The Changing Global Environement
We know a great deal about historical climate and its variations from various geo logical studies. There are two points worth remarking on. One is that the climate changes frequently and radically, but that the degree of variation and even sense of variation depends on the time scale which we are considering. Secondly, that this is a most unusual geological period for the Planet Earth; we are living in a period of mountain building and glaciations, whereas during most of the last 250 million years (m.y.) there was little ice and little topography. A good view of climate change of the last hundred m.y. can be gained by looking at the paper of Kellogg. We are now in a period of extensive glaciations. The previous interval occurred 300 to 250 m.y. ago, when even the Sahara was glaciated. (Of course, it was at that time near the position of the South Pole; we know that 300 m.y. ago the continents had not broken apart and formed one land mass.) Apparently between 250 and 20 m.y. ago there was little ice on the Earth, even at Antarctica. Continental basins were flooded by shallow seas. This was the period when plant life and marine life proliferated and when most of our fossil fuels were laid down.
Was andere dazu sagen - Rezension schreiben
Es wurden keine Rezensionen gefunden.
Andere Ausgaben - Alle anzeigen
aerosol agricultural Air Pollution albedo algae amount annual anthropogenic areas Atmos atmosphere average biosphere biota carbon dioxide Carbon Monoxide chemical climatic changes cloud combustion compounds concentration crops DDT residues dust Earth's surface ecosystem effects emissions energy environment Environmental equilibrium estimated eutrophication factor fertilizer Figure fossil fuels Fred Singer Geophys global heat human activities ice crystals ice nuclei impact increase indicate industrial input Junge Lake layer levels man-made man's Manabe marine Mauna Loa measurements mechanism Meteorol Methane natural sources nitrate nitrogen cycle nitrogen oxides northern hemisphere nutrients observed ocean oxidation oxygen ozone particle loading period photosynthesis plants precipitation present problem processes production radiative rainfall reactions recent reported Research result river Science sediments sewage soil solar radiation species stratosphere studies sulfur surface waters Table temperature tons trend troposphere turbidity urban values variations volcanic Washington water vapor Weather
Seite 426 - Pollution is an undesirable change in the physical, chemical, or biological characteristics of our air, land, and water that may or will harmfully affect human life or that of other desirable species, our industrial processes, living conditions and cultural assets; or that may or will waste or deteriorate our raw material resources...