The main task for negotiators at the United Nations climate talks in Lima last week was simple: lay out the rules for the emissions pledges that countries will submit over the next six months. Countries had already agreed to put forth plans, each according to its own needs, capabilities and circumstances, and were riding a small wave of optimism after the surprise announcement in the lead-up to the talks that China and the United States had agreed to cut their emissions. The question was how to register and interpret these commitments going into the headline summit in Paris next year.

It is hard to overstate the simplicity of this task, especially relative to the magnitude of the challenge at hand. And yet negotiators went into double overtime fighting old fights, and walked away with something that bears a clear resemblance to nothing.

Negotiators had various options on the table, ranging from a generic registry of commitments to a formal review process in which countries would be expected to provide the relevant data and then defend the adequacy of their pledges. But after days of bickering about what should be required of whom — led by China, which opposed the reviews — they wound up with a text that requires little of anybody.

The final system must allow everybody to evaluate all national commitments and track their progress over time. A treaty that formalizes such an approach would give all countries confidence that their investments are not in vain.

Sure, nations are beginning to take action, but it is the cumulative carbon emissions that matter. The end goal is a world with essentially zero emissions. That is not possible unless all countries play ball. We are in the middle of a trust-building exercise, and the first step is transparency.

One sticking point is that national commitments can (and will) be assessed in various ways. Wealthy countries will measure actual reductions in emissions; rapidly developing countries might opt for reductions from forecast growth. But commitments can also be assessed in terms of cost, either absolute or relative to economic activity, and even on technical capacity for the poorest nations. Both carbon emissions and investments can be assessed relative to population and per-capita income to get at the question of equity, which is at the heart of most disputes in the climate negotiations. All of these measures are legitimate, and academics are already busy with such analyses. But they all depend on one thing: information, which is what was dropped from the Lima agreement.

Some countries are likely to provide the relevant evidence to bolster their cases, but this process must be streamlined and must be required of every country. Governments, scientists and environmentalists will fill in any gaps as best they can over the coming year, but the challenge will only grow. Next year’s pledges will probably fall well short of what is needed to prevent the worst impacts of global warming, so commitments will need to be reviewed and updated regularly. Once governments can demonstrate progress, the plan is for them to initiate a virtuous cycle in which better policies and cheaper technologies help to push emissions ever lower.

This will only work, however, if governments can be held accountable and independent analysis can identify which policies are working — and which are not. And to do that, the world will need solid data and robust assessments. Simple or not, the treaty to be signed in Paris should recognize as much.