Carbon Dioxide and Methane as Greenhouse Gases

1. What do greenhouse gases do in the atmosphere?

Answer: Maintain temperature on Earth high enough to support life.

2. List three greenhouse gases found naturally in Earth’s atmosphere.

Answer: water vapour, carbon dioxide and methane

3. Which two greenhouse gases are humans adding to the Earth’s atmosphere?

Answer: carbon dioxide and methane

4. What is the major cause of global climate change?

Answer: Increase in average global temperatures.

5. What is a "carbon footprint" ?

Answer: The total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event.

6. Greenhouse gases like carbon dioxide are found naturally in the Earth’s atmosphere. These gases are important as they maintain the Earth’s temperature high enough to support life. In a sample of dry air, approximately 0.0035% of the gas is carbon dioxide.

a) Write the amount of carbon dioxide in dry air as a percentage in standard form.

Answer: 3.5 × 10−3 %

b) Draw the dot and cross diagram of carbon dioxide.


c) Describe the "greenhouse effect".

Answer: Water vapour, carbon dioxide and methane gases absorb longer wavelength (infrared radiation) reflected from the Earth, but they do not absorb short wavelength radiation (UV and visible light) from the Sun. This keeps the Earth warm enough to support life as we know it.

d) State the general trend in the amount of carbon dioxide in the Earth’s atmosphere over the last 100 years, and explain what has caused this trend.

Answer: The general trend is increasing amounts of carbon dioxide in the atmosphere. During and after the industrial revolution more fossil fuels were combusted and this has led to more carbon dioxide being released into the air. In addition, deforestation has occurred to make way for farming and settlements/towns/cities/houses. This has resulted in fewer plants photosynthesising and removing carbon dioxide from the atmosphere.

e) Describe an action that can be taken to reduce the amount of carbon dioxide in our atmosphere.

Answer: Increasing the use of alternative energy sources, use less energy, collect carbon dioxide emissions and store underground in rocks, plant trees, use carbon neutral fuels such as bioethanol and biodiesel.

7. Global warming is the rise in Earth’s average surface temperature. Many scientists believe that this is the main cause of global climate change.

a) List some predicted effects of global climate change.

Answer: Sea level rise, more extreme weather (such as drought, storms), the amount, timing and distribution of rainfall, reduction in availability of fresh water, changes to ecosystems, capacity of some regions to produce food due to changes in rainfall patterns.

b) Explain how animal farming has contributed to global climate change.

Answer: Animal farming produces a lot of methane. This is from the digestive systems of cattle, as well as the decomposition of their manure. Methane is a greenhouse gas. This means that it traps the energy from the reflected (longer wavelength) radiation from earth. This leads to increase in global temperatures and this is a major contributor to global climate change.

c) Describe and explain the importance of peer-reviewed research into global climate change.

Answer: Peer-review means that the work is looked at by other scientists in the same field before it is published in scientific journals or released to the public. This is an important step as it checks that the science is valid and not biased. As there is still debate that climate change is down to human activities and the changes suggested have a big impact (economic and social), so we need to be confident that the science is valid.

8. Scientists monitor the global mean surface temperature change. A graph of these data from 1880 until the present day is shown below in the figure below. This shows the change in global surface temperature relative to the average temperature over the period 1951–1980.

a) State the units of the dependent variable.

Answer: °C (celcius)

b) Describe the general trend shown in this graph.

Answer: The temperature of the Earth’s surface has increased. Except for the levelling off in 1940s and 1970s.

c) State which was the hottest complete decade in these records.

Answer: 2000 – 2009

d) Suggest a cause for this change in global mean surface temperatures.

Answer: Increase in greenhouses gases by human activity leading to increase greenhouse effect.

e) Suggest why a few scientists do not think climate change is due to human activity.

Answer: Evidence is difficult to collect over a long enough period to be sure that humans are the reason. Climate models have a high degree of uncertainty.