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Scientists predicting unprecedented drought

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22 April 2020

Today is Earth Day. The event began on this day in 1970 when 20 million Americans – said to be some 10% of the population at that time – took to the streets across hundreds of US cities to protest about environmental issues and demand action on them. This event is credited with launching the modern environmental movement. The theme for Earth Day 2020 is Climate Action.

Muriel Cozier

According to research carried out by scientists from the Earth Institute at Columbia University, US, a ‘climate driven mega-drought is emerging in the western United States and northern Mexico.’

The area has been suffering with an ever lengthening string of dry years since 2000 which researchers say may be pushing the region toward an extreme long-term drought ‘worse than any in recorded history.’

Publishing the findings in the journal Science the researchers assert ‘A mega-drought as bad or worse than anything even from known prehistory is very likely in progress and [the] warming climate is playing a key role.’ The study is based on modern weather observations, 1200 years of tree-ring data and many climate models. 

The study’s lead author Park Williams, bio-climatologist at Columbia University’s Lamont-Doherty Earth Observatory said ‘Earlier studies were largely model projections of the future. We’re no longer looking at projections, but at where we are now. We now have enough observations of current drought and tree-ring records to say that we’re on the same trajectory as the worst prehistoric droughts.’

The researchers say that reliable modern observations date only to about 1900, but tree rings have allowed scientists to infer yearly soil moisture for centuries. The new study is said to be the ‘most up-to-date and comprehensive long-term analysis. It covers an area stretching across nine US states…’

The researchers add that half the pace of the drought and its severity can be attributed to rising temperatures. If the overall warming were to be subtracted from the equation the current drought would rank as the 11th worst detected. So it would be bad, but nowhere near what it has developed into, the research team asserted. 

Angeline Pendergrass, a staff scientist at the US National Center for Atmospheric Research commented ‘It’s too early to say whether the region is on the cusp of a true mega-drought, because the study confirms that natural weather swings are still playing a strong role. That said even though strong natural variability will always play a large role in drought, climate change makes it worse.’ 

It was noted that the 20th century was the wettest century in the entire 1200-year record. ‘The 20th century gave us an overly optimistic view of how much water is potentially available,’ the researchers commented.

Science DOI:10.1126/science.aaz9600

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