The amount of greenhouse gases in the Earth's atmosphere reached another record high in 2014, surpassing the symbolic threshold of 400 parts per million across much of the planet in a continual rise that fuels climate change and could make the planet inhospitable for future generations, the United Nations' World Meteorological Organization (WMO) warned in report released Monday.

"We are moving into uncharted territory at a frightening speed," WMO Secretary General Michel Jarraud said in a statement. "Every year we say that time is running out. We have to act now to slash greenhouse gas emissions if we are to have a chance to keep the increase in temperatures to manageable levels."

The WMO report showed that carbon dioxide, the most dangerous greenhouse gas due to its long life cycle, has climbed steadily towards the 400 parts per million (ppm) level since reliable records began in 1984, hitting new records each year, reported The Washington Post.

Carbon dioxide concentrations reached 397.7 ppm in 2014, and in the northern hemisphere, concentrations "crossed the symbolically significant 400 ppm level in 2014 spring, when CO2 is most abundant," the report said. "In spring 2015, the global average concentration of CO2 crossed the 400 ppm barrier."

Carbon dioxide levels last reached 400 ppm concentration levels millions of year ago, according to USA Today.

Jarraud said the increased level "means hotter global temperatures, more extreme weather events like heatwaves and floods, melting ice, rising sea levels and increased acidity of the oceans."

Carbon dioxide is a naturally occurring chemical compound necessary for plant life. It also acts as an insulating blanket that traps heat from the sun and makes the planet warmer.

"Excess energy trapped by CO2 and other greenhouse gases is heating up the Earth surface which leads to increase in atmospheric water vapor which in turn is generating [and] trapping even more heat," Jarraud said, noting that carbon dioxide stays in the atmosphere for hundreds of years and in the ocean for even longer.

Prior to the Industrial Revolution in the late 1800s, carbon dioxide levels were around 280 ppm, but an increase in the burning of fossil fuels for energy sent levels soaring to 143 percent where they were, causing the Earth's temperature to rise to levels that cannot be attributed to natural occurrences, according to USA Today.

Levels of methane and nitrous oxide - the two other major man-made greenhouse gases - also continued to rise in 2014, reaching 1,833 parts per billion and 327.1 parts per billion, increasing at their fastest rate for a decade, reported Reuters.

The report comes three weeks before diplomats from more than 190 countries plan to meet in Paris for climate negotiations on a proposed treaty to cap global emissions and reduce carbon pollution. Most will be looking for the United States and China to lead the effort, as the two countries emit more greenhouse gases than any other nation.

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