The World Meteorological Organization (WMO) says the increase in CO2 in 2018 was just above the average rise recorded over the last decade. Levels of other greenhouse gases, such as methane and nitrous oxide, have also surged by above average amounts.

What does the report say?

The WMO report looks at concentrations of warming gases in the atmosphere rather than just emissions. The difference between the two is that emissions refer to the amount of gases that go up into the atmosphere from the use of fossil fuels, such as burning coal for electricity and from deforestation.

Concentrations are what’s left in the air after a complex series of interactions between the atmosphere, oceans, forests and land. About a quarter of all carbon emissions are absorbed by the seas, and a similar amount by land and trees.

Using data from monitoring stations in the Arctic and all over the world, researchers say that in 2018 concentrations of CO2 reached 407.8 parts per million (ppm), up from 405.5ppm a year previously.

This increase was above the average for the last 10 years and is 147% of the “pre-industrial” level in 1750.

What about the concentration of other gases?

The WMO also records concentrations of other warming gases. About 40% of the methane emitted into the air comes from natural sources, such as wetlands, with 60% from human activities, including cattle farming, rice cultivation and landfill dumps.

Methane is now at 259% of the pre-industrial level. The increase seen over the past year was higher than both the previous annual rate and the average over the past 10 years.

Nitrous oxide is emitted from natural and human sources, including oceans and fertiliser-use. According to the WMO, it is now at 123% of the levels that existed in 1750.

What concerns scientists is the overall warming impact of all these increasing concentrations. Since 1990 there’s been an increase of 43% in the warming effect on the climate of long-lived greenhouse gases. And there is no indication of this slowing down.

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