I just watched your excellent film on climate change, Before the Flood. I'm writing to applaud you for highlighting the urgency of this issue, but also to ask you to think again - especially now the election is over - about who the heroes and villains are.
The movie contains great sequences - Arctic ice melting, your interviews with Barack Obama and the Pope - but it also recycles the conspiracy theory that oil and gas companies are all out to obstruct progress. "Fossil fuel companies manipulate and dictate the science and policies that affect our future," you say.
Leonardo, this belongs with alien abductions and Elvis sightings. You're dismissing an entire industry in one sentence when it contains a lot of people who are every bit as concerned about this issue as you are. There is a very different story to tell.
Calling for action
BP, for example, acknowledged the risk of climate change around 20 years ago and led an exodus of oil and gas companies from the Global Climate Coalition (GCC), a lobby group that opposed change. Far from obstructing progress, many oil and gas companies are urging governments to do more. Last year, for example, the heads of BP, Shell, Statoil, Total and others wrote to the UN calling for a price on carbon.
Far from bankrolling sceptics, several energy companies fund world-leading independent climate research teams such as the BP-backed Carbon Mitigation Initiative at Princeton University. Ten major oil and gas companies have formed the Oil & Gas Climate Initiative which this month announced an investment of $1billion in measures to limit greenhouse gas emissions. Companies like Total, Shell and BP have large renewable energy arms. If this is all PR, it's the most expensive PR campaign ever. But it's not. There are good reasons why these firms support action on climate change.
The right side of history
First, they need good relations with governments, consumers and others worldwide, many of whom want to see progress. Second, a move to a lower carbon economy offers opportunities - in renewable energy and in providing gas as a substitute for coal. It's been calculated that switching all the world's coal-fired power plants to gas could cut global greenhouse gas emissions by around 10%. Third, smart companies want to be on the right side of history. Many of them have existed for a century and they want to be around for another.
Demonising these companies may boost protest groups, but it does nothing for the climate. As a liberal, I am ashamed to see environmentalists turning what should be an inclusive, positive movement for change into a tribal, negative campaign. By whipping up hostility instead of hope, they are adopting the tactics of demagogues.
A fairer challenge to Big Oil companies is why they don't stop producing fossil fuels and shift into renewables. And the simple answer is that they'd go bust. Renewable energy may be competitive in some situations - like a sunny day in LA - but generally it isn't. If the big companies abandoned fossil fuels and put their investment into loss-making businesses, their investors would sell and they'd be taken over by others who would probably care a lot less about the climate.
The villain is all of us
Despite all the debate, the world still gets 85% of its energy from fossil fuels. Over two centuries, they have powered the industrial and digital revolutions - homes, factories, cars, computers, hospitals, schools - and the planes that took you around the world to make your film. If fossil fuel providers didn't exist, we'd invent them.
The villain isn't the fossil fuel companies, Leonardo. It's us. It's society. It's each of us that enjoys the benefits of a civilisation fuelled by cheap hydrocarbons. The companies can't change it without failing in their duty to investors. You and I can't change it either - because a few rich people driving Teslas and fitting solar panels are outnumbered by millions who just want power and fuel to escape poverty.
Only governments can turn this juggernaut around. What is required is a collective global change of heart on a scale comparable to the abolition of slavery. Policy-makers need to change the rules of the game to make high-carbon energy more expensive and low-carbon energy less expensive.
Fortunately, there is time - just about. In ballpark terms, based on Intergovernmental Panel on Climate Change estimates, we need to stop emissions rising, halve them by 2050 and eliminate them by 2100. It isn't about throwing a single switch, but turning a set of dials. We need to use energy more efficiently, use less coal, use more gas, use oil as sparingly as possible and ramp up renewables.
For all the high-fiving at Paris last year, all that happened was a bunch of promises which were still not enough to keep the temperature rise to the goal of 2 degrees. And with Donald Trump's election, the US, one of the world's big emitters, may back off its pledges. The silver lining is that US emissions are already falling, partly because gas and renewables are so competitive.
But worldwide, politicians will only act when there is a groundswell of public demand. Right now, that is the biggest ask. Apathy is the biggest enemy. Climate change was barely mentioned in the Presidential debates and the follow-up to Paris, in Marrakesh this month, is getting little attention.
Leonardo - you are the UN's messenger for peace. You are taking a brave stand. Please use your position to spread peace among those who understand this issue and want to fix it. We are too few on the ground to fight among ourselves. We need to build a coalition for the climate and tell a different story. A story of hope. The story of how human beings can avert disaster by harnessing everything that is best in humanity. What better alternative narrative for progressive America - and the world? Let's inspire people and let's work together to shape a better future.
David Vigar is former Editor-in-Chief at BP, now a freelance writer, editor, coach and consultant for clients including BP. This post is written in a personal capacity.