Sixty-three years ago, scientists began measuring the concentration of carbon dioxide in the atmosphere at a weather station perched atop the approximately 13,700-foot Mauna Loa volcano in Hawaii—daily measurements that have continued ever since. The Mauna Loa Observatory record of carbon dioxide measurements are called the “Keeling Curve” (see chart below), which is named after Charles David Keeling, the scientist who began tracking carbon dioxide levels at Mauna Loa in 1958. The Keeling Curve serves as a global benchmark for atmospheric carbon levels steady march upward.
The adoption of the Paris Climate Agreement, emission reduction pledges by governments and private companies, the COVID-19 pandemic: none of these recent impacts on global emissions is yet visible in the Keeling Curve, and emission reductions on this relatively small scale may not be enough to slow down rising atmosphere concentrations. Atmospheric carbon levels in 2021 are approaching 420 parts per million, the highest since measurements began more than 60 years ago. The last time concentrations were this high was between 4.1 and 4.5 million years ago, when sea level was about 78 feet higher than it is today and the average global temperature was about 7°Fahrenheit (F) warmer than pre-industrial temperatures (for reference, observed global warming to-date is about 1°Celsius (C) or 1.8° F above pre-industrial temperatures).
Despite decades of climate negotiations, despite climate commitments from the public and private sectors, despite an unprecedented global pandemic, despite the increased occurrence of, and increasingly extreme, weather events around the world (see image below from Verviers, Belgium after heavy rains and floods across western Europe in July 2021)—growth in atmospheric carbon concentrations has not slowed, stopped or reversed.
The scale of action needed is daunting: to limit global warming to no more than 1.5°C (the threshold required by the Paris Climate Agreement), global carbon emissions need to fall off a cliff (see chart below, reproduced from Carbon Brief).
As of 2019, global emissions would need to fall by about 15 percent per year through 2040 to reach the 1.5°C target. Every year that passes without a decline in global carbon emissions serves to increase the rate at which emissions must decline to have any hope of achieve the 1.5°C target. There is no time to waste—immediate drastic action must be taken to reduce global emissions. Fortunately, we already have many of the tools and technologies needed to do so, like renewable wind and solar.
