THE amount of greenhouse gas in the Earth’s atmosphere has hit its highest level for three million years.

New data show the unrelenting rise in carbon dioxide in our air continued in 2018, despite global efforts to switch away from fossil fuels.

The World Meteorological Organisation (WMo), a Swiss-based agency of the United Nations, said the increase in CO2 concentrations was above average for the last decade.

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HeraldScotland: Camley's Cartoon: Greenhouse gas emissions continue to rise.Camley's Cartoon: Greenhouse gas emissions continue to rise.

Campaigners believe the latest rise - which means there is more carbon in the atmosphere than at any time since the human species evolved - represented a significant failure to act by governments.

WMO Secretary-General Petteri Taalas said: “There is no sign of a slowdown, let alone a decline, in greenhouse gases concentration in the atmosphere despite all the commitments under the Paris Agreement on Climate Change.

“We need to translate the commitments into action and increase the level of ambition for the sake of the future welfare of the mankind,” he said.

Mr Taalas added that the last time the planet experienced comparable concentrations of carbon dioxide in the atmosphere was three to five million years ago, when temperatures were 2C to 3C warmer and sea levels were 10-20 metres higher than today.

A 20-metre increase in water levels would - as things stand - threaten the very existence of low-lying cities like Glasgow and London and create new seas across flat parts of the world like Lincolnshire and the Netherlands.

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Concentrations of carbon dioxide, the main gas driving global heating, reached 407.8 parts per million in 2018, up from 405.5 parts per million (ppm) in 2017.

That is well above the level of around 280 ppm seen before the industrial revolution and the start of large scale burning of fossil fuels for energy and transport, which have driven up carbon dioxide in the atmosphere.

Concentrations of other climate-warming greenhouse gases, such as methane, which is linked with intensive cattle farming, and nitrous oxide, also surged by higher amounts in 2018 than in the past decade, according to the observations carried out by the WMO.

Global heating has already seeing glaciers melt and sea levels rise.

This year along the world has suffered its most northerly hurricane in history as oceans heat, devastating fires in Brazil and California and dramatic flooding in Siberia, and America’s mid-west.

This month Venice suffered its highest water in decades, raising concerns about its long-term future.

At the same time raging infernos in Australia destroyed much of the habitat of the koala, eucalyptus forests, prompting scientists to declare the iconic species “functionally extinct”.

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The WMO warns that even with the pledges made by countries under the international Paris deal, global emissions are not estimated to peak by 2030, let alone by the 2020 date that scientists have said is necessary to curb dangerous climate change.

Some developing economies - despite seizing opportunities of greener energy - are still growing CO2 emissions.

Caroline Rance, climate campaigner, Friends of the Earth Scotland, said: “Behind this figure of 407.8ppm lies the devastating reality that millions of people around the world are losing their homes, crops, and ultimately their lives as polluting governments and industries continue to ignore the science. “But we know what the solutions are. We must end the use of fossil fuels and deliver a just transition to a safe, renewable future for all.

“Governments around the world have been under increasing public pressure to act on the climate crisis.

“With the UN global climate talks beginning in Madrid next week, today’s news should act as catalyst to deliver the urgent action needed.

“With these talks coming to Glasgow next year, the Scottish and UK Governments need to wake up to the scale of this emergency and act accordingly.”

Robin Parker, Climate and Energy Policy Manager at World Wildlife Fund, stressed that the industrial revolution powered by coal and oil had begun in Scotland.

He said: “These figures are startling and show we have no time to waste to dramatically reduce our global emissions. “Richer countries, such as Scotland, that benefitted the most from the fossil fuel era now have a moral obligation to play a leading role in ending it. “We’ve already reduced emissions by around 50 per cent since 1990, but we need to keep up the pace and show the world it can be done.

“That means more action and money going to tackling the climate emergency. By the time world leaders gather in Glasgow next year for the UN climate talks, we should be able to say the fossil fuel era will end where it started.”

The WMO said current measures of CO2 were about 147% higher than they had been in 1750 - roughly the beginning of the industrial revolution. CO2 - which is released when, for example, coal or petrol is burned - accounts for four-fifths of global warming.

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Scottish environmental campaigner and school strike advocate Holly Gillibrand stressed that the rise in greenhouse gases was not only causing a climate emergency, but an extinction one.

The Lochaber 14-year-old said: “Our leaders need to start cutting CO2 before we go past the point of no return.”

The WMO report is based on observations from Global Atmosphere Watch network, a group of weather stations around the world.