Energy Science, History, Sustainability: ASU Lecture

Energy arrives from the Sun as electromagnetic radiation that travels at the speed of light. Wavelengths span from long radio waves to short gamma rays, with visible light positioned in the middle of the spectrum. The atmosphere, though thin and fragile, traps enough heat to maintain an average global temperature of about 14 °C (57 °F). Roughly half of the incoming solar energy is absorbed by land and sea, 20 % is reflected by clouds, 25 % is lost as heat, and the remaining 5 % is scattered.

Energy and Human Society

Photosynthesis captures solar photons and converts them into chemical energy stored in biomass. Over millions of years, ancient biomass is compressed and transformed into fossil fuels—coal, oil, and natural gas. Modern economies extract energy from these fuels by oxidizing (combusting) them, a process that powers industrial activity and economic growth. The shift from biomass to fossil fuels accelerated during the Industrial Revolution, reshaping societies worldwide.

Climate Change and Greenhouse Gases

Greenhouse gases—including carbon dioxide, methane, nitrous oxide, and human‑made fluorinated compounds such as CFCs and HFCs—absorb long‑wave infrared radiation emitted by the warmed Earth. This absorption traps heat and creates the “human‑enhanced greenhouse effect,” where rising concentrations of these gases retain more heat than the natural cycle. The Keeling Curve, recorded at Mauna Loa, Hawaii for more than 50 years, provides clear evidence of a steady rise in atmospheric CO₂ levels.

Practical Applications at ASU

Arizona State University monitors its carbon footprint through “Campus Metabolism,” a real‑time system that tracks emissions across its four campuses. Despite institutional growth, ASU has reduced its emissions by expanding solar generation to 24 MW and designing LEED‑certified buildings. The university emphasizes that sustainability requires a multi‑pronged approach—policy, technology, and cultural change—because “we created this problem and therefore humans can also solve it.”

Mechanisms & Explanations

Energy Balance – The Sun supplies incoming radiation; 50 % is absorbed by land and sea, 20 % reflected by clouds, 25 % lost as heat, and 5 % scattered.
Greenhouse Effect – Short‑wave solar radiation passes through the atmosphere, warming the surface. The Earth then radiates long‑wave heat, which greenhouse‑gas molecules trap via chemical bonds, sending part of the energy back toward the surface.
Scope Emissions – Emissions are categorized into Scope 1 (direct), Scope 2 (indirect from utilities), and Scope 3 (supply‑chain and travel).