1.5°C is better than 2°C

The 2015 Paris climate deal outlined two distinct goals

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Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change.

The Climate Home News website (http://www.climatechangenews.com/ ) has published the version sent by the Intergovernmental Panel on Climate Change to the governments of the 1.5°C executive group. This second draft of the report assesses the difference between the two goals, namely 2°C and 1.5°C, in terms of impacts on human life, economy and global environment. The report is due to be officially released in October after receiving some feedbacks from governments.
Here is list of the most significant assessed results:

The human-induced global warming reached approximately 1 ± 0.2°C above pre-industrial levels in 2017, and is currently increasing by 0.2 ± 0.1°C per decade.

Past emissions alone are unlikely to raise global average surface temperature (GMST) to 1.5°C above pre-industrial levels, but do commit to further changes, such as sea level rise and associated impacts. If emissions continue at the current rate, human-induced warming will exceed 1.5°C by around 2040.

Risks to natural and human systems are lower for global warming of 1,5°C compared to that of 2°C depending on geographical location, levels of development, vulnerability and adaptation strategies and mitigation options.

Sustainable development, poverty eradication and implications on human rights will be key considerations in mitigation efforts to limit global warming to 1.5°C and in efforts to adapt to global warming by 1.5°C.

There is no simple answer as to whether it is feasible to limit heating to 1,5°C and to adapt to global warming consequences. This is because multiple dimensions need to be considered simultaneously and systematically.

Currently, there are substantial increases in extreme weather events both in a world heated at 1.5°C, and between 1.5°C and 2°C. Such extreme events include high-level temperature in all inhabited regions, extreme precipitation in most regions, and extreme droughts in some regions.

On land, the risks of climate-induced impacts on biodiversity and ecosystems, including loss and extinction of species, are substantially less at 1,5°C than 2°C. Limiting global warming to 1.5°C will bring great benefits to terrestrial ecosystems, wetlands and the preservation of their services. Overheating, if much higher than 1.5°C (near 2°C), can have irreversible impacts on some species, ecosystems, their ecological functions and their services to humans, even if global warming stabilizes at 1.5°C until 2100.

Limiting warming to 1.5°C compared to 2°C would substantially reduce the risks to marine biodiversity, ecosystems and their ecological functions, and to the services provided to humans in coastal and oceanic areas, especially in the Arctic ecosystems and hot-water coral reefs. By 2100, the sea level rise would be about 0.1 m lower with global warming limited to 1,5°C.

Impacts on health, livelihoods, food and water supply, human security, infrastructure will increase with 1.5°C of warming compared to today, and even more with a heating of 2°C compared to 1.5°C.

Limiting global warming to 1.5°C in the context of sustainable development and poverty eradication requires a portfolio of mitigation and adaptation actions in all sectors and scales. These actions can be implemented only with adjustments in finance, technology and behaviour.

Implementing policies to successfully limit warming to 1.5°C, and to adapt humankind to this warming, implies international cooperation and the strengthening the institutional capacity of national and subnational authorities, civil society, the private sector, cities, local communities and indigenous peoples.