Droughts lasting more than two years will become the norm... even if the 1.5C warming limit is met, according to new research. Rising temperatures point to rain shortages across the planet - affecting plants and animals in both hot and mild climates.
Project head Professor Rachel Warren at the University of East Anglia said: "Not only does the area exposed to drought increase with global warming, but it also increases the length of the droughts. "In Brazil, China, Ethiopia, and Ghana droughts of longer than two years are projected to occur even in a 1.5C warming scenario."
A modest hike of 1.5C - the Paris Agreement's goal - will spell serious consequences in India, China, Ethiopia, Ghana, Brazil and Egypt. The six countries were selected for study as they provide a range of contrasting sizes and different levels of development.
They span tropical and temperate biomes on three continents and contain forest, grassland and desert habitats. Droughts will be more frequent and longer-lasting - posing significant risks to people and ecosystems around the world.
The research team estimated impacts of alternative levels of global warming upon their probability and length. In a 2C warming scenario, the length of droughts predicted in all countries except India are projected to exceed three years.
In a 3C warming scenario, droughts are projected to approach four to five years in length. In a 4C warming scenario, severe droughts of longer than five years are projected for Brazil and China.
Also, the percentage of land exposed to a severe drought of longer than 12 months in a 30-year period is expected to increase rapidly by the 1.5C warming scenario in Brazil, China and Egypt, and in areas of permanent snow and ice in India. India and China both have large areas currently under 'permanent' ice and snow cover.
But, in the 3C warming scenario, 90 per cent of these areas are projected to face severe droughts lasting longer than a year in a 30-year period. These areas form the headwaters of many major river systems, and thus the water supply for millions of people downstream.
Increasing probability and duration of severe drought points to potential declines 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. All six of the countries will need to deal with water stress in the agricultural sector, potentially through shifting crop varieties or through irrigation, if water is available.
The amount of adaptation required 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 headwater sources.
Prof Warren said: "Meeting the Paris Accords could have major benefits in terms of reducing severe drought risk in these six countries, in all major land cover classes and for large percentages of the population worldwide. “This requires urgent global scale action now to stop deforestation, including in the Amazon, in this decade, and to decarbonise the energy system in this decade, so we can reach global net zero greenhouse gas emissions by 2050."
In the 1.5C warming scenario, the model found droughts will triple in Brazil and China, nearly double in Ethiopia and Ghana, increase slightly in India, and substantially increase in Egypt. In a 2C warming scenario, they quadruple in Brazil and China, double in Ethiopia and Ghana, nearly double in India and reach greater than 90 per cent probability in Egypt.
In a 3C warming scenario, the probability of drought projected to be in Brazil and China is 30-40 per cent; 20-23 per cent in Ethiopia and Ghana; 14 per cent in India but nearly 100 per cent in Egypt. Finally in a 4C warming scenario, the probability of drought projected in Brazil and China is nearly 50 per cent; 27-30 per cent in Ethiopia and Ghana; nearly 20 per cent in India; and 100 per cent in Egypt.
Lead author Prof Jeff Price said: "Current pledges for climate change mitigation, which are projected to still result in global warming levels of 3C or more, would impact all the countries in this study. "For example, with 3C warming, more than 50 per cent of the agricultural area in each country is projected to be exposed to severe droughts lasting longer than one year in a 30 year period.
"Using standard population projections, it is estimated that 80 per cent to 100 per cent of the population in Brazil, China, Egypt, Ethiopia and Ghana, and nearly 50 per cent of the population of India, are projected to be exposed to a severe drought lasting one year or longer in a 30 year period.
"In contrast, we find meeting the long term temperature goal of the Paris Agreement, that is limiting warming to 1.5C above pre industrial levels, is projected to greatly benefit all of the countries in this study, greatly reducing exposure to severe drought for large percentages of the population and in all major land cover classes, with Egypt potentially benefiting the most."
In most countries, the projected increase in drought probability increases approximately linearly with increasing temperature. The exception is Egypt, where even slight amounts of global warming potentially lead to large increases in drought probability.
The study is published in the journal Climatic Change.
