Chaired by the Presidents of Mongolia, H.E. Mr Tsakhigiin Elbegdorj, and Guyana, H.E. Mr Donald Ramotar, the high level session was addressed by Aleqa Hammond, Premier of Greenland (Denmark), Thomas Stocker, Co-chair of the Intergovernmental Panel on Climate Change (IPCC) Working Group I, Julia Marton-Lefèvre, Director General of the International Union for the Conservation of Nature (IUCN), and Barbara Frost, Chief Executive of WaterAid.

The President of Mongolia opened the session by underlining that "climate science is critical to the future of the planet—this is why this Climate Change Summit is an opportunity we cannot miss.”

This was followed by an interactive discussion that focussed on the key findings of climate science relevant to policy, as well as how to harness knowledge and information more effectively and to educate and empower people for action.

Ms Hammond made the stakes clear—"We are experiencing climate change in our bodies, in our minds, in our country every day." The Arctic is warming about twice as fast as the global average, leading to a melting of Arctic Ice and the Greenland ice sheet.

For the IPCC, Mr Stocker said the impact of climate change is clear and unequivocal. Science is clear in showing the warming of the climate system, with unprecedented changes over decades to millennia, and that human influence is the dominant cause. Staying within the internationally-agreed 2 degree Celsius temperature rise limit—itself with a deep impact—can only be realized through urgent and ambitious action to move towards carbon-neutral economies and societies. A higher rise will have a tremendous impact on the planetary ecosystems.

Avoiding the worst impacts will require substantial and sustained reductions in greenhouse gas emissions starting now.

A particular challenge concerns the alteration of the water cycle, as mentioned. Adaptation is needed to protect poor and vulnerable communities from floods, droughts and resource shortages, according to Ms Frost.  "Urgent action is needed for 750 million men and women without access to safe water," she said.

The debate included interventions from participants from across the world. The Prime Minister of Tuvalu, Enele Sopoaga, who highlighted the extreme vulnerability of his islands, and John Holdren, Assistant to the US President for Science and Technology as well Professor E. Kalnay, from Argentina, member of the Scientific Advisory Board to the UN Secretary-General.

Speakers underlined that access to sound science, information and climate services is crucial to long term effective climate action. This calls for greater investment to further enhance knowledge and to reduce uncertainty, through stronger science and tighter links with policy.

The discussion highlighted also that the knowledge base for informed action is already available to guide climate policies and decisions from the national to the local scale—but this must be harnessed fully and nurtured by all actors.

Ms Marton-Lefèvre underlined the importance of partnership for joint action. "We need science to demonstrate it is good for nature and for the people who depend on it," she said.