A little less than a year from now, the executive lounges of Rio de Janeiro airport will be swarming with government delegates making their way home from what could be the most important environmental summit ever held.
So far, it's hard to argue that the summit has caught the imagination of many outside the community of professionally interested people who have been going to preparatory meetings, drawing up briefing papers, and contributing think-pieces to highbrow publications.
Among the people it's so far failed to attract are the heads of state and government whose involvement is crucial if the event is to produce more than pieces of paper.
And it's failed to attract a big idea.
Well... some insiders might argue that last comment is harsh, and point to two strands.
One is the "green economy", which the UN is keen to promote. The other is reforming the structures and mechanisms of international environmental governance, which - it's widely acknowledged - have grown organically and messily over the decades.
The green economy and process reform, then, will both feature large in Rio.
They may be important; but they're hardly eye-catching.
The exciting summits so far have happened at 20-year intervals, with less compelling ones in between.
The first, in Stockholm in 1972, saw ground-breaking discussion of urbanisation, nuclear weapons testing, chemical pollution and the expanding human population.
The headline outcome was a vote for ending commercial whaling, and perhaps the most significant was the establishment of the UN Environment Programme - but anyway, as the first summit of the bunch, Stockholm was novel in its own right.
Rio, 20 years later, was positively fecund.
Next year's Rio re-run should be the next in the sequence. And, as I wrote above, it could be the most important environmental summit ever; and here's why.
In all kinds of areas - glacier melt, Arctic ice melt, ocean acidification, Amazon drying, amphibian extinction, pollination, and many more - there's a serious chance that "tipping points" of no return will have been passed by the time 2032 comes along.
So if you're serious about stopping all this and putting society on a genuinely sustainable track, this is the big one.
Yet without a Big Idea, there must be a serious chance that it will fail to engage anyone - leaders, citizens, youth, business, civil society, trade unions, legislators or anyone else.
Quite why there's a dearth of ideas for this one isn't entirely clear, but it probably has something to do with the fact that vehicles already exist that in principle should be taking care of virtually every environmental issue.
The problem is that many are not being implemented as effectively as nature needs.
Behind the scenes, a few ideas are under discussion as candidate headline issues for Rio.
One is the oceans.
Outside countries' territorial waters, they are pretty much open for no-holds-barred exploitation.
Where there are constraints on fishing, through Regional Fisheries Management Organisations (RFMOs), they cover only certain species, and nothing except fishing.
There's a feeling in parts of the environmental community that this is seriously out of date. In the 21st Century, with nine billion mouths to feed in a few decades' time, is it feasible any longer to maintain a frontier-spirited free-for-all over half the planet's surface?
In a quiet way, discussions have begun that could lead to something concrete emerging at Rio. They could even nick a title from the BBC - Blue Planet.
With climate negotiations apparently going nowhere - reports from Bonn this week indicate a whole new outbreak of division - is there scope in Rio for a Big Idea on energy?
In 2009, G20 leaders pledged "to phase out and rationalize over the medium term inefficient fossil fuel subsidies while providing targeted support for the poorest".
Could Rio see targets and timelines set that would actually see fossil fuel subsidies end?
And if so, what would you call that - Top Gear, perhaps?
And what about a Big Name for the summit? The calendar is littered with "Rio pluses" - five, 10 and 20 have all been used - and few people would choose something that sounds like a re-run over a new release.
Is there a better, more captivating alternative?
One advantage of the new BBC comments format that you all love(!) so much is that a lot of ideas can be collected close together on a comments thread.
So how about telling me and everyone else what you want to see out of Rio Revisited - and what you think it should be called, officially or otherwise?
The best serious suggestions I'll forward on to places where they have a fighting chance of being looked at - but don't let that hold you back (as if anything could) from frivolity.