If all greenhouse gas emissions stopped completely today, what would most likely happen to global average surface temperatures over the next several decades?
ATemperatures would immediately stabilize at current levels because new forcing would stop
BTemperatures would decline rapidly as the atmosphere cooled without new greenhouse gas input
CTemperatures would continue rising for decades as the ocean releases stored heat into the atmosphere
DTemperatures would be unaffected because ocean heat content is independent of surface climate
This is the 'committed warming' effect of ocean thermal inertia. The ocean has already absorbed an enormous amount of excess heat and is not yet in thermal equilibrium with the current atmosphere. Even if forcing stopped, the ocean would continue releasing stored heat for decades to centuries, driving further surface warming. Thermal inertia means the ocean responds slowly — like a massive flywheel still spinning after you stop pushing. Emissions stopping prevents additional forcing but cannot cancel the energy already banked in the ocean-atmosphere system.
Question 2 Multiple Choice
The ocean dominates Earth's heat budget despite covering the same planet as the atmosphere. The primary physical reason is:
AThe ocean is darker than clouds and absorbs more solar radiation per unit area
BThe ocean's mass is roughly 260 times greater than the atmosphere's, and water has roughly 4 times the specific heat of air, giving it about 1,000 times the heat storage capacity
COcean currents distribute heat more efficiently than atmospheric circulation, minimizing energy loss
DThe ocean's depth means it has more total volume to store heat than the shallow atmosphere
The ocean's heat storage advantage is multiplicative: roughly 260× the mass of the atmosphere times roughly 4× the specific heat capacity per unit mass gives approximately 1,000× the heat storage capacity for the same temperature change. This is why over 90% of excess heat from greenhouse gases has gone into the ocean while the atmosphere has warmed comparatively little. Volume alone (option D) understates the advantage because specific heat capacity matters as much as mass.
Question 3 True / False
Thermosteric sea-level rise — caused by the thermal expansion of warming ocean water — is currently the largest single contributor to observed global sea-level rise.
TTrue
FFalse
Answer: True
Thermosteric expansion is the dominant term in the current sea-level rise budget, ahead of contributions from mountain glacier melt and ice sheet loss from Greenland and Antarctica. As ocean heat content increases and water warms, it expands in volume. While ice-sheet contributions are growing and projected to overtake thermosteric rise later this century under high-emission scenarios, thermosteric expansion has been the leading contributor to observed sea-level rise over recent decades.
Question 4 True / False
Because the ocean absorbs large quantities of CO₂ from the atmosphere, the energy stored in dissolved CO₂ offsets the heat the ocean would otherwise absorb, meaning ocean warming is slower than it would be without CO₂ uptake.
TTrue
FFalse
Answer: False
CO₂ absorption and heat absorption are distinct physical-chemical processes that do not offset each other. CO₂ dissolves into seawater through gas exchange — a chemical process that slightly acidifies the water. Heat absorption is a separate thermodynamic process driven by the ocean's energy balance. The ocean is simultaneously warming AND absorbing CO₂. In fact, as the ocean warms its capacity to dissolve CO₂ decreases (warm water holds less dissolved gas), creating a positive feedback that reduces future CO₂ uptake — the two processes interact, but not as mutual offsets.
Question 5 Short Answer
What is 'committed warming,' and why does ocean thermal inertia make some degree of future warming inevitable even if emissions were halted immediately?
Think about your answer, then reveal below.
Model answer: Committed warming refers to temperature increases already locked in by the energy imbalance stored in the ocean-atmosphere system, even if no additional greenhouse gases were emitted. Ocean thermal inertia makes this inevitable because the ocean has absorbed enormous amounts of heat and is not yet in equilibrium with the atmosphere — it will continue releasing that stored heat over decades to centuries, driving further surface warming. The ocean's massive heat capacity means it responds slowly; once it has taken on heat, it cannot release it quickly. Stopping emissions halts new forcing but does not cancel the energy already in the system.
Committed warming is critical for climate policy because it means some future warming is already determined regardless of current action — we are choosing which amount of committed warming to accept, not whether any occurs. Every ton of emissions avoided now determines the magnitude of future committed warming. The ocean's thermal inertia is the physical mechanism: it acts as a slow-release heat reservoir that guarantees surface warming continues after forcing stops, just more slowly than before.