New Delhi: The period from 2015 to 2019 will likely be the hottest five-year period on record since 1850, according to report released ahead of the United Nations Climate Action Summit to be held in New York on Monday.

The report, titled ‘United in Science’ prepared by world’s leading climate agencies pointed out that the gaps between agreed targets to combat global warming and the ground reality.

According to it, greenhouse gas concentrations in the atmosphere have risen to record levels, locking in the warming trend for decades to come. Global average temperature increased 1.1°C since the pre-industrial period (1850–1900), and by 0.2°C compared to 2011-2015.

The report has laid bare how the world is failing to avert climate change. Carbon dioxide concentration grew 2% in 2018, reaching a record high of 37 billion tonnes.

The key findings come ahead of the major UN Climate Summit being hosted by UN Secretary General Antonio Guterres on Monday, calling on participating countries to enhance their nationally determined contributions to combat climate change.

It will be attended by more than 60 world leaders including Prime Minister Narendra Modi. While India remains committed to its NDCs and is on target to achieve them, it has made clear that the critical issue of climate finance needs to be dealt first. Developed countries must fulfill their commitments before developing countries could be expected to step up any action on climate change.

Under the 2015 Paris Agreement, countries including India have committed to reduce their emissions to limit long-term temperature rise by either 2°C or 1.5°C. But, the report highlighted that even if all countries meet the set goals, the world will warmer by 2.9°C to 3.4°C.

The high-level report compiled by World Meteorological Organization (WMO) under the umbrella of the Science Advisory Group of the UN Climate Summit also highlighted that there was no sign yet of reaching what is known as "peak emissions," after which the levels are expected to start falling.

The observations showed that that the global mean sea level rise was accelerating to an extent that there has been an overall increase of 26% in ocean acidity since the beginning of the industrial era.

The Arctic summer sea ice has declined at a rate of 12% per decade over the past 40 years, with the four lowest values between 2015 and 2019 and the glacier loss for 2015-19 is also the highest for any five-year period on record.

'If emissions don't start falling there will be hell to pay. In 2018, global carbon dioxide was 407.8 parts per million (ppm), 2.2 ppm higher than 2017 and set to reach or exceed 410 ppm by 2019," said Professor Dave Reay from the University of Edinburgh.

According to the report, the last time Earth's atmosphere contained 400 parts per million CO2 was about 3-5 million years ago. At that time, global mean surface temperatures were 2-3 °C warmer, ice sheets at both poles had melted, and seas were 10 to 20 meters higher.

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