Climate and oceans: previous-year questions
53 real UPSC Prelims questions (2011–2026) with the official answer and a clear explanation. 24 of them came in the last five papers.
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Questions per year, counted from the official papers.
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The annual range of temperature in the interior of the continents is high as compared to coastal areas. What is/are the reason/reasons?
- 1. Thermal difference between land and water
- 2. Variation in altitude between continents and oceans
- 3. Presence of strong winds in the interior
- 4. Heavy rains in the interior as compared to coasts
Select the correct answer using the codes given below.
Answer (a) & explanation
Statement 1 only is correct (a). Land heats up and cools down much faster than water, which has a higher specific heat, mixes heat downwards and is partly transparent. Coasts are moderated by the sea, but far inland there is no such effect, so summers are very hot and winters very cold. This is continentality (1). Statement 2 is wrong: altitude affects temperature levels, not this contrast. Statement 3 is wrong: strong winds are not typical of interiors. Statement 4 is wrong: interiors usually get less rain, not more. So (b), (c) and (d) fail.
Notice the examples: Verkhoyansk in Siberia has an annual range of over 60°C, while Mumbai's is a few degrees; Delhi's range is much larger than Chennai's. Trap: rain and wind sound climatic but are not the cause here.
Answer as per the official UPSC answer key.
“Climate is extreme, rainfall is scanty and the people used to be nomadic herders.”
The above statement best describes which of the following regions?
Answer (b) & explanation
Central Asian Steppe is correct (b). The Central Asian steppes lie deep inside Eurasia, far from the sea, so they have an extreme continental climate with hot summers and bitter winters, and scanty rainfall. Peoples such as the Kazakhs, Kirghiz and Mongols lived as nomadic herders of horses, sheep and camels. (a) is wrong: the African savanna is hot all year with a wet season, and herders like the Maasai are semi-nomadic, but the climate is not 'extreme'. (c) is wrong: the North American prairies are now settled, mechanised grain farms. (d) is wrong: the tundra is cold, with reindeer herders, but rainfall and climate descriptions fit the steppe better.
Notice the history: steppe nomads, from the Scythians to Genghis Khan, shaped Eurasian history. Trap: 'used to be' signals traditional herding.
Answer as per the official UPSC answer key.
During a thunderstorm, the thunder in the skies is produced by the
- 1. meeting of cumulonimbus clouds in the sky
- 2. lightning that separates the nimbus clouds
- 3. violent upward movement of air and water particles
Select the correct answer using the codes given below.
Answer (d) & explanation
None of the above is correct (d). Lightning heats the air along its path to around 30,000°C in a split second, about five times hotter than the Sun's surface. The air expands explosively, and this shock wave travels as the sound of thunder. Statement 1 is wrong: clouds do not 'meet' and clap together. Statement 2 is wrong: lightning does not separate clouds. Statement 3 is wrong: updrafts build the charge in cumulonimbus clouds, but they do not themselves make the sound. So (a), (b) and (c) fail.
Notice the related facts: we see lightning before we hear thunder because light travels faster than sound; counting the seconds and dividing by three gives the distance in km. Lightning is notified as a disaster in several states; India's Damini app warns of strikes. Trap: updrafts cause lightning indirectly, but thunder comes from the heated air.
Answer as per the official UPSC answer key.
Electrically charged particles from space travelling at speeds of several hundred km/sec can severely harm living beings if they reach the surface of the Earth. What prevents them from reaching the surface of the Earth?
Answer (a) & explanation
The Earth's magnetic field is correct (a). The solar wind and cosmic rays are streams of charged particles. The Earth's magnetic field (magnetosphere) deflects them, traps some in the Van Allen belts, and steers others towards the poles, where they collide with air and cause the auroras. (b) is wrong: the ozone layer absorbs ultraviolet light, not charged particles. (c) is wrong: moisture in the upper atmosphere does not block them. (d) fails because (a) is correct.
Notice the recent events: the strong geomagnetic storms of May 2024 produced auroras visible even in Ladakh. India's Aditya-L1 (2023) studies the solar wind from the L1 point. Trap: the ozone layer protects against light, not particles.
Answer as per the official UPSC answer key.
Consider the following factors :
- 1. Rotation of the Earth
- 2. Air pressure and wind
- 3. Density of ocean water
- 4. Revolution of the Earth
Which of the above factors influence the ocean currents?
Answer (b) & explanation
Factors 1, 2 and 3 are correct (b). The Earth's rotation creates the Coriolis force, which deflects currents to the right in the north and left in the south, shaping gyres (1). Air pressure and winds, such as the trade winds and westerlies, drag surface water along (2). Differences in density, caused by temperature and salinity, drive deep thermohaline circulation (3). Item 4 is wrong: the Earth's revolution round the Sun gives seasons but does not move currents. So (a), (c) and (d) fail.
Notice the related ideas: the global 'conveyor belt', the AMOC, which scientists warn is weakening, and the Indian Ocean's monsoon-driven reversal of currents. Coastline shape and the sea floor also steer currents. Trap: revolution and rotation are easily confused.
Answer as per the official UPSC answer key.
Normally, the temperature decreases with the increase in height from the Earth’s surface, because
- 1. the atmosphere can be heated upwards only from the Earth’s surface
- 2. there is more moisture in the upper atmosphere
- 3. the air is less dense in the upper atmosphere
Select the correct answer using the codes given below :
Answer (c) & explanation
Statements 1 and 3 are correct (c). Sunlight passes through the air and heats the ground first; the ground then heats the air from below by radiation, conduction and convection (1). Higher up, the air is thinner, with fewer molecules and less water vapour and CO₂ to absorb and hold heat (3). So temperature falls about 6.5°C per km, the normal lapse rate. Statement 2 is wrong: moisture is greatest near the surface, not higher up. So (a), (b) and (d) fail.
Notice the exceptions: a temperature inversion, common on winter nights and in valleys, traps smog, as in Delhi each winter. In the stratosphere, temperature rises with height because ozone absorbs UV. Trap: statement 2 reverses where water vapour sits.
Answer as per the official UPSC answer key.
A person stood alone in a desert on a dark night and wanted to reach his village which was situated 5 km east of the point where he was standing. He had no instruments to find the direction but he located the polestar. The most convenient way now to reach his village is to walk in the
Answer (c) & explanation
Keeping the pole star to his left is correct (c). The pole star (Polaris) sits almost directly over the North Pole, so it marks north. The village lies to the east. Facing east, north is on your left, so he should walk with the pole star on his left. (a) is wrong: facing the pole star means walking north. (b) is wrong: walking away from it means going south. (d) is wrong: the pole star on the right means walking west.
Notice the related tricks: Polaris is found by following the two 'pointer' stars of the Big Dipper (Saptarishi). Its height above the horizon roughly equals your latitude, which is why it cannot be seen from the southern hemisphere. Trap: confusing left and right when imagining the turn.
Answer as per the official UPSC answer key.
Which one of the following is the characteristic climate of the Tropical Savannah Region?
Answer (d) & explanation
A definite dry and wet season is correct (d). The tropical savanna, or Sudan-type, climate lies between about 5° and 20° latitude, with a hot, wet summer when the ITCZ arrives and a long, dry winter when it retreats. This suits tall grasses with scattered trees, as in Africa's savannas and the Brazilian campos. (a) is wrong: rain throughout the year is the equatorial climate. (b) is wrong: winter-only rain is the Mediterranean climate. (c) is wrong: the savanna's dry season is long, not short.
Notice the fauna: savannas host the great herds of East Africa, with zebras, wildebeest and lions. Much of peninsular India has a tropical wet and dry (Aw) climate in Köppen's scheme. Trap: (c) describes the tropical monsoon fringe, not the savanna.
Answer as per the official UPSC answer key.
A layer in the Earth’s atmosphere called Ionosphere facilitates radio communication. Why ?
- 1. The presence of ozone causes the reflection of radio waves to Earth.
- 2. Radio waves have a very long wavelength.
Which of the statements given above is/are correct ?
Answer (d) & explanation
Neither statement is correct (d). The ionosphere (about 80–600 km up) reflects radio waves back to Earth because solar radiation fills it with ions and free electrons, which bend and reflect medium- and short-wave signals. Statement 1 is wrong: ozone sits much lower, in the stratosphere, and absorbs ultraviolet rays; it plays no part in radio reflection. Statement 2 is wrong: radio waves do have long wavelengths, but that alone does not explain why a layer reflects them; it is the electron density that matters. So (a), (b) and (c) fail.
Notice the wider idea: very high frequencies (TV, FM, satellite signals) pass through the ionosphere, which is why satellites are needed for them. Solar flares disturb the ionosphere and cause radio blackouts.
Answer as per the official UPSC answer key.
La Nina is suspected to have caused recent floods in Australia. How is La Nina different from El Nino ?
- 1. La Nina is characterised by unusually cold ocean temperature in equatorial Indian Ocean whereas El Nino is characterised by unusually warm ocean temperature in the equatorial Pacific Ocean.
- 2. El Nino has adverse effect on south-west monsoon of India, but La Nina has no effect on monsoon climate.
Which of the statements given above is/are correct ?
Answer (d) & explanation
Neither statement is correct (d). Statement 1 is wrong: both El Niño (unusual warming) and La Niña (unusual cooling) refer to the equatorial Pacific Ocean, not the Indian Ocean. Statement 2 is wrong: El Niño does tend to weaken India's south-west monsoon, but La Niña usually strengthens it, so it is not without effect. So (a), (b) and (c) fail.
Notice the wider frame: both are phases of ENSO (El Niño–Southern Oscillation). The Indian Ocean has its own see-saw, the Indian Ocean Dipole (IOD); a positive IOD can offset a bad El Niño year, as in 1997. La Niña brings floods to eastern Australia, as in 2010–11. Trap: the ocean is swapped in statement 1.
Answer as per the official UPSC answer key.
Westerlies in southern hemisphere are stronger and persistent than in northern hemisphere. Why ?
- 1. Southern hemisphere has less landmass as compared to northern hemisphere.
- 2. Coriolis force is higher in southern hemisphere as compared to northern hemisphere.
Which of the statements given above is/are correct ?
Answer (a) & explanation
Statement 1 only is correct (a). Between about 40° and 60° S there is almost only ocean, so the westerlies blow over water without mountains or land to slow them. They become strong and steady, called the Roaring Forties, Furious Fifties and Shrieking Sixties (1). Statement 2 is wrong: the Coriolis force depends on latitude and wind speed, not on the hemisphere; it is equal at the same latitude north and south, only deflecting in opposite directions. So (b), (c) and (d) fail.
Notice the related current: these winds drive the Antarctic Circumpolar Current, the strongest ocean current, around Antarctica. Sailors used the Roaring Forties for fast voyages to Australia. Trap: 'higher Coriolis in the south' sounds technical but is false.
Answer as per the official UPSC answer key.
What could be the main reason/reasons for the formation of African and Eurasian desert belt ?
- 1. It is located in the sub-tropical high pressure cells.
- 2. It is under the influence of warm ocean currents.
Which of the statements given above is/are correct in this context ?
Answer (a) & explanation
Statement 1 only is correct (a). The Sahara–Arabia–Thar desert belt lies under the subtropical high-pressure cells (about 20°–30° N), where air from the Hadley cell sinks, warms by compression and stays dry, so clouds and rain cannot form (1). Statement 2 is wrong: warm ocean currents add moisture and rain. Deserts on western coasts are linked to cold currents, such as the Canary (Sahara) and Benguela (Namib), which cool the air and stop rain. So (b), (c) and (d) fail.
Notice the wider pattern: the same high-pressure belt makes the Kalahari, Australian and Atacama deserts in the south. The Thar is also helped by the Aravallis lying parallel to the monsoon winds. Trap: the current's temperature is reversed.
Answer as per the official UPSC answer key.
The jet aircrafts fly very easily and smoothly in the lower stratosphere. What could be the appropriate explanation ?
- 1. There are no clouds or water vapour in the lower stratosphere.
- 2. There are no vertical winds in the lower stratosphere.
Which of the statements given above is/are correct in this context ?
Answer (c) & explanation
Both statements are correct (c). Weather happens in the troposphere. In the lower stratosphere, temperature stops falling with height and then rises, so warm air sits on cool air and there is no convection, meaning no vertical air currents (2). There is almost no water vapour or clouds (1), so storms and rain are absent. That makes flight smooth and free of turbulence, and jets save fuel in the thin air. So (a), (b) and (d) fail.
Notice the related facts: the tropopause is about 8 km at the poles and 18 km at the equator. The ozone layer lies in the stratosphere, at 15–35 km. Jet streams blow near the tropopause and help or hinder flights. Trap: 'no clouds' has rare exceptions, such as polar stratospheric clouds.
Answer as per the official UPSC answer key.