“ Because this is a decisive moment for New Yorkers, and for the people of all the cities represented at this C-40 summit. Since the.... “ Because this is a decisive moment for New Yorkers, and for the people of all the cities represented at this C-40 summit. Since the first C-40 conference in London in 2005, the world’s understanding of the causes and consequences of climate change has reached a true turning point.

“ While we still have much to learn; and while continued scientific investigation of global warming therefore remains of the utmost importance, it is now crystal clear that such ongoing research must be matched by decisive action in the political and economic spheres.

“ Because we now know beyond a doubt that global warming is a reality. And the question we must all answer is, “What are we going to do about it?” That’s a challenge that we all face, because, as proud as we all are of the cities and nations that we serve, global warming also makes us all global citizens. We are truly in this together.

“ Let me quote to you some of the conclusions reached by Sir Nicholas Stern, the former chief economist of the World Bank, in his authoritative review of global warming published last October. Of the effect of greenhouse gas emissions on the global climate, he said: ‘If no action is taken to reduce emissions, the concentration of greenhouse gases in the environment could reach double its pre-industrial level as early as 2035.’

“ This would, he warned, produce temperature increases that would ‘be very dangerous indeed, having serious impacts on world output, on human life, and on the environment.’ All countries would be affected, he wrote by ‘risks of major disruption to economic and social activity on a scale similar to those associated with the great wars and the economic depression of the first half of the 20th century.’

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