Monday marked the opening of the U.N. Climate Change Conference in Cancún, Mexico. The Mexican-born Nobel Prize-winning scientist Mario Molina spoke at the conference’s opening ceremony.

Mario Molina: “I urge you to reach agreement on concrete steps to move us closer to an international regime that formalizes the commitments that many nations have already made and that incorporates as well strong support for adaptation to climate change impacts. I also urge you to outline in some detail the steps that are required to reach a definitive agreement within the next few years.”

Rajendra Pachauri, the chair of the U.N.’s Intergovernmental Panel on Climate Change, also spoke.

Rajendra Pachauri: “We hope Cancún signifies a major step in action to deal with the challenge of climate change. The available scientific knowledge of this field justifies it, and the global community rightly expects it. Thank you very much.”

Only about 20 world leaders are expected to attend the Cancún talks. President Obama, British Prime Minister David Cameron, and most other leaders from the world’s wealthiest nations have no plans to attend. This is Mexico’s foreign minister Patricia Espinosa.

Patricia Espinosa: “Climate change has a very high cost for my country, Mexico. Like many of your countries, it is highly vulnerable to the effects of this phenomenon. The key to the success of these negotiations is to consolidate the legitimate individual interests and unite efforts in order to leave an important collective mark. It means that all countries should have access to sustained development that benefits our generation and those that follow.”