National Geographic : 1990 Oct
COCONCENTRATIREORDEendless power that drives and rules all life on earth: its 350 ATMAUNALOA,HAWA plant growth and the food chains of all its creatures; the winds, rains, and churning weather of the planet; the 40 ocean currents, forests, prairies, and deserts. Our home star in the heavens burns steadily, almost S33without variation. It is the "almost," coupled with what man's activities are doing to the atmosphere, that this story is about. It is becoming more and more appar ent that the effects of the sun upon our planet are chang 1960 1965 1970 1975 1980 1985 1990 ing. Our one and only home may be in harm's way, and we can scarcely sense just what is happening-or know to analysis of air trapped in ice what to do about it. sheets. Scientists say this evi- That burning energy of our sun works the miracle on earth dence shows the effects of called photosynthesis. Powered by sunlight, plants green with human activities such as burn- chlorophyll combine carbon dioxide from the air with water ing fossil fuels. Most believe the from soil or sea into energy-rich carbohydrates, releasing into the rising CO2 levellwill lead to atmosphere the oxygen we need to breathe. higher global temperatures and signcant climate change. It is the same process by which primitive bacteria of ocean significant climate change. shallows, more than two billion years ago, first produced enough oxygen to permit other life on earth to develop. And it is the Is Our World Warming?