Europe is known as a champion of combating climate change. But a developing country famous for its capital's polluted air is also a surprising front-runner: Mexico.

Mexico ranked fourth on the Climate-Change Performance Index, which scores countries on their greenhouse-gas emissions and policy. The policy group Germanwatch released the report this week during the U.N. climate-change conference in Bali. Only Sweden, Germany and Iceland outscored Mexico, with its 110 million people. The United States ranked 55th out of 56 countries, ahead only of Saudia Arabia.

"I don't think any developing country has spelled out as comprehensive a strategy as Mexico," said Pankaj Bhatia, director of the Greenhouse-Gas Protocol Initiative of the World Resources Institute, a sustainability think tank. "I think it's a great example for developing countries like China, Brazil and India."

With much of the wrangling at the international level occurring among the European Union, China and the United States, the strides of some smaller, non-European countries have been overlooked. Known for its manufacturing and natural-resource extraction industries, Mexico is not typically considered a paragon of environmental planning.

Recent years, however, have seen a marked change in government policy. The government adopted a comprehensive climate-change mitigation strategy in May, and the new mayor of Mexico City, Marcelo Ebrard, has received international acclaim for his $550 million plan to reduce the capital's emissions. Mexican companies were also the first in the developing world to begin voluntarily inventorying their greenhouse-gas emissions along World Resources Institute guidelines.

Germanwatch attributed Mexico's jump from No. 16 in last year's rankings up to No. 4 this year to "constructive international and national climate policy and its relatively favorable emissions trends."

Ned Helme, president of the Center for Clean Air Policy, said Mexico's aggressive direction on climate change stems from the country's new president, Felipe Calderon, who was sworn in last December.

"Calderon had come out of the ministry of energy and is really committed to moving on climate change," Helme said.

According to the World Resources Institute, Mexico produced 415.3 million tons of carbon dioxide in 2004. Helme's think tank believes Mexico's new policies, which include increasing renewable energy and energy efficiency as well as planting forests, will reduce the country's greenhouse-gas emissions by 110 million tons by the year 2020. The United States, starting with 10 times the emissions that Mexico creates, would only reduce emissions 180 million tons based on current policy.

"The Mexican government has been very courageous," Bhatia said. "Their success is inspiring similar programs in other countries."

In fact, the development of Mexico as a leader in the battle to reduce greenhouse-gas emissions has already proven to be a valuable model that other developing nations are looking to follow.

"When we went to China, the authorities said, 'We'd like to see how other developing countries have done,'" Bhatia said. "We provided the Chinese with the Mexican success story, and that enabled us to get a program started there."

Other Latin American countries have made strides to reduce their contributions to global warming. Costa Rican President Oscar Arias declared that his country would be carbon-neutral by 2020, even as he admitted the goal would be difficult to reach.

Both Mexico and Costa Rica have engaged in ambitious tree-planting efforts. A far cry from the community efforts often seen in the United States, Mexico wants to put 250 million trees in the ground by the end of 2007, and Costa Rica's goal is 6.5 million. The trees are a natural way to sequester carbon dioxide through their normal metabolic processes.

Mexico's vigorous activity domestically has also given it a new voice internationally. At the Bali climate-change conference, Helme said the Mexican delegation became a leader among developing nations.

"Stay tuned. Mexico is going to be very aggressive in the next year," he said. "They're saying, 'We're actually doing more than the Europeans, and it's time we beat our chests and asked the (developed world): What are you doing?'"