Challenging a French government decision evoking security considerations to ban demonstrations coinciding with the COP21 Climate Change Conference in Paris, tens of thousands of protesters took to the streets of Paris. Police detained 300 demonstrators. The COP21 conference begins today, with the expected participation of 147 heads of states. An agreement is being sought to prevent the planet's temperature from increasing more than 2°C. Luis Arroyo reports from Paris. teleSUR