* Financial crisis an opportunity to embrace greener economy
* $100 billion green fund to developing world still possible
* Nations will decide "middle ground" on Kyoto Protocol
By Nina Chestney
LONDON, Aug 31 (Reuters) - A record rise in global greenhouse emissions and ever tighter economic constraints make it crucial for United Nations climate talks in South Africa in November to overcome years of deadlock and deliver a solution, the U.N.'s climate chief told Reuters.
Nearly two decades of U.N. climate change negotiations have so far failed to find a new binding approach to curbing the release of climate-warming gases.
The world's biggest emitters, the United States and China, have never formally signed up to mandatory emissions caps and the previous head of the U.N. Framework Convention on Climate Change (UNFCCC) stepped down after 2009 talks collapsed.
"It is self-evident that (climate change) is a complex challenge but it is to governments' credit that they are not shying away from (it)," Christiana Figueres, UNFCCC executive secretary, said in an interview.
"If climate change were a simple problem, we would have solved it in 1992."
Hopes faded for a new global climate pact to replace the Kyoto Protocol, which expires at the end of 2012, after U.S. President Barack Obama and other leaders could not agree in Copenhagen in 2009 on a new deal for limiting global warming.
Leaders of 193 countries are set to meet for the next annual U.N. climate summit in November in Durban, where talks could stall again if rich and poor nations renew squabbling over how to share out emissions cuts and whether to extend the existing protocol.
Talks could also be over-shadowed by data showing that the world's carbon dioxide emissions hit their highest level ever in 2010, driven mainly by booming coal-reliant emerging economies like China.
At the same time, the threat of another global economic slowdown has tightened governments' purse-strings and diverted public attention.
Figueres said the difficulties could be a positive spur.
"Governments have a huge opportunity here to address some of that economic recovery while addressing climate change. It is win-win," she said
"What is very clear is that we need a dramatic shift in our economic structure and that needs to happen at the earliest possible point, because the more we continue along the current path the more we get into technology lock-in."
Figueres said governments were very much "on track" to deliver on the main commitments agreed at a Mexico summit last year, related to finance, technology and adaptation measures.
At the 2010 talks in Cancun, governments agreed to set up a Green Climate Fund to manage $100 billion a year by 2020 in aid to the poor nations most at risk of climate change.
Asked whether the U.N. would succeed in securing the full $100 billion -- which already fell far short of the hopes of developing nations -- Figueres said it would "definitely not be easy" but it could be achieved.
Durban should decide on financing for the short term, medium term covering 2013-2020, and then the longer term, she said.
While governments have struggled for a breakthrough, Figueres said a "visionary and enlightened" part of the private sector had already made strides towards a low-carbon economy and the whole world could follow that example.
"It is the responsibility of every single actor and human being. Everyone needs to accept their responsibility -- the private sector, civil society, NGOs, national governments and individuals -- and to contribute to the solution," she said.
As well as tackling the financing challenge, Durban will also focus on what will follow the Kyoto Protocol from 2013.
China and some developing nations want to extend the protocol into a second commitment period, while Japan, Russia and Canada are opposed. European Union states have been trying to find a middle road.
"An important group of countries has opened up a conversation about if the EU engages in a type of second commitment period, what would that be like?" Figueres said.
"I would say governments are in a creative phase and will explore what would be a middle ground which has to be acceptable to all countries." (Additional reporting by Barbara Lewis in London and David Fogarty in Singapore)