The planet is already two-thirds of the way there, with global temperatures having warmed about 1°C above pre-industrial levels.
When the target was put into the Paris Agreement, relatively little was known about the climate risks that would be avoided in a 1.5C warmer world compared with a 2C warmer world, or about the action needed to limit temperature rises to that level.
Society would have to enact "unprecedented" changes to how it consumes energy, travels and builds to meet a lower global warming target or it risks increases in heat waves, flood-causing storms and the chances of drought in some regions as well as the loss of species, a United Nations report said on Monday.
The planet will begin to see the effects of climate change sooner ー and more broadly ー than experts originally thought, according to a landmark report by a United Nations commission of dozens of climate scientists released Monday.
The latest IPCC report comes ahead of the Katowice Climate Change Conference in Poland in December, where the world's governments will examine progress made in holding to the Paris Agreements of 2015.
Camera IconFederal Environment Minister Melissa Price.
"Limiting warming to 1.5 degrees Celsius is possible within the laws of chemistry and physics but doing so would require unprecedented changes", said Jim Skea, another co-chair at the IPCC and an expert in sustainable energy at the Imperial College of London.
Meanwhile, the climate group 350.org said the report supports the call for a halt to the use of oil, gas and coal and a "rapid transition to energy systems based on 100% renewable energy".
"International cooperation is absolutely imperative to limit emissions and therefore global warming and its impacts, as well as coordinating effective and widespread adaptation and mitigation", said Sarah Perkins-Kirkpatrick, a fellow at the Climate Change Research Center at the University of New South Wales.
Prime Minister Scott Morrison stressed that the report did not "provide recommendations to Australia" and his Government's focus would be ensuring that electricity prices were lower for households and small businesses.
A spokeswoman for the state department said the USA is "leading the world in providing affordable, abundant, and secure energy to our citizens, while protecting the environment and reducing emissions through job-creating innovation". And that would have the side benefit of avoiding more than 100 million premature deaths through this century, the report said.
A rise in global temperatures by another 0.5 degree Celsius would increase, deepen and spread the impacts wider, the scientists concluded.
WA's Ningaloo Reef could be wiped out within three decades unless fossil fuels are phased out and the world changes dramatically to deal with a warming planet, according to a landmark report.
One of the key goals of the accord was to limit the increase in global temperature to well below 2°C relative to pre-industrial levels, and to attempt a more aspirational goal of containing the rise to 1.5°C by the end of the century. "Global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate".
Temperatures are now on track to rise 3 degrees Celsius by 2100.
The Paris Agreement asked the IPCC to report on the impacts of global warming of 1.5℃, and this new publication is the result. Most coral reefs will die, which could trigger rippling effects throughout the oceans.
Coal power would also need to be reduced to nearly nothing. To get there, emissions would have to be cut by 45 per cent from 2010 levels by 2030, with further action required by 2050. "Consequently, limiting global warming to 1.5°C is projected to reduce risks to marine biodiversity, fisheries, and ecosystems, and their functions and services to humans, as illustrated by recent changes to Arctic sea ice and warm water coral reef ecosystems".
By the end of the century, if warming stops at 1.5 degrees, the sea level rise may be almost four inches lower than if it stops at 2 degrees.