More frequent and prolonged droughts caused by rising global temperatures pose significant risks to people and ecosystems around the world.
A study by the British University of East Anglia (UEA) shows that even a modest temperature increase of 1.5°C will have serious consequences in India, China, Ethiopia, Ghana, Brazil and Egypt.
Drought in India
These six countries were selected for study in the UEA project, which has been published in the journal Climatic Change because they provide a range of contrasting sizes and different levels of development across three continents spanning tropical and temperate biomes, containing forests, grasslands, and deserts.
The study has quantified the risks of severe drought, its probability and duration in scenarios of temperature increase of 1.5ºC to 4ºC.
Dr. Jeff Price, Associate Professor of Biodiversity and Climate Change at UEA and leader of the research, noted that “Current commitments to climate change mitigation are projected to result in global warming levels of 3°C or more, which will have a major impact on these six countries For example, with 3°C warmings, more than 50% of agricultural land in each country is projected to be exposed to severe drought lasting more than one year in a period 30 years old”.
“Using standard population projections, it is estimated that between 80 and 100% of the population of Brazil, China, Egypt, Ethiopia and Ghana (and almost 50% of India) would be exposed to a severe drought lasting one year or more over a 30-year period,” says Price.
In contrast, meeting the long-term temperature target of the Paris Agreement, which limits warming to 1.5°C above pre-industrial levels, would benefit all countries in this study, greatly reducing exposure to severe droughts for large percentages of the population and throughout the world.
Temperature increase scenarios
- Under the 1.5°C warming scenario, the probability of drought is projected to triple in Brazil and China, almost double in Ethiopia and Ghana, increase slightly in India, and increase substantially in Egypt.
- Under a 2°C warming scenario, the probability of drought is projected to quadruple in Brazil and China; double in Ethiopia and Ghana; reach more than 90% probability in Egypt and almost double in India.
- In a 3°C warming scenario, the projected drought probability in Brazil and China is 30-40%; 20-23% in Ethiopia and Ghana; 14% in India and almost 100% in Egypt.
- Finally, in a 4°C warming scenario, the projected probability of drought in Brazil and China is almost 50%; 27-30% in Ethiopia and Ghana; almost 20% in India; and 100% in Egypt.
- In most countries, the projected increase in the probability of drought increases roughly linearly with increasing temperature. The exception is Egypt, where even small amounts of global warming can lead to large increases in the probability of drought.
Duration of droughts
Professor Rachel Warren, a participant in the study, explains that “not only does the area exposed to drought increase with global warming, but the duration of droughts also increases. In Brazil, China, Ethiopia and Ghana, droughts of more than two years are expected even under a 1.5°C warming scenario.”
Under a 2°C warming scenario, the duration of droughts in all countries (except India) is projected to exceed three years. In a 3°C warming scenario, droughts are projected to approach 4-5 years in duration and in a 4°C warming scenario, severe droughts of more than five years are projected for Brazil and China, with severe droughts being the new reference condition.
In addition, the percentage of land projected to be exposed to the severe drought of more than 12 months in a 30-year period is expected to increase rapidly under the 1.5°C warming scenario in Brazil, China and Egypt, and in areas of permanent snow and ice in India.
India and China have large areas currently under ‘permanent’ ice and snow cover. However, under the 3°C warming scenario, 90% of these areas are projected to face severe drought lasting more than one year in a 30-year period.
Decreases in water storage
These areas form the headwaters of many of the major river systems and thus the water supply for millions of people downstream. The increased probability and duration of severe droughts point to possible decreases in water storage in the Chinese Himalayas in the form of snow and ice.
Drought can have major impacts on biodiversity, agricultural yields, and economies. This study indicates that all six countries will need to deal with water stress in the agricultural sector, possibly by changing crop varieties or through irrigation, if water is available. Therefore, the amount of adaptation needed to cope with this increase in drought increases rapidly with global warming.
Urban areas fare only slightly better and generally show the same pattern as above. Areas along rivers and streams or with reservoirs may work better, depending on the competition for water resources and headwater sources.
Warren states that “complying with the Paris Agreements could have significant benefits in terms of severe drought risk reduction in these six countries, across all major land cover classes, and for large percentages of the population worldwide. This requires urgent action on a global scale to reach net zero greenhouse gas emissions by 2050.”
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