Scientists

Targeted marine cloud bleaching is a proposed geoengineering method to increase the amount of light reflected by clouds and reduce the heat reaching Earth. A US team has taken advantage of a natural experiment that generated this effect—through aerosols produced by the massive Australian bushfires of 2019 and 2020—to study the possibilities and risks of using it to modify an extreme weather event like El Niño. According to the models used in the study, its early application could weaken El Niño, but it could also have unintended consequences, such as altering the timing and increasing the magnitude of the subsequent La Niña event. The work is published in Science Advances.

Rising sea temperatures are promoting the spread of Vibrio vulnificus, the marine bacterium nicknamed the “carnivore,” which can cause serious infections. Last summer, the European Center for Disease Prevention and Control (ECDC) warned of an increased risk during the summer months, especially in the Baltic Sea. This bacterium has also been identified along the Spanish coast, but experts explain that swimming in the Mediterranean is safe for the general public, as the bacterium thrives in waters with lower salinity. Even so, they recommend that vulnerable individuals remain vigilant and avoid swimming if they have open wounds.

A Spanish study rules out men’s lifestyle habits as an explanation for geographical differences in semen quality. The findings, presented at the annual congress of the European Society of Human Reproduction and Embryology (ESHRE), the abstract of which is to be published today in the journal Human Reproduction, are based on data from 386 men who attended seven assisted reproduction centres across the country between June 2024 and December 2025. They answered questions about their lifestyle habits (physical activity, tobacco use, alcohol consumption, coffee intake, etc.), their place of residence and their body mass index, amongst other factors. Semen quality was higher among men from northern Spain, even though lifestyle habits were similar across all regions, suggesting that differences in quality may be due to exposure to environmental pollutants, says the lead author.

According to the findings of two clinical trials published in Annals of Internal Medicine, adults at high cardiometabolic risk who slept almost 80 minutes less per night for six weeks gained nearly half a kilogram on average and experienced an increase in waist circumference. The studies included a total of 95 participants, all of whom had a habitual sleep duration of at least seven hours per night. Sleep restriction was also associated with increased leptin levels, a hormone involved in regulating energy balance, and with greater sedentary time.

According to an observational study, from which no causal relationship can be inferred, each additional hour per day of sedentary behaviour is associated with a 10% increase in the risk of death from cancer. The association depends not only on total sedentary time, but also on how it is accumulated: if that hour of inactivity is interrupted, the risk is reduced by 19%. In addition, replacing one hour of sedentary behaviour with light physical activity reduces the risk by 12%. The study, published in PLOS Medicine, included nearly 91,300 participants from the UK Biobank who were monitored for seven days using an accelerometer and followed for a median of 12.38 years.

The team led by scientist Kate Adamala of the University of Minnesota has released the news—under an embargo—to several media outlets regarding the creation of a synthetic cell capable of feeding, growing, and replicating, which they have named Spudcell. Their work, which, according to Science News, was rejected by the journal Cell, is published on the team’s website, pending peer review.

An international team has analyzed data collected between 1990 and 2024 from nearly one million people in seven countries regarding their body mass index, cholesterol levels, and blood pressure. The results indicate that, in adults over 40, these levels have been converging, becoming quite similar overall in obese and non-obese individuals, possibly due to the widespread use of treatments. Despite these findings, the authors note that there are other risks associated with obesity not included in the study, such as diabetes, kidney disease, and cancer, among others. The work is published in The Lancet. 

An essay published today in the journal PLOS Climate examines the need for “immediate and sustained” investment to safeguard urban forests. The article reviews the necessary policies, ranging from maintenance and management to legal protections. The authors call on policymakers to “prioritize” these spaces in their strategies to combat climate change, given their positive role in climate resilience, biodiversity, and public health.

Two Copernicus services have independently confirmed that global sea surface temperatures have broken records for this time of year. Daily data from the Copernicus Climate Change Service exceeded the 2024 levels on 21 June, reaching 20.86 °C, higher than the 20.83 °C recorded in 2023 and 2024. Data from the Copernicus Marine Watch Service show temperatures of 21.0 °C on 21 June, beating the 2023 and 2024 records by 0.1 °C. This unprecedented warming is linked to the onset of El Niño (announced by the WMO and declared by NOAA on 11 June) and to record-breaking sea surface temperatures in the North Pacific; consequences are anticipated for weather patterns, the global climate and marine ecosystems.