London , England ( CNN ) -- Thousands of people tuned in to watch the CNN/YouTube climate change debate , which took place Tuesday at the COP15 climate conference in Copenhagen , Denmark . CNN 's Becky Anderson was joined by a distinguished panel of guests who answered questions posted on YouTube in the weeks leading up to the debate . The panel included Yvo de Boer , Executive Secretary of the United Nations Framework Convention on Climate Change ; U.S. journalist and author Thomas L. Friedman ; Bjorn Lomborg , author of the `` The Skeptical Environmentalist ; '' Hollywood actress and environmental activist Daryl Hannah and former U.N. Secretary-General Kofi Annan . The panel tackled a range of climate change issues head on , addressing some of the major concerns of YouTube 's users . John from the Republic of Ireland wanted to know whether the panel thought that world leaders were taking climate change seriously enough . The message from Yvo de Boer was clear . Watch the debate : Part 1 I 2 I3 I4 I5 I6 . `` I 've never seen a moment in history when so many world leaders have taken an interest in this topic , '' de Boer said . `` We have 115 coming on Friday to get a strong resounding result out of this week . '' Daryl Hannah agreed : `` This is definitely a defining moment for our politicians and world leaders to take a stand to make real change from a fossil fuel economy to a new energy independent economy . '' But Bjorn Lomborg questioned whether world leaders would sign an agreement . `` One-hundred-and-fifteen leaders are coming to Copenhagen but what are they going to agree on ? '' he said . `` Do n't they want to do something smarter that will actually work this time . '' Thomas Friedman urged the United States to take a lead on climate change . `` Right now , '' he said , `` that is very much up in the air . The uncertainties surrounding climate change are not a reason for inaction . They are a reason to act . '' The panel answered a range of questions from YouTube users all over the world from the United States to Bangladesh and Brazil . A questioner from Morocco wanted to know if African countries had a loud enough voice at the climate talks . Kofi Annan was in no doubt that the continent did not . `` What is clear , '' he said , `` is that Africa and the least developed countries , which are not so much responsible for the problem of climate change , are bearing the greatest brunt . '' Annan , who joined the debate via a live satellite link from Geneva , Switzerland , said the whole world was in the same boat . `` We must come together to protect the planet , '' he said . `` It is our collective responsibility . We can not resolve climate change in one nation , or one continent ND not in another , '' he continued . The Web broadcast was attended by an audience of delegates who are attending the U.N. climate conference at the Bella Center . The program also showcased the winners of the Raise Your Voice video competition and featured a recorded video message from Archbishop Desmond Tutu , who warned about the impacts of climate change . `` The consequences could be conflict and instability , which are things we must avoid at any price , '' he said .
CNN/YouTube Climate Change Debate links thousands of Web users . Distinguished panel of guests includes former U.N. secretary general Kofi Annan . Debate also showcased winners of the Raise Your Voice video competition .