Since 1958, a continuous measurement of the carbon dioxide content of the atmosphere has been made at Mauna Loa Observatory in Hawaii. These observations were initiated by Charles Keeling, who died in 2005, and have been maintained by his son Ralph ever since.
Sunshine is a manifestation of solar radiation and when it is absorbed by the surface of the Earth, the surface heats up and emits a different kind of radiation, known as infrared radiation. Carbon dioxide is a special chemical in that it is transparent to solar radiation and yet it absorbs infrared radiation. Thus, the presence of carbon dioxode in our atmosphere allows sunshine to penetrate to the surface but inhibits the emission of infrared radiation to space.
The consequence of the absorption of infrared radiation by carbon dioxide in the atmosphere is that Earth is much warmer than it has any right to expect based upon its distance from the Sun. In fact, Earth’s average surface temperature is 59 degrees Fahrenheit when it would be 0 if carbon dioxide and other such greenhouse gases (like water vapor and methane) did not exist in our atmosphere.
When Keeling began his measurements in 1958, the atmosphere contained 315 carbon dioxide molecules for every million molecules of gaseous atmosphere. April 2014 was the first month in 56 years in which the monthly average carbon dioxide fraction topped 400 molecules per million (it was 401.33).
The continual increase in this carbon dioxide fraction is considered to be the main contributor to the global temperature increase known as global warming. Such values are a first in human history and likely represent the highest carbon dioxide fraction in our atmosphere in at least the last 800,000 years. It is high time that we had a sober, data-driven discussion about the hazards presented by this dangerous trend. Analytical, skeptical science has to be central to this discussion.