As a series of UN climate reports have warned recently, drastic reductions in greenhouse gas emissions – a halving over the next decade – are needed if we are to keep global warming down to manageable levels. No sign of that happening.

An emergency measure to buy time that’s sometimes discussed is solar geoengineering – creating an atmospheric sunscreen that reduces incoming solar heat. Sulphate compounds in volcanic gases or in industrial fumes attract water vapour to make a fine haze and have that effect. The difference would be starting a deliberate programme of injecting sulphate particles into the stratosphere.

There are a host of arguments against it, including a revulsion against adding another pollutant to the atmosphere to offset the one, carbon dioxide, that’s giving us problems in the first place. Another objection, outlined this week, is that it could set back the global fight against malaria - a major killer in its own right. University of Cape Town ecologist Chris Trisos tells Roland Pease what his team’s modelling study revealed.

Yale University neurologist Kevin Sheth talks to us about a revolution in medical scanning – small-scale MRI machines that can be wheeled to the patient’s bedside.

According to palaeontologist Maria McNamara, an amazingly preserved pterosaur fossil from Brazil proves that some of these flying reptiles did have feathers similar to those of birds (and some dinosaurs), and that the feathers were of different colours, possibly for mating display.

Primatologist Adrian Barnett has discovered that spider monkeys in one part of the Brazilian Amazon seek out fruit, full of live maggots to eat. Why?

The ancient Maya flourished in modern day Mexico and Central America for millennia. They built incredible cities and they had sophisticated knowledge of astronomy, architecture and the natural world. But although Maya culture continues to exist today, around 900 AD, many of their great settlements collapsed, and today they lie in ruins.

CrowdScience listener Michael wants to know - how did the Maya sustain their populations successfully for so long? And what happened 1000 years ago that led them to abandon their cities?

To find out, Melanie Brown travels to the forests of Western Belize. She visits the archaeological site of Xunantunich to learn about what life would have been like for the Maya living in what was once a prosperous city. She hears about the importance of water to the Maya way of life in this region, and their ingenious methods for capturing and storing rainfall.

She meets archaeologists using lasers and drones to map Maya settlements that have lain hidden by jungle for centuries. And she discovers what material from the bottom of lakes can tell us about how the Maya faced a changing climate, which may have had huge consequences for their society.

(Photo: Illustration of a mosquito biting

Presenters: Roland Pease and Melanie Brown