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You point out that electricity shortages will probably develop during peak periods in areas of North America, in part due to the lack of new transmission lines to connect new sources of renewable power to population centres. There are similar concerns in Australia ( 6 January, p 13 ). However, little has been written about …

Cheaper goods in local shops, and so on, is only tinkering at the edges of the problem of excessive car use. Modern urban areas are designed, and modern life is run, with the expectation of access to motor vehicles. Perhaps motorists should pay the real costs of having a car (building infrastructure and the environmental …

Your article got me thinking about indirect contributors to the Mediterranean diet's healthful properties ( 13 January, p 32 ). Specifically, with large amounts of fresh and unprocessed foods, how many more beneficial microorganisms are supported? We are learning of the importance of our intestinal microbiome: has anyone yet compared that of long-lived Mediterraneans with …

It seems that the Mediterranean diet as described manages to minimise added sugars. No desserts, no sugary breakfast cereals, no sweets or cakes or pastries. And no fruit smoothies, sugary soft drinks or sugary, ultra-processed food. I assume sugary treats are allowed on occasional celebration days. Could this be the simple reason why the diet …

Common descriptions of a healthy Mediterranean diet don't reflect typical diets in much of the region today. For example, a reliance on whole grains better matches German and Danish diets. What's more, deaths from cardiovascular disease don't support an obvious correlation with better health . Portugal, Italy, Greece and Cyprus all have higher rates than …

You report the supposed 5 per cent chance that artificial intelligence will make us extinct, according to a survey of AI experts. Asking only such people about the consequences of AI is analogous to asking only Manhattan Project scientists about the consequences of developing atom bombs ( 13 January, p 16 ). Predicting the broader …

From Letters, 13 January

Tony Green suggests that, billions of years from now, only the mega-rich will be able to afford to decamp to the moons of the gas giants to avoid the sun's expansion, while the rest of us plebs are left behind. I think he is taking too pessimistic a view about the survival of economic systems …

It is evident that the shortage of qualified mathematics and science teachers in many countries must be addressed, or the next generation of scientists, particularly researchers, may be lost. A combination of online and live teaching is the best solution when qualified and inspirational high-school teachers are in such short supply. Perhaps the best teachers …

The possibility of North American electricity shortages, partly as the rollout of renewables fails to keep pace with demand, highlights what is probably the biggest stumbling block to a zero-carbon future. It is clear we have very little chance of replacing every fossil joule with a renewable joule. Therefore, we have no choice but to …