Country-wide lockdowns and quarantine acted to temporarily decrease emissions of global greenhouse gas. However, as the yearly May benchmark was released it appears to have done little to slow the ever-increasing rise in carbon dioxide in the atmosphere.
May 2020 hit a record high, 417 parts per million (ppm) carbon dioxide as measured at the Mauna Loa Observatory, which has continually measured CO2 in the atmosphere since 1958.
The reading of 417 ppm is up from 414.7 ppm in May of 2019. How do we put these carbon dioxide concentrations into a historical perspective? The reading of 417 ppm is likely the highest it has ever been in the history of humans on Earth. On top of that, it is likely the highest concentration seen on Earth in 3 million years.
The last time the atmospheric carbon dioxide was this high, sea level was 50 to 80 feet higher than it is today and 3.6°–5.4°F warmer than pre-industrial temperatures. There is a delay in the physical response of a forced increase in carbon dioxide to temperature and sea level, meaning this acts as a benchmark for where we are likely headed into the future.
Carbon dioxide levels rise in the atmosphere largely in response to two things, human emission from the combustion of fossil fuels and volcanic eruptions. As we can measure and quantify both in historical and geologic records, we can separate the relative contribution of each.
While volcanic eruptions previously played a significant role in increasing CO2 in the atmosphere and thus warming the planet, we know that the modern rise in CO2 is a response to burning fossil fuels.
The coronavirus-related lockdowns did cause a temporary drop in CO2 emissions, estimated at 17 percent. However, the lockdowns were too short-lived and not significant enough to alter the course of CO2 rising each year consistently on Earth.
“Well-understood physics tells us that the increasing levels of greenhouse gases are heating Earth’s surface, melting ice and accelerating sea-level rise,” said Pieter Tans, senior scientist with NOAA’s Global Monitoring Laboratory. “If we do not stop greenhouse gases from rising further, especially CO2, large regions of the planet will become uninhabitable.”
Atmospheric scientists at Scripps estimate that it would take a 20-30% reduction in emissions for 6-12 months to see a downward impact on global atmospheric concentrations. If a worldwide pandemic-induced lockdown couldn’t do it, likely nothing apart from coordinated carbon dioxide reduction policy would.
