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s the world counts down to the landmark United Nations climate change conference in Copenhagen in December, all eyes are on the evolution of the draft treaty text and countries' negotiating stances.

These are indications of whether the world is serious about avoiding dangerous climate change.

World leaders have two critical opportunities this week to show they are indeed serious. The United Nations High Level Meeting on Climate Change in New York and the G20 summit in Pittsburgh will be tests of progress and political will.

Ever since the United Nations Framework Convention on Climate Change (UNFCCC) came into force in 1994, the world has struggled to come to terms with climate change and how to reduce the load of greenhouse gases humans are pumping into the atmosphere.

These gases have only two other places to go: the oceans and the terrestrial system (including land and vegetation). With our atmosphere overloaded, we have two complementary mitigation options: We can reduce ongoing emissions into our atmosphere (especially from burning fossil fuel and forests), and we can suck greenhouse gases from the atmosphere back into our terrestrial system and oceans.

For the terrestrial system, this means both maintaining the carbon stored in trees, vegetation and soils, and sequestering new carbon. Both require significant changes in the way we use land around the world. Land use (including forestry and agriculture) is currently the source of about one-third of all human-caused greenhouse gas emissions.

In Indonesia, forests and peatlands assume massive importance. Emissions from deforestation and forest fires are five times those from non-forestry emissions. It is these terrestrial emissions that catapult Indonesia into the top five emitting countries in the world.

The UNFCCC obliged all parties to "mitigate climate change by addressing anthropogenic emissions by sources and removals by sinks of all greenhouse gases". In other words, to do everything possible.

The 1997 Kyoto Protocol was less ambitious than its parent UNFCCC, and when it came to the terrestrial system, the world faltered. For all intents and purposes, the Protocol excludes incentives for the better management of terrestrial carbon in developing countries. It excludes incentives to improve forest and agricultural management practices to avoid deforestation. It excludes improved agricultural practices. And it effectively excludes growing new carbon as trees and other vegetation and associated soil carbon.

The Kyoto Protocol indirectly locks in terrestrial carbon emissions.

But the science is clear. We essentially need to decarbonize the global economy. We cannot afford to continue to pick and choose between action on fossil fuel emissions and terrestrial carbon emissions, and between technological sequestration and terrestrial sequestration. That game is over. We have to do it all: the industrial solution and the natural solution. And we have to do both at the required scale, not just piecemeal fiddling.

The risk is that the Copenhagen agreement repeats the mistake of the Kyoto Protocol, locking terrestrial carbon out of the solution and negligently wasting the rapidly diminishing time we have to combat climate change. And, in many ways, terrestrial carbon represents a "limited time only" offer.

Fortunately, it appears that countries are ready to include terrestrial carbon in the Copenhagen agreement, under a broadly defined mechanism referred to as "REDD-plus" (Reducing Emissions from Deforestation and Forest Degradation in developing countries plus other activities).

It is essential that this mechanism is comprehensive, even if phased, starting with forests and peatlands and expanding as rapidly as science allows to all terrestrial carbon.

As a party to the UNFCCC and Kyoto Protocol, Indonesia has been instrumental in driving the terrestrial carbon agenda forward, both domestically and internationally. Indonesia has been clear about its intentions and expectations, rather than taking the easy option of hedging its bets.

Rather than playing poker with climate change, Indonesia has laid its cards clearly on the table. It might not have offered everything that is required, but it has offered more than many other countries and it has been clear. Importantly, it has followed words with action.

Indonesia was the first OPEC country to begin the Kyoto ratification process. It was the first country to establish regulations on how REDD would be implemented within its borders, including how revenue from REDD projects would be shared. Joint submissions to the UNFCCC by Indonesia and Australia mark another milestone in Indonesia's diplomatic efforts to secure a successful outcome at Copenhagen.

It is a long way from Jakarta to the edges of the archipelagic nation's forests, and Indonesia is the first to admit that implementation won't be easy. In a country where hard-to-control forest fires cause major land-use change and the majority of farms are smaller than one hectare, a strong national framework becomes even more crucial. This is why Indonesia's efforts to focus on the detailed technical and policy issues of long-term implementation are so important. It will be at this level that any international agreement becomes real.

In partnership with other countries and NGOs, Indonesia is building systems to collect and analyze satellite and ground data, and undertaking large-scale demonstration activities. It is working with Australia to develop a national Forest Resource Information System and National Carbon Accounting System.

Indonesia is harnessing and enhancing its strong scientific capacity. In 2007 in Bali, Indonesia convened the first finance ministers' meeting on climate change. And last year it established the National Council on Climate Change to coordinate climate change policy, negotiations, and implementation across all levels and portfolios of government in Indonesia's decentralized system.

Much has been achieved in Indonesia, but much remains to be done long after the ink dries on an international deal. That is why partnerships and hard work on detail are so important.

At their meetings in New York and Pittsburgh this week, world leaders can build on Indonesia's leadership by committing to the key elements of Indonesia's success to date.

To long-term partnerships on policy, technology, and implementation - not only between developed and developing countries but also among developing countries.

To enhancing knowledge on the science and economics of terrestrial carbon. To action at the required scale.

To a coordinated whole-of-government approach.

To elevating terrestrial carbon (including REDD) to the level of finance ministers, heads of government, and overall national planning.

A lack of clear commitment from world leaders in the remaining two-and-a-half months before Copenhagen will jeopardize a strong agreement.

Rather than prevaricating, world leaders must learn from Indonesia's commitment and progress to an essential part of the climate change solution - one that is feasible, immediately available, and at the heart of the transition to a low emission economy: terrestrial carbon.

The writer is convener and chair of the International Terrestrial Carbon Group, senior policy fellow at the H. John Heinz III Center for Science, Economics and the Environment, and visiting scholar at Columbia University.