New Scientist comment on latest from the IPCC

Adam Vaughan of New Scientist publishes a periodic climate change newsletter 'Fix the Planet'. This week his newsletter follows Monday’s climate report from the Intergovernmental Panel on Climate Change. He says he found himself "overwhelmed at times when reading the 4000-page document and speaking to some of its authors. It’s hard not to feel that way when being told the planet is already committed to changes that will be irreversible for hundreds or even thousands of years, reminded of how much worse heatwaves and flooding will become for every fraction of warming and shown how soon we will hit crucial warming thresholds." What follows here is a straight lift from his newsletter.

Solutions aren’t strictly speaking the remit of this IPCC report – they are the subject of another one due to be published next year – but it does show we can still avoid the darkest futures.

The IPCC report makes clear CO2 removals, such as by this Climeworks facility in Europe, will be vital to stopping dangerous warming. Photo: Orjan Ellingvag / Alamy

Where’s the hope? The report made clear that deep and rapid cuts to greenhouse gas emissions this decade are the only route to a world below 1.5°C of warming, the level governments have promised to hold warming to. The good news is that world is still possible, but only just. “Our activities today have changed and continue to change the planet we live on, and it will be activities and choices that will determine where we end up over the next decades and over the next centuries,” says Joeri Rogelj of Imperial College London, an IPCC lead author. “Now, better than ever, we understand what needs to be done. We understand this needs to be done over the next decade if we want to avoid the worst of climate change. That is both a hopeful but also an urgent message.” What precisely needs to be done? You’ve heard it before, but here the message is clearer and louder than ever: the world must get to net-zero CO2 emissions by the year 2050. Given we emit about 40 billion tonnes of CO2 a year now, and emissions are still rising, that is a gargantuan challenge. But it is the only path, out of five future emissions scenarios that the IPCC report considered, that ends up with a world below 1.5°C of warming. As IPCC author Amanda Maycock at the University of Leeds, UK, explains, it’s not that everything is “catastrophic” after 1.5°C and fine before, but that every fraction of warming matters. “Every tonne of CO2 matters,” says Ed Hawkins at the University of Reading, UK, who is also an IPCC author. Didn’t we already know net zero is the answer? We now have even more certainty that reducing global emissions to net zero will really work, by stabilising future temperature rises. That’s partly because the scientists who worked on the IPCC report have honed their estimates of how sensitive Earth’s system is to each tonne of CO2 we are emitting. The new report gives a narrower range for future temperature rises if we double CO2 emissions from pre-industrial levels: it is now seen as being 2.5 to 4°C rather than 1.5 to 4.5°C in the IPCC’s 2013 report. The other reason is researchers have more confidence in the effectiveness of removing CO2 from the atmosphere.

On the right, from top to bottom, are our worst and best case futures for temperature rises, based on whether we have very high emissions, very low emissions, or something in between. Photo: Malte Meinshausen / IPCC

How important are those CO2 removals? Very. The very low emissions scenario, where we collectively hit net zero by mid-century, would see the world temporarily overshoot 1.5°C by about 0.1°C in coming decades, later falling back down to 1.4°C by the end of the century. But that only happens by using methods such as tree planting and machines to suck CO2 from the air. The IPCC report authors say they now have “high confidence” that we can remove and durably store CO2 from the atmosphere. “It [the report] concludes it [CO2 removal] can work, that it would actually reverse warming. So that is good news,” says Rogelj. Tamsin Edwards of King’s College London, an IPCC lead author, says: “I do think CO2 removal is a really important concept. People are familiar with the idea of planting trees. But the more people can become familiar with not only rapidly reducing emissions but also extracting them from the air, then the better informed we are as a society of what the future is going to look like.” Presumably there are risks with those removals? Yep. The IPCC report notes that CO2 removal could have “potentially wide-ranging effects” on the climate, and could influence water supplies, food production and biodiversity. A big feature in New Scientist next week delves into those dangers in detail. Meanwhile, as Zeke Hausfather at Berkeley Earth, a US non-profit organisation, points out , the technologies needed to do those removals are “largely untested at anything close to the scale required”. Today they are removing a few thousand tonnes of CO2 a year – they need to be extracting billions of tonnes. The scale issue and risk of side effects are both reminders that our best option is deep emissions cuts today, not tomorrow. As Edwards says: “Reducing emissions to net zero around 2050 doesn’t mean waiting until 2045. It does mean immediate reductions, otherwise there’s no chance of getting there. It’s easy to focus on ‘oh, 2050, 2100 is a long time away’ but really, everything starts now.”