Why is the head of a quiet, careful Boston money management firm writing in Nature, one of the two most prestigious science journals in the world, that we need to risk being arrested to stop further global warming?
Here's his argument. The price of 33 crucial commodities went down 70% in the 20th century, helping a lot of economies to grow, but since 2002, prices of most of those commodities have tripled, mostly because of economic growth in the developing world. Climate change is wreaking havoc with food production.
We're facing shortages of two fertilisers, phosphate and potash. Grain productivity growth is now no higher than world population growth, 1.2%. That's a safety margin of zero.
If we're to avoid huge worldwide climate and food disaster, oil producers need to leave 80% of remaining oil reserves in the ground, but they own the US congress so the world's biggest economy is still driving climate change and doing virtually nothing about it.
To the world's scientists he says "Be arrested if necessary. This is not only the crisis of your lives - it is also the crisis of our species’ existence. I implore you to be brave."
That's advice we all need to hear.