27 May, 2025

Martha Henriques This week, we look back 50 years to the Soviet Union's grand plan to reverse Siberia's rivers. It was a mega-engineering project that could have changed the face of the USSR's agriculture – and transformed the local climate in unpredictable ways, as Howard Amos writes. Plus, how taking pictures of the weather can boost your mood.

CLIMATE CONVERSATION The nuclear plan to reverse Siberia's rivers Nuclear Lake today is an ostensibly calm and peaceful place. Credit: Andrei Fadeev In what many Soviet leaders saw as a lamentable accident of Russia's geography, many of Siberia's major rivers flow north, emptying into the Arctic Ocean. Meanwhile, to the south of the USSR, the productive crop-growing regions were growing increasingly parched. ‌ In the 1970s, an old idea to reverse the flow of these rivers was put to the test. Using three nuclear devices, each as powerful as the bomb that detonated over Hiroshima in 1945, the USSR sought to begin construction of a canal to divert water from the Pechora River onto a southerly path instead. ‌ Despite the force of these explosions, the crater they formed wasn't big enough. Today, Nuclear Lake is an ostensibly peaceful spot, with only a few rusty signs warning of radiation levels revealing its dramatic origins.  ‌ To discover how the USSR tried and failed to reverse Siberia's rivers, click the button below – and find out why the idea has never fully gone away. Read more

THE BIG PICTURE Warmer waters lead to 'Shrinking Nemo' When the water gets hot, clownfish shrink. Credit: Getty Images As ocean temperatures rise, some fish are responding by getting smaller. Clownfish, popularised by the film Finding Nemo, were seen to shrink in 2023 when waters heated up. "It's not just them going on a diet and losing lots of weight, but they're actively changing their size and making themselves into a smaller individual that needs less food and is more efficient with oxygen," Theresa Rueger, senior lecturer in tropical marine sciences at Newcastle University, UK, told the BBC's Victoria Gill. See more pictures

CLIMATE QUIZ On the Calf of Man, a hard-to-access island in the Irish Sea, a bird once preyed upon by invasive rats has seen its numbers bounce back. Which bird is it? A. Puffin B. Golden eagle C. Manx shearwater Scroll to the bottom of this newsletter for the answer.

MORE CLIMATE FROM THE BBC Hurricane forecasters fear cuts in a busy season An above-average number of storms is expected this Atlantic hurricane season, as cuts affecting US research begin to bite.   Keep reading >‌ Tropical forests destroyed at fastest rate last year The world's tropical forests, which provide a crucial buffer against climate change, disappeared faster than ever last year.   Keep reading >‌ The search to stay cool without refrigerants Can we find ways to keep cool using fewer polluting refrigerant compounds – or without any refrigerants at all?   Keep reading >‌

And finally... Ten years since its inception, the online weather photography group BBC Weather Watchers has posted more than seven million photographs. A survey of the 355,000-strong group found participation came with a number of benefits. Some members said it helped with depression, grief, fitness and a new sense of purpose and pride in life, as Sabitha Prasher writes for BBC Weather. This group focuses on the UK, Isle of Man and Channel Islands, but taking part in your local group may come with its own benefits – from spending time outside to connecting with nature.