The more the world warms, the worse the impacts of climate change become.
Nearly 200 countries pledged to try to limit global warming to 1.5C above pre-industrial levels in the 2015 Paris agreement.
That target is generally understood to mean an average annual increase of 1.5C over 20 years rather than a one-off rise in a single year.
Long-term warming of 1.5C would bring serious consequences for many populations.
But an increase of 2C or more would bring even greater impacts, the IPCC says.
These include:
more people exposed to extreme heat
increased risks to food security in some regions due to more extreme weather
greater chances of some climate-sensitive diseases spreading, such as dengue
more species being threatened with extinction
The call to restrict temperature rise to 1.5C was partly designed to avoid crossing so-called “tipping points”.
It is not clear exactly where they sit, but once these thresholds are passed, changes could accelerate and become irreversible.
These could include the collapse of the Greenland Ice Sheet, warm Atlantic Ocean currents or further loss of the Amazon rainforest.
