As France's top climate envoy, Laurence Tubiana has to be light on her diplomatic feet and has gained a reputation both for her frank, unpretentious style -- and her sporty sneakers.

In a world of button-down diplomats, Tubiana's Converse shoes have become a fitting trademark as she has sprinted around the globe pushing for a climate rescue pact.

She will be back in Paris on Sunday to welcome about 60 foreign ministers for discussions aimed at clinching an 195-nation agreement against global warming at UN talks that kick off this month in the French capital.

Since being named France's climate ambassador to the world in mid-2014, Tubiana has been everywhere from Saudi Arabia to China to India to help encourage a deal.

Her role in the process "is going to see people, understand where they are and see where we can take them, and do it repeatedly to encourage them to develop," she told AFP.

Yet this straight-shooting academic -- who has never held elected office -- is not your average diplomat.

"Let me talk to you very frankly, by now you should have understood that it is my style and I think it will continue to be my style," she said during a negotiation session in Germany last month.

The 64-year-old, an economist by training, believes the climate crisis shines a harsh light on humanity's ravenous consumption of the Earth's resources.
"The situation is unbearable, untenable, unequal -- favouring ways of consumption and behaviour that are harmful to everyone," she told AFP.

"So there is an aspect of justice in climate matters, which is a real motivation for me."

Firmly on the left of the political spectrum, her first big job in government was as an adviser to socialist prime minister Lionel Jospin in 1997.

The posting plunged her into the negotiations for the landmark Kyoto Protocol on the reduction of greenhouse gas emissions, the precursor to the agreement hoped for in Paris.

After founding a sustainable development think tank at Paris's prestigious Sciences Po university, she joined the doomed climate negotiations in Copenhagen in 2009, which ended in confusion and without a deal.

- Big business links? -

In her time on the world stage, the multilingual Tubiana -- who was born in Algeria and moved to France in 1962 when the north African country became independent -- has won her share of fans.

"I think she is doing a very, very good job," said UN climate chief Christiana Figueres. "If I would bring it down to two words it is 'tough love'."

Figueres added that Tubiana is a good listener and has respect for others' perspectives, but at the same time is possessed of the assertiveness needed to push negotiators toward an agreement.

"Laurence has made a lot of friends," said Seyni Nafo, a spokesman for the African bloc at the Paris talks.

"She has an ability to listen and respond, without arrogance or pretention."

However, Tubiana has come in for sharp criticism for her ties to a handful of France's biggest corporations -- some of them major carbon polluters.

A 2015 piece in satirical magazine Charlie Hebdo noted the board of directors of the think tank she founded -- the Institute for Sustainable Development and International Relations (IDDRI) -- includes the likes of energy giants EDF and GDF Suez.

"I created the institute as a bridge between ecologists, academics, scientists, governments and civil society organisations," Tubiana said.

"The businesses are a minority on the board of directors, they don't make the decisions."