How much will all this cost?
It won’t come cheap. The report says that to limit warming to 1.5C, it will involve “annual average investment needs in the energy system of around $2.4 trillion” between 2016 and 2035.
Experts believe that this number needs to be put in context.
“There are costs and benefits you have to weigh up,” said Dr Stephen Cornelius, a former UK IPCC negotiator now with WWF, who says that cutting emissions hard in the short term will cost money, but is cheaper than paying for carbon dioxide removal later this century.
“The report also talks about the benefits as there is higher economic growth at 1.5 degrees than there is at 2C, and you don’t have the higher risk of catastrophic impacts at 1.5 that you do at 2.”
What happens if we don’t act?
The researchers say that if we fail to keep temperatures below 1.5C, we are in for some significant and dangerous changes to our world.
You can kiss coral reefs good-bye, as the report says they would be essentially 100% wiped out at 2 degrees of warming.
Global sea-level will rise around 10 centimetres more if we let warming go to 2C, That may not sound like much but keeping to 1.5C means that 10 million fewer people would be exposed to the risks of flooding.
There are also significant impacts on ocean temperatures and acidity, and the ability to grow crops like rice, maize and wheat.
“We are already in the danger zone at one degree of warming,” said Kaisa Kosonen from Greenpeace.
“Both poles are melting at an accelerated rate; ancient trees that have been there for hundreds of years are suddenly dying; and the summer we’ve just experienced – basically, the whole world was on fire.”