What can we expect from the next round of international climate negotiations, which begin next week in Cancún, Mexico? A lead negotiator from a major developing country recently told me that the probable outcome was "anybody's guess". That gives me an uncomfortable feeling that Cancún will be Copenhagen revisited. There are many good reasons why that climate conference last year proved so difficult, and delivered what it did (or did not). Two should be borne in mind.

First, there was no shared understanding of what the conference was supposed to deliver. The 2008 Bali Action Plan, the document that underpinned the process intended to culminate in Copenhagen, spoke of decisions being taken. But what decisions? Some countries argued that the world needed to adopt a new legal treaty under the United Nations Framework Convention on Climate Change, which would set a series of binding targets for industrialized countries and herald the demise of the Kyoto Protocol. Others expected agreement on a second period under the Kyoto Protocol and a new legal arrangement largely directed at the United States. Still more nations sought only an operational step towards a legal instrument or instruments. In the weeks before the Copenhagen meeting, a growing number of world leaders expressed the need for a political declaration as the best outcome. In the end, that is what the conference delivered.

I hope that the lack of a shared sense of direction will not bedevil the talks in Cancún. ,

The second reason is the widespread fear that ambitious climate-change policy will damage economic growth. Concerns over energy prices, energy security and material scarcity in the face of a ballooning world population have done much to drive global desire for a greener, leaner and meaner economic model. Although many nations pay lip service to this green growth model, most of them, deep in their hearts, are still unsure. In fact, many developing nations fear that the intent of the West is to use climate as an excuse to keep developing nations poor and maintain the current economic status quo.

The lessons for Cancún therefore seem obvious: keep it practical, keep it simple and don't overreach. The negotiations must explore ways for all nations, especially those in the developing world, to consider the merits of green growth. No sensible country will accept a new legal agreement if the economic consequences remain unclear.

I believe that this requires a practical framework in each of the following six areas. Only then will countries responsibly be able to decide whether a new legal instrument is the proper route to take global climate action forward.

First, we need a mechanism that helps developing countries to assess their green growth potential, develop a clear strategy and access international financial support to implement it. The 'prompt start' finance that was promised in Copenhagen offers a foundation to develop that strategy. Long-term financial commitments and a widened range of market-based mechanisms will be crucial to its implementation. Second — and essential — is an increased capacity to assess and plan the probable national responses to a changing climate, especially in the smaller and poorer developing nations. We need a capacity-building programme driven by institutions that can deliver the required hard economic analysis.

A third critical element for success in Cancún is to strike a better balance when considering climate adaptation and mitigation. The lack of attention to adaptation is one of the main shortcomings of the Kyoto Protocol. A fourth point would be to ensure that the delivery mechanism helps to push key technologies into developing economies. Private-sector investment must be mobilized to drive innovation and to lower the cost of generic but essential technologies, such as renewable-energy equipment.

Fifth, an agreement to reward action to combat deforestation and forest degradation would offer a real premium for countries with no other significant mitigation potential, and would help to limit the cost of future action on emissions. Sixth, a robust framework to monitor, report and verify both action and support will ensure that nations pull their weight.

You will notice that more ambitious targets are not on my list. The realist in me suggests that we need to work with what we have, in the same way as President Mohamed Nasheed of the Maldives accepted the Copenhagen Accord — not because he liked it, but because he realized that it was the best he could get. Am I selling the climate short? Yes. The approach I outline here will not be enough to limit temperature increase to a maximum 2 °C rise, and I would happily trade any of my six points for a stronger outcome.

Experience with sulphur dioxide trading in the United States and carbon trading in the European Union suggests that a modest start can be an effective way to get the ball rolling and to 'learn by doing'. The Copenhagen Accord's promise to review action in 2015 at least offers the chance to reconsider our ambition once we have a clearer picture of the tools that will be available. Above all, I hope that the lack of a shared sense of direction will not bedevil the talks in Cancún as it did last year. Those familiar with the rules of football will know that many people issued the UN climate process in Copenhagen the equivalent of a cautionary yellow card. It should tread carefully to avoid the unfortunate consequences of a second.