The main threat to the Australian coral reef is climate change. 35 per cent of the corals making up the reef have died as a result of bleaching caused by excessively high sea water temperatures (Photo by Reinhard Dirscherl/ullstein bild via Getty Images)

A debilitated and dehydrated sheep in Australia, one of the countries most at risk from severe drought (Photo NEIL SANDS/AFP/Getty Images)

Penguins are threatened above all by climate warming, which is severely testing their survival in Antarctica. The steady rise in temperatures is literally melting their habitat (Photo credit EITAN ABRAMOVICH/AFP/Getty Images)

In Bangladesh the monsoon season brings destruction every year, with vast masses of dark water relentlessly sweeping away homes, crops and livestock. Climate change threatens to worsen the intensity and duration of flooding (Photo by: Shaikh Mohir Uddin/Majority World/UIG via Getty Images)

Erosion caused by rising sea levels "eats away" around six metres of coastline per year in Alaska, causing serious damage to homes built along the coast (Photo credit should read GABRIEL BOUYS/AFP/Getty Images)

The Aletsch glacier in Switzerland, the largest in the Alps, is shrinking rapidly due to rising temperatures. Glaciers across Europe have been retreating since 1870; the process accelerated from the early 1980s, a phenomenon that many scientists attribute to global warming (Photo by Sean Gallup/Getty Images)

The chronic water scarcity of the African savannah, exacerbated by climate change, is endangering the survival of wildlife (Photo by: JTB/UIG via Getty Images)

A flooded village in Pakistan's Punjab province. In the north of the country the great glaciers are melting, while its population continues to grow; floods produce millions of climate refugees every year (Photo credit should read Arif Ali/AFP/Getty Images)

In Russia rising temperatures melt the ice and force polar bears to travel great distances — including by swimming — in search of food, or to venture close to human settlements, where they come into conflict with guard dogs (Photo Vladimir Melnik)

The most polluting sector, and the one that contributes most to climate change, is livestock farming, which generates more greenhouse gases than the entire transport sector. According to the FAO, livestock contribute to nearly two thirds of agricultural greenhouse gas emissions and 78 per cent of agricultural methane emissions (Photo credit should read LOIC VENANCE/AFP/Getty Images)

China's heavy dependence on coal has made the country the source of nearly one third of global CO2 emissions, contributing decisively to global warming (Photo by Kevin Frayer/Getty Images)

The extent of Arctic ice is in alarming and steady decline. The area of sea ice during the autumn months decreased by 27.3% between 1979 and 2010 (Photo by Mario Tama/Getty Images)

Climate change is fragmenting the Arctic ice — the bears' hunting ground — forcing the animals into ever longer periods without food. Many bears, exhausted by hunger and fatigue, fail to survive (Photo by Wolfgang Kaehler/LightRocket via Getty Images)

A girl from Kenya's Turkana tribe digs a hole in a dry riverbed in search of water. More than 23 million people across East Africa are facing severe shortages of water and food, a situation made worse by climate change (Photo by Christopher Furlong/Getty Images)

A blanket of pollution-generated haze hangs over the centre of Hong Kong. Levels of carbon dioxide, methane and nitrous oxide in the air have reached levels never recorded in the past 800,000 years (Photo credit should read Alex Ogle/AFP/Getty Images)

In Kenya the traditional nomadic way of life and pastoral farming are threatened by increasingly frequent periods of drought (Photo by Christopher Furlong/Getty Images)

Limiting the rise in global temperature

The effects of climate change are now evident and threaten the survival of millions of people across the planet. The twenty-second United Nations conference on climate change (Cop 22) is under way in Marrakech, Morocco. The aim is to make the Paris Agreement operational — signed at Cop 21 and entered into force on 4 November — which provides for limiting the growth of the global average temperature "well below 2 degrees Celsius".

The effects of climate change, in photos