Concentrations of key gases in the atmosphere that are driving up global temperatures reached a new high in 2017.
In their
, the World Meteorological Organization (WMO) says there is no sign of reversal in this rising trend.
Carbon dioxide levels reached 405 parts per million (ppm) in 2017, a level not seen in 3-5 million years.
Researchers also note the resurgence of a banned gas called CFC-11.
What are concentrations?
Concentrations differ from emissions in that they represent what remains in the atmosphere after some of the gases are absorbed by the seas, land and trees.
Since 1990 the warming impact of these long lived gases on the climate has increased by 41%.
How does the latest data compare to previous years?
2017 continues the rise in concentrations of CO2 which are now 46% greater than the levels in the atmosphere before the industrial revolution.
The increase from 2016 to 2017 was smaller than the rise from 2015 to 2016, but is close to the average growth rate seen over the last decade.
The scientists at the WMO believe that the amount of CO2 in the atmosphere right now hasn't been seen in a long, long time.
"The last time the Earth experienced a comparable concentration of CO2 was 3-5 million years ago, when the temperature was 2-3C warmer and sea level was 10-20 metres higher than now," said WMO Secretary-General Petteri Taalas.
Why did CO2 concentrations not rise as fast in 2017?
That's because of the impact of El Niño, the naturally occurring weather phenomenon which peaked in 2015 and 2016. This triggered droughts in some parts of the world, which in turn reduced the ability of forests and vegetation in these areas to soak up CO2, hence more of it stayed in the atmosphere.
Does that lower rise mean that some progress is being made?
Not so much. Scientists are very worried that when they measure the chemistry of the atmosphere they find that things are still going in the wrong direction.
"I am very concerned that the three greenhouse gases most responsible for climate change (CO2, methane, and nitrous oxide) are all rising upwards unabated," said Prof Corinne Le Quéré from the University of East Anglia.
"CO2 concentrations are now well above 400ppm - levels were 321ppm when I was born, that is a big rise in a human lifetime!"
What about this mysterious CFC-11 gas?
There have been a number of reports about CFC-11, a gas that's used in home insulation. Unfortunately, production is a real double whammy for the environment, damaging the ozone layer while also contributing to global warming.
Why did CO2 concentrations not rise as fast in 2017?
That's because of the impact of El Niño, the naturally occurring weather phenomenon which peaked in 2015 and 2016. This triggered droughts in some parts of the world, which in turn reduced the ability of forests and vegetation in these areas to soak up CO2, hence more of it stayed in the atmosphere.
Does that lower rise mean that some progress is being made?
Not so much. Scientists are very worried that when they measure the chemistry of the atmosphere they find that things are still going in the wrong direction.
"I am very concerned that the three greenhouse gases most responsible for climate change (CO2, methane, and nitrous oxide) are all rising upwards unabated," said Prof Corinne Le Quéré from the University of East Anglia.
"CO2 concentrations are now well above 400ppm - levels were 321ppm when I was born, that is a big rise in a human lifetime!"
What about this mysterious CFC-11 gas?
There have been a number of reports about CFC-11, a gas that's used in home insulation. Unfortunately, production is a real double whammy for the environment, damaging the ozone layer while also contributing to global warming.
Will this new study have any impact?
The scientists behind it certainly hope so. They believe that their analysis needs to be seen alongside the recent IPCC 1.5C report which warned that the world needed to be essentially carbon neutral by 2050.
The WMO bulletin comes out just a week or so before climate negotiators begin at the
in Katowice, Poland, where countries will discuss putting the Paris climate agreement into practice and increasing their ambitions when it comes to cutting warming gases.
"The new IPCC Special Report on Global Warming of 1.5C shows that deep and rapid reductions of emissions of carbon dioxide and other greenhouse gases will be needed in all sectors of society and the economy," said IPCC Chair Hoesung Lee.
"The WMO greenhouse gas bulletin, showing a continuing rising trend in concentrations of greenhouse gases, underlines just how urgent these emissions reductions are."