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«Now is when we must act,» said the UN secretary general.

Leaders of 125 countries meet this Tuesday at the United Nations headquarters in New York, United States, at the summit on climate change.

The objective of the meeting is to obtain the support of the member states so that next year they sign a global agreement on climate change at a meeting that will take place in Paris.

«Climate change is the defining issue of our time. Now is the time to act,» UN Secretary-General Ban Ki-moon said before the summit began.

With so many nations participating in the one-day meeting, there will be three separate sessions taking place simultaneously.