La Niña is a part of the El Niño southern oscillation, a climate fluctuation that slowly sloshes vast bodies of water and heat between different ocean basins and disrupts weather patterns around the world.

The past two years have seen month after month become the planet's hottest recorded. Climate scientists say human-produced greenhouse gases account for the majority of the warming.

The European climate service Copernicus says the world warmed to yet another monthly heat record in January, despite an abnormally chilly United States, a cooling La Nina and predictions of a slightly less hot year.