Atmospheric levels of carbon dioxide hit a record high in 2017, a major international report has revealed.

Scientists are unsure when the last time CO2 levels were this high, however, there is strong evidence to suggest it was during the Pliocene era.

During this warm period between two and 4.6 million years ago, global temperatures were 3C warmer and sea levels were 20 metres (35 feet) higher.

The damming state-of-the-environment report also warned about rising temperatures, melting ice caps and coral bleaching.

Scientists revealed that the amount of carbon dioxide in the atmosphere reached unprecedented levels in 2017, with the average monthly level of CO2 in the atmosphere exceeding 405 parts per million (ppm) for the first time in recorded history.

The annual 'State of the Climate Report', which is compiled by more than 450 scientists from 60 countries, describes how climate change conditions have worsened worldwide throughout 2017.

According to the 28th annual report, annual record high temperatures were observed in Argentina, Bulgaria, Spain and Uruguay last year, while Mexico broke its annual record for the fourth consecutive year.

The latest 'State of the Climate Report' covers a period when US President Donald Trump pulled the superpower out of the landmark Paris climate deal.

The United States is the world's second leading polluter after China, but has rolled back environmental safeguards under Trump, who has declared climate change a 'Chinese hoax' and exited the Paris deal signed by more than 190 nations.

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Atmospheric levels of carbon dioxide have hit a record high in 2017, a major report has revealed. Pictured is a photo of a polar bear testing the strength of thin sea ice in the Arctic

The 300-page annual report issued by the American Meteorological Society and the National Oceanic and Atmospheric Administration refers to a number of meteorological events observed on Earth within the last year as 'abnormal'.

These include storms, droughts, scorching temperatures and record low ice cover in the Arctic.

Planet-warming greenhouse gases surged to new highs as abnormally hot temperatures swept the globe and ice melted at record levels in the Arctic, the major US report states.

Last year, the top three most dangerous greenhouse gases released into Earth's atmosphere – carbon dioxide, methane and nitrous oxide – reached new record highs.

The annual global average carbon dioxide concentration at the Earth's surface climbed to 405 parts per million, 'the highest in the modern atmospheric measurement record and in ice core records dating back as far as 800,000 years,' said the report.

In total, the global growth rate of CO2 has nearly quadrupled since the early 1960s, researchers found.

The record for hottest year in modern times was set in 2016, but 2017 was not far behind, with 'much-warmer-than-average conditions' across most of the world, the report found.

Annual record high temperatures were observed in Argentina, Bulgaria, Spain and Uruguay, while Mexico broke its annual record for the fourth consecutive year.

The 300-page report issued by the American Meteorological Society and the National Oceanic and Atmospheric Administration mentioned the word 'abnormal' a dozen times, referring to storms, droughts, scorching temperatures and record low ice cover in the Arctic

Some parts of the world suffered extended droughts, demonstrating that 'extreme precipitation is not evenly distributed across the globe', the report found

WHAT WERE THE KEY FINDINGS FROM THE 2017 ANNUAL STATE OF THE CLIMATE REPORT? Greenhouse gas surge Last year, the top three most dangerous greenhouse gases released into Earth's atmosphere - carbon dioxide, methane and nitrous oxide - reached new record highs. The annual global average carbon dioxide concentration at the Earth's surface climbed to 405 parts per million, 'the highest in the modern atmospheric measurement record and in ice core records dating back as far as 800,000 years,' said the report. The global growth rate of CO2 has nearly quadrupled since the early 1960s. Heat records The record for hottest year in modern times was set in 2016, but 2017 was not far behind, with 'much-warmer-than-average conditions' across most of the world, it said. Annual record high temperatures were observed in Argentina, Bulgaria, Spain and Uruguay, while Mexico 'broke its annual record for the fourth consecutive year.' Smashing more heat records, the highest temperature ever noted - 110.1 degrees Fahrenheit (43.4 Celsius) - so far south anywhere in the world was marked January 27 at Puerto Madryn, Argentina. The world's highest temperature ever for May was observed on May 28 in Turbat, western Pakistan, with a high of 128.3 degrees Fahrenheit. 'The 10 warmest years on record have all occurred since 1998, with the four warmest years occurring since 2014,' said the report. Last year marked either the second or third hottest since the mid 1800s, depending on which data is consulted. In another alarming milestone, 2017 was also 'the warmest non-El Nino year in the instrumental record,' referring to the absence of the occasional ocean warming trend that pushes temperatures higher than normal. Abnormal Arctic Unprecedented heat enveloped the Arctic, where land surface temperature was 2.9 degrees Fahrenheit (1.6 Celsius) above the 1981-2010 average. Arctic temperatures were the second highest - after 2016 - since records began in 1900. 'Today's abnormally warm Arctic air and sea surface temperatures have not been observed in the last 2,000 years,' it said. In March, sea ice extent saw its lowest maximum in the 37-year satellite record. Meanwhile, the Arctic sea ice minimum in September was the eighth lowest on record and covered 25 percent less area than the long-term average. Glaciers across the world shrank for the 38th year in a row. 'Cumulatively since 1980, this loss is equivalent to slicing 22 meters off the top of the average glacier.' In the Antarctic, sea ice extent remained below average all year, with record lows observed during the first four months. Extreme rain 'Precipitation over global land areas in 2017 was clearly above the long-term average,' said the report. Warmer ocean temperatures has led to increasing moisture in the air, particularly in the last three years, causing more rain. Climate change can also exacerbate extreme weather. Some parts of the world suffered extended droughts, demonstrating that 'extreme precipitation is not evenly distributed across the globe.' 'Most destructive' coral bleaching Ocean warming over the last few years has been blamed for widespread coral bleaching, as disease spreads in this precious habitat for fish and marine life. 'The most recent global coral bleaching lasted three full years, June 2014 to May 2017, and was the longest, most widespread and almost certainly most destructive such event on record,' said the report. Advertisement

The world's highest temperature ever for May was observed on May 28 in Turbat, western Pakistan, with a high of 128.3°F (53°C).

Last year, the annual Greenhouse Gas Bulletin delivered similarly dire warnings.

Atmospheric concentrations of CO2, the main man-made greenhouse gas, hit 403.3 parts per million (ppm) in 2016, the report found.

This is up from 400.0 in 2015, according to the research compiled by the UN World Meteorological Organisation.

That growth rate was 50 per cent faster than the average over the past decade, driving CO2 levels 45 per cent above pre-industrial levels and further outside the range of 180-280 ppm seen in recent cycles of ice ages and warmer periods.

Human CO2 emissions from sources such as coal, oil, cement and deforestation reached a record in 2016, and the El Niño weather pattern gave CO2 levels a further boost, the WMO said.

The annual State of the Climate Report, compiled by more than 450 scientists from over 60 countries, describes worsening climate conditions worldwide in 2017, the same year that US President Donald Trump pulled out of the landmark Paris climate deal

As far as scientists can tell, the world has never experienced a rise in carbon dioxide like that of recent decades, which has happened 100 times faster than when the world was emerging from the last ice age (graph pictured)

The record for hottest year in modern times was set in 2016, but 2017 was not far behind, with 'much-warmer-than-average conditions' across most of the world, the report found

KEY GOALS OF THE PARIS AGREEMENT The Paris Agreement on Climate Change has four main goals with regards to reducing emissions: 1) A long-term goal of keeping the increase in global average temperature to well below 2°C above pre-industrial levels 2) To aim to limit the increase to 1.5°C, since this would significantly reduce risks and the impacts of climate change 3) Goverments agreed on the need for global emissions to peak as soon as possible, recognising that this will take longer for developing countries 4) To undertake rapid reductions thereafter in accordance with the best available science Source: European Commission Advertisement

'The 10 warmest years on record have all occurred since 1998, with the four warmest years occurring since 2014,' said the annual State of the Climate Report.

Last year marked either the second or third hottest since the mid 1800s, depending on which data is consulted.

Unprecedented heat enveloped the Arctic, where land surface temperature was 2.9 degrees Fahrenheit (1.6 Celsius) above the 1981-2010 average.

'Today's abnormally warm Arctic air and sea surface temperatures have not been observed in the last 2,000 years,' the report read.

In March, sea ice extent saw its lowest maximum in the 37-year satellite record.

Meanwhile, the Arctic sea ice minimum in September was the eighth lowest on record and covered 25 percent less area than the long-term average.

Glaciers across the world shrank for the 38th year in a row.

'Cumulatively since 1980, this loss is equivalent to slicing 22 meters (72 feet) off the top of the average glacier.'

In the Antarctic, sea ice extent remained below average all year, with record lows observed during the first four months.