Already, greenhouse gas levels in the atmosphere are high enough to guarantee climate disruption for decades if not centuries, the report from the scientists of the Intergovernmental Panel on Climate Change (IPCC) warned.

In other words, the deadly heat waves, gargantuan hurricanes and other weather extremes that are already happening will only become more severe UN Secretary-General António Guterres described the report as a "code red for humanity".

The IPCC report gives the most comprehensive and detailed picture yet of how climate change is altering the natural world -- and what could still be ahead.

Unless immediate, rapid and large-scale action is taken to reduce emissions, the report says, the average global temperature is likely to reach or cross the 1.5-degree Celsius warming threshold within 20 years.