New climate metrics for new climate conversations

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Cast your mind back to the height of the Covid-19 pandemic, when the world seemed to have a single shared obsession – the “R number”. This simple metric, which measured the reproductive rate of the virus, gave a tangible sense of the invisible threat that lurked around us. Was it above one, meaning that the virus was spreading exponentially? Or had lockdowns and other public health measures successfully brought it below that threshold? The R number became a predictor of the public mood like a barometer – forecasting impending storms, or clear skies.

Covid is very much still out there, but swift measures on social distancing, travel restrictions, and vaccine distribution mean that it’s no longer seen by most as a major threat to humankind. These policies demonstrated what fast action, strong leadership and global cooperation can achieve, but their success was judged almost entirely by that R number.

This brings us to a crucial question. Do we need new metrics for communicating climate change?

Now that the urgency of the pandemic has receded for much of the world, another major threat looms larger than it ever has before – and it’s one that policymakers have so far failed to get a grip on. Climate change is already dramatically raising the likelihood of extreme weather events, causing shortages of food, water and other crucial necessities, and displacing people from their homes with increasing regularity.

In light of the swift action that we saw on Covid, why don’t we see a similar sense of urgency on what is arguably a much larger problem? One that threatens not just our health, but the habitability of our planet?

The answer is complex, and multifaceted. But surely part of it is that we lack a compelling, easy-to-understand “R number” for climate change – a single, digestible indicator that can galvanise public attention and be used to judge the success (or lack thereof) of political action. The ways in which humans are changing our planet are measured in various ways, but none of these metrics resonate with the immediate and clarity that the R number brought to the Covid-19 pandemic.

This brings us to a crucial question. Do we need new metrics for communicating climate change? Metrics that clarify the stakes, and guide effective policy? Metrics that bridge the gap between the abstract and invisible threat of climate change, and the concrete steps needed for action? Metrics that could transform public understanding, and finally instil the urgency that the escalating climate crisis desperately demands.

Kris de Meyer, director of the Climate Action Unit at UCL, thinks we do. His team has spent the last year developing a prototype of a new climate dashboard which is inspired by the R-number. The dashboard, which brings together the causes of climate change, the rate at which it’s happening, and the impacts that it’s having on our weather systems, is designed to offer journalists and other science communicators a set of tools to tell stories about the changes that humans are making to the planet, and how they’re linked to the experiences people have in their day-to-day lives.

It does this in just three numbers. “The first metric is the Earth’s energy imbalance and that is the primary driver of climate change,” de Meyer explains. “It’s the difference between the amount of energy coming into the Earth system from the Sun, and the amount of energy that the Earth radiates back into space. We’re losing some heat into space, but there’s a constant stream of energy arriving from the Sun.”

If climate change wasn’t happening, that number would be hovering around zero, meaning that the amount of energy coming in and the amount going out is more or less equal. Unfortunately, human activity has pushed it out of balance. “We’re adding more energy to the Earth’s system than we’re losing back into space, which means that the Earth is storing that energy and that energy is leading to all sorts of downstream changes in weather,” explains de Meyer.

The second metric is the speed at which the Earth is warming, expressed as the number of degrees per decade. “The reason why we picked the speed of warming is because it tells us something about what is happening to global temperatures, or regional temperatures, right now,” says de Meyer. He argues that the traditional climate metric of how much warmer the Earth is than during the pre-industrial period hides the real pace of change. “Most of the 1.2 degrees that we’ve had has been happening in the last 40 years alone,” he says.

Finally, the third metric featured in the dashboard ties directly into people’s experiences – it’s an index of the ‘unusualness’ of the weather we’re experiencing. “Every event where the temperature is being broken is being counted and then compared to the amount of these record-breaking temperatures that we would have if climate change wasn’t happening,” de Meyer explains.

“Where the speed of warming tells us something about the average, this tells us something about the extremes. Climate change is changing ocean currents and wind currents. It is changing precipitation. It is making heatwaves longer and stronger, as we’re seeing at this very moment in much of Europe and the US. It can also generate more storms and change seasonal wind patterns, like monsoons. So by absorbing all of that energy, trapping all of that energy in the Earth’s system, we are supercharging the weather.”

Together, de Meyer believes, these three metrics tell a compelling story that link the physical causes of climate change to people’s experiences of how the weather is changing.

You’ll notice several things missing from these numbers that are commonly seen in communication around climate change. There’s no sea level rise. There are no tonnes of carbon, or parts per million of greenhouse gases. There’s no “net zero” or “1.5C”. There aren’t any friendly “human” comparisons – like bathtubs full of gasoline, or barrels of oil being stacked to the moon.

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