Latest from Columns
Hpac 5196 Observatory Telescopes At Mauna Kea Hawaii 800

One World Record We Didn’t Want to Break

May 16, 2018
This spring, the Mauna Loa Observatory in Hawaii recorded its first-ever CO2 reading in excess of 410 ppm. Many climate scientists now believe that CO2 levels are at a dangerously high level.

When I first became involved with demand-controlled ventilation (DCV) a decade ago, background CO2 levels were well under 400 parts per million (ppm).

DCV, for those not familiar with it, is the process by which outside air is varied based on the amount of CO2 – generally reflecting the human occupancy – in a space. Most DCV systems operate on indoor-to-outside air differential CO2 concentrations, rather than on an absolute value of indoor CO2. In an August 2009 article for HPAC Engineering on multi-parameter DCV, I noted average background levels were, depending on location and time of day, approximately 360-380 ppm. The prevailing ventilation standard at the time was ASHRAE 62.1-2007, which established the ideal ventilation rate to be approximately 17 cubic feet per minute, per person (CFM/person) based on typical occupant densities.

That value correlates to a CO2 differential of about 617 ppm above ambient outside air conditions. So at a background level of, say 380 ppm, a 617 ppm differential results in 997 ppm indoor CO2 concentration. If the outdoor level rises to 410 ppm, then the indoor level – at the same differential – becomes 1,027 ppm. That doesn’t sound like much of a difference, but in 2012, it was conclusively demonstrated that even concentrations as low as 1,000 ppm impair thinking, concentration, and logical thought processes.

In case you missed it in the popular press, the 410 ppm reference is important. Last month, on April 17, the Mauna Loa Observatory (MLO) in Hawaii recorded its first-ever CO2 reading in excess of 410 ppm. Located on the Big Island, MLO has been taking daily measurements of atmospheric CO2 since 1958. Originally directed by Charles David Keeling, for whom the Keeling Curve (see below) is named, the Scripps CO2 program is now under the direction of his son, Ralph Keeling, also a researcher at the Scripps Institute of Oceanography.

Mauna Loa is an ideal location for these types of measurements, since its CO2 sensors are at an altitude of over 11,000 feet and sample the prevailing ocean winds. There are no artificial CO2 sources, such as cars, nor – at that altitude – is there any local absorption due to dense foliage. The measurements taken there are, as a result, well-mixed and an accurate indicator of global averages.

Most climate scientists agree that CO2 levels are now at the highest level in human history. According to a 2011 study in the journal Paleoceanography, atmospheric CO2 levels have probably not been this high since the Pliocene epoch, between 2 and 4.6 million years ago. And an earlier, 2009 study published in Science, concluded that present CO2 levels are the highest since the Miocene epoch, 10 to 15 million years ago. Regardless of which study is correct, it is clear that if the increase in CO2 concentrations due to global greenhouse gas emissions continues to rise at current rates, atmospheric CO2 concentrations will likely exceed 450 ppm. Some climate scientists, notably James Hansen, believe that current CO2 levels may already be past the threshold of truly dangerous to our climate and planet.

A regular contributor to HPAC Engineering and a member of its editorial advisory board, the author is a principal at Sustainable Performance Solutions LLC, a south Florida-based engineering firm focusing on energy and sustainability. He can be reached at [email protected]