CFA Institute Sustainable Investing Certificate Climate System Science: practice questions

Question 1 · medium

AR6 assessed the Earth's energy imbalance for 2006–2018. Which statement correctly describes it and where the extra energy has gone?

1. About 0.8 W m⁻², with roughly 60 per cent going into melting ice and the rest into the ocean
2. About 8 W m⁻², with roughly 91 per cent of the accumulated energy going into the atmosphere
3. About 2.7 W m⁻², equal to the total human forcing, with most going into warming the land
4. About 0.8 W m⁻², with roughly 91 per cent of the accumulated energy going into the ocean

Question 2 · medium

Why does stopping sulphur dioxide emissions produce a near-term warming, while stopping CO₂ emissions does not cause a rapid drop in temperature?

1. Clean-air rules increase black carbon from replacement fuels, which more than offsets any benefit
2. Sulphate aerosol washes out in days, removing its cooling at once, while CO₂ persists for centuries
3. Carbon dioxide is removed within a year, so its warming vanishes even faster than aerosol cooling
4. Sulphur dioxide is itself a strong greenhouse gas whose removal frees space for water vapour to absorb

Question 3 · medium

Which statement about observed extremes matches the AR6 assessment?

1. Tornado frequency has been shown with high confidence to have risen worldwide since the 1950s
2. Heavy precipitation has grown more frequent and intense since the 1950s over most well-observed land
3. Cold extremes have become more frequent across most land regions since the 1950s
4. Global tropical cyclone numbers have been shown with high confidence to have doubled since 1900

Question 4 · medium

An analysis finds that a heatwave of a given intensity has a 1-in-20 chance per year in today's climate and a 1-in-100 chance in a counterfactual climate without human influence. What are the probability ratio (PR) and fraction of attributable risk (FAR)?

1. PR = 5; FAR = 0.2
2. PR = 5; FAR = 0.8
3. PR = 80; FAR = 0.05
4. PR = 0.2; FAR = 0.2

Question 5 · hard

A newspaper reports that climate change made a recent flood-producing rainfall event 'five times more likely'. Which interpretation is correct?

1. The rainfall was five times heavier than it would have been without human warming, measured in millimetres
2. Such floods will now occur every year, five times more often than the single event that has just been studied
3. Events at least that extreme are now five times as probable as in a counterfactual climate without human warming
4. The flood was caused entirely by climate change and would not have happened at all in a pre-industrial climate

Question 6 · medium

Why does stopping CO₂-driven warming require net zero CO₂ emissions rather than merely reducing emissions?

1. The ocean releases stored heat whenever emissions fall, so cuts raise temperature
2. CO₂ is removed within a decade, so emissions must stop before sinks can act
3. Warming tracks the annual emission rate, so it stops once emissions fall by half
4. Warming tracks cumulative CO₂, so any positive net emission keeps adding to it

Question 7 · hard

Two companies each plan to emit 1 MtCO₂ more over the next decade. Company A says this is acceptable because it will buy credits from a methane-capture project. Why is this not climate-equivalent in the long run under the cumulative-emissions framework?

1. Methane has a GWP100 below one, so each tonne avoided is worth less than a tonne of carbon dioxide
2. Avoided methane cuts a short-lived forcing, but the CO₂ adds to the cumulative total setting long-term warming
3. The cumulative-emissions framework applies only to methane, so carbon dioxide emissions are ignored
4. Methane capture projects always fail, so any credits bought from them have no climate value whatever

Question 8 · medium

For a risk manager, what is the most defensible way to treat climate tipping points given current science?

1. As purely speculative ideas with no physical basis, which can be safely ignored in planning
2. As events that only matter after 2300, beyond any business or policy planning horizon
3. As events at precisely known thresholds, such as exactly 1.5 °C for every tipping element
4. As tail risks whose likelihood rises with each increment of warming, with uncertain thresholds

Question 9 · medium

According to the IPCC Special Report on Global Warming of 1.5 °C, how much further would warm-water coral reefs decline at 1.5 °C and at 2 °C of global warming?

1. No further decline at 1.5 °C and 50 per cent at 2 °C
2. 70–90 per cent at 1.5 °C and more than 99 per cent at 2 °C
3. 10–20 per cent at 1.5 °C and 30–40 per cent at 2 °C
4. More than 99 per cent at 1.5 °C and recovery at 2 °C

Question 10 · medium

A coastal resort's planners ask whether a solar-radiation-modification programme would protect their coral reef. What is the key physical point?

1. It would raise dissolved oxygen enough to offset any loss of carbonate ions in seawater
2. It would reverse acidification fully by cooling the water and so increasing its pH value
3. It would stop both warming and acidification, provided it continues for at least a century
4. It might limit warming, but it would not stop acidification, which follows directly from CO₂