Michael Specter

The passengers in our microbiome contain at least four million genes, and they work constantly on our behalf: they manufacture vitamins and patrol our guts to prevent infections; they help to form and bolster our immune systems, and digest food.

By themselves, genetically engineered crops will not end hunger or improve health or bolster the economies of struggling countries. They won't save the sight of millions or fortify their bones. But they will certainly help.

Many climate scientists say their biggest fear is that warming could melt the Arctic permafrost - which stretches for thousands of miles across Alaska, Canada, and Siberia.

There are many theories about the best way to remove excess carbon from the atmosphere - some are ludicrous, others are at least worth study. The most commonly discussed plan is to lace the sky with reflective chemicals.