Understanding the Impact of Anthropogenic CO2 on Atmospheric Levels
Are we responsible for just 5% of the total atmospheric CO2, or is it much more? The truth is that the amount of anthropogenic CO2 in the atmosphere is much higher, accounting for nearly a third of the current concentration.
Anthropogenic CO2 in the Atmosphere
Before the Industrial Revolution, the level of atmospheric CO2 was around 280 parts per million (ppm). Today, that number has risen to over 420 ppm, an increase of approximately 140 ppm. This can be attributed to the extensive burning of fossil fuels, which has led to a 50% increase in CO2 levels.
Science supports this: isotope analysis of fossilized carbon shows that the additional carbon is from burning fossil fuels, and records of coal and oil production also corroborate this increase.
Therefore, the 140 ppm of CO2 is anthropogenic, making up about 1/3 of the current concentration, or rounded to 30%.
Understanding the Arrhenius Doubling Scenario
Over a century ago, Arrhenius theorized that a doubling of CO2 would increase global average temperature by about 4 degrees Celsius. Modern calculations with advanced computing power and improved understanding indicate that these predictions were remarkably accurate. Currently, the average temperature has risen by 1.2 degrees Celsius, with continued increases expected.
The impacts of this increase are widespread and varied: storms and cyclones have become fiercer and more frequent, heat waves, droughts, and wildfires are also on the rise.
Without a significant reduction in the burning of fossil fuels, this trend will continue to worsen. However, there are alternatives available. Renewable energy sources like solar, wind, hydro, geothermal, and even nuclear with battery backup can be used to phase out coal, oil, and gas. Such transitions not only help to mitigate climate change but are also cost-effective.
The CO2 Load and the Keeling Curve
Each year, we add about 1 ppmv of CO2 to the 420 ppmv of total atmospheric CO2. About half of this additional CO2 is absorbed by the oceans, but the remaining amount accumulates in the atmosphere. Consequently, the Keeling Curve, which tracks CO2 levels, rises by approximately 2 ppmv per year.
Today, the total anthropogenic CO2 content of the air is roughly 33% of the current CO2 concentration. Compared to pre-industrial levels of 280 ppmv, the current levels are about 50% higher. This count does not include CO2 equivalents, as I am focused solely on CO2 derived from fossil fuel consumption and concrete production.
Understanding the Long-Term Carbon Cycle
While 5 ppmv of CO2 is often cited as the yearly addition, this number is misleading. The carbon cycle is long and complex. Only about half of the CO2 added through burning fossil fuels remains in the atmosphere for 100 years. For example, CO2 added through burning coal in 1923 still persists in the atmosphere today.
The accumulation of CO2 over the past decades means that the amount added in the last 20 years is equivalent to doubling the amount of CO2 that was in the atmosphere in 2003. As natural sinks cannot keep up with the rapid increase, CO2 levels will only continue to rise unless significant action is taken.
Analogy-wise, if the increase in CO2 was like a 5% reduction in your annual salary, you would quickly seek a new job. Similarly, the planet cannot tolerate the continued increase in CO2 levels without severe consequences.