World in new era of 'climate change reality' as carbon dioxide levels hit new average high

The world has entered a new era of "climate change reality", with carbon dioxide levels in the atmosphere reaching a new average high.

In 2015, for the first time, carbon dioxide levels in the atmosphere were at 400 parts per million (ppm) on average across the year as a whole, a symbolic threshold which it will not fall below for many generations, scientists have said.

Between 2014 and 2015 there was a bigger-than-average increase in the greenhouse gas in the atmosphere, researchers at the longest established greenhouse gas monitoring station in the world, at Mauna Loa in Hawaii, found.

Before the Industrial Revolution, the levels of carbon dioxide in the atmosphere stood at 278ppm, a concentration the World Meteorological Organisation (WMO) said represented a natural balance on Earth.

The strong El Nino, which started in 2015 and continued into this year, triggered droughts in tropical regions and reduced the ability of forests, vegetation and oceans to absorb carbon dioxide, leaving more in the atmosphere.

However, the long term increase of greenhouse gases such as carbon dioxide, methane and nitrous oxide from human activity including industry and agriculture have caused a 37% increase in the warming effect on the planet between 1990 and 2015. Two-thirds of the warming effect is due to carbon dioxide.

The research was published in the annual greenhouse gas bulletin ahead of the next round of climate talks, which will mark the early entry into force of the Paris Agreement, the world's first comprehensive deal to tackle climate change agreed in the French capital last year.

WMO secretary-general Petteri Taalas said: "Without tackling carbon dioxide emissions, we cannot tackle climate change and keep temperature increases to below 2C above the pre-industrial era.

"It is therefore of the utmost importance that the that the Paris Agreement does indeed enter into force well ahead of schedule on November 4 and that we fast-track its implementation."

The Paris agreement commits countries to keeping temperature rises to "well below" 2C and to pursue efforts to limit increases to 1.5C, by cutting greenhouse gas emissions to net zero in the second half of the century.