John Holdren

Any objective look at what science has to say about climate change ought to be sufficient to persuade reasonable people that the climate is changing and that humans are responsible for a substantial part of that - and that these changes are doing harm and will continue to do more harm unless we start to reduce our emissions.

I think we ultimately ought to look to put all uranium enrichment and fuel reprocessing, if any is done, under multinational control. Those are the two technologies by which nuclear energy can be translated into nuclear weapons programmes.

The plumbing and pluvial dynamics of the Amazon, the largest freshwater system on Earth, are still far from understood. This is partly because it is a semi-open system. Moisture flows in and out unpredictably. A lot of nonlinear feedback loops and 'remote influences' - continental, transcontinental, oceanic, meteorological - come into play.

First-class delivery of children's palliative care is life-changing. When families are confronted with the shattering news that their children have a life-limiting condition, their world can fall apart.