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UK energy firm Drax wants to build the world's first carbon-negative power station by burning wood and storing the carbon dioxide that is produced ( 5 June, p 13 ). But CO 2 isn't the only byproduct of burning wood, a whole list of carcinogenic and other harmful substances is also produced. Surely it would …

The proposals proclaiming Drax power station as potentially "carbon negative" seem to fall short in my view. Even if Drax's carbon emissions can be tackled using carbon capture and storage (CCS), there is no merit in fuelling the station by chopping down trees in North America and shipping the wood pellets made there to the …

You raise questions about the effectiveness of the global fossil fuel divestment movement ( 5 June, p 40 ). By making a public commitment to divest from fossil fuels, institutions like universities and pension funds can send a powerful signal to the world's governments, helping to pave the way for the legislation and international agreements …

Regarding an unexpected spike in methane emissions, I wanted to add another possibility: small but continuous leaks from domestic gas pipes ( 22 May, p 16 ). This could be due to deteriorating seals or pipes in the vast buried network of pipes, maybe due to a network's age. It is possible that small leaks …

An avalanche of 27 million cubic metres was blamed for the deadly 2021 flood that struck Uttarakhand, India ( 19 June, p 21) . In our report on the UK's first long covid clinic ( 26 June, p 14 ), we should have said that Rachel Lommerzheim is an occupational therapist and Maddison Rigg is …

I read with interest your article on long covid – how some people may take a long time to recover after a coronavirus infection 26 June, p 10 . I wonder whether similar things may happen with covid-19 vaccination. When I had my second shot of the Pfizer/BioNTech vaccine two months ago, I was really …

Your article covered much-needed information about the causes of long covid and its similarities with chronic fatigue syndrome. However, it is a pity that the discussion wasn't broadened to other comparable conditions, such as functional neurological disorder and conversion disorder . The similarities of these to long covid have been reviewed in recent medical publications. …

Daniel Kahneman and Olivier Sibony give a lucid account of variability, or noise, in expert judgements, including a definition of what constitutes such a decision ( 19 June, p 40 ). In essence, any choice that can't be reduced to an algorithm can be classed as an expert judgement. Until about 10 years ago, so-called …

Regarding the story "Cosmic collisions may push huge black holes off kilter", what would happen if and when two galaxies merged and their supermassive black holes collided? Maybe it would generate an explosion that would be the largest since the big bang ( 12 June, p 18 ). Both galaxies would surely be ripped apart. …

I would fully endorse Paul Gulliver's sentiments about the climate-harming pollution of space tourism, but I wonder how the principle of not "generating greenhouse gases for amusement" might be extended and, if this were done, how we should rank the pastimes involved ( Letters, 12 June ). For example, would Formula 1 and other big …