What’s in a Number? The goals of the 2021 UN climate summit in Glasgow, Scotland, called on nations to keep a warming limit of 1.5 °C “within reach”. But when it comes to taking climate change to the masses, some scientists worry that putting too much emphasis on a specific number is a bad strategy.
Focusing on one number obscures a more important point, he says: even if nations do not meet this goal to halt global climate change, any progress is better than none. Maybe it’s time to stop talking so much about a number.
On 13 November, the 26th Annual Climate Change Meeting of the United Nations, or COP26, culminated in a new climate agreement, the Glasgow Climate Treaty. In that agreement, the 197 assembled nations reaffirmed a common “ideal” goal: to limit global warming to no more than 1.5 °C by 2100 relative to pre-industrial times (SN: 12/17/18,
Researchers have found that as temperatures rise to 1.5 °C, this will be a significant improvement in limiting warming to 2 °C, as agreed in the 2015 Paris Agreement (SN: 12/12/15) A more stringent threshold would mean fewer global threats, ranging from extreme weather to habitat loss for species at the rate of sea level rise (SN: 12/17/18,
The problem is that current national pledges to reduce greenhouse gas emissions are not enough to meet either of those goals. Even taking into account the most recent national pledges to cut emissions, by 2100 the average global temperature is likely to be between 2.2 and 2.7 °C warmer than it was about 150 years ago (SN: 10/26/21,
Jessica Tierney, a paleontologist at the University of Arizona in Tucson, says this appalling disparity is leading not only to fury and despair for many, but to despair and widespread emotion.
“It’s something I’ve been thinking about for a while, but I think it was definitely made more front and center with COP,” Tierney says. She describes a news story in the wake of the conference that “mentioned 1.5 °C, and then added that this is the limit at which scientists have told us that catastrophic climate change will occur.”
Tierney points out that this article reveals a fundamental misunderstanding of what the agreed-upon limit actually represents. “A lot of my students, for example, are really concerned about climate change, and they’re really worried about crossing some sort of border. People have this idea that if you cross that border So you are like the tip on a rock.
There are certainly tipping points in the climate system – past the threshold, for example, an ice sheet begins to collapse and it is not possible to stop or reverse the process. But, Tierney says, “we really should start communicating more about the continuum of climate change. Obviously, less warming is better.” However, “if we blow by 1.5, we don’t need to panic.” It’s okay if we can stop at 1.6 or 1.7.”
Tierney notes that climate communications expert Susan Hassol, director of the Colorado-based nonprofit Climate Communications, likens the approach to exiting when driving on the highway. “If you miss exit 1.5, you just slow down and take the next one, or the next one,” Tierney says. “It’s still better than hitting the gas.”
The target numbers have some uses, notes Joeri Roselj, a climate scientist at Imperial College London. After decades of international climate negotiations and wrangling over targets and strategies, the world has now agreed that 1.5°C of warming is the cause of many countries, says Rogel, one of the lead authors of the Intergovernmental Panel on Climate Change 2018. is a desirable goal. Special report on global warming.
A global temperature range “is a good proxy for avoiding some impacts,” he adds. “These numbers are basically how to say it.”
But Rogelj agrees that focusing too much on a particular number can be counterproductive, even misleading. “There’s a lot of layered meaning under those numbers,” he says. “The true interests, the true goals of countries, are not the numbers, but the avoidance of the influences that are subject to them.”
And setting goals for where we should be by the end of the century – such as staying below 1.5 °C by the year 2100 – could give too much leeway to curb emissions. For example, such framing means the planet could exceed a temperature threshold by mid-century and rely on still-unproven carbon dioxide removal strategies to reverse warming over the next few decades, Rozelj said. and his colleagues wrote in 2019 Nature,
Banking on future technologies that have not yet been developed is worrying, Rogelj notes. After all, some extreme heat-related extreme events, such as heat waves, are more reversible than others, such as sea level rise (SN: 8/9/21) Once carbon is removed from the atmosphere, heat wave events may subside, but seas will remain high.
Roselj acknowledged that it is a challenge to communicate the urgency of taking action to reduce emissions without spinning off climate catastrophe or cliff edge narratives. For his part, Roselj says he is trying to tackle this challenge by adding a huge dose of reality to his scientific presentations, especially those aimed at non-scientists.
He begins with photographs of wildfires and floods in Europe from 2021. “I say, ‘Look, it is today, 1.1 degrees hotter than in pre-industrial times,'” Rozelj explains. “‘Do you think it’s safe? today not secure. And so, 1.5 will be no more secure than today; It will be worse than today. But it will be better than 1.6. And 1.6 will not be the end of the world.’ And that’s how people think about it a little differently.”