Earth Day April 22 — Dark Sky Week, Part 2

Last week we imagined what could be seen overhead: Dark Sky Week April 15-21 – Turn on the Night. This week, with Earth Day following directly on the tail of International Dark Sky Week, we cast our gaze back to our planet for a look at the cost of light pollution, and to understand one detail that makes all the difference: the color temperature of the light itself.

The market is full of energy-saving bulbs, whether compact fluorescent or LEDs, with new lighting arriving in the form of OLEDs (think of these as liquid LEDs). While these new bulbs come with higher up-front costs, the energy saved and the cost savings  (in the long run) are worth it. As can be seen in the chart above, we are wasting a lot of energy when it comes to outdoor lighting. Even when we get that figured out—by placing lighting only where we need it, and turning lights on only when we need them—we still need to address the color temperature of the light being emitted from the fixtures.

By now most people are familiar with color temperature, either from in-store display units demonstrating the light effects of a variety of bulbs, or simply from the experience of buying a replacement bulb only to discover the new bulb runs too warm or too cool. From car headlamps to holiday lighting, we’ve all noticed and probably even come to prefer cool over warm or vice versa, depending upon the use or setting. For outdoor lighting, there really is only one direction: on the WARM side.

Color temperature, measured in Kelvins (K), is the standard for rating the light emitted from a bulb used in the actual lighting fixture: with 5000k and above generally considered the closest to daylight and 2700k giving that warm glow we’ve come to associate with tungsten bulbs. The Dark Sky Association recommends using 2700K or less for outdoor lighting.

So while  saving on energy is important, when it comes to exterior lighting, color temperature is of equal importance. Watch as cities and counties around the country address this issue. Tucson, Arizona and the entire State of New Mexico got it right when they made eliminating light pollution a priority—you can now look up and see the Milky Way from anywhere in the city or the state. San Francisco is making great progress—the city has been upgrading thousands of street lights to warm LEDs—whereas it’s back to the drawing board for the City of Los Angeles (LA went cool).

Big Picture: Cool lights are highly disruptive and wash out the sky.
Local Action: Switch from cool to WARM LEDs — and educate your neighbors to do the same.

post by Jenny Stein, environmental committee