By Elizabeth Blunt
BBC News, Buenos Aires
China and Brazil have presented details of their greenhouse gas emissions to an international summit on climate change.
China has seen huge economic growth with modest emissions
Both countries also explained how they plan to contribute to the fight against global warming.
The presentation aroused a good deal of interest amid discussions about whether such rapidly developing countries should be expected to reduce emissions.
Greenhouse gases do not just come out of the smokestacks of factories or the exhaust pipes of cars, they said.
In Brazil it seems a staggering 75% of the country's carbon dioxide is produced by the destruction of the Amazon rainforest, with carbon dioxide being given off as trees are burned or allowed to rot.
The Chinese presentation revealed a more conventional programme with its power industry by far the largest contributor to greenhouse emissions.
But it also included a discreet reference to what it called "animal enteric fermentation" - a reminder that some greenhouse gases like methane are produced by pigs and cows and that these agricultural emissions can be quite significant in developing countries.
But although Brazil and China are very different, both are keen participants in the movement to arrest climate change and both can boast real achievements.
Brazil has pioneered the use of ethanol made from renewable sources such as sugar cane to replace petrol for cars and lorries.
China has cleaned up some of its older, coal-fired power plants and has succeeded in growing economically with a relatively modest rise in greenhouse gas emissions.
At the moment neither country has any obligation to cut back.
The Kyoto Protocol only imposes binding cuts on the developed countries who caused the problem.
But some delegates are starting to think about what should happen after the first phase of Kyoto cutbacks.
Some are suggesting that China and Brazil might be offered the chance to gain some kind of benefit from voluntary cutbacks, perhaps by being able to sell their carbon reduction credits on the international market.