Cullen speaks to crowd marching for sound science in Washington D.C.
A new study shows air pollution from Canada's oil sands could be 4 times higher than previously reported.
As rich countries have foundered, India and China have emerged as global leaders in tackling warming.
Here's why the March for Science was the perfect vehicle to talk about climate change.
Over Trump's first 100 days, we're going to show what science tells us about our warming world.
One of the March for Science's most remote marches will focus heavily on climate change.
Removing carbon dioxide from the air may be the most effective way to meet the globe's ambitious climate goals.
Communities across the West will have to adapt to living with the ever-increasing threat of wildfires.
Major oil companies, feeling pressure from low oil prices and global climate policy, are fleeing Canada's oil sands.
U.S. energy-related carbon pollution fell in 2016, part of a decade-long trend as utilities use less coal.
A California appeals court rejected a claim that payments required to release greenhouse gases are a tax.
Coal use in the U.S. fell 9 percent in 2016, even as the Trump administration seeks a coal industry revival.
Dozens of GOP-sponsored bills have been introduced in Congress that seek to hamstring federal climate action.
President Trump's executive order also targets local efforts to adapt to climate change.
President Trump's executive order on energy calls for the removal of "burdens" to domestic energy use.
President Trump's climate order and swift federal efforts to implement it contrasted with his bungled travel ban.
China and the EU are rallying around global climate action as President Trump moves to undo Obama-era plans.
Environmentalists and some states may spend years battling President Trump over his climate rule rollbacks.
President Trump signed an executive order Tuesday aiming to overturn federal climate policies.
Polling shows that President Trump's climate actions aren't in line with most Americans' opinions.