Over a decade post the 2015 Paris Climate Conference, it appears we remain stagnant in climate action efforts. While the rise of electric vehicles and the dominance of renewable energy over coal present positive trends, fossil fuel companies are still expanding and global emissions exceed 41 gigatonnes of CO2 annually.

At the Paris Conference, a hopeful vision emerged: nations committed to restricting the increase in global temperatures to 1.5 degrees Celsius above pre-industrial levels. Despite this ambition, little has changed in a decade. The framework to determine when we exceed this temperature threshold may not be confirmed until 2040, long after it’s already transpired.

The crucial 1.5°C threshold has become synonymous with dangerous climate change, significantly influencing global climate policy. Warnings about exceeding this limit’s risks have not translated into the aggressive emissions reductions that science necessitates.

But why the inaction? The core issue is the misconception that 1.5°C is a target to aim for instead of a limit we must prevent crossing. In 2015, global average temperatures had only risen by 1°C, suggesting ample time to react. This false sense of security allowed governments and fossil fuel industries to argue for a status quo while still contributing 37 gigatonnes of CO2 to our atmosphere.

As we inch closer to the 1.5 degrees Celsius mark, debates continue about alternative indicators to measure our progress. Options like the rate of renewable energy adoption have been proposed, but the most pressing indicator remains the global temperature rise — a crucial standard that reflects climate system responses and allows for comparisons to historical episodes of rapid warming.

Some advocate for considering 1.6°C or 1.7°C as new thresholds, as every fraction of a degree is critical. However, this approach is flawed; it risks becoming another target rather than a limit, and given the current rate of temperature increase (0.27°C per decade), we might surpass these figures as soon as the mid-2030s. Swift action on emissions is unlikely to keep us below these revised limits.

The reality is that premature restrictions could worsen the scenario, linking policy to restrictive measures that could lead to further failures. Instead, we should focus on impactful methods for tracking the rise in average global temperatures, providing clear visibility. First, we need a reliable methodology that allows us to track this figure in real-time without a decade-long wait. Career scientist Richard Betts and his colleagues from the Met Office have already developed an effective approach.

Next, we require a visual representation that resonates with the public. Imagine a global thermometer that updates annually, akin to the Bulletin of the Atomic Scientists’ Doomsday Clock. Such a periodic event could highlight the gradual increase in global temperatures, emphasizing crossing or approaching critical thresholds, thereby communicating the urgent need for action against escalating climate threats.

Bill McGuire serves as an Emeritus Professor of Geophysics and Climate Hazards at University College London. His forthcoming book, The Fate of the World: The History and Future of the Climate Crisis, will be published by HarperNorth in May.