Earth's solar reflectance, or albedo, is one of the most significant influences on climate change. Over the past decade we've observed an alarming decrease in albedo, which effectively means that Earth is absorbing more solar energy. However, one consequence of this is an increase in the intensity and frequency of hurricanes -- and since the low-lying clouds associated with hurricanes are especially reflective, we expect to observe a cloud-radiation feedback system that "self regulates" global warming to some degree. Although previous analyses have identified a strong positive correlation between cloud cover and albedo, no work has been done to understand these trends during severe spikes in cloud cover during hurricanes. So we used high-resolution cloud data from the GOES satellite and solar flux data from the CERES instruments to identify trends in the northern Atlantic, a hotbed of tropical storm activity. After correcting the data and deriving the desired values, we performed a superposed epoch analysis to filter out extraneous signals and isolate the relationship between cloud cover and albedo. Our results strongly support previous conclusions on the positive correlation between cloud cover and albedo. However, we also identified interesting patterns in the timing and rate of albedo variations surrounding cloud cover spikes, for which we were unable to identify any underlying physical phenomena and warrant further study. This analysis will soon be repeated with data from BBSO's Earthshine project, which will help us understand the evolution of Earth's climate in light of extreme global warming.
We expect global warming to increase the frequency of hurricanes, which would increase Earth's albedo (solar reflectance) because clouds are more reflective than most land/water. This would cause a sort of "self-regulating" decrease in global temperatures. However, a recent landmark study (Google "The Earth is Dimming") has observed an unprecedented decrease in Earth's albedo over the past 20 years, which seems to contradict our model. Goode et al hypothesized that this is because of a warming of the eastern pacific and consequent reduction in low-lying cloud cover. Our research seeks to hone in on whether albedo measurements/observations over the past two decades reflect short-term anomalies or long term trends. This is signfificant because the latter would indicate a gap in our understanding of how cloud-cover affects global temperatures.
In short, we're trying to quantify the correlation between cloud cover over the Northern Atlantic and Earth's albedo.
We used GOES satellite data for cloud coverage and CERES data for the albedo measurements. The CERES data however did not contain the albedo average as we would have liked so we used the raw data and calculated the average albedo for a given moment in time. Since both data sets are over time, we can use a technique called superposed epoch analysis. Then we looked for spikes in in cloud coverage to see if there was any effect to the albedo plot.