Friday marked a day of worldwide protest around climate change. Children skipped classes and took to the streets ahead of the UN Climate Action Summit next week. Also, anti-government protests in Hong Kong have grown in size, and clashes with police have become more violent. What's the strategy going forward, and what risks are activists willing to take? Plus, the drive to thwart diseases like malaria and dengue by altering the genes of mosquitos. Scientists warn, however, that the work needs monitoring to avert unintended consequences.