The US secretary of state John Kerry will arrive in Lima today to push forward global climate negotiations, taking place in the city.
Mr Kerry is the most senior American official to attend the talks since President Obama went to Copenhagen in 2009 - an event that didn't end particularly well.
The Secretary of State has long been the most engaged American politician on the issue of climate and environment and his attendance at these UN negotiations is being seen as further evidence that the US is determined to make up for the failures of Copenhagen in 2009 and deliver a strong agreement in Paris next year.
For once, the US is not being seen as the Great Satan of CO2.
Thanks to their joint initiative with China, the two countries are taking a bow as leaders of the fight against rising temperatures.
The change in atmosphere could be seen on the poker face of US special climate envoy Todd Stern, who in recent days has been a veritable ray of sunshine.
The way he sees it, the deal that is being negotiated here - and will likely be signed in Paris - is a truly historic event.
'We are trying to do an agreement that is intended to last for decades. This is supposed to be not an agreement that we come back and renegotiate every five years, but an agreement that establishes a stable and durable structure.'
Here in Lima, the parties are trying to get the 'elements' of a deal together, which essentially means a chunky negotiating text with plenty of options still on the table.
One of the ideas that's getting a lot of attention from environmental activists is the aim to have zero emissions by 2050.
This item is still alive in the draft text and has support from a large number of developing countries. Green groups believe that the politicians are heeding the message from the streets.
'The public call for 100% clean energy has gone mainstream, and finally leaders are starting to respond with ambitious targets,' said Iain Keith from Avaaz.
But the idea is not popular with the boys from the black stuff, the countries who make their living from oil and coal.
'The zero-emissions concept - or let's knock fossils fuels out of the picture without clear technology diffusion and solid international cooperation programmes - does not help the process,' said Saudi Arabia's chief negotiator in Lima, Khalid Abuleif.
'I do not think this is realistic when two billion people do not have access to energy,' he added, a tad sniffily.
While arguments about the long term goal are unlikely to be settled by Mr Kerry, his presence might increase the pressure on the countries that are dragging their heels on their commitments.
India has been noticeably silent on the idea that it might peak its emissions at a specified date in the future.
The Indians are said to be feeling a bit bruised after their great ally, China, seems to have sided with the US.
Perhaps they are waiting for the kind of in-depth love and attention the US lavished on China to get them to move forward?
Don't hold your breath says Mr Stern.
'We don't have that kind of process going on with India,' he told reporters.
Another challenge for Mr Kerry will be the need to try and usher some recalcitrant countries to join the party - especially Australia.
The Lucky Country has been vilified here for its stance on climate change.
'Since the Abbott government came in, it has replaced Australia's comprehensive climate legislation with a regime where emissions are now set to increase substantially, against decreasing trends in the US,' said Bill Hare, from the Climate Analytics think-tank.
'Many in the government are denying the yeti-scale footprint of climate change impacts being felt by people from one end of the country to the other.'
The Australians have surprised many attendees by making a $160m contribution to the Green Climate Fund.
According to foreign minister Julie Bishop, it was part of Australia's 'commitment to play our part in the global response to climate change'.
But money doesn't seem to buy friends here in Lima. Green groups have given the country their mocking 'fossil of the day' award several times during this conference of the parties.
Mr Kerry will have his work cut out.
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