climate changes in the last 200 years

8/2/2019 Climate Changes in the Last 200 Years

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Climate Changes in the Last200 Years


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What is climate change?

Climate change is

a shift in the

average weatherconditions that aregion

experiences overa long period oftime.


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What are the causes of climatechange?

Main reason: human activities Accelerated climate changes in the last 200

years.

Leading to a sharp rise in greenhouse gas

emissions and bringing about thephenomenal increase in carbon dioxidelevels.

Increase in global temperatures ->enhanced greenhouse effect


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What is enhanced greenhouse effect?

The greenhouse effect is a natural process whereby greenhousegases absorb heat from the Suns rays and trap it in theatmosphere.

Theses gases help to maintain the Earths average temperature ataround 15C. This keeps the Earth warm enough for life to be

sustained. (Greenhouse effect = positive)

Enhanced greenhouse effect is when more greenhouse gases arereleased and trapped in the atmosphere with an increase inhuman activities. (Enhanced greenhouse effect = negative)

Example of human activities: industrial activities, large-scale

deforestation and agricultural activities -> main causes of increasein greenhouse gases (hence trapping more heat!)


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Comparison between the two types:


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List examples of human activities thatincrease the emission of greenhouse gases. Rapid increase in the use of fossil fuels in vehicles, factories and power

plants since the start of industrialisation.

Led to high levels of carbon dioxide and nitrous oxides being releasedinto the atmosphere.

Use of chlorofluorocarbons (CFCs) in aerosol cans, refrigerators and air-conditioners also contributed to the enhanced greenhouse effect by

causing a hole in the ozone layer. (though now use of CFCs havebeen banned in most countries in an effort to slow down climatechange.)


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Explain how deforestation lead to anincrease in carbon dioxide levels. Amount of vegetation cover on the Earths surface have been

reduced at alarming rates due to large-scale deforestation andforest fires.

Forests are cleared for timber and mining as well as to make moreland for agriculture and urban development. (human activities)

Leading to lesser plants to photosynthesis and take in carbondioxide and restore oxygen levels. (result)

When more trees and other plants are cut down or destroyed byforest fires, less carbon dioxide is absorbed from the atmosphere.

Hence resulting in an increase in carbon dioxide levels in the

atmosphere.

Less plants > less photosynthesis going on > less oxygen, morecarbon dioxide. (consequences)


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Describe how agriculture activities contributeto the increase in greenhouse gases. Agricultural activities like wet rice cultivation and cattle ranching.

Cultivation of rice in padi fields and the use of inorganic fertilisers releasemethane and nitrous oxides into the atmosphere.

Rearing of cattle and other livestock also release methane as a result of theanimals digestive processes.

Hence leading to an increase in the levels of greenhouse gases through

agricultural activities.

*Methane is 23 times more effective than carbon dioxide in causing globalwarming.


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Effects of climate change

Effects of climate change: Global warming Four effects of global warming:

-Melting ice and rising sea levels

-Extreme weather conditions

- Impact on plants and animals

Common misconception: There is no difference between climatechange and global warming.

Correct concept: Climate change is NOT global warming and globalwarming is an effect of climate change.


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Describe the melting of ice caps and how it affectspeople living in coastal areas. Ice caps cover much of the Artic region in forms of large icebergs

or ice blocks, containing about 70% of the Earths ice.

Satellite images from space have shown the decreasing area ofice cover in the polar regions.

Melting of these frozen stores of water has caused sea levels torise.

Low-lying coastal countries are especially vulnerable to rising sea

levels as they are prone to flooding.

The lives and property of an estimated 100million people who liveon land within on meter above sea level are threatened by thepossibility of flooding.


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Explain how global warming hascaused an increase in rainfall.

Regions with wetter climates like China, Southeast Asia and theWestern United States experience higher relative humidity ashigher global temperatures have increased evaporation rates.This increases rainfall in these places, which causes floods.

Describe the formation of tropical storms.

Tropical storms form when the surface of the ocean is heated above27C. This causes the warm air above the ocean to rise rapidly,leaving room for the surround cold air to spiral inwards quickly. Denseclouds, strong winds, and heavy rain form as a result.

A tropical storm is known as a hurricane in the Caribbean and NorthAmerica, a typhoon in the western Pacific and a cyclone in theIndian Ocean and around Australia.

Therefore: Tropical storm = hurricane = typhoon =cyclone


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Explain the after-effects ofhurricanes on people.

Resulted in large-scale flooding, destruction of homes, industries andinfrastructure.

The strong winds also disrupted economic activities like tourism andcaused heavy economic losses as property, crops and businesses weredestroyed.

*Also to note that it is costly to build back whatever that has been

destroyed and may take on toll on the economy of that country as it hasalready suffered heavy economic losses.

*Poorer countries will take longer to recover and often countries need aidin terms of food and shelter from other countries or the UN. (UnitedNations)

* = own research


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Explain the formation of a drought.

High temperatures increases evaporation rates, causing lakes andrives to dry up quickly in these places. When the river bodies havedried up, there will be less water vapour in the atmosphere. This willprevent clouds from forming and hence there is little or no rain.

Define what is a heat wave andelaborate on the effects of a heat waveon humans.

A heat wave is an usually prolonged period of hot weather. InEurope, increasing summer temperatures have led to heat wavesand caused many deaths. The significant temperature increase

resulted in high numbers of death, where up to 70 deaths wererecorded per day. Apart from deaths, heat waves can also causeforests fires which lead to destruction of environment.


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Case study: drought in Texas

Fig 1. Drought maps for December 6 and January 3, showingthe progression of the drought over Texas, and the relaxing ofthe drought over the Northwestern U.S.


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Elaborate on examples how plants areaffected by increasing temperatures. Increasing temperatures have caused changes in the flowering patterns of

plants.

Plants in Europe now flower a week earlier and shed their leaves a weeklater compared to 50 years ago.

The warmer weather also encourages the rapid breeding of insects such asmosquitos and diseases like malaria and dengue fever can now spreadmore easily.


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Describe how are animals in the polarregions affected by increasingtemperatures. When habitats are affected, animals are forced to migrate or they may

be threatened with extinction. For example, the number of Adliepenguins in Biscoe Island in the Antarctic has reduced from 2800 to 1000pairs.

These penguins are dependent on polar ice for survival but rising

temperatures have caused the ice to melt.

Fig. 2: Amount of

ice over the years


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What can the government on its part toreduce emissions of greenhouse gases?

The government, on an international level, can sign treaties such

as the Kyoto Protocol where countries agree to reduce theiremissions of six major greenhouse gases and work towards it.

On a national level, the government can pass laws to helpreduce the impact of climate change.

For example, in Singapore, the National Environment Agency(NEA), made it compulsory since 1978 for all vehicles to pass asmoke emission test to ensure that gases they emit are withinacceptable limits.

climate changes in the last 200 years

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