Rising global temperatures indicate generalization

More frequent and longer-lasting droughts caused by rising global temperatures pose significant risks to people and ecosystems around the world, according to a new study from the University of East Anglia (UEA).

The study 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 sizes and different levels of development across three continents spanning tropical and temperate biomes, and contain forests, grasslands and desert habitats.

The results, “Quantification of meteorological drought risks between 1.5°C and 4°C of global warming in six countries”, are published today in the journal Climate change.

The paper, led by Dr Jeff Price and colleagues at UEA’s Tyndall Center for Climate Change Research, quantified the projected impacts of alternative levels of global warming on the likelihood and duration of severe drought in the six country.

Dr Price, Associate Professor of Biodiversity and Climate Change, said: “Current promises of climate change mitigation, which are still expected to result in levels of global warming of 3°C or more, would impact all countries. of this study.

“For example, with a warming of 3°C, more than 50% of the agricultural area of ​​each country is expected to be exposed to severe droughts for more than one year in a 30-year period.

“Using standard population projections, it is estimated that 80-100% of the population of Brazil, China, Egypt, Ethiopia and Ghana (and almost 50% of the population of India ) are expected to be exposed to a severe drought that lasts a year or more over a 30-year period.

“In contrast, we find that achieving the long-term temperature goal of the Paris Agreement, which limits warming to 1.5°C above pre-industrial levels, stands to greatly benefit all countries from this study, significantly reducing exposure to severe drought for large percentages of the population and across all major land cover classes, with Egypt potentially the most beneficiary.

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; reach more than 90% probability in Egypt; and almost double in India.

In a 3°C warming scenario, the projected probability of drought in Brazil and China is 30-40%; 20-23% in Ethiopia and Ghana; 14% in India but nearly 100% in Egypt.

Finally, in a 4°C warming scenario, the projected probability of drought in Brazil and China is nearly 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 approximately linearly with increasing temperature. The exception is Egypt, where even small amounts of global warming can lead to large increases in the likelihood of drought.

Professor Rachel Warren, head of the global study of which this paper is one of the results, said: “Not only is the area prone to drought increasing with global warming, but it is also increasing the duration of droughts.

“In Brazil, China, Ethiopia and Ghana, droughts longer than two years are expected to occur even under a 1.5°C warming scenario.

Under a 2°C warming scenario, the duration of projected droughts in all countries (except India) is expected to exceed three years. Under a 3°C warming scenario, droughts are projected to last about 4-5 years and under a 4°C warming scenario, severe droughts lasting more than five years are projected for Brazil and China, severe drought being the new reference condition.

In addition, the percentage of land that is projected to be exposed to severe drought lasting more than 12 months over a 30-year period is projected to increase rapidly under the 1.5°C warming scenario in Brazil, China and in Egypt, and in areas with permanent snow. and ice cream in India.

India and China both have large areas currently under ‘permanent’ ice and snow cover. However, under the 3°C warming scenario, 90% of these areas are expected to experience severe droughts lasting more than one year over a 30-year period.

These areas form the headwaters of many major river systems, and thus the water supply for millions of people downstream. The increased likelihood and duration of severe drought indicates a potential decline 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 the six countries will have to deal with water stress in the agricultural sector, potentially by changing crop varieties or by irrigation, if water is available. The amount of adaptation needed to cope with this increase in drought therefore 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 fare better, depending on competition for water resources and upstream sources.

Professor Warren said: “Compliance with the Paris Agreements could have major benefits in terms of reducing the risk of severe drought in these six countries, in all major land cover classes and for large percentages of the world’s population.

“This requires urgent global action now to stop deforestation (including in the Amazon) in this decade and to decarbonize the energy system in this decade, so that we can achieve net zero global gas emissions. greenhouse effect by 2050.

“Quantification of meteorological drought risks between 1.5°C and 4°C of global warming in six countries”, was published in Climate change September 28, 2022. DOI: 10.1007/s10584-022-03359-2

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