Evidence suggesting the shortening of the day from 'sunrise' to 'sunset' due to global change

摘要

The effect of global change in the past century, which led to increased levels of pollution and augmented values of cloud coverage, on the time of the apparent Sunrise and Sunset, is suggested to have shortened the day by 1-1.5 minutes in the past 4 decades in northern mid-latitudes. This is supported by photographs of the setting Sun taken in Jerusalem during the months of July and August 2001, which reveal that in over 95% of the cases the Sun completely disappear to the naked eye below marked atmospheric layers at an average elevation angle of 0.5 - 2.5° above the solid earth horizon. Based on trends in past Sunshine Duration measurements, the day shortening effect is expected to increase in the future.