Mission Briefing: Questions for a Methane Satellite

Read methane data and ask questions about what is warming Earth.

Answer Key

The briefing data

Read the passage, Table 1 and the graph. Then answer the questions.

A Satellite to Track a Gas

1On a Saturday at a space agency's visitor center, a group of sixth graders worked as a mission planning team. Their task was to help plan a new satellite that would measure methane in the air from orbit. Mission scientist Dr. Sunniva Haugland led the briefing. The mission is made up, but the data she shared are based on real measurements, rounded.

2Earth's average surface temperature has risen by about 1 °C since the late 1800s. Gases that absorb energy given off by Earth's surface and send some of it back down are called greenhouse gases. Carbon dioxide (CO₂) is the best known, but methane is another. There is far less methane in the air than CO₂, yet each methane molecule absorbs much more energy than a CO₂ molecule does. Methane does not last as long, though: most of it breaks down in the air within about ten years.

3Methane comes from both natural processes and human activities. Microbes that live where there is little oxygen give off methane. They live in wetland mud, in the stomachs of cattle and other livestock, in flooded rice fields and in buried garbage at landfills. Methane also leaks from coal mines, oil wells and natural gas pipelines. Termites, lakes and wild animals add a smaller natural amount.

4Dr. Haugland showed the team measurements from ground stations around the world (Table 1) and scientists' estimates of how much methane each source releases each year (the graph). "A satellite gives us numbers," she said. "Your job is to ask the questions those numbers should answer." Team members Kofi Asante and Mireille Dubois took notes.

Table 1. Methane in the Air and Global Temperature
Year	Methane (ppb)	Temp change (°C)
1985	1,660	0.1
1995	1,750	0.4
2000	1,770	0.4
2005	1,775	0.7
2015	1,835	0.9
2020	1,880	1.0

ppb = parts per billion (how many methane molecules there are in every billion molecules of air). Temp change = how much warmer the year was than the 1951–1980 average.

From 1985 to 2020, methane in the air rose by 220 ppb.

Use paragraph 3 and the graph. Count fossil fuels, livestock, landfills and waste, and rice farming as human activities.

Human activities release about 300 million metric tons of methane each year, which is 60% of all the methane in the graph.

Which statement best describes Table 1?

A. Methane fell from 2000 to 2005, and the temperature fell with it.
B. Methane and temperature rose by the same amount in each period.
C. The temperature rose the most from 2000 to 2005, when methane rose the most.
D. Methane rose overall but barely changed from 2000 to 2005, while temperature rose.

The satellite will map how much methane is in the air over every part of Earth, year after year. Circle each question that its data could help answer.

Which oil and gas fields leak the most methane?Is the methane over rice-growing regions rising from year to year?Has the Sun's energy reaching Earth changed since 1985?Is a warmer world better or worse for people?Is there more methane over large wetlands in warm years than in cool years?How many people think methane is a serious problem?

Asking better questions

Use the passage, Table 1 and the graph to choose and write questions for the mission.

From 2000 to 2005, methane barely changed, but the temperature change rose by 0.3 °C. Which question would best help Kofi explain this?

A. Did other greenhouse gases, such as CO₂, keep rising from 2000 to 2005?
B. Did each methane molecule absorb more energy in 2005 than in 2000?
C. Was Earth closer to the Sun in 2005 than it had been in 2000?
D. Did people stop raising cattle and growing rice from 2000 to 2005?

Mireille notices that wetlands are the largest single source in the graph. She says, "So nature, not people, is behind the rise in methane." Which question would best test her idea?

A. Do wetlands release more methane in a year than landfills do?
B. Have wetlands released more methane each year since 1985, or about the same?
C. Which continent has the largest area of wetlands today?
D. How much methane does one hectare of wetland give off in a day?

Which question would best help the team find out whether raising livestock added to the rise in methane since 1985?

A. How has the number of cattle and other livestock on Earth changed since 1985?
B. How much land do the world's livestock farms cover at the present time?
C. How much methane does one cow give off on a typical day this year?
D. Do cattle give off more methane each year than sheep of the same weight?

Suppose methane leaks from oil wells, gas pipelines and coal mines were cut sharply starting this year. Use paragraph 2 and the graph. What would the satellite most likely show over the next 20 years?

A. Methane in the air would stay at today's level for at least a hundred years.
B. Methane would fall to almost nothing, since fossil fuels are the largest source.
C. Methane would level off or fall, since old methane keeps breaking down.
D. Methane would rise faster, since less fossil fuel use makes wetlands grow.

Write a claim about what has most likely caused the rise in methane since 1985. Support it with data from Table 1 and the graph, and explain your reasoning. Then write two questions the satellite mission should answer to test your claim, and name the data that would answer each one.

Claim: Human activities have most likely caused most of the rise in methane since 1985. Evidence: Methane in the air rose from 1,660 ppb in 1985 to 1,880 ppb in 2020, a rise of 220 ppb. The graph shows that human activities (fossil fuels 110, livestock 100, landfills and waste 60 and rice farming 30) release about 300 million metric tons a year, about 60% of the total, while wetlands and other natural sources release about 200. Reasoning: Methane breaks down within about ten years, so the amount in the air rises only if more is being released than breaks down. A large natural source like wetlands could have been about the same for a long time, but human activities such as oil and gas use and raising livestock have grown, so they are the most likely reason for the rise. Because methane traps a lot of energy per molecule, its rise likely added to the 0.9 °C of warming from 1985 to 2020, along with CO₂. Question 1: Has the methane over oil and gas fields grown since the satellite began measuring? Data: satellite methane maps over those fields each year. Question 2: Have wetlands released more methane each year, or about the same? Data: yearly satellite methane measurements over large wetlands, compared with their temperatures.