4. Global Warming and the Greenhouse Effect

Question 1

What does the sun emit?

Answer 1

radiation

Question 2

What is radiation?

Answer 2

predominantly short wavelength

Question 3

How much is absorbed by the atmosphere? How much, therefore, reaches the earth?

Answer 3

• 25%
• ozone absorbs much of the ultraviolet
• 75%

Question 4

What happens to solar radiation when it reaches the earth?

Answer 4

it is absorbed and converted to heat

Question 5

What re-emits radiation? At what wavelength is radiation re-emitted?

Answer 5

• the surface of the earth

- much longer wavelength, usually infrared (heat)

Question 6

The earth re-emits radiation. What percentage of this is absorbed by the atmosphere, before passing on out into space? How is it absorbed? What happens next? What is this process called?

Answer 6

• 70-85%
• trapped by gases in the atmosphere
• gases re-emit the radiation, some of it back to the surface of the earth, causing warming
• greenhouse effect; gases that trap the radiation = greenhouse gases

Question 7

Can all gases be greenhouse gases?

Answer 7

no - only certain gases have the ability to trap long-wave radiation

Question 8

What does the impact of a gas depend on?

Answer 8

• its ability to absorb long-wave radiation

- its concentration in the atmosphere

Question 9

What are the most significant greenhouse gases?

Answer 9

carbon dioxide and water vapour

Question 10

What other gases, other than carbon dioxide and water vapour, produce the greenhouse effect?

Answer 10

methane and nitrogen oxides

Question 11

What is the difference between methane and carbon dioxide in their impact on the greenhouse effect?

Answer 11

methane causes more warming per molecule than carbon dioxide (but it is present in lower concentrations)

Question 12

Which level of the ozone does not affect greenhouse gases?

Answer 12

stratospheric ozone is not a significant greenhouse gas - it intercepts more incoming short-wave radiation than outgoing long-wave radiation

Question 13

Name 4 gases that have a significant impact in the greenhouse effect.

Answer 13

1 carbon dioxide
2 methane
3 nitrous oxide
4 halocarbons

*water vapour not included

Question 14

Compare the warming effects of these gases (%)
1 carbon dioxide
2 methane
3 nitrous oxide
4 halocarbons

Answer 14

1 - 63.4%
2 - 18.3%
3 - 6.1%
4 - 12.2%

*water vapour not included because its effects are hard to measure

Question 15

What would the mean temperature of the Earth’s surface be without the greenhouse effect? What is the actual mean temperature of the Earth’s surface?

Answer 15

-18°C

12°C ; that’s 30°C higher

Question 16

What 3 claims linking greenhouse gases, global temperatures, and human activities are indisputable?

Answer 16

• global temperatures and climate patterns are influence by concentrations of greenhouse gases
• human activities cause increases in concentrations of greenhouse gases in atmosphere
• empirical data shows the earth has warmed over the past 200 years

Question 17

What is claim linking greenhouse gases, global temperatures, and human activities is ‘strongly’ disputed?

Answer 17

whether global warming is due to greenhouse gas emissions from human activity

• most believe human activity to be influencing global temperatures and climate patterns