The concentration of atmospheric carbon-dioxide surged past 420 parts per million (PPM) for the first time in recorded history this past weekend, according to a measurement taken by the National Oceanic and Atmospheric Administration (NOAA) at the Mauna Loa Observatory on the Big Island of Hawaii.
When NOAA began collecting carbon-dioxide measurements in the late 1950s, atmospheric CO2 concentration sat at around 315 PPM. On Saturday, the daily average was measured at 421.21 PPM – the highest ever daily average measured at the site and the first time in human history that number has been so high.
Carbon-dioxide levels in the atmosphere fluctuate slightly during the year, dropping as some is absorbed during the spring and summer by plants growing in the northern hemisphere, before it rises again in autumn and winter.
But the annual fluctuations are negligible if compared to the long-term trend caused by human activity, increasing carbon-dioxide levels through the burning of fossil fuels and also from deforestation, as cutting trees eliminates an important sink for carbon-dioxide.
Since pre-industrial times carbon-dioxide concentrations in Earth’s atmosphere doubled. Global emissions reduced temporarily in 2020 as a result of global lockdowns to limit the spread of the coronavirus. But the reduction was not enough to substantially affect the buildup of carbon-dioxide in the atmosphere, which continues to rise at an unprecedented rate in Earth’s history.
According to most recent reconstructions, one must go back 15 million years to find carbon-dioxide levels as high as they are today. At the time global temperatures were 5 to 10 degrees Fahrenheit higher than they are today.