Analyze and interpret quantitative data

Rising carbon dioxide and temperature

Units 1 and 9
10 points
About 23 minutes

You can use a calculator on this question, just like on exam day.

You read values and trends from a data table or described graph, explain what the data show about an environmental problem, and propose and justify a solution. On the exam: Question 2 of 3 in the 70-minute free-response section (Section II is 40% of the exam score).

The question and its sources

Scientists have measured carbon dioxide (CO₂) in the air at a remote mountain observatory in the Northern Hemisphere since the late 1950s. Table 1 shows the yearly average CO₂ concentration and the global average temperature anomaly (the difference from the 1951–1980 average) for selected years. Table 2 shows the monthly average CO₂ concentration at the observatory for one recent year.

Table 1: Yearly CO₂ and global temperature

Year	Average CO₂ (ppm)	Global temperature anomaly (°C)
1960	317	0.0
1980	339	+0.3
2000	370	+0.4
2020	414	+1.0

Source: Rounded from NOAA Global Monitoring Laboratory (Mauna Loa Observatory) annual mean CO₂ and NASA GISS global temperature (GISTEMP) records

Table 2: Monthly average CO₂ at the observatory in one year

Month	Jan	Mar	May	Jul	Sep	Nov
CO₂ (ppm)	415.5	417.5	419.0	416.5	412.5	414.0

Source: Hypothetical data, simplified from the general pattern of long-term measurements

Suggested time: 23 minutes

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Part (a)

1 point

Using Table 1, calculate the average rate of increase in CO₂ concentration from 1960 to 2020, in ppm per year.

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Part (b)

1 point

Describe the relationship between CO₂ concentration and the global temperature anomaly shown in Table 1.

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Part (c)

1 point

Using Table 2, identify the month with the highest CO₂ concentration and the month with the lowest.

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Part (d)

1 point

Explain why CO₂ at the observatory decreases from May to September each year.

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Part (e)

1 point

Identify the main human activity responsible for the long-term increase in CO₂ shown in Table 1.

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Part (f)

1 point

Explain how an increase in atmospheric CO₂ leads to a warmer Earth.

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Part (g)

1 point

Identify one source of evidence scientists use to determine CO₂ concentrations from thousands of years ago, before direct measurements began.

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Part (h)

1 point

Explain how melting permafrost can create a positive feedback loop that increases global warming.

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Part (i)

1 point

Explain how rising global temperatures cause sea level to rise.

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Part (j)

1 point

Propose one realistic way to increase the amount of carbon stored in forests or soils.

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