Topic 9 - Earth's Atmosphere

The earth’s atmosphere step by step changes

1. Steam from volcanoes (H2O)

→ steam condensed into oceans (when below 100 degrees)

2. CO2 from volcanoes

→ dissolved into oceans

3. Formation of carbonates

→ dissolved CO2 reacted in oceans, which formed carbonates

→ eventually became limestone + shells

4. Photosynthesis begins

→ algae + early plants evolved

→ they used CO2 + released O2 via photosynthesis

5. Methane reacted with O2 → CO2 + H2O

6. Ammonia reacted with O2 → H2O + N2

Gas % in the atmosphere now vs 4.5 billion years ago

Now:

• O2 = 21%

• N2 = 78%

• CO2 = 0.04%

• Ar = 0.9%

4.5 billion years ago:

• O2 = none

• N2 = Tiny

• CO2 = 96-97%

Explain the main changes in the percentages of Nitrogen in the earth’s atmosphere

Nitrogen - Increases due to volcanic eruptions and ammonia reacted with oxygen

Explain the main changes in the percentages of oxygen in the earth’s atmosphere

Oxygen - Increases due to plant photosynthesis:

• Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis

• Algae first produced oxygen about 2.7 billion years ago, and soon after, this oxygen appeared in the atmosphere. Over the next billion years, plants evolved, and the percentage of oxygen gradually increased to a level that enabled animals to evolve.

Explain the main changes in the percentages of carbon dioxide in the earth’s atmosphere

It increased because of volcanic eruptions, it decreased because CO2 was absorbed by the ocean, it decreased again by plant photosynthesis

What is the name of the process that caused the changes in the percentages of gases

Plant photosynthesis

Why are scientists not certain about the percentage of each gas in the early atmosphere

Because it was billions of years ago so no direct evidence

Explain the formation of deposits of limestone, coal, crude oil and natural gas

When plants, plankton, and marine animals die in the oceans, they sink to the seabed and, over time, get buried under layers of sediment. Over millions of years, they become compressed and form sedimentary rocks, oil, and gas, trapping the carbon within them and helping to keep carbon dioxide levels in the atmosphere reduced

Things like crude oil, coal and natural gas that are made by the process are called fossil fuels.

• Crude oil and natural gas are formed from deposits of plankton and form reservoirs under the seabed.

• Coal is a sedimentary rock made from thick plant deposits

• Limestone is also a sedimentary rock. It’s mostly made of calcium carbonate deposits from the shells and skeletons of marine organisms. A lot of the carbon from the carbon dioxide in the early atmosphere is now locked away in limestones

Evidence for the evolution of the atmosphere

Evidence from volcanoes:

• The gases released by volcanoes today are likely to be similar to those produced when volcanoes were erupting billions of years ago. So this gives evidence about what gases were present in the early atmosphere

Evidence from other planets:

• The atmosphere of planets where there isn’t life, such as Mars and Venus, can be used to predict what Earth’s atmosphere might have been like before life evolved

Evidence from rocks:

• Certain rocks, called ‘red beds’ contain lots of iron oxide. The iron oxide in these red beds could only have formed when there was enough oxygen in the atmosphere to react with the iron. So the age of red beds can be used to predict the point at which oxygen levels reached a certain level in the atmosphere

Evidence from living things:

• Some simple organisms, such as early bacteria, don’t rely on reactions that use oxygen to release energy. Instead, they use other gases, such as carbon dioxide. Fossils of these bacteria have been found which are older than fossils of creatures that depend on oxygen. This implies that life first evolved without the need for oxygen, so there wasn’t much oxygen in the early oxygen

What do green house gases do

- Greenhouse gases keep the temperature on Earth high enough to support life

This is called the greenhouse effect, which means:

• gases in the atmosphere absorb long-wavelength radiation, warming Earth’s surface & lower atmosphere

What are the main greenhouse gases

• Carbon dioxide

• Methane

• Water vapour

What are the main greenhouse gases:

• Natural sources

• Human activities (increased population causes an increase in…)

Methane:

Natural sources - dead organisms decomposing

Human activities - cattle farming & growing to meet increased food demand, and waste in landfill sites

Carbon dioxide:

Natural sources - volcanoes, respiration, forest fires

Human activities - burning fossil fuels to meet increased energy needs, and deforestation to meet the increased need for land for crops

Water vapour:

Natural sources - evaporation from oceans, lakes, rivers

Human activities - burning fossil fuels

How green house gases cause the greenhouse effect

• The sun’s rays enter the earth’s atmosphere

• Energy is absorbed by the earth’s surface and re-emitted at longer wavelengths, such as infrared radiation (heat)

• Some emitted heat passes through the atmosphere into space

• Some heat is absorbed by carbon dioxide (a greenhouse gas). Heat is re-emitted in all directions and some becomes trapped within the earth’s atmosphere. The earth becomes hotter as a result

How greenhouse gases work

• Short wavelength radiation enters the atmosphere

• It is absorbed by the Earth’s surface & re-emitted as longer wavelength radiation

• Some of it is trapped by greenhouse gasses & re-emitted in all directions

• Temperature of lower atmosphere & Earth’s surface increases

CO2 graph

The pattern & explanations in the graph:

• little change up to 1800 - coincides with pre-fossil fuel use

• Increase from 1800 - fossil fuels are being burnt

• Rapid increase after 1875 - large increase in fossil fuel use to meet demand for increased energy

Increased deforestation to meet demand for more land

Burning fossil fuels releases new CO2 (this had been taken in millions of years ago by trees & algae that eventually formed fossil fuels)

Deforestation means less CO2 is taken so the amount in the atmosphere is rising

Temperature graph

The pattern in the graph shows:

• An overall rise in average temperature since 1860

• The temperature varies within this overall rise

Both of the graphs together (CO2 and temperature)

It suggests this is the evidence that CO2 from human activity is causing global warming because:

• Both CO2 and temperature have increased over the same timescale

It also suggests this is not evidence that CO2 from human activity is causing global warming because:

• Both CO2 and temperature have increased over the same timescale but the average temperature varied within the rise

• Factors other than human activity must be considered

What are the effects of climate change

• Melting of glaciers/polar icecaps, leading to rising sea levels

• Floods or droughts

• Habitat destruction and extinction of species

• Extreme weather

• Coastal erosion

• Famine

• Increase in desert areas

Consequences of climate change

• An increase in global temperature could lead to polar ice caps and glaciers melting, causing a rise in sea levels, increased flooding in coastal areas and coastal erosion

• Changes in rainfall patterns (the amount, timing and distribution) may cause some regions to get too much or too little water. This, along with changes in temperature, may affect the ability to certain regions to produce food

• The frequency and severity of storms may also increase

• Changes in temperature and the amount of water available in a habitat may affect wild species, leading to differences in their distribution

Risks of climate change

How many people might be affected:

• Some changes will affect fewer people than other. For example, people living inland are unlikely to be affected by coastal errosion. However, if the climate in a region that’s important for global food production changes so that crops can no longer be grown, million of people may be affected

What impact the change could have:

• Some changes have short-term impacts. For example, more severe blizzards may disrupt transport links, but things will return back to normal once the snow melts again. However some things aren’t so reversible. For example, rising sea levels could permanently flood towns or cities close to the sea.

How to reduce CO2 and methane emmisions

CO2:

• Use renewable energy sources (eg wind, solar) & rely far less on fossil fuels

• Reduce/stop deforestation

• Invest in CO2 capture technology

Methane:

• Reducing cattle farming by eating less meat

• Reducing landfill use by recycling

What do most scientists believe extra green house gases from human activity are causing

• Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will result in global climate change.

• However, it is difficult to model such complex systems as global climate change. This has led to speculation about what is causing climate change and what impact it might have. This speculation happens a lot in the media where stories may be biased or only give some of the information

Scientific findings:

Peer-reviewed means…

• checked by expert scientists to check data is reliable or valid

Any climate change data is only reliable or valid if…

• it has come from many known sources and been peer-reviewed

Climate change data is unreliable or not valid if…

• if sources are unknown or only from one source

• it has not been peer-reviewed

Peer-reviewed evidence suggests climate warming is due to human activities…

• for example, increased burning fossil fuels, more deforestation, more agriculture, increased rotting waste

However, climate is a very complex system so…

• future predictions are just simple ideas because there is a lot of uncertainty

Some scientists/people do not accept that human activities have added to climate change because…

• earth goes through natural variations in temperature so it is hard to model/predict

What is a carbon footprint

A carbon footprint is the total amount of carbon dioxide and other greenhouse gases released over the full lifecycle of a service (eg school bus), product (eg an iphone) or event (eg the olympics)

Why can’t the total carbon footprint be accurately measured

• There are many factors to consider

• It is difficult to accurately know the amount of greenhouse gases produced for each part of any activity

For example:

An iPhone -

There will there be CO2 emissions from:

• Extracting & processing materials from the earth to make it

• Transporting the product to wherever it is sold

• Generating the electricity used to recharge it

• Disposal/recycling on the phone

Your own footprint during one year is determined by your activities & anything you use, for example…

• Using electricity (generated by burning fossil fuels & releases CO2)

• Heating your home & cooking (burning gas releases CO2)

• Travelling by vehicle (releases CO2)

• Travelling by aeroplanes (releases CO2)

• Eating beef or rice (cattle farming & rice growing releases methane)

• Waste that ends up rotting in landfill (releases methane)

How can the carbon foot print be reduced

By reducing emissions of carbon dioxide and methane

Ways to reduce carbon footprint

• Energy conservation - home insulation; energy efficient light bulb, reduced use of devices, switch off appliances instead of leaving on standby

• Carbon tax - government tax companies on amount of CO2 they produce

• Financial incentives - convince companies to go green

• Renewable energy - solar, wind power

• Nuclear power - nuclear power produces no CO2

• Recycling & reusing - reduces amount of decomposing waste in landfill

• Capping emissions - set an upper limit on emissions with big fines for companies who do not

• Carbon neutral - processes that produce no new CO2

• Carbon capture & storage (CCS) - CO2 captured & stored in porous rock underground

• Food - reduce meat consumption (vegetarian/vegan diet), use loaclly sourced food

• Journeys - use public transport; electric vehicles, hydrogen-powered cars, walking/cycling

Difficulties in reducing carbon footprint

• Expensive new methods & the technology is still very new

• governments do not want an impact on their economies

• More deforestation to make extra land for increased demand for vegetarian/vegan diets

• People are not willing to change their lifestyle

Examples of climate mitigation strategies which could go alongside carbon footprint reduction

• Changing the type of crops grown in different regions

• Investing in flood defence systems or building houses on stilts

• Changing buildings to them more resistant to extreme weather

what does carbon neutral mean and new CO2 mean

Carbon neutral:

• it Means no CO₂ released into the atmosphere

New CO₂:

• It means it was taken in millions of years ago by trees/algae & was locked up in them when they died

• The trees/algae eventually formed fossil fuels so CO2 from burning them is now new to us

Examples of things regarded as carbon neutral but are not

1. Biofuels:

It is carbon neutral because:

• Plants take in CO₂ when growing and release the same amount of CO₂ when burnt

• No new CO₂ is produced

Overall, using biofuels is not carbon neutral because:

• Harvesting plants & transporting them uses fossil fuels, this produces new CO₂

2. Hydrogen Power:

It is carbon neutral because:

• Some cars use hydrogen fuel cells instead of petrol

• burning H₂ is carbon neutral because it only forms water when burnt: zero CO₂ emissions

Overall, burning H₂ is not carbon neutral because:

• Hydrogen is made by passing electricity through water

• Electricity is generated by burning fossil fuels

• This produces new CO²

How could the production of hydrogen be made better

By using renewable energy to generate the elctricity

How is pollution caused by combustion

• The combustion of fuels is a major source of atmospheric pollutants

• Most fuels, including coal, contain carbon and/or hydrogen and may also contain some sulfur.

The gases released into the atmosphere when a fuel is burned may include carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen. Solid particles and unburned hydrocarbons may also be released that form particulates in the atmosphere.

Describe how carbon monoxide, soot (carbon particles), sulfur dioxide and oxides of nitrogen are produced by burning fuels

• Fossil fuels such as crude oil, and coal, contain hydrocarbons. During combustion, the carbon and hydrogen in these compounds are oxidised so that carbon dioxide and water vapour are released into the atmosphere

• When there’s plenty of oxygen, all the carbon in the fuel is oxidised to carbon dioxide - this is called complete combustion. If there’s not enough oxygen, some of the carbon in the fuel isn’t completely oxidised - this is called incomplete combustion. Under these conditions, solid particles (called particulates) of soot (carbon) and unburnt fuel are released, and carbon monoxide can be produced as well as carbon dioxide and water

• If a fuel contains sulfur impurities, the sulfur will be oxidised to produce sulfur dioxide when the fuel is burnt. Oxides of nitrogen will also form if the fuel burns at high temperature, for example, in internal combustion engines of cars. This is because at very high temperatures, nitrogen and oxygen in the air react with one another

Problems caused by the products of combustion

Problems with carbon particulates:

• Particles in the air can cause many problems. If the particles are inhaled, they can get stuck in the lungs and cause damage. This can then lead to respiratory problems. They are also bad for the environment - they reflect sunlight back into space and help to produce more clouds. This means that less light reaches the earth, causing global dimming

Problems with carbon monoxide:

• Carbon monoxide is really dangerous because it can stop your blood from doing its proper job of carrying oxygen around the body. It does this by binding to the haemoglobin in your blood that normally carries oxygen, so less oxygen is able to be transported around your body. A lack of oxygen in the blood can lead to fainting, a coma, or even death. Carbon monoxide doesn’t have any colour or smell, so it’s very hard to detect. This makes it even more dangerous

Acid rain:

• When sulfur dioxide or oxides of nitrogen mix with the water in the clouds, they react with water to form sulfuric acid or nitric acid. This then falls as acid rain.

• Acid rain causes lakes to become acidic, and many plants and animals die as a result. Acid rain also kills trees, damages limestone buildings and ruins some stone statues. There are also links between acid rain and human health problems

Breathing problems:

• Sulfur dioxide and nitrogen oxides don’t only cause acid rain - they can also be bad for human health. This is because they cause respiratory problems if they are breathed in