Five confronting facts about climate change we can no longer ignore.

We’ve got 12 years, according to the world’s leading climate scientists. Twelve years to limit global warming from rising above 1.5°C. Even then we and our natural environment are facing a monumental crisis. But just half a degree more, and severe weather will become a new reality for billions, coral reefs will be entirely wiped out, and hundreds of millions more lives and livelihoods will be at stake.

That’s according to a landmark report by the UN Intergovernmental Panel on Climate Change (IPCC) released this week.

Policymakers commissioned the report at the Paris climate talks in 2015, during which world leaders pledged to work toward a global warming cap of between 1.5°C-2°C. With a review of the Paris Agreement coming up in December, the report highlights the need to aim for the more ambitious end of that target.

To achieve that would require transformation of the world’s economy, agriculture and infrastructure on such a substantial scale that, as the UN reported noted, there is “no documented historic precedent”.

But it’s not like the incentive isn’t there. Because according to the UN report, this is what were facing. This is what that half a degree means.

1. At least 10 million more people affected by rising sea levels.

One of the most significant outcomes of global warming is higher average sea levels. This occurs courtesy of melting polar ice sheets and the expansion that water undergoes at higher temperatures, and can lead to flooding, destruction of vital coastal ecosystems and property.

At 1.5°C of warming this rise is projected to be between 26cm and 77cm by 2100. At 2°C, it would be a further 10cm higher, exposing an extra 10 million people to the related risks.

At 3°C of global warming scientists have predicted that several major cities – including Osaka, Shanghai, Rio de Janeiro, Miami and Sydney- could be partially swallowed by the ocean by 2100, displacing roughly 100 million people.

2. Hundreds of millions more people likely to be in poverty.

According to the UN report, global warming of 2°C, compared to 1.5, could increase the number of people both exposed to climate-related risks and susceptible to poverty by up to several hundred million by 2050. This is thanks to the impact of global warming on health (including the increased risk of heat-related death and insect-borne illnesses like malaria), livelihoods, food security, water supply and economic growth.

In fact, according to Carbon Brief, an analysis of 70 peer-reviewed climate studies, it’s estimated that global GDP, per capita, will be cut by 13 percent at 2°C of warming, compared to just 8 per cent at 1.5°C.

3. More severe weather events, from floods to heat waves.

The UN report states that the extra half-a-degree of global warming will lead to further increases in: the average temperature in most parts of the world, hot extremes in most inhabited regions, heavier rainfall in several regions, and the intensity and frequency of droughts and wildfires in some areas.

For example, according to Carbon Brief, the percentage of the world’s population that will experience a severe heat wave every five years will jump from 14 per cent at 1.5°C of warming, to 37 per cent 2°C. That’s more than double.

4. Coral reefs almost entirely wiped out.

It’s frightening enough to consider that coral reefs are projected to decline by a further 70–90 per cent at 1.5°C. Well, with an extra half a degree, that stands to be more than 99 per cent.

5. Three times as many insects and twice as many animals experiencing significant habitat loss.

According to the UN report, 6 per cent of insects, 8 per cent of plants and 4 per cent of vertebrates would lose over half of their habitat at 1.5°C global warming. Should that bump up to 2°C, those figures would triple for insects, and double for plants and vertebrates.