Four years ago, I traveled around America, visiting historical archives. I was looking for documents that might reveal the hidden history of climate change – and in particular, when the major coal, oil and gas companies became aware of the problem, and what they knew about it.
I pored over boxes of papers, thousands of pages. I began to recognize typewriter fonts from the 1960s and ‘70s and marveled at the legibility of past penmanship, and got used to squinting when it wasn’t so clear.
What those papers revealed is now changing our understanding of how climate change became a crisis.
On 28 October 2021, executives from Exxon, BP, Chevron, Shell and the American Petroleum Institute were on Capitol Hill to face questions from a Congressional subcommittee about the oil industry’s efforts to downplay the role of fossil fuels in climate change.

