The heat budget of the earth

After thirty five units are reflected from hundred units sixty five units remain absorbed. Use simple subtraction in exams.

Direct answer: Option A, Earth’s albedo can increase when cloud and snow cover increase. Albedo means the fraction of incoming sunlight reflected back by a surface or by the Earth system. Step by step: snow is bright and highly reflective; clouds can reflect a substantial amount of sunlight; increasing these reflective components sends more solar energy back to space; the reflected fraction rises, so albedo increases. Option A is correct. Option B is wrong in the usual comparison because increasing dark surfaces generally lowers reflectivity and therefore lowers albedo. Option C is not the best answer: increased absorption by forests describes more energy taken in, not increased reflection; it would generally not raise albedo. Option D is wrong or insufficient because greater ocean depth by itself does not necessarily make the Earth system more reflective, and ocean water is generally dark compared with snow. The exact effect of clouds can vary with their type, thickness, altitude, and lifetime, but the textbook relationship between increased snow/cloud cover and higher albedo is valid. Memory cue: bright snow and reflective clouds send sunlight back.

When snow is removed darker surfaces can absorb more energy. Link snow cover decrease with higher absorption in exams.

The atmospheric window explains direct escape of longwave energy. In exams link it with seventeen units of direct outgoing energy.

Greenhouse gases absorb and radiate back terrestrial radiation. Link greenhouse effect with longwave energy in exams.

Positive net radiation shows energy surplus and possible warming. In exams link positive with energy gain.

Negative net radiation shows energy deficit and possible cooling. In exams link negative with energy loss.

Shortwave energy arrives by day while longwave loss dominates at night. Understand day and night as different energy situations.

Low latitudes have surplus and high latitudes have deficit. In exams consider atmosphere and oceans as means of heat transport.

Sun rays fall more directly at low latitudes. In exams link low latitudes with greater solar energy.

At high latitudes rays are oblique and reflection can be high. Link poles with energy deficit in exams.

Energy surplus could accumulate in low latitudes. In exams treat heat transfer as a means of global balance.

Heat transport reduces energy deficit at high latitudes. Link polar temperature with global heat transport in exams.

Currents carry heat over long distances in oceans. In exams link ocean currents with heat transport.

Atmospheric circulation moves warm and cold air. Treat it as reducing energy inequality in exams.

A warmer surface emits more terrestrial radiation. Remember the relation between surface temperature and longwave emission.

A warmer surface emits more energy which supports balance. Remember this feedback mechanism in exams.

During daytime clouds can send more solar energy back. In exams treat daytime clouds as reducing net energy.

Clouds absorb terrestrial heat and send part of it back. Link cloudy nights with less energy loss in exams.

The surface absorbs and emits energy and the atmosphere receives part of it. Treat them as a combined energy system in exams.

Higher global albedo sends more solar energy back. Link albedo increase with lower energy gain in exams.

When reflection decreases more energy can remain in the Earth system. Remember the inverse relation between reflection and absorption.

The surface receives incoming solar energy and then emits terrestrial radiation. Treat the surface as an energy conversion centre in exams.

More longwave absorption can strengthen the greenhouse effect. Link longwave absorption with heat retention in exams.

Both reflected solar and outgoing terrestrial energy leave the Earth system. Treat them as parts of total outgoing energy in exams.