They have done it one after another, the two Miliband brothers, first David, now Ed: running British policy for coping with the world's most intractable problem, climate change. And in the face of growing gloom among many scientists – and not a few politicians and environmentalists – about the possibility of cutting the world's carbon emissions fast enough to halt a runaway rise in temperatures, they exhibit exactly the same unusual characteristic: rational optimism.
Sitting in his relatively new Department of Energy and Climate Change (DECC) in Whitehall, the shirtsleeved younger Miliband talks enthusiastically about the carbon budget – the world's first – that will be announced by the Chancellor with the traditional Budget next week. It is an innovation that was brought about by his brother David, who as Environment Secretary two years ago seized the political opportunity to push a Climate Change Bill through Parliament.
It will fall to Ed to implement his sibling's innovation and he sees it, rightly, as another positive step forward in the long struggle to make Britain and the rest of the world change the way life is lived, to keep the planet habitable. It is a struggle that will reach an interim climax at the Copenhagen climate treaty talks in December.
Nowhere in an hour's talk about global warming policy is there a scintilla of doubt that this is a problem which can be solved. Nowhere is there any hint of the pessimism beginning to possess some of the world's leading climate scientists, who believe carbon emissions are rising so rapidly that they cannot be scaled back in time to stop global temperatures going off the scale. It's not an act. It's a genuinely held belief. But it seems so deep-rooted, in the face of growing concern from many at the heart of the problem, that the question puts itself forward: why?
Ed Miliband says he's an optimist by nature and by upbringing. "I suppose I have faith in human ingenuity. People often talk about the Apollo project, when JFK said 'we're going to put a man on the moon by the end of the decade', and they just about managed it. I mean, I think there's the political will, if you talk to the Prime Minister here, if you talk to President Obama: this is an urgent priority. It's difficult."
But it's a solvable problem? "Absolutely it's a solvable problem."
Does he accept that, historically, it appears to be a uniquely difficult problem? "Yes, definitely. But human ingenuity and human beings have overcome these problems before."
The mention of JFK is telling. The political parallels between the Milibands and the Kennedy brothers, Jack and Bobby, are uncanny. Not just the youth and the good looks, the family closeness, but the shared and unshakeable left-liberal belief in progress, the belief that rational action, that people and politics combined, can do wonders. You might call it the Apollo spirit.
It put a man on the moon. Let's hope it can save the Earth.