This year started with big hopes - in 2015, the world would finally unite in a fight against climate change. It needed to.

The weather was getting more extreme and the planet was becoming hotter, with 2014 the hottest year in recorded history. Storms, floods and droughts were all growing in strength and millions of people were being affected.

Failed United Nations climate talks in Copenhagen in 2009 had set back efforts.

After years of diplomacy, a major UN meeting in Paris from Nov 30 to Dec 11 this year was meant to finally seal a deal in which all nations would cut greenhouse gas emissions to slow the pace of global warming.

The French government was determined a deal would be done. President Francois Hollande marshalled an army of diplomats, led by Foreign Minister Laurent Fabius, to travel the globe during the year to overcome deep divisions and mistrust that had held back a universal climate deal for more than two decades.

On Dec 12, their efforts, and those of the UN, prevailed. After intensive negotiations involving delegates from nearly 200 nations, the Paris talks concluded with a global deal.

All nations will cut emissions through national action plans that are regularly reviewed and boosted over time. The pact commits all nations to hold warming to well below 2 deg C and pursue efforts to aim for a 1.5 deg C rise over pre-industrial levels.

To achieve this, fossil fuel pollution will have to be slashed, and quickly, while renewable energy and energy efficiency investments need to be greatly expanded.