The United Nations’ top environmental panel is warning the world has just 15 years to stave off devastating climate change. In a new report, the Intergovernmental Panel on Climate Change says countries have taken so long to act that only immediate steps will prevent a climate catastrophe by century’s end. The IPCC says action by individual states has not been enough to tackle the problem, highlighting the need for a binding global treaty in the coming years. Emissions have increased at twice the rate in this century’s first decade than in the last decades of the 20th century. The report says the lowering costs of alternative energies have made transitioning on a mass scale practical and affordable.