While most scientists agree that the last deglaciation was driven by an increase

Question

While most scientists agree that the last deglaciation was driven by an increase in summer insolation, two important positive feedbacks played a role in amplifying that insolation signal. Those two feedbacks are... (choose two)

A. Greenhouse Gas - Ice Feedback, wherein insolation changes drive ice-sheet response, which in turn creates conditions that control the concentration of greenhouse gasses. In particular a reduction in ice volume and extent allows for higher greenhouse gas concentrations, leading to warmer conditions.

B. Ice - Albedo Feeback, wherein insolation changes drive ice-sheet response, which in turn changes the planetary albedo (reflectivity). In particular, as ice extent decreases, the planetary albedo is reduced, leading to more absorption of solar radiation, yielding warmer conditions.

C.Chemical Weathering Thermostat, wherein insolation driven warming increases both global temperature and precipitation, producing an increase in the removal of carbon-dioxide from the atmosphere through weathering of silicate rocks, yielding a reduced greenhouse effect.

Explanation / Answer

Chemical weathering is negative feedback.

Chemical weatering over geological long term acts to remove co2 from the atmosphere.

So remaining two options a and b are positive feed backs

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