Albedo Its effects on global warming in Polar Regions STEM Polar Connections

Global Warming and Polar Regions Why are Polar Regions warming more rapidly than temperate areas? One reason: as sea ice melts and more open water appears, more solar energy is absorbed, and warming accelerates. This is a form of positive feedback and it makes the polar climate change faster. Increasing vegetation on land also has a similar positive feedback effect.

What is albedo? Albedo is the fraction of light from the sun reflected by a surface. Close to 1 for fresh snow – reflects most of the solar energy to 0.1 for light incident on liquid water at up to 70º – absorbs most of the energy. Example: Clear snow from a dark driveway – adjacent snow melts faster.

How Can We Measure Albedo? Pyranometer – measures temperature of a dark absorbing material, pointing alternately at surface and sky. Expensive. Digital camera and free imaging software – compare reflections from surfaces. Free if you have the camera, computer. Somewhat complicated. Light meters – fast, easy to use, inexpensive.

What are sun rays? The sun emits several kinds of electromagnetic radiation: Visible, Infrared, Ultra Violet, etc. Source:

The Sun’s Radiation Spectrum ~ 43% of energy is in the visible range ~ 49% in near infrared range ~ 7% in ultraviolet range < 1% in x-rays, gamma waves, and radio waves. Source: Adapted from

A Caveat Light meters designed for illumination measurements and most digital cameras only detect visible light. Light meters are also designed to be most sensitive to green light, matching sensitivity of human eye. The fraction of light that is reflected may depend on the frequency. Thus albedo results from light meter and camera measurements may not be really accurate.

Light Meter Mastech Digital 4-Range 200,000 Lux Luxmeter, LX1330B, Sold by: Kaito Electronics, Inc $ shipping from Amazon.com 4 ranges, lux or ft- candles; ± 3% accuracy. Lux – measures intensity of light per unit area, weighted according to human brightness perception

Typical Lux Values Brightest sunlight200,000 lux Well lit office400 lux Full moon0.25 lux Minimum value for meter0.1 lux