The heat budget of the earth

The correct answer is A, carbon dioxide (CO₂). Burning fossil fuels releases CO₂, which absorbs some of the infrared radiation Earth sends back toward space and contributes to human-caused warming. Water vapour is also a greenhouse gas, but CO₂ is the gas identified by the fossil-fuel clue in this question.

Heat budget is the account of energy received and lost by Earth. For exams remember it as energy balance.

Most of Earths heat comes from solar radiation received from the Sun. In exams treat the Sun as the main energy source.

Incoming energy is solar energy reaching Earths atmosphere and surface. In exams understand incoming as energy from the Sun.

Earth sends absorbed energy out as longwave radiation. In exams link outgoing energy with terrestrial radiation.

Energy from the Sun comes as shortwave radiation. In exams call solar energy shortwave radiation.

Earth emits its absorbed energy as longwave heat. In exams understand terrestrial radiation as Earths heat.

Heat budget is commonly explained by taking solar energy as hundred units. In exams remember the hundred unit base.

About thirty five units are reflected by clouds atmosphere and surfaces. In exams remember the reflected part as thirty five units.

Out of hundred units about sixty five units are absorbed by Earth and atmosphere. In exams remember the absorbed part as sixty five units.

In heat budget about fifty one units are absorbed by Earths surface. In exams remember the surface share as fifty one units.

A part of solar energy is directly absorbed by the atmosphere. In exams remember atmospheric absorption as fourteen units.

Clouds reflect a part of solar rays back to space. In exams treat clouds as a major cause of reflection.

Albedo is the ability of a surface to reflect solar energy. In exams remember higher albedo means higher reflection.

The direct answer is B, high. Albedo means the fraction of incoming sunlight that a surface reflects back. Fresh snow is bright white and reflects a large part of solar radiation instead of absorbing it. Therefore, its albedo is generally high. Option A, very low, is incorrect because dark surfaces such as asphalt absorb more sunlight and usually have low albedo. Option B is correct because snow and ice are highly reflective. Option C, zero, is incorrect because snow does reflect sunlight; zero would mean complete absorption. Option D, always equal, is incorrect because albedo can change with snow age, dirt, melting, grain size, and the angle of sunlight. Thus the correct fact chain is white snow → strong reflection → high albedo. Memory cue: bright surfaces reflect, while dark surfaces absorb.

Direct answer: Option C, a dark-coloured surface generally absorbs more solar energy. Solar energy can be reflected, absorbed, or transmitted. Dark surfaces usually reflect a smaller share and absorb a larger share, so they warm more. Step by step: sunlight reaches the surface; a light surface sends more energy back by reflection; a dark surface sends less back; the remaining larger share enters the surface as absorbed energy and raises its temperature. Option A is wrong because dark surfaces generally reflect less, not more. Option B is wrong because every real surface absorbs at least some energy; darkness does not mean zero absorption. Option C is correct because it states the usual relationship between dark colour and absorption. Option D is irrelevant and scientifically wrong: solar energy is not converted only into sound. Memory cue: dark absorbs, light reflects. This is a general rule, though the exact amount also depends on the material and wavelength.

Over long periods Earth sends out nearly as much energy as it receives. In exams link balance with stable average temperature.

Direct answer: Option A, Earth’s average temperature will tend to rise. Earth’s energy balance compares incoming energy with outgoing emitted energy. Step by step: Earth receives solar energy; it emits infrared energy back to space; if incoming energy is greater than outgoing energy, energy is stored in the Earth system; stored energy increases heating, so the average temperature tends to rise until balance is restored or other conditions change. Option A is correct because an energy surplus produces warming. Option B is the opposite of the expected result and would fit an energy deficit, not a surplus. Option C is wrong because receiving extra energy does not make the Sun stop producing energy. Option D is unrelated: the Moon does not disappear because Earth has an energy imbalance. The word ‘tend’ matters: this describes the general physical response, not an instant identical warming everywhere. Memory cue: incoming greater than outgoing means surplus and warming; outgoing greater than incoming means loss and cooling.

The governing concept is Earth’s heat budget, which compares incoming solar energy with energy leaving the Earth system. If outgoing energy exceeds incoming energy for a sustained period, the system has a net energy deficit. The surface and lower atmosphere must lose thermal energy, so the average temperature tends to decrease until a new balance is approached. Therefore option B is correct. Option A would require energy balance, not an ongoing deficit. Option C has no physical basis in this energy-budget relationship. Option D is an exaggerated claim: atmospheric water vapour may change with temperature, but an energy deficit does not mean that all water disappears from the atmosphere. The result described is cooling, not an immediate absolute transformation.

Gases in the atmosphere absorb some terrestrial longwave energy. In exams link this with greenhouse effect.

Greenhouse gases absorb longwave energy emitted by Earth. In exams link greenhouse effect with longwave energy.

These gases absorb longwave heat and help keep Earth warm. In exams count them among key greenhouse gases.

The surface absorbs solar energy and emits it as longwave radiation. In exams remember the surface as a longwave emitter.

Clouds return part of incoming solar energy to space. In exams link clouds with both reflection and counter radiation.

Dust particles scatter solar rays and affect energy reaching the surface. In exams link dust with scattering.