Given today's (Jan. 20) announcement that the year 2015 was by far the warmest on record for Earth, it's a good time to check current carbon dioxide readings. An ever-increasing CO2 content in our atmosphere is the major reason we are heating up.

The carbon dioxide content of the atmosphere on Jan. 19 was 402.30 parts per million. At one point on Jan. 13 the measurement touched 405 ppm. Scientists predict that the measurement will continue to ride at 400 or higher, never again to drop below that point.

The reading one year ago was 399.44 ppm.

Measurements are made by two independent CO2 monitoring programs (NOAA and Scripps) at the Mauna Loa Observatory in Hawaii, about 3,400 meters above sea level.

"The continued rapid rise in CO2 ensures that levels will rise far beyond 400 ppm before they stabilize. If the pace of the last decade continues, carbon dioxide will reach 450 ppm by the year 2040. Carbon dioxide is the most important man-made greenhouse gas, produced mainly by the burning of fossil fuels such as coal, oil and natural gas. The pace of rise depends strongly on how much fossil fuel is used globally." (Taken from the Scripps Institution of Oceanography web site: scripps.ucsd.edu)

The United Nations' announced goal for co2 in the atmosphere is 450 ppm. Scripps prediction for hitting that level is the year 2040, given continuation of present fossil fuel use. That's 24 years from now.

A safe level for Earth is said to be 350 ppm.

Below: a Western Meadowlark trying to cool down on a hot South Dakota day.