NAIROBI – The last two years have been a roller coaster ride in respect to securing a new global treaty to combat climate change. Some even despair that the window for action is closing fast.

But giving up is not an option. The latest round of climate negotiations, held last month in Cancún, Mexico, put the world’s efforts on climate change back on track – albeit at a pace and on a scale that will undoubtedly leave many onlookers frustrated.

President Felipe Calderón’s government in Mexico and the Executive Secretary of the United Nations Framework Convention deserve credit for gains in a range of important areas, including forestry, a new Green Fund to assist developing nations, and the anchoring of the emission-reduction pledges made at the December 2009 climate-change conference in Copenhagen.

But, as the UN Environment Program and climate modelers made clear in the run-up to the Cancún meeting, a significant emissions gap exists between what is being promised by countries and what is needed to keep the rise in global temperature below two degrees Celsius, let alone move towards the 1.5-degree threshold needed to protect low-lying island states.

Despite some gains, that gap – which, under the most optimistic scenario, amounts to the combined emissions of all the world’s cars, buses, and trucks – remains firmly in place post-Cancún. Indeed, no one should underestimate the magnitude of the challenge now facing South Africa, the host of next year’s talks, in terms of midwifing a new legally binding agreement to bridge this gap and securing the finance needed to bring the Green Fund into operation.

Yet, while the official summit in Cancún struggled to a conclusion, an unofficial one being held a few minutes away also concluded. This parallel summit brought together progressive heads of state, regional and local government, business, and civil society, and underscored just how far and how fast some sectors of society will make the transition to a low-carbon future and build the green and clean-tech economies of the twenty-first century.

Calderón’s policies echo this momentum: by some estimates, he is transforming his country into the world’s fastest-growing wind-power market. Moreover, Mexico will also phase out old, inefficient light bulbs by 2014.

And it has just retired 850,000 inefficient household refrigerators in favor of modern, energy-efficient models, with millions more earmarked over the coming years. Mexican homeowners who install energy-saving systems such as solar water heaters are becoming eligible for lower-rate "green mortgages.”

Mexico is not alone in adopting a national strategy for the transition to a low-carbon, resource-efficient green economy. Uruguay, for example, announced a strategy to generate half its electricity from renewable sources by 2015.

Sixty regional and local governments, responsible for 15% of global greenhouse-gas emissions, are also taking action. Québec and São Paolo, to cite just two examples, are aiming for cuts of 20% below 1990 levels by 2020.

Big companies, from banks to airlines, are contributing as well. The US retailer Wal-Mart, for example, plans to cut emissions equivalent to 3.8 million cars, in part by implementing energy-efficiency measures at its Chinese stores.

Indeed, the world is witnessing an extraordinary mobilization of national-level projects and policies that are shifting economies onto a low-carbon path. In Kenya, a new feed-in tariff is triggering an expansion of wind and geothermal power. Indonesia is not only addressing deforestation, but will begin phasing out fossil-fuel subsidies for private cars next month. Many countries and companies are forging ahead, signaling a determination not to be held hostage by the slowest at the official negotiating table.

All this may lead some to wonder why time-consuming international negotiations and UN climate summits are needed at all. But the fact is that this groundswell has in large part been catalyzed by the existing targets, timetables, and innovative mechanisms of the UN climate treaties, and not least by the momentum generated around the often-criticized 2009 Copenhagen summit.

This momentum would continue to grow with a new global treaty that not only brings certainty to carbon markets and triggers accelerated investments in clean-tech industries, but that also ensures that more vulnerable countries are not marginalized. The challenge today is to unite these goals in a mutually reinforcing way.

Only then will the world have a fighting chance to keep the global temperature rise in this century under two degrees, build resilience against a changed climate, and truly transform the energy structures of the past – and thus the development prospects for six billion people in the future.

Achim Steiner is UN Under-Secretary General and Executive Director of the UN Environment Program (UNEP).

Copyright: Project Syndicate, 2011.