According to new research from the University of East Anglia (UEA), more frequent and prolonged droughts caused by rising global temperatures pose significant risks to people and ecosystems around the world.
The research shows that even a modest temperature increase of 1.5°C will have serious consequences in India, China, Ethiopia, Ghana, Brazil and Egypt. These six countries were selected for study in the UEA project because they offer a range of contrasting dimensions and different levels of development on three continents that include tropical and temperate biomes, and include forest, grassland and desert habitats.
The findings, “Quantification of meteorological drought risks between 1.5 °C and 4 °C from global warming in six countries,” are published today in the journal Climate change.
The paper, led by Dr. Jeff Price and his colleagues at the Tyndall Center for Climate Change Research at UEA quantified the expected effects of alternative levels of global warming on the likelihood and duration of severe drought in the six countries.
dr. Price, associate professor of Biodiversity and Climate Change, said: “Current commitments to climate change mitigation, which are still expected to result in global warming of 3°C or more, would impact all countries in this study. .
“With a 3°C warming, more than 50% of agricultural land in any country is expected to be exposed to severe drought lasting more than a year in any 30-year period. Using standard population projections, it is estimated that 80% to 100% of the population in Brazil, China, Egypt, Ethiopia and Ghana (and nearly 50% of the population of India) is expected to be exposed to a severe drought of a year or more in a 30-year period.
“In contrast, we find that meeting the long-term temperature goal of the Paris Agreement of limiting warming to 1.5°C above pre-industrial levels is expected to greatly benefit all countries in this study, allowing the exposure to severe drought for large percentages of the population and in all major land cover classes, with Egypt possibly benefiting the most.”
Under the 1.5°C warming scenario, the probability of drought is expected to triple in Brazil and China, almost double in Ethiopia and Ghana, increase slightly in India and increase significantly in Egypt.
Under a 2°C warming scenario, the probability of drought is expected to quadruple in Brazil and China; double in Ethiopia and Ghana; achieving a 90% chance in Egypt; and almost double in India.
With a warming scenario of 3 °C, the probability of drought in Brazil and China is 30-40%; 20-23% in Ethiopia and Ghana; 14% in India, but almost 100% in Egypt.
Finally, in a warming scenario of 4 °C, the probability of drought in Brazil and China is almost 50%; 27-30% in Ethiopia and Ghana; nearly 20% in India; and 100% in Egypt.
In most countries, the expected increase in the probability of drought increases approximately linearly with increasing temperature. The exception is Egypt, where even a small amount of global warming can lead to a large increase in the likelihood of drought.
Prof Rachel Warren, leader of the general study of which this article is one result, said: “Not only does the area exposed to drought increase with global warming, but it also extends the duration of droughts. In Brazil, China, Ethiopia, and Ghana are expected to experience droughts of more than two years even under a 1.5°C warming scenario.”
Under a warming scenario of 2°C, the expected duration of drought in all countries (except India) will be more than three years. In a 3°C warming scenario, droughts are expected to last 4-5 years and in a 4°C warming scenario, severe droughts lasting longer than five years are predicted for Brazil and China, with severe droughts as the new baseline condition.
Also, the percentage of land that is expected to be exposed to severe droughts of more than 12 months in a 30-year period is expected to increase rapidly due to the 1.5°C warming scenario in Brazil, China and Egypt, and in areas of permanent snow and ice in India.
India and China both have large areas that are currently under “permanent” ice and snow cover. However, in the 3°C warming scenario, 90% of these areas are expected to experience severe droughts lasting more than a year over a 30-year period.
These areas form the headwaters of many major river systems and therefore the water supply for millions of people downstream. Increasing probability and duration of severe drought points to possible decrease in water storage in the Chinese Himalayas in the form of snow and ice.
Drought can have major consequences for biodiversity, agricultural yields and economies. This study indicates that all six countries will experience water stress in the agricultural sector, possibly from shifting crop varieties or from irrigation, if water is available. The amount of adaptation needed to cope with this increase in drought is therefore increasing 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 fare better, depending on competition for water resources and headwaters.
Prof. dr. Warren said: “Complying with the Paris accords could have major benefits in terms of reducing the risk of severe drought in these six countries, across all major land cover classes and for large percentages of the population worldwide. This requires urgent global action to to stop deforestation (including in the Amazon) in this decade, and to decarbonise the energy system in this decade so that we can achieve net-zero global greenhouse gas emissions by 2050.”
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Quantification of meteorological drought risks between 1.5°C and 4°C from global warming in six countries, Climate change (2022). DOI: 10.1007/s10584-022-03359-2
Quote: Rising global temperatures point to future widespread droughts (2022, September 27) retrieved September 27, 2022 from https://phys.org/news/2022-09-global-temperatures-future-widespread-droughts.html
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