Worldwatch focuses on climate change because human energy use drives greenhouse gas emissions, which affect vital life-support systems like forests, soils, and oceans. The greenhouse effect, discussed in Worldwatch's publications, is a key aspect of the climate debate. The Earth's atmosphere, transparent to sunlight but absorbing reflected energy, acts as a regulator of climate. Changes in this atmospheric layer's transparency can alter Earth's reflectivity and ultimately lead to shifts in climate, including average temperature.