Carbon dioxide (CO2) is an important greenhouse emitted to the atmosphere by both natural and human industrial sources. Just prior to the onset of the Industrial Revolution, CO2 was maintained at a concentration near 280 ppm through the global carbon cycle, which involves a web of sources and sinks that develop from biological, oceanic, and atmospheric processes. Emissions from fossil fuel burning have perturbed the natural carbon cycle, leading to a dramatic and ongoing rise of atmospheric CO2 to more than 360 ppm. Most physical scientists agree that rising levels of CO2 from human activities have altered the circulation of Earth's atmosphere, which in turn has had the net effect of increasing surface air temperature in most places around the globe. Information source: U.S. EPA, World Health Organization.
Global Greenhouse Gas Levels
The major greenhouse gases are globally mixed and their current levels have greatly exceeded their pre-industrial levels. The current levels of greenhouse gases are all considered unhealthy.
See evidence of just how drastically their levels have increased in the ice core record.
There are no known direct health impacts associated with atmospheric carbon dioxide. However, because carbon dioxide is a greenhouse gas, it can impact health indirectly from contributing to global climatic change. The most prominent health impacts associated with climate change include heat stress from summer heat waves, and the spread of vector-born diseases facilitated by poleward migration of wild animals and biota. Information source: U.S. EPA, World Health Organization.