UN researchers are urging people to be less polite to artificial intelligences after a report found that cutting words from prompts could reduce ChatGPT’s energy consumption by up to 25 per cent.

Removing “please”, “thank you” and other unnecessary words from AI prompts could save 87 to 98 gigawatt-hours of electricity per year, the report from the UN University Institute for Water, Environment and Health (UNU-INWEH) found. That is the equivalent of the annual residential electricity use of up to 760,000 people in sub-Saharan Africa.

To reduce their energy consumption and carbon footprint, people should write concise prompts, avoid getting sucked into conversation loops and refrain from starting relationships with AI, the researchers said.

“We are not saying be rude to your AI. But don’t fall into the interaction trap and don’t go falling in love with it either,” says at UNU-INWEH.

The large language models behind AI chatbots process text in small units known as tokens. Madani says concise prompts can save energy because they can reduce both the number of tokens the model has to process and the number it generates in response. In some cases, shorter prompts may also simplify the task, further reducing the power required.

The UN study – one of the most comprehensive assessments of the environmental costs of AI to date – warns of rapidly increasing energy, land and water use due to the growing adoption of the technology.

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ChatGPT alone now processes around 2.5 billion queries every day and Google 16 billion, the majority of which have integrated AI summaries.

Tech companies disclose little information on their energy use, so the researchers used the available data for their data centres.

AI currently accounts for about 20 per cent of the energy used by data centres, but that share is projected to double to around 40 per cent in the next few years. By 2030, AI alone could consume around 378 terawatt-hours a year and data centres could use 945 TWh in total — almost 3 per cent of projected global electricity use.

The 9.3 trillion litres of water projected to be needed by data centres by 2030 is enough to meet the minimum annual domestic water needs of all 1.3 billion people in sub-Saharan Africa.

“You’re looking at something on a global scale that is being adopted faster than any other technology in the history of technology, so the energy use is increasing very rapidly,” says at UNU-INWEH.

The researchers said AI companies should be required to publish their energy consumption, while governments should introduce energy caps on companies and individuals, but it is also crucial to educate the public on how to use AI efficiently.

People should be encouraged to avoid using AI unnecessarily and, when they do use it, to cut words and use less powerful models, says Madani.

They should also be aware that generating an image uses 60 times more energy than a text query, enough to power a 10-watt LED bulb for about 17 minutes.

A complex video uses up to 8000 times more than text and could power the same bulb for about 1.7 days.

“We are not saying AI is bad,” says Madani. “We are just saying let’s use it in a proper way. It’s like a knife: you can save a patient’s life in the operating theatre, but you can also kill someone with it.”

Covid-19 seems to accelerate the ageing of blood vessels, but perhaps only among women.

The infection has previously been , like heart disease, but how it has this effect isn’t entirely clear. To learn more, at the UniversitĂ© Paris CitĂ© in France and her colleagues recruited 2390 people, aged 50 on average, from 16 countries – including the UK and US – between September 2020 and February 2022.

Some of them had tested positive for SARS-CoV-2, the virus that causes covid-19, or had antibodies against it despite not being vaccinated, a sign that they had been infected. The others had only ever tested negative for the virus and had no signs of prior infection.

The health of their arteries was assessed by measuring how fast a pressure wave passed between the carotid artery in their neck and the femoral arteries in their legs. This is a measure of artery stiffness, which increases naturally with age, with less flexible arteries raising the risk of heart disease.

The researchers found that among the women in the study, a known SARS-CoV-2 infection was linked to stiffer arteries. This also seemed to increase alongside the severity of their infection. For instance, women who were hospitalised with covid-19 had a vascular age that was around five years older than their uninfected counterparts, rising to 7.5 years among those admitted to intensive care.

The researchers controlled for other factors that can influence artery stiffness, like smoking and obesity.

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But none of these effects occurred among the men. Previous research suggests that and are , which could lead to damaging inflammation. Bruno says she was expecting to see some difference between the sexes, but not this much.

The findings could also shed some light on long covid, which . At a six-month follow-up, the stiffness of the women’s arteries had improved slightly, but was still particularly high among those with lingering covid-19-related complications. “Here we have demonstrated there is something measurable in the blood vessels that corresponds to the symptoms of long-covid patients,” says Bruno.

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It’s possible that some of the people in the uninfected group may have unknowingly had a mild infection, affecting the validity of the results.

Nevertheless, at the University of East Anglia in the UK says the study is robust and could help identify people with long covid. “The study is the first large international multicentre investigation to demonstrate that covid-19 is associated with accelerated vascular ageing,” he says. “The findings may also contribute to a better mechanistic understanding of post covid-19 syndrome, potentially paving the way for targeted pharmacological interventions.”

The amount of tropical forest lost in 2024 was double that in 2023 and the highest in at least two decades as climate change made rainforests susceptible to uncontrollable fires.

A record 67,000 square kilometres of primary rainforest was lost from the tropics in 2024, according to an annual assessment of satellite imagery by Global Forest Watch and the University of Maryland. Primary forest refers to mature forest that has never been disturbed by logging.

The report’s authors attributed the surge in forest loss to the El Niño weather phenomenon and the warming global climate, which made the rainforest a tinderbox.

“We are in a new phase where it’s not just clearing for agriculture that’s the main driver [of forest loss],” says at Global Forest Watch, an initiative of the World Resources Institute. “Now we have this new amplifying effect, which is the real climate change feedback loop, where fires are much more intense and ferocious than they have ever been.”

Tropical forests regulate weather systems and store carbon, cooling the planet, but in recent years deforestation has brought them to a tipping point at which they sometimes emit more carbon than they absorb, creating a feedback loop.

Five times more primary forest was lost from fires in the tropics in 2024 than in 2023, accounting for 48 per cent of all primary rainforest loss, the report found.

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Globally, fires caused greenhouse gas emissions equivalent to 4.1 gigatonnes of carbon dioxide last year, more than four times the amount from air travel in 2023.

El Niño events are associated with warmer and drier weather in tropical regions. Although El Niño officially subsided in April 2024, its effects continued to be felt as rainforest soils and vegetation remained dried out from scorching temperatures and previous wildfires.

The world’s warming climate also played a role, with 2024 the hottest year on record and Brazil’s driest in seven decades, says at the Amazon Environmental Research Institute in BelĂ©m, Brazil.

Brazil lost 28,000 kmÂČ of primary forest – its highest figure since 2016 – accounting for 42 per cent of all tropical primary forest loss.

In the Brazilian Amazon, fires accounted for 60 per cent of forest loss, as people exploited dry conditions to clear land for agriculture.

There were also massive wildfires outside the tropics in countries such as Canada and Russia. Globally, the area of forest lost was 300,000 kmÂČ, another new record.

“Some scientists say we’re not in the Anthropocene but the Pyrocene – the age of fire – and I think this report shows that,” says at the University of Oxford.

While forest fires are concerning, Berenguer cautions that the figures may include degradation, where some of the tree canopy is lost, and this should not be conflated with deforestation, where forest is cleared entirely.

“Degradation reduces carbon storage [and] biodiversity and increases vulnerability to future fires, but it’s not the same as transforming land into a soy field or pasture,” she says.

The report shows how successive years of degradation and the warming climate have made the rainforest fragile, says Alencar.

“Usually with fires in the Amazon, you see degradation, but the forest can recover,” she says. “However, this report shows that when you have a very strong drought it creates the perfect conditions for the forest to burn intensely and you reach a point where the forest is lost entirely.”