He is clear a more nuanced article would likely have been rejected by Nature and shunted off to a less prestigious journal. It would have accurately described his findings, including several other factors climate alarmists at the prestige journals don't want confusing the issue.
As an untenured assistant professor he accurately believed his career would suffer if he didn't score publication in prestige journals like Nature and Science. These are committed to the climate alarmism party line emphasizing greenhouse gas emissions.
Working at universities that didn't offer the doctorate, my pressure to publish was less. And I was fortunate that policy positions had not been politicized in my field. Yet I tried to write papers I believed would find acceptance, and often enough they did.
Fortunately self-censorship wasn't an issue for me and my coauthor colleagues. Without it, we still had trouble getting our papers past cranky editors and opinionated reviewers. Hat tip to RealClearPolitics for the link.