Answer: Equilibrium global surface temperature increase due to a doubling of atmospheric CO 2 concentration (currently estimated 2.5-4 degrees C).
- A The measured rate at which global sea levels rise per degree of atmospheric warming, a sea-level metric rather than the equilibrium temperature response to CO<sub>2</sub> doubling
- B Equilibrium global surface temperature increase due to a doubling of atmospheric CO<sub>2</sub> concentration (currently estimated 2.5-4 degrees C)
- C The minimum global temperature threshold required to begin melting polar ice caps, a melting-point threshold rather than an equilibrium temperature response metric
- D The total annual rate of carbon dioxide emissions released worldwide each year, an emissions rate rather than a measure of equilibrium temperature response
Correct answer: B. Equilibrium global surface temperature increase due to a doubling of atmospheric CO<sub>2</sub> concentration (currently estimated 2.5-4 degrees C)
Explanation: Equilibrium climate sensitivity (ECS): temperature increase expected from doubling pre-industrial CO<sub>2</sub>. IPCC AR6 likely range: 2.5-4 degrees C (best estimate: 3 degrees C).
Energy pyramid showing a simple food chain (producer to herbivore to carnivore) with energy decreasing roughly tenfold at each trophic level.
Concept context
Ecosystems, food chains, energy flow, nutrient cycles, biodiversity, and conservation.