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Good morning, I’m Tim Walker with today’s essential stories. The briefing is taking a short summer break next week, but will return to your inbox on 12 August.

US retailers line up against administration’s new China tariffs

The global markets have taken a tumble after Donald Trump unexpectedly announced on Thursday a fresh escalation in his administration’s trade war with China, threatening to slap tariffs on a further $300bn of Chinese goods in September. Wall Street falls late on Thursday were followed by a sharp drop in Asian share prices on Friday morning, while retailers warned that the president’s “flawed strategy” was already acting as a drag on economic growth.

Broken promises. Trump said on Twitter that the new tariffs were a response to China reneging on several of its promises, which he had previously touted as progress in negotiations between the two economic superpowers.

Heatwaves drive near-record ice melt in northern hemisphere

Facebook Twitter Pinterest An iceberg floats near the seashore of King’s Point in Newfoundland, Canada. Photograph: Johannes Eisele/AFP/Getty Images

The biggest ice sheet in the northern hemisphere is likely to have shrunk more in the past month than in an entire average year, as a series of summer heatwaves have sparked forest fires in Siberia and sent glaciers into retreat across Europe. Greenland’s ice sheet is second only to Antarctica in size; in July, say experts, it shed the equivalent of 80m Olympic swimming pools in surface ice.

Melt season. With more than a month of the melt season still to go, 2019 is already one of the top 10 years for ice loss in Greenland, although the extent of the melt is considered unlikely to beat the record set in 2012.

17m Americans purged from voter rolls since 2016

Facebook Twitter Pinterest Voting rights advocates rally outside the US Supreme Court in 2018. Photograph: Michael Reynolds/EPA

A 2013 supreme court decision that freed counties with histories of voter discrimination from federal oversight has led to an alarmingly rapid purge of voter rolls, according to a study by the Brennan Center for Justice. At least 17 million voters were struck from the rolls nationwide between 2016 and 2018, the study found: a number similar to the previous two-year period. Yet election jurisdictions with a record of egregious voter discrimination have been purging their rolls at a rate 40% higher than the national average.

Voting Rights Act. The supreme court’s Shelby County v Holder ruling in 2013 released historically discriminatory counties from the federal oversight that had previously been enshrined by the 1965 Voting Rights Act.

Will Hurd, lone black House Republican, to retire in 2020

Facebook Twitter Pinterest Hurd has represented Texas’s 23rd district in Congress since 2015. Photograph: Eric Gay/AP

Congressman Will Hurd, the only black House Republican and one of the party’s rare remaining Trump critics, has announced he will not seek re-election to his Texas seat in 2020. Hurd is one of many Republicans to have announced his retirement in recent weeks, and his departure deals a blow to the GOP – and not merely by diminishing its diversity. The former CIA officer only just clung to his seat at last year’s midterms, making it a key target for Democrats in 2020.

House resolution. Hurd was one of just four Republicans to vote for a House resolution condemning Trump’s suggestion that the four congresswomen known as The Squad should “go back” to their home countries. Three of the four were born in the US.

Ilhan Omar. The fourth, Ilhan Omar, was born in Somalia. On Thursday, she posted a photograph on Instagram of herself with Speaker Nancy Pelosi on a congressional trip to Ghana, another African country, with the caption: “She went back with me.”

Crib sheet

Robert F Kennedy ’s granddaughter, Saiorse Kennedy Hill, has died aged 22, her family announced on Thursday. Hill was the daughter of Robert and Ethel Kennedy’s fifth child, Courtney, and Paul Hill, who was falsely convicted of a 1974 IRA bombing.

Scientists at the Washington University School of Medicine in St Louis say they have developed a blood test that predicts the onset of Alzheimer’s up to 20 years before the disease’s debilitating symptoms become apparent.

The US defense department is reviewing the bid process for the military’s $10bn cloud-computing contract, after Trump echoed criticisms from competitors that the process is potentially biased towards Amazon.

Shin Ok-ju, the founder of the South Korean Grace Road Church cult, who persuaded 400 of her followers to decamp to Fiji, where she held them captive and subjected them to violent beatings, has been sentenced to six years in jail.

Must-reads

Facebook Twitter Pinterest Climate activists remove a portrait of President Macron from a French government building. Photograph: Clement Tissot

The climate change protesters taking down Macron (literally)

French climate change protesters are taking an unusual but eye-catching approach to civil disobedience: removing framed portraits of President Macron from more than 100 town halls the length and breadth of the country. Angelique Chrisafis reports from Paris.

How we became suckers for self-optimisation

Today’s “ideal woman” uses Instagram to flaunt an optimised lifestyle of athleisure and kale to which her peers are compelled to aspire. In this essay from her new collection, Trick Mirror, Jia Tolentino says “the psychological parasite of the ideal woman has evolved to survive in an ecosystem that pretends to resist her.”

My unexpected life as a private detective

Emmanuelle Welch was working as a journalist when a magazine asked her to track down several people it had written about years earlier. The experience inspired her to “get better at finding people”. Now she’s a private investigator, whose cases include embezzlers, drug mules – and even the occasional lost teddy bear.

Trump campaign targets Latinx voters in Florida

Donald Trump may have routinely disparaged Hispanic immigrants, but his campaign team believes conservative Latinx voters in Florida could hold the key to his re-election in 2020. And Democrats fear they may be right, as Sabrina Siddiqui discovers.

Opinion

This week’s televised debates have still not provided a solution to the Democrats’ biggest dilemma, says Geoffrey Kabaservice: do they win by swinging left, or by clinging to the moderate centre?

The moderates, by and large, are concerned not only with practicality but also with restoring the sense of national unity shredded by Trump, while the progressives call for fighting fire with fire.

Sport

Thirty horses have been fatally injured at California’s Santa Anita racetrack in the past six months alone, a death toll that leaves US horse racing in crisis, and gives its critics a case for banning the sport altogether, as Daniel Ross reports from Los Angeles.

Arsenal have completed the signing of Ivory Coast international Nicolas Pépé from Lille, for a club-record fee of €80m ($89m). The 24-year-old scored 22 goals in the French league last season.

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