Fatigue, shattered expectations, disappointment and despair drove away all but the scientists, the hard-core activists and the civil servants whose job it is to keep the talks going.
But now climate change is back on the public and political agenda, as increasing damage to lives and livelihoods becomes impossible to ignore. We have an opportunity to make a big step forward in the run-up to the next big United Nations Climate Change Conference (COP21) in Paris in December 2015. It is urgent that we get it right this time.
The 400,000 people who marched in New York in September, before UN secretary general Ban Ki-moon's climate summit to push the issue higher on the political agenda, have got the message. So have the many major corporations who reportedly, behind closed doors, pounded the tables also demanding action; and so have the struggling farmers in India, sub-Saharan Africa, California and Australia. Now all it takes is political will, and leadership from a few governments.
We have the tools now
The good news is that unlike 25 years ago when the climate issue first emerged, we have the technology to solve the problem, and to do so cost effectively. Wind and solar are increasingly taking over the power sector. Electric mobility and improved battery technology are on the rise. Improved materials science, energy-efficiency equipment and practices, and an almost inexhaustible list of other technologies and processes have given us many of the tools we need, and the rest can be picked up along the way.
It is not going to be easy. We are talking about retooling the entirety of human civilisation in the next 40 years - which, by the way, we are probably going to do anyway; the question is whether we do it right this time, at least in terms of the climate.
The real obstacle lies in the political, economic and institutional inertia which have bogged down the discussion for too long now. The fossil-fuel industry, the most powerful vested interest in the world today continues to do everything it can to obfuscate the science and slow down political progress. Not their least pernicious influence is on the politicians they own, particularly those in the US Congress - and in the places where the fossil fuel industry is a family business masquerading as a national government - and in the places where fossil-fuel exports have become a blunt political and military instrument to bludgeon recalcitrant neighbours into submission.
But we're running out of time
All of the science indicates that global emissions need to peak in the next five years if we are to have any reasonable chance of avoiding the worst ravages of man-made climate change, to prevent the global mean temperature rising more than 2 degsC above pre-industrial levels, or 1.5 degsC as the more vulnerable countries are advocating.
For that, there is one clear and immediate imperative: global emissions must peak and begin to decline before the end of this decade. This is not impossible, but is becoming increasingly difficult - and the longer we wait the more expensive it will be.
The power sector is not the whole problem, but it is the biggest one - about 40% of energy-related CO2 emissions, and about 25% of overall greenhouse-gas emissions. To make a difference in the next five to ten years, the options include: first and foremost increase energy efficiency, which will yield the greatest benefit in the shortest period of time; second, no new coal plants should be built and fuel-switching from coal to flexible gas plants should be implemented wherever possible; and finally, continue and accelerate the dramatic growth of renewable-energy generation technologies. Solar will make a significant contribution in the period after 2020, and may be the largest energy source of all by 2050, but in the next five to ten years the big contribution to emission reductions will come from hydro and wind. That is what we should focus on for now.
As Morgan Freeman said in a recent film he narrated for the New York summit: "One day very soon we'll be asked: 'what did we do?' ... and we'll say: 'We did everything we could.' We have to. Because if we don't, there won't be anyone left to ask."
For those of us in the wind industry, when our children and grandchildren ask that question, I think we can all say 'We did everything that we could.'
Let's hope there are enough others who can give the same answer.
Steve Sawyer is CEO of the Global Wind Energy Council