The world has reached a fork in the road with two paths ahead: a planet that’s 2°C warmer than pre-industrial levels and a planet that’s 1.5°C warmer. But what difference can a measly 0.5°C really make? It turns out, a hell of a lot.

This is one of the key findings of a landmark new report by the Intergovernmental Panel on Climate Change (IPCC), the UN’s body to assesses research on climate change. At the Paris Climate Agreement in 2015, international leaders agreed to keep global warming “well below 2°C above pre-industrial levels” with the hopes to limit this to just 1.5°C. The science now clearly states that the  2°C target is simply not good enough.

“You don’t want to live in a 2°C world,” Hunter Cutting, Director of Strategic Communications at Climate Nexus who observed the IPCC plenary, told IFLScience.

A world with 2°C of warming will be a planet without coral reefs. Corals have already been battered by our current rise in global temperatures, which has risen by 1°C over the past 150 or so years. Even if the world limits global warming to 1.5°C, it is a pretty bleak situation for coral reefs as we can expect to see a further 70 to 90 percent loss of cover. However, by 2°C, it is almost certainly game over for over 99 percent of the world’s coral reefs.

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.

Along with the planet's ecosystems and biodiversity, humans are also under threat. At a 2°C warming compared to 1.5°C, we could see several hundred million people subjected to climate-related poverty. With 1.5°C, between 24 million and 357 million will be at increased risk of extreme poverty. Just 0.5°C more and we could see between 86 million to 1,229 million people in this situation.

A lot of this poverty risk will be caused by shifts in weather patterns, such as increased risks of drought and heat waves. For example, under 2°C of warming 37 percent of the world's population could be subjected to extreme heat events compared to 14 percent at 1.5°C. Food security will equally become a big issue with up to 10 times more people exposed to lower crop yields at 2°C versus 1.5°C.

It's certainly a grim picture, but not all hope is lost. The IPCC report has also highlighted that it is potentially possible to stabilize the climate at 1.5°C by 2100, however, there needs to be an astronomical shift in the way we all think, act, and organize ourselves. 

“This report will force some radical honesty,” Kaisa Kosonen, Senior Policy Advisor for Greenpeace, explained to IFLScience. “It will make us face the facts like we haven’t really done before because now the impacts are already here. It will force us to look at the options we have left.”

“The question now is: What are we going to do about this? This involves all of us,” added Kosonen. “If you were hoping for someone else to do this for you, then don’t count on that anymore. You need to be part of the solution because it’s now clear what we’re heading towards.”