Since the turn of this century, the US south-west has spent more than a decade in drought. Last year was the warmest on record in California, which is in the middle of its driest spell for more than 400 years. But according to a new scientific study, that’s nothing compared to what comes next.
In the paper, published by the journal Science Advances, researchers from Nasa and Columbia and Cornell universities warn that a vast swathe of the US, including the south-west states and the central plains, should prepare for “unprecedented drought conditions” unlike anything in the past 1,000 years.
Within 35 years, the region’s millennia-long natural cycle of droughts and occasional rainfall is likely to bring an end to the relative dampness of the last century. The effects of that drying, the scientists warn, would be exacerbated by man-made climate change.
“Nearly every year is going to be dry toward the end of the 21st century, compared with what we think of as normal conditions now,” said Ben Cook from Nasa’s Goddard Institute for Space Studies, the lead author of the study. “We’re going to have to think about a much drier future in western North America.”
The long-term dry conditions could devastate the region’s agricultural capability, decimating both crops and cattle herds, and sending some food prices sky-rocketing. It would directly affect more than 60 million people from San Diego to San Antonio and from Oakland to Omaha, who depend on increasingly scant water resources and on infrastructure designed during an abnormally moist 20th century.
The scientists said the effects of a mega-drought, which would be especially pronounced in desert cities such as Las Vegas and Phoenix, should be considered a slow-motion natural disaster, of a piece with earthquakes or hurricanes.
Data discovered in tree rings shows that between the ninth and the 14th centuries, the region also endured lengthy periods of intense drought, an era referred to by paleoclimatologists as the “Medieval Climate Anomaly”, which is believed to have hastened the demise of some early civilisations. But decades of dry conditions, beginning in about 2050, could be even worse, the study predicts.
Dr Jason Smerdon, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory and co-author of the study, said: “We are the first to do this kind of quantitative comparison between the projections and the distant past, and the story is a bit bleak. Even when selecting for the worst mega-drought dominated period, the 21st century projections make the [previous] mega-droughts seem like quaint walks through the Garden of Eden.”
A mega-drought would lead to major water shortages, which would cause vegetation to dry up, bringing about regular, massive wildfires in Arizona and California. But while the drought in California and its neighbouring states has grabbed recent headlines, the study suggests a far larger area would be hit, encompassing all, or parts, of Nevada, Utah, Colorado, New Mexico, Texas, Oklahoma, Kansas, Nebraska, South Dakota, Iowa, Minnesota, Missouri, Arkansas and Louisiana.
In pictures: Changing climate around the world
In pictures: Changing climate around the world
Calved icebergs from the nearby Twin Glaciers are seen floating on the water in Qaqortoq, Greenland
Oroumieh, one of the biggest saltwater lakes on Earth, has shrunk more than 80 percent to 1,000 square kilometers in the past decade. It shrinks mainly because of climate change, expanded irrigation for surrounding farms and the damming of rivers that feed the body of water
A boat navigates among calved icebergs from the nearby Twin Glaciers in Qaqortoq, Greenland. Boats are a crucial mode of transportation in the country that has few roads. As cities like Miami, New York and other vulnerable spots around the world strategize about how to respond to climate change, many Greenlanders simply do what theyve always done: adapt. 'Were used to change, said Greenlander Pilu Neilsen. 'We learn to adapt to whatever comes. If all the glaciers melt, well just get more land
The Svalbard Global Seed Vault is seen after being inaugurated in Longyearbyen, Norway. The 'doomsday' seed vault built to protect millions of food crops from climate change, wars and natural disasters opened deep within an Arctic mountain in the remote Norwegian archipelago of Svalbard
A technician preparing to drain a vast underground lake at the Tete Rousse glacier on the Mont Blanc Alpine mountain, to avert a potentially disatrous flood. Some 65,000 cubic metres (2.3 million cubic feet) of water have gathered in a cavity, dangerously raising the pressure beneath the mountain, a favourite spot for holiday makers in Saint-Gervais-les-Bains
Cracked mud is picture at sunrise in the dried shores of Lake Gruyere affected by continuous drought near the western Switzerland village of Avry-devant-Pont. A leading climate scientist warned that Europe should take action over increasing drought and floods, stressing that some climate change trends were clear despite variations in predictions
Cattle graze on grassland that remains dry and brown at the height of the rainy season in south of Bakersfield, California. Its third straight year of unprecedented drought, California is experiencing its driest year on record, dating back 119 years, and dating back as far as 500 years, according to some scientists who study tree rings
An aerial view shows tents of flood-displaced people surrounded by water in southern Sehwan town. United Nations Framework Convention on Climate Change (UNFCCC) executive secretary Christiana Figueres met with people displaced by last year's devastating floods. Catastrophic monsoon rains that swept through the country in 2010 and affected some 20 million people, destroyed 1.7 million homes and damaged 5.4 million acres of arable land
An aerial view of flooding in North Wagga Wagga. Climate change is amplifying risks from drought, floods, storm and rising seas, threatening all countries but small island states, poor nations and arid regions in particular, UN experts warned
Damages caused by a landslide on the Pan-American highway near La Moramulca, 55 Km south of Tegucigalpa. International highways have been washed out, villages isolated and thousands of families have lost homes and crops in a region that the United Nations has classified as one of the most affected by climate change
A resident sprays water on a peatland fire in Pekanbaru district in Riau province on Indonesia's Sumatra island. Indonesia, an archipelago of 17,000 islands, is one of the world's biggest carbon emitters because of rampant deforestation. US Secretary of State John Kerry Sunday issued a clarion call for nations to do to more to combat climate change, calling it 'the world's largest weapon of mass destruction'
An excavator clearing a peatland forest area for a palm oil plantations in Trumon subdistrict, Aceh province, on Indonesia's Sumatra island. As Southeast Asia's largest economy grows rapidly, swathes of biodiverse forests across the archipelago of 17,000 islands have been cleared to make way for paper and palm oil plantations, as well as for mining and agriculture. The destruction has ravaged biodiversity, placing animals such as orangutans and Sumatran tigers in danger of extinction, while also leading to the release of vast amounts of climate change-causing carbon dioxide
Stagnant rain water with tannery waste make the Hazaribagh area in Old Dhaka as well as Buriganga River the most polluted. Each year during the seven-month long dry season between October and April the Buriganga River becomes totally stagnant with its upstream region drying up and becoming polluted from toxic waste from city industries
Waste water from Dhaka city drained to the River Buriganga contributes to its pollutions. On the World Water Day observed in 2007 under the theme Coping with Water Scarcity, under the leadership of the Food and Agriculture Organization of the United Nations, DrikNEWS explores some of the images of the river. UN-Water has identified coping with water scarcity as part of the strategic issues and priorities requiring joint UN action. The theme highlights the significance of cooperation and importance of an integrated approach to water resource management of water at international, national and local levels
Heavy smog has been lingering in northern and eastern parts of China, disturbing the traffic, worsening air pollution and forcing the closure of schools. China's Environment Ministry said it will send inspection teams to provinces and cities most seriously affected by smog to ensure rules on fighting air pollution are being enforced
According to the study, there is a greater than 80 per cent chance of a mega-drought of 35 years or longer occurring in the US this century, unless swift and aggressive action is taken to alleviate the speed and impact of climate change, which would lower the risk. The authors said their research differed from other recent reports in its level of certainty about future droughts because they had taken into account the rise in carbon emissions.
Their conclusions were based on the rate of rising emissions and on complex climate simulations produced by 17 different computer models, which all broadly agreed on the results. The natural cycle, they found, would probably bring far less rain and snowfall to the region than in recent decades. But rising temperatures would also speed evaporation, shrinking the annual snowpack and parching soil.
This time last year, the President Barack Obama’s administration announced a $200m (£130m) drought aid package for California. But that will be of little use in combating the effects of a decades-long regional drought. “These mega-droughts during the 1100s and 1200s persisted for 20, 30, 40, 50 years at a time, and they were droughts that no one in US history has ever experienced,” Dr Cook said.
“The droughts people do know about, like the 1930s ‘dustbowl’ or the 1950s drought or even the ongoing drought in California and the south-west today – these are all naturally occurring droughts that are expected to last only a few years or perhaps a decade. Imagine instead the current California drought going on for another 20 years.”
Cook and Smerdon’s co-author Toby Ault, from the Department of Earth and Atmospheric Sciences at Cornell, said climate change increased the likelihood of a mega-drought “considerably”. Presenting the findings to reporters during the annual American Association for the Advancement of Science (AAAS) conference in San Jose, California, he said: “We’re not necessarily locked into these high levels of mega-drought risk, if we take actions to slow the effects of rising greenhouse gases on global temperatures.”