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BEST IELTS Academic Reading Test 515
IELTS ACADEMIC READING TEST 515 – PASSAGE – 1
IELTS ACADEMIC READING TEST – 515
READING PASSAGE – 1
Climate change heralds thirsty times ahead for most
A new modelling study suggests that increasing temperatures will dramatically affect the world’s great rivers
Veteran climate modeller Syukuro Manabe, and colleagues at Princeton University, modelled what effect a quadrupling of atmospheric carbon dioxide above pre-industrial levels would have on the global hydrological (water) cycle over the next 300 years. That looks further ahead than most climate models, but the scenario is inevitable unless governments take drastic action to limit greenhouse gas emissions. Rising CO2 levels will trigger higher temperatures not only at the Earth’s surface, but also in the troposphere, the team says.
By factoring this into the models together with changes to levels of water vapour, cloud cover, solar radiation and ozone, the team predicted the effect that climate changes could have on evaporation and precipitation (rain). Both would increase, the researchers found, causing the discharge of fresh water from rivers around the world to rise by almost 15 per cent.
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However, while water is going to be more plentiful in regions that already have plenty, the net effect will be to take the world’s water further from where the people are. ‘Water stresses will increase significantly in regions that are already relatively dry,’ Manabe reports in the journal Climate Change. He goes on to predict that evaporation will reduce the moisture content of soils in many semi-arid parts of the world, including north-east China, the grasslands of Africa, the Mediterranean and the southern and western coasts of Australia. Soil moisture will fall by up to 40 per cent in southern US states, representing the greatest reduction.
The effects on the world’s rivers will be just as dramatic. The biggest increases will be in the far north of Canada and Russia. For instance, the flow of the river Ob in Siberia is projected to increase by 42 per cent by the end of the 23rd century. This prediction could encourage Russia’s plans to divert Siberian Rivers to irrigate the deserts around the Aral Sea. Similar changes could increase pressure from the US for Canada to allow transfers from its giant Pacific rivers to water the American West. Manabe predicts a 47 per cent increase in the flow of the Yukon River.
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By contrast, there will be lower flows in many mid-latitude rivers, which run through heavily populated regions. Those that will start to decline include the Mississippi, Mekong and especially the Nile, one of the world’s most heavily used and politically contested rivers, where his model predicts an 18 per cent fall in flow.
The changes will present a ‘profound challenge’ to the world’s water managers, Manabe says. They are also likely to fuel calls for a new generation of super-dams and canals to move water round the planet, like China’s current scheme to transfer water between north and south.
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Some of the findings are controversial. The UK Meteorological Office’s climate model predicts that flows in the Amazon could fall this century, while Manabe’s team predicts greater rainfall could increase its flow by 23 per cent. And while Manabe foresees a 49 per cent increase in the flow of the Ganges and Brahmaputra rivers that drain the Himalayas, an international study reported that the Ganges would lose flow as the glaciers that feed it melt away.
Global warming has already increased glacier melting by up to 30 per cent. ‘After 40 years, most of the glaciers will be wiped out and then we will have severe water problems,’ says Syed Iqbal Hasnain of Calicut University, Kerala, reporting the results of a three-year study by British, Indian and Nepalese researchers.
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The study finds the biggest impact in Pakistan, where the River Indus irrigates half the country’s crops. Flows here could double before crashing to less than half current levels by the end of the century. But the declining flows predicted for the Ganges will also throw into disarray a vast Indian government scheme to avoid drought by diverting water from the country’s glacier-fed northern rivers to the arid south.
Meanwhile, a team of researchers in France say that climate change is already affecting the world’s rivers. David Labat and colleagues at the government’s CNRS research agency in Toulouse in France reconstructed the monthly discharges of more than 200 of the world’s largest rivers since 1875. They took discharge data held by the Global Runoff Data Centre in Germany and the UNESCO River Discharge Database and used a statistical technique to fill in gaps left by missing data, or changes to run-off caused by dams and irrigation projects.
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Their findings reveal that changing temperatures cause river flows to rise and fall after a delay of approximately 15 years, and the team predicts that global flows will increase by about 4 per cent for every 1° C rise in global temperature. However, climate change over the past few decades has already caused discharge from rivers in North and South America and Asia to increase. Run-off in Europe has remained stable, but the flow of water from Africa’s rivers has fallen.
Questions 1-7
Choose NO MORE THAN THREE WORDS AND/OR A NUMBER for each answer.
Syukuro Manabe’s climate model
Based on: fourfold increase of (1)…………….
Period covered: looks (2)……………. Ahead
Processes monitored: effects of climate change on (3)……………. As well as (4)…………….
Syed Iqbal Hasnain’s predictions
Based on: the loss of (5)…………….
Period covered: looks (6)……………. Ahead
David Labat’s predictions
Based on: data going back to (7)…………….
Features studied: 200 of the world’s largest rivers
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Questions 8-12
Choose NO MORE THAN THREE WORDS AND/OR A NUMBER from the passage for each answer.
Predictions about increasing temperatures
| Rivers | Soil | |
| Syukuro Manabe | Overall increase in flow of approximately (8)………….. Decreases in flow at mid-latitudes, in particular for the (10)………….. | Most significant decline in water content will be in (9)………….. |
| Syed Iqbal Hasnain | Greatest flow increase in (11)………….. e.g. River Indus Flows will rise and then fall. | |
| David Labat | Flow rates change about (12)………….. after the change in temperature occurs. |
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Question 13
Choose TWO letters, A-E.
Which TWO of the following countries are developing systems to solve their own water problems?
A. China
B. Africa
C. Canada
D. India
E. France
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ANSWERS
1. (ATMOSPHERIC) CARBON DIOXIDE
2. 300 YEARS
3. EVAPORATION
4. PRECIPITATION (RAIN)
5. GLACIERS
6. 40 YEARS
7. 1875
8. 15% / 15 PER CENT
9. SOUTHERN US STATES
10. (RIVER) NILE
11. PAKISTAN
12. 15 YEARS
13. A AND D
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