4. Rising Carbon Dioxide Concentrations

Question 1

What can be deduced by drilling columns of ice in the Antarctic?

Answer 1

CO2 concentrations and temperatures of the past

Question 2

How can CO2 concentrations and temperatures of the past be deduced by drilling columns of ice in the Antarctic?

Answer 2

• ice has built up over 1000s of years
• ice deeper down is older than surface ice
• bubbles of air in ice can be extracted and CO2 concentration tested
• global temperatures can be deduced from ratios of hydrogen isotopes in water molecules

Question 3

What has happened to CO2 levels and global temperatures over the last 800,000 years? What can we say about the relationship between the two? (p.61)

Answer 3

fluctuated:

• rapid increasing, followed by longer periods of decreasing
• rapid warming, followed by longer periods of cooling
• correlates very strongly…
• correlation does not equal causation
• but from previous research, we know that carbon dioxide is a greenhouse gas…so some of the temperature variation is due to variation of atmospheric carbon dioxide concentrations

Question 4

What has happened to atmospheric carbon dioxide concentrations in the last 150 years?

Answer 4

they have risen above the normal range (considering where we are in the cycle)

Question 5

Why have atmospheric carbon dioxide concentrations increased in the last 150 years?

Answer 5

due to the combustion of fossilized organic matter (coal, oil and gas)

Question 6

When did the burning of fossil fuels really take off? What else has dramatically increased since this time?

Answer 6

• industrial revolution 200 years ago
• CO2 concentration

both are increasing faster and faster

Question 7

How much have global temperatures increased by since the industrial revolution?

Answer 7

0.8°C with most of the increase coming since 1980

Question 8

Are CO2 concentrations and global temperature directly proportional?

Answer 8

NO - they are correlated but there are other factors that affect global temperature so they are NOT directly proportional

Question 9

There are other factors that affect global warming. What does this result in?

Answer 9

uneven temperature rises compared to CO2:

- there may be steady rises in CO2 concentrations, but sudden slows/ rapid increase in temperature

Question 10

Apart from global warming, what else do CO2 concentrations effect?

Answer 10

the acidity of the sea and therefore coral reefs

Question 11

“500 billion tonnes of CO2 has dissolved …. since the start of the industrial revolution.” Fill in the blank.

Answer 11

in the sea

Question 12

How many tonnes of CO2 has dissolved into the sea since the start of the industrial revolution?

Answer 12

500 billion tonnes

Question 13

How has the pH of the sea changed since the start of the industrial revolution?

Answer 13

ph drop from 8.25 to 8.14

represents 30% change in acidification

Question 14

What marine animals are massively effected by increasing CO2 concentrations? Why?

Answer 14

reef-building corals:

• they deposit calcium carbonate in their skeletons
• so they need to absorb carbonate ions from seawater

Question 15

Is the concentration of carbonate ions high or low in sea water? Why?

Answer 15

low

- they are not very soluble

Question 16

How does carbon dioxide affect concentrations of carbonate ions?

Answer 16

• CO2 + H2O –> carbonic acid
• carbonic acid disassociates into hydrogen ions and hydrogen carbonate ions
• hyrdrogen ions + carbonate –> hydrogen carbonate
• thereby reducing carbonate concentrations

Question 17

How does carbon dioxide affect coral?

Answer 17

• CO2 reduces concentration of carbonate ions in seawater
• new calcium carbonate - the skeletons of coral - cannot be made
• additionally, the existing calcium carbonate dissolves in carbonic acid*

*carbonic acid formed by CO2 + H2O