The heat budget of the earth

Correct answer: A. Initial ice loss can expose darker surfaces, increase solar-energy absorption, and cause further melting

The correct answer is A. When ice melts, it can reveal darker land or water with lower albedo. The darker surface absorbs more solar energy, which can promote further warming and ice loss. The initial change is therefore amplified, which is why the feedback is called positive.

Correct answer: A. When trapping of outgoing longwave radiation is stronger than reflection of incoming shortwave radiation

The correct answer is A. Clouds can cool by reflecting incoming shortwave sunlight and warm by absorbing and re-emitting outgoing longwave radiation. Their net effect is warming when the longwave-trapping effect is stronger than the shortwave-reflection effect; the balance varies with cloud properties and conditions.

Correct answer: A. Winds and ocean currents transport heat from lower latitudes

The correct answer is A. Winds and ocean currents carry heat from warmer, lower latitudes toward higher latitudes. This redistribution of energy affects high-latitude climate in addition to the region’s own incoming solar radiation.

Correct answer: B. The deficit may become more pronounced

The correct answer is B. Ocean currents transport heat from warmer regions toward the poles. If this transport weakens, less heat reaches the polar regions, so their energy deficit may become more pronounced, all else being equal.

Correct answer: A. Energy spreads over a larger area, and the rays travel through a longer atmospheric path

The correct answer is A. At a low solar angle, the same incoming beam is spread over a larger surface area, reducing energy per unit area. The rays also pass through more atmosphere, where some energy is scattered or absorbed.

Correct answer: A. Because a larger share of the available energy can be used for evaporation as latent heat

The correct answer is A. At a moist surface, more available energy can drive evaporation and become latent heat. This leaves less energy to warm the air directly, so sensible heat flux can be lower.

Correct answer: A. When evaporation takes energy from the surface and condensation releases that energy into the atmosphere

The correct answer is A. Evaporation uses energy to change liquid water into water vapour, storing it as latent heat. When the vapour condenses, that latent heat is released into the atmosphere, transferring energy from the surface to the air.

Correct answer: A. Some aerosols scatter or reflect incoming sunlight, while others absorb radiation

The correct answer is A. Aerosols differ in their properties: scattering or reflecting sunlight can reduce the solar energy absorbed by Earth, while absorbing radiation can warm the aerosol layer and affect energy reaching the surface. Their net effect therefore depends on the aerosol type and conditions.

Correct answer: A. Comparing an irrigated field with dry paved ground under the same insolation

The correct answer is A. Even with the same incoming solar energy, a moist irrigated field can use more energy for evaporation, while dry paved ground may direct more energy into sensible heating or ground heating. Comparing them therefore requires looking at how energy is partitioned, not just the net balance.

Correct answer: A. Local cloud cover, surface moisture, winds, and seasonal sunlight vary.

The correct answer is A. Global heat balance describes the long-term balance of energy for the Earth as a whole, not identical energy conditions at every place and time. Local weather, surface properties, and seasonal sunlight create local temperature changes.

Correct answer: A. It absorbs more solar energy, but its temperature may rise slowly.

The correct answer is A. Low albedo means that a surface reflects less and absorbs more incoming solar energy. A surface with high heat capacity needs more energy to warm by each degree, so its temperature can rise relatively slowly during the day.

Correct answer: A. Because absorbed solar energy and downward atmospheric radiation may also be sufficiently high.

The correct answer is A. A warm surface emits more terrestrial radiation, but its temperature depends on the balance of energy flows. If absorbed sunlight and downward longwave radiation from the atmosphere remain sufficiently high, the surface can stay warm despite increased emission.

Correct answer: A. A large increase in albedo that reduces absorbed shortwave radiation.

The correct answer is A. A negative energy imbalance means that the Earth system gains less energy than it loses. If albedo rises, more incoming sunlight is reflected and less shortwave energy is absorbed; with other factors unchanged, this can reduce energy input enough to produce a negative imbalance.

Correct answer: B. Warming tendency

The correct answer is B, a warming tendency. Greater absorption of outgoing terrestrial longwave radiation means less energy escapes to space at first. With solar input unchanged, this creates a positive energy imbalance that tends to warm the Earth system.

Correct answer: A. Because both the surface and atmosphere absorb and emit energy, and the atmosphere also reradiates energy

The correct answer is A. The surface absorbs solar energy and emits terrestrial longwave radiation. The atmosphere also absorbs and emits radiation, including energy reradiated toward both space and the surface. The energy balance therefore involves the combined Earth–atmosphere system, not the surface alone.

Correct answer: A. High albedo and high evaporation

The correct answer is A. High albedo reflects a larger share of incoming solar energy, so less is absorbed at the surface. Evaporation also uses energy as latent heat rather than leaving all of it to raise surface temperature. Together, these effects can keep the surface relatively cool.

Correct answer: A. It is a negative feedback that tends to restore the energy balance

The correct answer is A. A warmer surface emits more longwave radiation. If more energy then escapes to space, this reduces the energy surplus that caused the warming, so the response acts as a stabilizing, negative feedback.

Correct answer: A. Warmer air can contain more water vapour, which absorbs more outgoing longwave radiation

The correct answer is A. As air warms, it can generally contain more water vapour if moisture is available. Water vapour absorbs outgoing longwave radiation, so the added vapour can strengthen the greenhouse effect and amplify the initial warming. This makes it an important positive feedback in the heat budget.

Correct answer: A. The balance applies to the total amount, while energy can still be unevenly distributed between regions.

A is correct. A global heat budget can balance over time even though some regions have an energy surplus and others have a deficit. The atmosphere and oceans transfer energy between regions, so transfer continues despite the overall balance.

Correct answer: A. For a while after maximum insolation, the surface continues gaining more energy than it loses.

A is correct. The surface does not reach its highest temperature as soon as insolation peaks. For a period afterward, incoming energy still exceeds energy lost from the surface, so the surface and nearby air continue warming. The temperature peaks once energy loss becomes greater than energy gain; this delay is called thermal lag.

Correct answer: A. Because it includes conduction, convection, and latent heat transfers as well as radiation

The correct answer is A. A radiation budget accounts for incoming and outgoing radiant energy. A heat budget is broader because it also considers other heat transfers, including conduction, convection, and latent heat carried during changes of state.

Correct answer: A. Their altitude, thickness, and radiative properties differ

The correct answer is A. Cloud height, thickness, and properties affect how clouds reflect incoming sunlight and absorb or emit outgoing longwave radiation. High, thin clouds and low, thick clouds therefore need not have the same overall effect on the heat budget.

Correct answer: A. It indicates how effectively the surface emits longwave radiation

The correct answer is A. Emissivity describes how effectively a surface emits thermal radiation compared with an ideal emitter at the same temperature. Since Earth's surface emits longwave radiation, its emissivity helps describe an important part of the heat budget.

Correct answer: A. Their surface types, moisture, cloud cover, altitude, and influence from the sea may differ

The correct answer is A. Latitude influences the amount of solar energy received, but it is not the only control on a place's heat budget. Differences in surface properties, moisture, clouds, altitude, and nearby oceans can alter how energy is reflected, absorbed, and exchanged.

Correct answer: A. High albedo reflects more incoming sunlight, while counter-radiation reduces the surface’s net longwave heat loss

The correct answer is A. High albedo reduces the solar energy absorbed by the surface, but strong downward longwave radiation from the atmosphere reduces the surface’s net heat loss. Since these effects oppose one another, temperature depends on their combined energy balance, not on albedo alone.