Here is what you need to know.
"The goal of climate change now must be firmly fixed to 1.5°C to give the communities and nations a fighting chance to avoid the worst impacts of climate change".
Even a fraction of additional warming would worsen the impact, said the report, warning that he world is off track to meet its 2015 Paris Agreement commitment to keep the average global temperatures "well below" 2°C.
"The window on keeping global warming below 1.5 degrees C is closing rapidly and the current emissions pledges made by signatories to the Paris Agreement do not add up to us achieving that goal", added King.
Lowering emissions to this degree, while technically possible, would require widespread changes in energy, industry, buildings, transportation and cities, according to the report.
What does the report say? Temperatures would be 1.5C higher between 2030 and 2052 if the world continued at its current pace, it warned.
It is thought that by 2100, global sea rise levels would be 10cm lower that if global warming were to be at 2C.
Coal power would also need to be reduced to nearly nothing.
How can all that be done?
The report, fully titled as Global Warming of 1.5°C, an IPCC special report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty, can found on the IPCC website.More news: Trump vows to "get to bottom" of Jamal Khashoggi's disappearance
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The report summary said renewable energy would need to supply 70 percent to 85 percent of electricity by 2050 to stay within a 1.5C limit, compared with about 25 percent now. It will be very hard to meet the ambitious Carbon dioxide targets without technological innovations, the report says, such as solar energy, wind energy and electricity storage.
Taking excess carbon from the atmosphere requires measures such as planting new forests or, more controversially, burning plant material for energy and capturing the carbon to store underground, which is known as "BECCS".
Why make all that effort for 0.5C?
University of New South Wales climate scientist Sarah Perkins-Kirkpatrick says "virtually all" coral reefs would start dying off if global temperatures increased by 2C.
Around 6 percent of insects, 8 percent of plants, and 4 percent of vertebrates are projected to be negatively affected by global warming of 1.5°C, namely by shrinking their natural geographic range, compared with 18 percent of insects, 16 percent of plants and 8 percent of vertebrates for global warming of 2°C.
- 20-40% of the global population have experienced more than 1.5C of warming in at least one season.
How has this report been drawn up?
"In line with our evidence based approach to tackling climate change, we are committed to considering the report carefully, including seeking updated independent, expert advice from the UK Committee on Climate Change on its implications for our targets".
McKibben believes the odds of governments taking action in the wake of this report are slim.
Countries around the world must now act to completely cut out global carbon emissions by 2050, the UN-backed research says, or risk mass food shortages, more floods, droughts, storms.