At 1.5C the proportion of the global population exposed to water stress could be 50% lower than at 2C, it notes. Food scarcity would be less of a problem and hundreds of millions fewer people, particularly in poor countries, would be at risk of climate-related poverty.
At 2C extremely hot days, such as those experienced in the northern hemisphere this summer, would become more severe and common, increasing heat-related deaths and causing more forest fires.
But the greatest difference would be to nature. Insects, which are vital for pollination of crops, and plants are almost twice as likely to lose half their habitat at 2C compared with 1.5C. Corals would be 99% lost at the higher of the two temperatures, but more than 10% have a chance of surviving if the lower target is reached.
Sea-level rise would affect 10 million more people by 2100 if the half-degree extra warming brought a forecast 10cm additional pressure on coastlines. The number affected would increase substantially in the following centuries due to locked-in ice melt.
Oceans are already suffering from elevated acidity and lower levels of oxygen as a result of climate change. One model shows marine fisheries would lose 3m tonnes at 2C, twice the decline at 1.5C.
Or, to put this in very small words so politicians can understand it: a lot of people are going to die or have their lives made miserable unless you sort this out. The insect result is the worst, and they're basicly saying that two degrees commits us to global famine, and all the instability that brings. Sea-level rise means involuntary migration, and more instability. This is not a pretty future the Olds are building for us, and we need to fight for a better one.
How do we stop it? The report is clear: we need a 45% cut in emissions by 2030, and a reduction to zero by 2050. Which puts James Shaw's wibbling about everyone being "equally unhappy" with his climate change targets on Saturday in perspective: we can't afford his bullshit. Anything other than a target of net zero across all gases is committing to burning the planet. And if a Green climate minister commits to that, he and his party can kiss their jobs goodbye at the next election. I will not vote for any party which promises to destroy the world, and I strongly suspect that feeling will be shared by a significant number of Green supporters.
Debra Roberts, one of the IPCC working group co-chairs, called the report a line in the sand for our species. It needs to be a line in the sand for our politicians as well. They need to decide whose side they are on: humanity's, or that of the polluters. And if its the latter, we need to vote them out as quickly as possible.