But what is also clear from the IPCC report is that our internationally agreed target of keeping global warming below 2 C remains within our grasp. And we must ensure this is reflected in bold contributions to the global climate change agreement.

The new deal must mirror the evolving national responsibilities in the world economy, as well as today's geopolitical realities and the capacity of countries to contribute. What is critical is a commitment from all countries to play their part.

This is why the summit in Lima is crucial. It will be an opportunity to put pressure on other countries, particularly the other members of the G20, to come forward with their own targets soon. The sooner they do this the more time we all have to assess if the commitments add up to what scientists tell us is required to keep global warming to below 2 C.

Countries will also discuss the methodology for evaluating the different contributions, to make sure they are fair and add up to the effort we need. Last but not least, they will discuss the important topic of climate finance to the most vulnerable countries.

UN Secretary-General Ban Ki-moon has called on world leaders to turn climate change from "the greatest collective challenge facing humankind today into the greatest opportunity for common progress towards a sustainable future." If we are to succeed in this, we must have the political courage to act decisively now, with ambition and collectively.

Federica Mogherini is high representative of the Union for Foreign Affairs and Security Policy and vice-president of the European Commission, Miguel Arias Ca?ete is commissioner for Climate Action and Energy.