Time Mag’s ‘Hero of the Environment’ Michael Shellenberger:
Excerpt: Last week, a group of scientists including Rockström argued in an opinion “Comment” at the journal Nature that “evidence is mounting” that the loss of the Amazon rainforest and West Antarctic ice sheet “could be more likely than was thought.”
What they described, however, would take place over hundreds and perhaps thousands of years. At no point do they predict “billions will die.”
I interviewed the lead author of the Nature Comment, Professor Timothy Lenton of the University of Exeter, I asked him about a verb tense I found curious.
Lenton notes that the West Antarctic ice sheet “might have passed a tipping point” but goes on to say “when this sector collapses, it could destabilize the rest of the West Antarctic ice sheet like toppling dominoes — leading to about 3 metres of sea-level rise on a timescale of centuries to millennia.”
“When you say ‘when,’” I asked, “does that mean it’s an inevitability that it will collapse?”
“Well, we can’t rule out that it’s on the way out,” he said. “Any glaciologist specialist will tell you that we really want more data. Because it’s not trivial to monitor what’s going on in West Antarctica.”
“So the right word in your view is ‘when’ not ‘if’?” I asked.
“We can’t be absolutely sure,” Lenton said, “but if it is, it will have knock-on effects. With the limited data, it’s hard to rule out that it’s already collapsing.”
I wasn’t the only person who felt confused by the multiple “ifs” and “coulds” in the commentary. “The paper has a strange array of rising risks lumped as ‘tipping points,’” noted Columbia University Earth Institute’s Andy Revkin.
Justin Ritchie, a researcher at the University of British Columbia, highlighted 11 conditional statements in the four paragraphs summarizing the complicated causality for a “global cascade” of tipping points.
“I might be the only one,” writes Ritchie, “but after reading it I’m actually less convinced about imminent climate tipping points. One example: if it takes 11 ‘if’ statements to support an opinion, then it’s time to revisit the opinion’s substance.” (The word “could” is used 26 times.)