Despite what the press release says, if you look at the study, you see that they only looked at 3 nights (March 20, 2006, March 21, 2007 and December 17, 2007) over the mentioned time frame (the fourth day they looked at was in 2003). What if there were power outages on December 17, 2007? If so, all of the studies conclusions would seem to be very flawed. If scholars are going to attempt to answer questions like this, shouldn't they be as thorough as possible? Does this study actually meet the criteria of being a credible study?
By tracking the amount of light emitted by Baghdad neighborhoods at night, a team of UCLA geographers has uncovered fresh evidence that last year's U.S. troop surge in Iraq may not have been as effective at improving security as some U.S. officials have maintained.
Night light in neighborhoods populated primarily by embattled Sunni residents declined dramatically just before the February 2007 surge and never returned, suggesting that ethnic cleansing by rival Shiites may have been largely responsible for the decrease in violence for which the U.S. military has claimed credit, the team reports in a new study based on publicly available satellite imagery.
The researchers ... looked at the sectarian makeup in the 10 security districts for which the DMSP satellite took readings on four exceptionally clear nights between March 20, 2006, when the surge had not yet begun, and Dec. 16, 2007, when the surge had ended.
Here is a study and an Iraqi public opinion poll which shows evidence that the Surge has had some success:
Those number's cannot be reconciled logically with the conclusions of the above study.