Final answer:
The level of carbon dioxide in the atmosphere has risen significantly in the past several decades from around 280 ppm in pre-industrial times to well above 400 ppm, with a steep increase over the last 50 years due to the burning of fossil fuels.
Step-by-step explanation:
In the past several decades, the level of carbon dioxide (CO2) in the atmosphere has increased significantly. Historically, CO2 levels have cycled between 180 and 300 parts per million (ppm) by volume. However, due to the burning of fossil fuels, recent data indicates a dramatic rise in CO2. As of the late 20th and early 21st century, measurements from the Mauna Loa Observatory show that CO2 levels are now higher than they have been at any point over the past 700,000 years. Specifically, CO2 concentrations stood around 280 ppm in the pre-industrial era, while recent measurements indicate levels have risen well above 400 ppm.
This rise in atmospheric CO2 has been linked to climate change and global warming. Graphs from ice core samples and direct measurements illustrate this unprecedented increase in atmospheric CO2, which accelerated particularly in the past 50 years. Scientists expect that the amount of CO2 could double its preindustrial level before the end of the twenty-first century if current trends continue.