Unlikely, extreme climate outcomes are still possible
Graham Lawton does well to point out that a civilisation-destroying climate catastrophe with warming of 4掳C to 5掳C, also known as the “business as usual” scenario, is no longer the most likely outcome, if indeed it ever was(14 January, p 28).
However, as he acknowledges, there is much uncertainty in our understanding of the climate system. Assessments say that, under current global policies, the most likely rise by 2100 . But that is only the midpoint of a range, with a roughly 5 per cent risk that the rise will .
If we get that much heating, it would still be hard to sustain an even partially prosperous and liberal civilisation. Faced with this all-too-plausible risk, the world needs to accelerate its efforts. As a noted climatologist once said: “Nobody would board an aircraft with a 5 per cent risk of crashing.”
Why a space sunshade isn't such a bright idea
There is a fundamental contradiction between two of Vaclav Smil’s innovations to save humanity. He calls for more efficient photosynthesis, while also suggesting the need for a planetary sunshade to control global warming(7 January, p 38).
However, such geoengineering wouldn’t only cool Earth, but also reduce the efficiency of photosynthesis at the global level. We are already destroying much of the photosynthetic capacity of the planet through deforestation, changes in land use and impacts on ocean phytoplankton. A tipping point where the energy captured by photosynthesis is no longer sufficient to support all life may be closer than we think.
New web may be a great opportunity for predators
There is nothing democratising about web3, which runs on the blockchain, the technology that underpins cryptocurrencies. It is about replacing control of the web by giant tech corporations with possible future control of it by criminals and feudal lords(21 January, p46).
And, as with cryptocurrencies, you would trade ownership of the web by giant amoral corporations, who are at least interested in minimising fraud, for ownership by a much wider base, possibly one that would include many amoral individuals who are only interested in obtaining your money by whatever means possible, criminal if necessary. If you think web 2.0 is unsafe, you have seen nothing yet.
Precedent for rethinking the pre-op fluid rule
Clare Wilson reports on challenges to the “nil by mouth” rule that patients shouldn’t consume liquids for 2 hours before surgery. It is surprising how entrenched medical practices can be!
However, she might like to know that, more than 30 years ago, women were allowed to drink and to suck sweets during labour, despite the increased acidity and resting volume of their stomach contents and the risk that they might require anaesthesia(21 January, p 27).
For general anaesthesia, they would routinely be given a in which the oesophagus would be compressed by pressure on the cricoid cartilage of the larynx to prevent reflux and lung contamination, and the trachea would be intubated to exclude any refluxed acid thereafter. This policy had been shown to be safe and effective.
If it looks like animal fun, then it probably is fun
Marlene Zuk warns against attributing feelings to non-human animals that are more commonly ascribed to us, saying it is stifling inquiry. It appears that the notion that any non-human might have fun is something of an anathema(14 January, p 27).
Just as we can’t know what goes on in a pre-verbal toddler’s head when they seem to be having fun, we can never understand what goes on in a non-human’s head when it appears to be doing the same. We can, however, identify behaviours consistent with fun. If it looks like fun and has any other necessary attributes of fun, chances are it is some sort of fun.
In defence of guidance for cutting Alzheimer's risk
We are concerned your coverage of Alzheimer’s Research UK’s Think Brain Health campaign will undermine a vital initiative to raise awareness of widely accepted modifiable dementia risk factors(28 January, p 19).
Your article is critical that evidence for dementia prevention comes chiefly from observational studies rather than randomised controlled trials (RCTs).
For many exposures associated with dementia, such as smoking, diet and air pollution, RCTs are either impossible, unethical or impractical. The implication that observational studies are intrinsically flawed also misunderstands high-quality medical evidence. Standards for observational studies of causation exist and have generally been followed when gauging dementia risk. Also, a review by Cochrane, a body that assesses health research quality, found “little evidence for significant effect estimate differences between observational studies and RCTs”.
Public health is about prevention using the best available evidence, which is what the Think Brain Health campaign aims to do.
Beyond experience and beyond imagination too
Your look at the limits of knowledge asks us to imagine a woman who has been brought up in a black, white and grey room, so that everything she sees is in monochrome. She studies colour in the abstract, then goes out to witness a polychromatic world. This is used to exemplify that some knowledge can only truly be gained by direct experience(14 January, p 42).
Now, think of all human knowledge as bounded by our experiences and our deductions from them. Is there stuff of some unknowable nature out there, which neither our experiences nor powers of abstract thought can ever hope to touch?
I repeat a question that I asked in your pages some years ago: could a life form deprived of sensations resulting from electromagnetic radiation discover the theory of relativity? We don’t know what sensations we are deprived of.