Sustainable Construction, 5th Edition

Chapter 2Background

On May 9, 2013, for the first time in the 200,000 years of existence of the species of bipedal primates known as humans, a pivotal event occurred that now threatens their future on Earth. On that date the Mauna Loa Observatory in Hawaii recorded that, for the first time in human history, atmospheric carbon dioxide (CO₂) levels exceeded 400 parts per million (ppm), an event that had last occurred over 800,000 years ago. In preindustrial times—that is, prior to 1760—CO₂ concentrations had averaged 280 ppm and had slowly increased to 310 ppm by 1958, the year that instruments at the observatory first began measurements (see Table 2.1). As of 2020, CO₂ levels averaged 415 ppm, and they are expected to continue to increase unless dramatic action is taken by the world's nations to limit greenhouse gas emissions from their power generating systems, industries, and transportation systems (see Figures 2.1 through 2.5)

Human activities have been identified as the cause of the shift in Earth's carbon cycle, which is trapping the sun's energy in the planet's atmosphere and oceans, with likely consequences for all life-forms.¹ Dr. Carmen Boening, a scientist with the Climate Physics Group of the NASA Jet Propulsion Laboratory, described the event in this way:

Reaching the 400 ppm mark should be a reminder for us that CO₂ levels have been shooting up at an alarming rate in the recent past due to human activity. Levels that high have only been reached during the Pliocene ...