atmosphere!

Human (3) Changing land use

Cattle Ranching Rice Cultivation

Cattle release methane as waste gas

Requires the use of tractors which run on fossil fuel and it releases carbon dioxide

Methane is a greenhouse gas

Use of fertilisers increases nitrous oxide in soil and is eventually released when rain flows through soil

Dead leaves and manure (organic matter) releases methane when they decompose.

Human (3) Changing land useIndustrialisation A lot of carbon dioxide is produced when

fossil fuels are burnt for manufacturing industries

E.g. manufacturing a mobile phone releases 60kg of carbon dioxide.

Countries like China and India are contributing more to global carbon dioxide emissions in recent years due to rapid industrialisation

Human (3) Changing land useUrbanisation Process by which an increasing number

of people live in urban areas such as cities/towns. Large amount of fossil fuels burnt to

provide energy for household activities like cooking, lighting

High concentration of cars, buses increase amount of greenhouse gases