A comparison of monthly anomalies in Northern Hemisphere SCA derived from two satellite data sets: the NOAA snow charts revised by D. Robinson that map snow cover from primarily visible-wavelength sensors like AVHRR and GOES, and passive microwave (PM) algorithms using SMMR and SSM/I EASE-Grid brightness temperatures. Since both data sets exhibit significant month-to-month autocorrelation, we have estimated monthly trends with an autoregressive lag-1 model (AR(1)), using the method described by Weatherhead et al. (1998).
Around 10 million pairs of usable spectacles are discarded each year in Europe and North America. These can be used to help people in the developing world to afford glasses. Most opticians now act as collection points for old glasses, so drop yours off and give them a new lease on life.
More green tips