Antonio Guterres, speaking at the 73rd General Assembly in New York, called out all world leaders, but particularly the members of the G-20, for not setting an example in cutting emissions. The world's 20 leading and emerging economies produce about 80 percent of global greenhouse gas emissions, he said.

A target set in the 2015 Paris Agreement was to keep global warming below an increase of 1.5 degrees Celsius (2.7 degrees Fahrenheit). That goal is not achievable unless hard choices are made, Guterres said.

Guterres called for world governments to end subsidies for fossil fuel producers and instead embrace renewable energy production.

Another high cost in 2017 came in the form of climate-related disasters, which Guterres said totaled $320 billion. If global warming continues to increase at a larger-than-intended rate, then the result is likely to be more fires and floods that scientists have tied to increases in temperatures.