The Summit, together with a People's Climate March in which the Secretary-General participated, demonstrated the power of civil society and business as catalysts for national action. The close of the Summit brought renewed hope, not only that a universal agreement might be possible in 2015, but also that the high-level engagement of leaders, civil society and business would help galvanize it. Among its conclusions, the IPCC again found that human influence on the climate system was clear. It stated that anthropogenic GHG emissions were the highest in history, and that recent climate change had widespread impacts on human and natural systems.91 AR5 emphasized that climate change risk would more severely impact already vulnerable and marginalized communities92 Limiting global warming to 2°C would require "substantial emission reductions over the next few decades and near zero emissions of C02 and other long-lived GHGs by the end of the century"93 In addition, AR5 indicated that effective mitigation would require international cooperation.