9) Global Warming

7/29/2019 9) Global Warming

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Causes, effects, and questions


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Global warming is the increase in the average T of Earth's surface air andoceans

Global surface temperature increased 0.74 0.18 C between the start andthe end of the 20th century

Very likely caused by increasing concentrations ofgreenhouse gasesresulting from human activity such as fossil fuel, burning anddeforestation.And also caused by natural phenomena such as solarradiation and volcanic eruptions


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Global warming is linked to the accumulation of a variety of gases inthe atmosphere

These gases, which include carbon dioxide, methane, nitrous oxide,and water vapor trap infrared radiation that would normally escapefrom the earths atmosphere into space

This increased gas serves to increase the capacity of the atmosphere toabsorb heat


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o Greenhouse gases are the ingredients of the atmosphere that add to thegreenhouse effect

o Some greenhouse gases are present naturally in the atmosphere, whereas fewgreen house gases a consequence of human activity. The greenhouse gases that arepresent in the atmosphere naturally include water vapor, carbon dioxide, nitrous

oxide, methane and ozone.

By their percentage contribution to the greenhouse effectthe four major gases are:water vapor3670%

carbon dioxide926%methane49%ozone37%
http://en.wikipedia.org/wiki/Water_vaporhttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Ozonehttp://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Carbon_dioxidehttp://en.wikipedia.org/wiki/Water_vapor


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The mechanism of the greenhouse effect

The radiant energy

reaching the Earth from

the Sun includes visible

light, infra-red radiation &

ultra-violetwarm up the

sea & land

As is it warmed, the Earth

radiates infra-red radiation

back towards space

Much of this heat does

not escape from

atmosphere; some is

reflected back by clouds &

much is absorbed by gases

in the atmosphere

warmed

Without it, surface T would be too cold for life to exist on Earth


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The heat from the Sun can go

straight through glass

windows. Once inside, it can

become trapped and the inside

of a greenhouse will get hotter

and hotter

Greenhouse Gas


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Greenhouse gasses

in the atmosphere

act like the glass ina greenhouse

or car.


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Global warming is caused by green house gases, which trap in the suns

infrared rays in the earths atmosphere, which in turn heat up the earthsatmosphere. These green house effect warming is called as global warming. The effects of green house effect are visible more prominently in the recentyears, with number of natural calamities on the rise in the whole world.

The global warming has happened in the past few years and is evidentfrom the rise in mean temperature of the earths atmosphere.The main causes for the global warming are attributed to release of greenhouse gases by human activities.The main gases contributing to green house effect are carbon dioxide, water

vapor, methane and nitrous oxide.The largest producers of these gases are the thermal power plants, which burnthe fossil fuels and produce these gases in large quantities.The second biggest sources of these green house gases are the road vehiclesand industries.

An enhanced greenhouse effect leading to global warming


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The Greenhouse Effect is the natural phenomenon that warms the Earth, enablingit to support life. The sun's warmth passes easily through the blanket of gases aroundthe Earth to reach the Earth's surface

However, instead of this heat being lost back to space when it is reflected by theEarth's surface, certain gases in the atmosphere (called greenhouse gases) block thisheat.

Greenhouse gases are a naturalpart of the atmosphere andwithout them we could not live

on Earth

However, the problem we nowface is that human actions, areincreasing the concentration ofthese gases

This is believed to be raising theEarth's temperature, creating theprospect of global climatechange. This is the EnhancedGreenhouse Effect.


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Methane is a potent greenhouse gas, and over a period of 20 years has a 72times greater effect on warming than CO2

Main source; from the decay of organic material by some kinds of bacteria

It naturally breaks down high in atmosphere in a series of reactions;

eventually form CO2 & H20 molecules

Methane levels have risen by about 150% since 1750 for several reasons:1. Levels of rice production have been increasing; rice paddy fields are

waterlogged Bacteria in waterlogged soil release methane as theygrow

2. As the human population grows, so animals (cattle) increased for food the amount from methane released from their digestion increasestoo


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Water vapor Does much tokeep planet warm. We haveno control over water vapor

CO2 is the most significantgreenhouse gas. Levelsincreasing because of fossilfuel burning. We should beconcerned about this one


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Methane - from wetlands, ruminants and commercial production.20-30 times more potent than CO2. Levels going up slowly.

Nitrogen oxides (NOx or NxO) - formed during combustion from N2thats in air. 200-300 times more potent than CO2.

Chloroflurocarbons (CFCs) - Foam insulation, refrigeration gas,used to be an aerosol propellant. Being phased out.

Ozone- formed from lightning, electrical arcs, and a reaction of gasvapors and sunlight.


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Climate proxies are devices that suggest the climate patterns of the past

The study of past climates is known as paleoclimatology

Examples of proxies include ice cores, tree rings, boreholes, corals, andlake and ocean sediments


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One widely used source of T proxies comes from Antarctic

& Greenland ice cores

Scientist drill deep down into the ice and then analyze the

air trapped in the different layers This provides a record

which goes back thousand of years

Presence of water molecule (melted ice) isotopic compositions of16O and 18O in an ice core help determine past temperatures and

snow accumulations

The heavier isotope (18O) condenses more readily as T decrease

and falls as precipitation, while the lighter isotope (16O) can fall in

even colder conditions. The farther north an 18O isotope is

discovered means a warming over time


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Air bubbles in the ice contain trapped gases, especially those of greenhouse

gases, such as carbon dioxide and methane, and are also helpful indetermining past climate changes

From 1989-1992, the European Greenland Ice Core Drilling Project drilled in

central Greenland at coordinates 72o 35' N, 37o 38' W. In their project, ice at adepth of 770 m were 3840 years old; 2521 m were 40,000 years old; and

3029 m at bedrock were 200,000 years old or more. However, ice cores can

reveal the climate records for the past 650,000 years


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Also known as dendroclimatology

The rings are more visible in temperate zones, where the

seasons differ more markedly

Using this method to study climate change

Dendrochronology is the dating of past events (climatic changes) through study

of tree ring growth

Discovered by A.E. Douglass, who noted that

the wide rings of certain species of treeswere produced during wet years and,

inversely, narrow rings during dry seasons.

To better understand cycles of sunspot

activity and reasoned that changes in solar

activity would affect climate patterns on earthwhich would subsequently be recorded by

tree-ring growth patterns (i.e., sunspots

climate tree rings)


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Each year a tree adds a layer of wood to its trunkand branches thus creating the annual rings wesee when viewing a cross section.

In the spring, when moisture is plentiful, the treedevotes its energy to producing new growth cells.These first new cells are large, but as the summerprogresses their size decreases until, in the fall,growth stops and cells die, with no new growth

appearing until the next spring.

The contrast between these smaller old cells andnext year's larger new cells is enough to establisha ring, thus making counting possible.


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Wood Morphology

Bark, Phloem, Cambium, Xylem

Late Wood:

dense, dark; deposited in late summer/fallEarly Wood:

large cells and thin walls, spring


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By knowing environmental conditions

that operated in the past (by analyzing

such conditions in tree rings), we canbetter predict or manage such

environmental conditions in the future

Rates of plant processes can occur

only as fast as allowed by the factorthat is most limiting

For example, if rainfall is the most

limiting factor, then the amount of

wood produced by a tree in any

single year will reflect mostly theamount of rainfall that fell within

that year.


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Peat bogs are made of partly decomposed plant material, mainly

Sphagnum mosses

The peat is very acidic, cool, anaerobic prevents bacteria from

decomposing organic material pollen grains, moss spores & plant

tissues are preserved in a peat

By sampling cores of peat, we can look back in time at the plant &mosses growing in and around that area from hundreds & even

thousand years ago

The pollen/moss record can give a clear reflection of how the climate

has changed with time


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Method of determining the age of once-living material. It depends on the

decay of the radioactive isotope carbon-14 (radiocarbon) to nitrogen. All

living plants and animals continually take in carbon: green plants absorb it in

the form of carbon dioxide from the atmosphere, and it is passed to animals

through the food chain

When an organism dies it stops taking in carbon, so the amount of carbon-14 in its tissues steadily decreases. Because carbon-14 decays at a

constant rate, the time since an organism died can be estimated by

measuring the amount of radiocarbon in its remains.

The method is a useful technique for dating fossils and archaeological

specimens from 500 to 50,000 years old and is widely used by geologists,anthropologists, and archaeologists.


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Most famous evidence Mauna Loa curve The air is sampled continuously at the top of four 7-metre tall

towers & an hourly average of CO2 concentration is taken

The air in the area is relatively free from local pollutants

Measurements started in 1958 & the monitoring methods &

instruments used have remained similar throughout that time

The records show that the level of atmospheric CO2 has increasedfrom 315.98 ppmv (1959) to 381.74 ppmv (2006)

The annual fluctuations in the levels of CO2 seem to be the result of

seasonal differences in the fixation of CO2 by plants (temperate regions)

Law Dome ice cores

Ice core data also show clear changes in CO2 concentration

Please answer the questions in Pearson, pg 45

Answer ALL questions

Time: 30minutes


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A lot of evidence from many studies a clearcorrelation between the

increase T, increase CO2 levels

There is a causal relationship how 1 factor changes the other

From our understanding of the greenhouse effect :

1. Industrial revolution burnt increasing quantities of fossil fuels

2. Solar activity affects cloud formation; effect T

The IPCC reached the conclusion:

Sum of these activities over the past 50years would most likely

have produced cooling rather than warming

Now, increase in atmospheric CO2 , causes increase T

Human CO2 emissions are responsible for at least current warming

GW is multifactorial, with many different inputs, not just CO2 levels

From the fig 5.3.13, 5.3.14 & 5.3.15;

Please answer all questions Pearson, pg 47

Answer All questions


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1. Polar ice melt2. Glacier retreats

3. Rising sea levels

4. Changing weather & ocean current patterns

5. Coral bleaching

6. Risk of flooding

7. Climate change8. The effect on organisms

9. Changes in species distribution

Global warming also lead to changes in metabolism & development:

1. T & Enzyme activity

2. T & sex determination in reptiles3. T & plant growth & development


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Polar ice melt Changing weather & ocean

current patterns

Rising sea levels Coral bleaching


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Melt

descendinginto a moulin,

a vertical shaft

carrying water

to ice sheet

base.

Source: Roger

Braithwaite,

University of

Manchester (UK)

Surface Melt on Greenland


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In 2002, 500 billion tonnes of ice broke away from Antartic peninsula& eventually melted into the sea

Antartic T have increased by average 2.5 C in the past 50 years

Many scientist believe that the thinning ice is a clear indication of GW

As the ice melts, the volume of water in seas will increase, sea levels

also inrease Impact to human life; around 100 million people live

less than 1 metre above current sea levelsEg: UK large areas of the east coast could be lost for good

Netherlands might disappear completely


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Rising T affect weather and rainfall patternsStatistical evidence suggests; there is an increase in extreme weather

linked to the rise in global T

Eg: Africa

Trend of low rainfall; it has been predicted that by the year 2020

between 75 and 250 millions people will be short of water for

their crops & to drinkIn contrast, in some areas rainfall has been both higher &

extremely heavy leading to flooding; devastation & carries

away the vital topsoil

International group of scientist found that many changes correspond

to global warming factor


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T has an effect on E activity; affects the whole organism

The effect of T on organisms is direct; T influences the rate of all biochemical

reactions

As T rises molecules have increased active energy reactions go faster In chemical reactions, for every 10 C rise in T, the rate of reaction become

doubles

As a result, increasing T could have different effects on processes

rate of growth and reproduction

T may exceed the optimum for some E, the organisms will die

Enzyme activity


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Sex determination in reptiles

In many species of reptiles (but not all) it is the T of incubation of

fertilised eggs determines whether they are male or female

Temperature Sex Determination (TSD)

Eg: Alligators

When the eggs of alligator were incubated at various T, thismechanism was confirmed

Male alligators develop only if the eggs are incubated at 32-33 C

If the eggs are cooler, females develop

Lizards show the same pattern, turtles the reverse pattern


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Growth & development

Plant growth will be effect by limiting factor

Experimental data suggest that a change of just a couple degrees could

be fatal to many species

In higher latitudes, seasonal cycles affect life cycles

GW appears to be affecting the onset of the seasons; affecting life

cycles & distribution of species

Eg: the breeding cycle oftits in Wytham Woods near Oxford in the UK

Pearson pg 50

Impact of heat on growth & development:

Brine shrimp hatching rates


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A change in climate could affect the range of many different species Eg: Study by Parmesan et al. 1999

The distributions of parasites causing diseases may also effected by

climate change

Eg: Malaria

Widespread in Europe & North America

Climate change may establish conditions in which the mosquitocan breed & complete their life cycles in the UK

Some pest & disease organisms may benefit from climate change


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Explanation of the effects of global warming


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Explanation of the effects of global warming


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We must start putting less carbon dioxide into theair.

Most the CO2 in the air will be around for 100years.

We need to burn less gasoline in our cars.

Burn less coal (or burn it cleaner) for ourelectricity.

Use less gas to heat our homes. Use less gas and electricity in our factories and on

our farms.


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Solar

Biofuels

Wind

Nuclear Power

Geothermal


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Higher mileage cars Live and work closer to home

Walk, ride bikes

Better insulated homes Use more efficient lights (fluorescent/LED)

More efficient factories


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Explanation of the causes of global warming

9) Global Warming

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