From the Paris Agreement to the accelerating clean energy revolution, 2015 was a big year for stories on energy and the environment, including its status as perhaps the last year in human history to see atmospheric concentrations of CO2 below 400 parts per million. Here are the leading stories published by Scientific American this year:

(5) How the Deadly Nepal Earthquake Happened [Infographic]

This terrible earthquake was the most recent outcome in an ongoing collision of giant pieces of our planet, a slow-moving disaster that started about 50 million years ago

(4) 11 Natural Wonders to See Before They Are Gone [Slide Show]

Global warming may transform these sites beyond recognition

(3) Mass Deaths in the Americas Start New CO2 Epoch

A new proposal pegs the start of the Anthropocene to the little ice age and the Columbian Exchange

(2) The World Really Could Go Nuclear

Nothing but fear and capital stand in the way of a nuclear-powered future

(1) U.S. Drought Will Be the Worst in 1,000 Years

The Southwest and central Great Plains will dry out even more than previously thought

Looking forward, 2016 promises to be another big year for the environment as stratigraphers decide whether to formally debate this idea of a new geologic epoch set off by humanity’s impact on the planet as well as an election in the U.S. that may determine whether or not this country continues to combat climate change.