For nearly a decade, author Robert Macfarlane has been venturing into ice caves, exploring underwater rivers and crawling through catacombs. His latest book, "Underland: A Deep Time Journey," documents these travels and explores the human relationship with the "deep time" of down below.
Secretary-General António Guterres has asked countries to come to the UN summit with specific plans for how they intend to cut carbon emissions in line with the most recent science, which says global greenhouse gas emissions must fall 45% by 2030 and reach net zero by 2050 to avoid the worst impacts of climate change.
US President Donald Trump announced a planned withdrawal from the Paris climate accords two years ago, but states and local governments haven't all followed suit. What impact has US policy whiplash had on the climate two years later?
Deforestation in Brazil's Amazon is on the rise since the election of President Jair Bolsonaro, who has backed farmers and corporations bent on turning old growth forest into soy fields and cattle ranches.
The UN climate report found that limiting warming to 1.5 degrees Celsius (or 2.7 degrees Fahrenheit) this century is still technically possible. But to keep that possibility alive, the world would have to cut its global greenhouse gas emissions by a whopping 45% from 2010 levels by 2030.
A demonstration across the street from the White House Friday marked the first high-profile event of Greta Thunberg's six-day visit to Washington, intended to pressure the Trump administration ahead of a United Nations Climate Summit.