Earth's orbital parameters shift slightly, reducing solar input at high latitudes in summer. Through the ice-albedo feedback, what follows?
AThe feedback stabilizes climate by increasing cloud cover, which compensates for the reduced solar input
BIce and snow expand, increasing surface albedo, which reflects more solar radiation, causing further cooling beyond the initial orbital forcing
CIce and snow expand, but the increased albedo has negligible effect because most solar energy is absorbed by the oceans anyway
DThe feedback reverses the cooling by releasing stored heat from the ice, warming the atmosphere
This is the ice-albedo positive feedback loop: initial cooling → ice/snow expansion → higher surface albedo → more solar radiation reflected → further cooling → more ice expansion. The feedback amplifies rather than counteracts the initial forcing, which is why glacial periods were substantially colder than orbital forcing alone would produce. Climate models estimate ice-albedo feedback roughly doubled the cooling during glacial maxima. Options A and D describe negative (stabilizing) feedbacks, which is the common misconception — students often confuse 'positive feedback' with 'beneficial' and assume climate feedbacks must be restoring.
Question 2 Multiple Choice
The 'Snowball Earth' episodes were so difficult to escape because the extreme ice coverage created a self-reinforcing cooling loop that could only be broken by a forcing strong enough to overcome maximum albedo reflection.
AFalse — Snowball Earth ended quickly because ice sheets are unstable and collapse spontaneously
BTrue — with ice sheets extending to equatorial latitudes, nearly all solar input was reflected, and only millions of years of volcanic CO₂ accumulation (which is not reflected) could eventually overcome the albedo-driven cooling
CTrue — but the mechanism was geothermal heat from the mantle, not CO₂, that eventually melted the ice
DFalse — Snowball Earth was ended by a large meteor impact that locally melted the ice and started a cascade of deglaciation
Snowball Earth represents the ice-albedo feedback taken to its extreme stable state. With ice at equatorial latitudes, planetary albedo was maximized (~0.6 or higher), meaning most incoming solar radiation was reflected before it could warm the surface. The only escape mechanism was volcanic outgassing of CO₂ — which accumulates in the atmosphere regardless of surface albedo — until greenhouse warming eventually overcame the albedo-driven cooling and initiated melting. Once melting began, the feedback reversed: less ice → lower albedo → more absorption → more melting, producing rapid deglaciation. This is why Snowball Earth was both so stable and so abrupt in its ending.
Question 3 True / False
The ice-albedo feedback is called a 'positive feedback' because it has a net beneficial effect on the climate system, helping to moderate temperature extremes.
TTrue
FFalse
Answer: False
In climate science (and systems theory generally), 'positive' and 'negative' feedbacks describe directionality, not desirability. A positive feedback amplifies the initial perturbation in the same direction — cooling causes more cooling, warming causes more warming. A negative feedback opposes the perturbation and stabilizes the system. The ice-albedo feedback is positive because it reinforces rather than resists initial forcing, amplifying temperature swings. Far from moderating extremes, it makes them more extreme. This naming convention confuses many students who associate 'positive' with 'good.'
Question 4 True / False
During a warm interglacial period, the ice-albedo feedback acts to further amplify warming by reducing the amount of solar radiation reflected to space.
TTrue
FFalse
Answer: True
The ice-albedo feedback is symmetric: it amplifies both warming and cooling. During warming, ice and snow melt and retreat, exposing darker ocean and land surfaces that absorb more solar radiation (ocean absorbs >90% vs. ice at 50-90%), further warming the climate. This is directly observable today in Arctic amplification — the Arctic is warming roughly 2-4× faster than the global average, partly because sea ice loss is exposing absorptive dark ocean water. The feedback works in both directions because it is fundamentally about the albedo contrast between ice-covered and ice-free surfaces.
Question 5 Short Answer
Explain why paleoclimate temperature changes during glacial cycles were larger than orbital forcing alone would predict.
Think about your answer, then reveal below.
Model answer: Orbital forcing (Milankovitch cycles) changes the distribution and intensity of solar energy reaching Earth's surface, but these changes are relatively modest in terms of global mean energy. The large temperature swings of glacial cycles (~5-8°C global cooling during glacial maxima) require amplification by positive feedbacks. The ice-albedo feedback is the primary amplifier: as orbital forcing cools high latitudes, ice sheets expand and increase planetary albedo, reducing absorbed solar radiation and causing additional cooling beyond the initial forcing. Climate models estimate this feedback roughly doubles the cooling from orbital forcing. Other feedbacks (CO₂ and methane changes, vegetation-albedo changes) further amplify the signal, producing glacial-interglacial swings far larger than orbital forcing alone would generate.
The key concept is that Earth's climate system is not passive — feedbacks within it respond to forcing and amplify or dampen it. Positive feedbacks like the ice-albedo effect are why relatively small orbital changes can drive large climate swings. Without these feedbacks, the Pleistocene glacial cycles would have been far subtler, and understanding them is central to interpreting the paleoclimate record and projecting future climate change.