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.
How often UPSC asks this
Questions per year, counted from the official papers.
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Consider the following statements :
- 1. High clouds primarily reflect solar radiation and cool the surface of the Earth.
- 2. Low clouds have a high absorption of infrared radiation emanating from the Earth’s surface and thus cause warming effect.
Which of the statements given above is/are correct ?
Answer (d) & explanation
Neither statement is correct (d). The roles are reversed. Statement 1 is wrong: thin, icy high clouds such as cirrus let most sunlight pass through but trap the outgoing infrared heat from the Earth, so on balance they warm the surface. Statement 2 is wrong: thick, bright low clouds such as stratocumulus reflect a lot of incoming sunlight back to space, so on balance they cool the surface. Low clouds are warm, close to the ground, and give off almost as much heat as the surface does, so their trapping effect is small.
Notice why this matters for climate: cloud changes are the biggest uncertainty in climate models. This is also why cloudy nights stay warmer than clear nights, when heat escapes freely.
Answer as per the official UPSC answer key.
With reference to the water on the planet Earth, consider the following statements :
- 1. The amount of water in the rivers and lakes is more than the amount of groundwater.
- 2. The amount of water in polar ice caps and glaciers is more than the amount of groundwater.
Which of the statements given above is/are correct?
Answer (b) & explanation
Only statement 2 is correct (b). About 97% of Earth's water is salty, in the oceans. Of the 2.5–3% that is fresh, roughly 69% is locked in ice caps and glaciers, about 30% is groundwater, and only about 1% is surface water in lakes, rivers and swamps. Statement 1 is wrong: rivers and lakes hold far less water than groundwater. Statement 2 is right: ice caps and glaciers hold more water than groundwater.
Notice that Antarctica holds most of the world's ice. India has about 18% of the world's population but only about 4% of its freshwater. India is the largest user of groundwater in the world.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. The Global Ocean Commission grants licences for seabed exploration and mining in international waters.
- 2. India has received licences for seabed mineral exploration in international waters.
- 3. ‘Rare earth minerals’ are present on seafloor in international waters.
Which of the statements given above are correct?
Answer (b) & explanation
Statements 2 and 3 are correct (b). Statement 1 is wrong: licences for the deep seabed beyond national limits come from the International Seabed Authority (Kingston, Jamaica), set up under UNCLOS. The Global Ocean Commission was only an advocacy group. Statement 2 is right: India holds ISA contracts for polymetallic nodules in the Central Indian Ocean Basin (since 1987 as a pioneer investor) and for polymetallic sulphides on the Indian Ocean ridge. Statement 3 is right: seabed nodules and muds contain rare earth elements.
Notice India's Deep Ocean Mission (2021) and Samudrayaan, which plans to send people to 6,000 m in the submersible Matsya-6000.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. In the tropical zone, the western sections of the oceans are warmer than the eastern sections owing to the influence of trade winds.
- 2. In the temperate zone, westerlies make the eastern sections of oceans warmer than the western sections.
Which of the statements given above is/are correct?
Answer (c) & explanation
Both statements are correct (c). Statement 1 is right: in the tropics, the trade winds blow from east to west, piling warm surface water on the western side of oceans, while cold water upwells on the eastern side, near South America and Africa. Statement 2 is right: in temperate latitudes, the westerlies carry warm currents, such as the North Atlantic Drift, towards the eastern side of the oceans. That is why north-west Europe is mild in winter, while places at the same latitude in eastern Canada are frozen.
Notice that when the trade winds weaken, warm water moves east across the Pacific: that is El Niño, which often weakens India's monsoon. Cold eastern currents include the Humboldt and Benguela.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Jet streams occur in the Northern Hemisphere only.
- 2. Only some cyclones develop an eye.
- 3. The temperature inside the eye of a cyclone is nearly 10°C lesser than that of the surroundings.
Which of the statements given above is/are correct ?
Answer (c) & explanation
Only statement 2 is correct (c). Statement 1 is wrong: jet streams blow in both hemispheres; the subtropical and polar-front jets circle each pole. Statement 2 is right: only mature, strong tropical cyclones develop a clear eye; weaker storms and temperate cyclones do not. Statement 3 is wrong: sinking air in the eye warms as it compresses, so the eye is warmer than its surroundings, by up to about 10 °C, not colder. The eye is calm, with light winds and clear skies, ringed by the violent eyewall.
Notice that the sub-tropical westerly jet shifting north of the Himalayas helps the Indian monsoon set in, and the tropical easterly jet blows over India in summer.
The 10 °C figure is real. Statement 3 is wrong because it says lesser instead of warmer.
Answer as per the official UPSC answer key.
On 21st June, the Sun
Answer (a) & explanation
On 21 June the Sun does not set at the Arctic Circle (a). On the June solstice, the Northern Hemisphere is tilted towards the Sun, and the Sun is overhead at the Tropic of Cancer (23.5°N) at noon. So places on and north of the Arctic Circle (66.5°N) have 24 hours of daylight, the "midnight sun". Option (b) is wrong because the Antarctic Circle has 24 hours of darkness then. Option (c) is wrong because the Sun is overhead at the equator only at the equinoxes (about 21 March and 23 September). Option (d) is wrong because it is overhead at the Tropic of Capricorn on about 22 December.
Notice that 21 June is also International Yoga Day, chosen as the year's longest day in the north.
Answer as per the official UPSC answer key.
Why are dewdrops not formed on a cloudy night?
Answer (b) & explanation
Clouds reflect the Earth's radiation back (b). Dew forms when the ground loses heat at night by sending out long-wave radiation, cooling the air touching it below its dew point. The water vapour then condenses into drops. On a cloudy night, clouds send much of this outgoing radiation back to the ground, so the surface stays warm and does not cool to the dew point. Option (a) is only partly true, since clouds absorb and re-radiate the heat, but the key's answer is the return of heat. Option (c) is wrong because cloudy nights are warmer. Option (d) is wrong because clouds do not deflect wind.
Clear, calm nights with moist air give the heaviest dew. Notice the same idea in winter frost and radiation fog over North India.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. The Earth’s magnetic field has reversed every few hundred thousand years.
- 2. When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide.
- 3. When living organisms originated, they modified the early atmosphere of the Earth.
Which of the statements given above is/are correct ?
Answer (c) & explanation
Statements 1 and 3 are correct (c). Statement 1 is right because magnetic stripes in ocean-floor basalt show the Earth's field has reversed many times, roughly every few hundred thousand years. The last full reversal, Brunhes–Matuyama, was about 780,000 years ago. Statement 2 is wrong because the early atmosphere had almost no free oxygen. It was full of carbon dioxide, water vapour, nitrogen and other gases from volcanoes. Statement 3 is right because life changed the air: cyanobacteria began photosynthesis, releasing oxygen in the Great Oxidation Event about 2.4 billion years ago, which later allowed the ozone layer to form.
Notice the link: today's air is about 78% nitrogen and 21% oxygen, the result of billions of years of life at work.
Answer as per the official UPSC answer key.
What explains the eastward flow of the equatorial counter-current?
Answer (b) & explanation
The North and South Equatorial Currents flow westward and pile up water on the western side of the oceans. This raised water flows back eastward as the counter-current, between the two westward currents, so the answer is convergence of the two equatorial currents (b). Option (a), Earth's rotation, drives the westward currents but does not explain the return flow. Salinity (c) is not the main driver, and the calm belt (d) only allows the flow to happen.
Notice how ocean currents act like a giant conveyor belt, and how shifts in this system are linked to El Niño and monsoon rainfall in India.
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. The winds which blow between 30° N and 60° S latitudes throughout the year are known as westerlies.
- 2. The moist air masses that cause winter rains in North-Western region of India are part of westerlies.
Which of the statements given above is/are correct?
Answer (b) & explanation
Only statement 2 is correct (b). The westerlies blow between 30° and 60° latitude in each hemisphere. Statement 1 is wrong because "30° N to 60° S" would stretch across the tropics, where the trade winds blow. Western disturbances, which bring winter rain and snow to north-west India, travel from the Mediterranean region on the westerly jet stream, so they are part of the westerlies.
Their winter rain is vital for the rabi wheat crop of Punjab and Haryana. Notice how a wind belt far away shapes Indian farming, and how the "roaring forties" mark strong westerlies in the south.
Statement 1 changes one letter, N to S, and the band then covers the tropics as well.
Answer as per the official UPSC answer key.
Tides occur in the oceans and seas due to which among the following?
- 1. Gravitational force of the Sun
- 2. Gravitational force of the Moon
- 3. Centrifugal force of the Earth
Select the correct answer using the code given below.
Answer (d) & explanation
All three contribute (d). Tides come from the Moon's gravitational pull (2), which is the strongest effect; the Sun's pull (1), which is weaker but still important; and the centrifugal force of the Earth–Moon system turning around a common centre (3). The pull creates a bulge facing the Moon, and the centrifugal effect creates one on the opposite side.
When Sun, Moon and Earth line up at new and full moon, the pulls add up to give spring tides. At right angles, during quarter moons, they partly cancel to give neap tides. Notice how the Gulf of Khambhat's high tides make it a site for tidal energy.
Answer as per the official UPSC answer key.
“Each day is more or less the same, the morning is clear and bright with a sea breeze; as the Sun climbs high in the sky, heat mounts up, dark clouds form, then rain comes with thunder and lightning. But rain is soon over.” Which of the following regions is described in the above passage?
Answer (b) & explanation
The passage describes the equatorial climate (b). Strong heating every day drives convection: cumulonimbus clouds build up by afternoon and bring a short thunderstorm at about the same time each day, often called "four o'clock rain". There is hardly any seasonal change, so "each day is more or less the same". The savannah (a) and monsoon (c) climates have distinct wet and dry seasons, and the Mediterranean (d) has dry summers and wet winters.
Such climate supports dense tropical rainforests, as in the Amazon and Congo basins. Notice how daily weather can reveal the climate type.
Answer as per the official UPSC answer key.
In the South Atlantic and South-Eastern Pacific regions in tropical latitudes, cyclone does not originate. What is the reason?
Answer (b) & explanation
Tropical cyclones grow out of disturbances along the ITCZ. Over the South Atlantic and south-east Pacific, the ITCZ rarely moves south of the equator, so the seed disturbances seldom form. UPSC's key gives this as the reason (b). Option (a) is partly true, as cold currents cool the sea, but the key does not accept it. Option (c) is wrong because the Coriolis force at these latitudes is strong enough. Option (d) is wrong: cyclones need open ocean, so an absence of land would help, not hinder.
The cold Benguela and Humboldt currents and strong wind shear also help keep these seas cyclone-free.
Cool water there is real, but the official key picks the ITCZ. Learn the keyed reason.
Answer as per the official UPSC answer key.
Which of the following phenomena might have influenced the evolution of organisms?
- 1. Continental drift
- 2. Glacial cycles
Select the correct answer using the code given below.
Answer (c) & explanation
Both shaped evolution (c). Continental drift split and joined landmasses, isolating populations and changing climates; Australia's marsupials evolved in isolation after it separated from Gondwana. Glacial cycles shifted habitats, cut off species in refuges and drove extinctions as well as new species. Options (a), (b) and (d) each leave out one real factor.
Isolation is a key driver of speciation, as Darwin's finches on the Galápagos show. Notice how a geography topic (plate tectonics and ice ages) becomes a biology answer: earth history and the history of life are told together.
Answer as per the official UPSC answer key.
The seasonal reversal of winds is the typical characteristic of
Answer (c) & explanation
Seasonal reversal of winds is the hallmark of the monsoon climate (c). The word comes from the Arabic mausim, meaning season. Land heats faster than the sea, so winds blow from sea to land in summer (south-west monsoon) and from land to sea in winter (north-east monsoon). The equatorial climate (a) has steady heat and rain all year without such reversal. The Mediterranean climate (b) sees a seasonal shift of rain belts, not a full wind reversal, so (d) fails too.
Notice how the monsoon links geography to farming, the economy and even festivals across India.
Answer as per the official UPSC answer key.
Variations in the length of daytime and nighttime from season to season are due to
Answer (d) & explanation
Revolution of the earth on a tilted axis is correct (d). The Earth's axis is tilted about 23.5°. As the Earth revolves round the Sun, each hemisphere leans towards the Sun for part of the year, getting long days and summer, and away from it for the rest, getting short days and winter. (a) is wrong: rotation alone gives day and night, but not their changing lengths. (b) is wrong: the elliptical orbit changes the Earth–Sun distance only slightly and does not cause seasons. (c) is wrong: latitude affects how much day length varies, but it does not cause the seasonal change.
Notice the dates: the equinoxes (about 21 March and 23 September) give equal day and night everywhere; the solstices (21 June and 22 December) give the longest and shortest days. Trap: the Earth is actually closest to the Sun in January.
Answer as per the official UPSC answer key.
On the planet earth, most of the freshwater exists as ice caps and glaciers. Out of the remaining freshwater, the largest proportion
Answer (c) & explanation
Groundwater is correct (c). About 69% of the Earth's fresh water is locked in ice caps and glaciers. Most of the rest, about 30%, is groundwater. (a) is wrong: the atmosphere holds only about 0.04% as vapour and clouds. (b) is wrong: lakes and rivers hold well under 1%. (d) is wrong: soil moisture is also a tiny share. Fresh water itself is only about 2.5% of all water on Earth.
Notice India's case: India is the world's largest user of groundwater, drawing about a quarter of the global total, and the CGWB finds over 10% of assessment units over-exploited. Atal Bhujal Yojana promotes community groundwater management. Trap: rivers are visible, but groundwater is far larger.
Answer as per the official UPSC answer key.
Consider the following :
- 1. Electromagnetic radiation
- 2. Geothermal energy
- 3. Gravitational force
- 4. Plate movements
- 5. Rotation of the earth
- 6. Revolution of the earth
Which of the above are responsible for bringing dynamic changes on the surface of the earth?
Answer (d) & explanation
All six are correct (d). The Earth's surface is shaped by exogenic forces driven by solar radiation (1) and gravity (3): weathering, running water, wind, glaciers and mass movement. Endogenic forces come from geothermal energy (2) and plate movements (4): mountain building, volcanoes and earthquakes. Rotation (5) sets wind and ocean-current patterns through the Coriolis force and drives tides with the Moon. Revolution (6) brings the seasons, which change weathering, rivers and glaciers. So (a), (b) and (c) leave out real factors.
Notice the frame: geomorphology sees landforms as a balance between endogenic building and exogenic wearing down. Gravity also drives landslides on young slopes such as the Himalaya. Trap: rotation and revolution seem astronomical, but they shape climate and so the surface.
Answer as per the official UPSC answer key.
The most important fishing grounds of the world are found in the regions where
Answer (c) & explanation
Where warm and cold ocean currents meet is correct (c). When warm and cold currents meet, the mixing brings up nutrients from deep water; plankton thrives in the sunlit surface and feeds huge fish stocks. Examples are the Grand Banks off Newfoundland (Gulf Stream and Labrador current) and the waters off Japan (Kuroshio and Oyashio). (a) is wrong: atmospheric currents are winds, not the cause. (b) is wrong: river mouths can be rich, but they are not the main world fishing grounds. (d) is wrong: a shallow, broad continental shelf helps, but 'undulating' is not the key.
Notice the other cause: cold upwelling off Peru (Humboldt current) gives the anchovy fishery, which collapses in El Niño years. The North Sea's Dogger Bank is another rich ground. Trap: wind and water currents are confused.
Answer as per the official UPSC answer key.
Which of the following is/are unique characteristic/characteristics of equatorial forests?
- 1. Presence of tall, closely set trees with crowns forming a continuous canopy
- 2. Coexistence of a large number of species
- 3. Presence of numerous varieties of epiphytes
Select the correct answer using the codes given below.
Answer (d) & explanation
All three are correct (d). Constant heat and heavy rain all year give equatorial rainforests tall, closely set trees whose crowns form a continuous canopy, with emergents rising above (1). They hold the highest species diversity of any land ecosystem, with many species living side by side (2). Many epiphytes, such as orchids, ferns and bromeliads, grow on tree branches to reach the light (3). So options (a), (b) and (c) leave out real features.
Notice the structure: layers of emergent, canopy, understorey and a dim forest floor; soils are surprisingly poor, as nutrients are locked in plants. The Amazon, Congo and South-East Asian forests are the main blocks; India's nearest equivalents are in the Western Ghats, the north-east and the Andaman Islands. Trap: 'unique' does not exclude any of the three.
Answer as per the official UPSC answer key.