This month, for the first time in our history, carbon dioxide readings at the Mauna Loa observatory, Hawaii, will exceed 400 parts per million for a full month. It is a symbolic breach – for global warming to keep under 2 °C, atmospheric CO2 must stabilise at 400ppm, models suggest. But at the minute, the only way for CO2 is up.
Monkeying with maths
Monkeys can add. The animals have been taught to do addition using the numbers 1 to 25 – the best evidence yet that primates have a talent for mathematics (PNAS, doi.org/sfj). But just like people, the monkeys made more mistakes when the numbers to be added were nearly the same size.
Five into one does go
A pill that contains five different heart drugs appears to be as effective as taking the drugs individually, concludes a review of data from 7050 adults. Advocates of the polypill hope it will reduce the number of deaths from cardiac disease (Cochrane Database of Systematic Reviews, doi.org/sdv).
Vulnerable to burgers
For some, eating burgers and other processed meat might be an even worse health choice than first thought. A genome analysis involving more than 18,000 people has identified a common gene variant that raises the risk of developing colorectal cancer among those who eat a lot of processed meat (PLoS Genetics, doi.org/sfm).
SpaceX gets its sea legs
Private space wants to go green. As part of a cargo delivery run to the International Space Station on 18 April, SpaceX made the first test flight of a rocket with landing legs – a step towards reusable rockets. The leggy stage later made a controlled Atlantic splashdown. The same day, the firm released video of a reusable version of its Falcon 9 rocket making its first test flight over Texas.