EARTHSHINE RESEARCH TRACKS UNEXPECTED CLIMATE CHANGES
Researchers at NJIT's Big Bear Solar Observatory who study the sunlight reflected off the Earth onto the moon -- known as earthshine -- made international news in 2004 when they observed an unexpected dimming in the Earth's reflectivity.
The team lead by Philip Goode, distinguished professor of physics and center director, found that the planet appeared to dim from 1984 to 2001 and then reversed its trend and brightened from 2001 to 2003. The shift appears to have resulted from changes in the amount of clouds covering, and potentially cooling, the planet. The changes in brightness could signal climate change. Findings were reported in Science.
The study was part of the center's earthshine project, a collaboration with California Institute of Technology, supported by NASA, The project studies the amount of light reflected by the Earth to detect changes in brightness. According to the research team, Earth's climate depends on the new amount of sunlight that reaches the globe, which is affected by the reflective quality of the Earth, known as earthshine.
The illustration above, left, shows mean cloud cover map for 15th October 1999 (top) and 4th September 1999 (middle) over the area contributing to the earthshine during about 4 hours of observation from Big Bear each night. The mean lunar phases were -115.8 degrees (waxing) and +109.7 degrees (waning), respectively. Such coverages are typical for a single night's observations. Bottom panel: The weighted contribution of each part of the Earth to the ES observations during the 1999-2001 period. The arbitrary normalized scale reflects the number of times that each area of the Earth has contributed to the earthshine, weighted by the Earth-Moon cosine at each observation. The darker blue areas are those we cannot see in the earthshine from California.
The image on the right, above, is a composite image of the dark (earthshine) and bright (moonshine) sides of the Moon. Researchers use a blocking filter to dim the moonshine crescent, typically about 10,000 times brighter than the earthshine.