By David Shukman
Science correspondent, BBC News, Bali
Activists brought a world of their own to the conference in Bali
Bali is only a relatively small island but at the moment it can feel like it's home to no fewer than three very different planets.
There's the planet of the official business of the United Nations climate conference - the hermetically-sealed bubble of the thousands of delegates, activists and media where the daily currency is speeches, statements and press conferences.
This is the public face of this massive event; a world of suits, documents and slogans.
Hardly a minute goes by without some distinguished minister uttering one or more of the following words or phrases: "urgent", "catastrophe", "action" and - most commonly - "the time for talk is over."
This is also the planet where worried delegates from Belize, Burkina Faso and Mauritania plead for help to cope with floods and droughts and hurricanes.
There are genuine cases of need and a real hope that something will come out of all this.
The UN conference even has a presence in the virtual world
But then there's another planet here at the talks, one inhabited by a mysterious and mostly invisible breed of negotiators.
We rarely see these shadowy figures, but occasionally hear word of their efforts behind the scenes.
They gather for formal meetings and huddles and one-to-ones, and their trade is in the minutely calibrated meanings of particular words.
A treaty is different to an arrangement, a process is something distinct from a dialogue, a commitment doesn't necessarily mean a promise to do something.
This is a world of impenetrable acronyms and bewildering language. Days can be lost in the haggling over a single phrase.
But it's on this planet that the outcome of the whole event depends, whether anything concrete is agreed, whether this meeting actually leads to cuts in greenhouse gases.
Real world, real problems
And then there's a third planet, the real one; a world recognisable to most of humanity.
Back in the real world, life goes on as normal on the Indonesian island
I ventured into it during a break in the conference.
I drove for two hours up into the hills in the centre of Bali, guided by two experts from Conservation International.
Amid the terraces of the steep bright green hills, dotted with ornate temples and pretty villages, I met a rice farmer harvesting his crop.
We talked about how Mangku Candra is faring. The weather has become unpredictable, he told me.
The rains arrive late and haven't delivered enough water in the past four years. Yields of rice on his small plot are down by about a quarter.
For a subsistence farmer this really matters. And it's a foretaste of what the UN climate panel said could happen in South-East Asia - changing patterns could threaten crops and the availability of food for millions of people.
I realised that this man - barefoot and poor - was living through what the experts were talking about on their air-conditioned planets.
He didn't have much time for talk, he had work to do. And I had a conference to return to.