IB Environmental Systems and Societies: Atmosphere and climate change practice questions

Question 1

Which set of values best describes the composition of dry air in the troposphere by volume?

Accepted Answer

nitrogen 78 %, oxygen 21 %, argon 0.93 %, carbon dioxide about 0.04 % — Dry air is overwhelmingly nitrogen and oxygen, argon is the third most abundant gas, and carbon dioxide is a trace gas despite its climatic importance. Water vapour is excluded from these figures because it varies from almost nothing to about 4 % of the air.

Question 2

In one layer of the atmosphere the temperature rises with increasing altitude because ozone there absorbs ultraviolet radiation. That layer is

Accepted Answer

the stratosphere, 12-50 km — Absorption of UV by ozone creates a temperature inversion in the stratosphere, which makes the layer very stable and is why substances that reach it, such as CFCs, remain there for decades. The troposphere below is heated from the surface, so its temperature falls with height.

Question 3

Sea ice with an albedo of about 0.6 melts and is replaced by open ocean with an albedo of about 0.06. The consequence for the local radiation budget is that

Accepted Answer

more shortwave radiation is absorbed, so the warming is reinforced — Dark water absorbs almost all of the shortwave radiation that bright ice previously reflected, so melting drives further melting. That is a positive feedback, and positive here means amplifying, not beneficial.

Question 4

Greenhouse gases raise the mean surface temperature of the Earth because they

Accepted Answer

let shortwave radiation in but absorb outgoing longwave radiation — The selective absorption is the whole mechanism: solar radiation passes through, the warmed surface re-emits at longer wavelengths, and those wavelengths are absorbed and re-radiated in all directions, including downwards. Reflecting incoming radiation would cool the surface, not warm it.

Question 5

Sulphate aerosols released alongside carbon dioxide when coal is burned reflect incoming sunlight. A country fits flue-gas desulphurisation to its power stations while continuing to burn the same quantity of coal. The most likely short-term effect on regional temperature is

Accepted Answer

a rise, because a cooling influence has been removed — Sulphate aerosols scatter incoming shortwave radiation and have masked part of the warming caused by greenhouse gases, so removing them unmasks that warming. Desulphurisation removes sulphur compounds and not carbon dioxide, so the greenhouse forcing itself is unchanged.

Question 6

Tonne for tonne, methane released today warms the climate far more over the next twenty years than carbon dioxide does, yet carbon dioxide is treated as the greater long-term problem because

Accepted Answer

methane has a much shorter residence time in the atmosphere — Methane is oxidised over roughly a decade, whereas a large share of any carbon dioxide pulse stays in the atmosphere and ocean for centuries, so its warming accumulates. Global warming potential therefore depends on the time horizon chosen, not on the gas alone.

Atmosphere and climate change practice questions.

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