Scientists increasingly agree that the earth's atmosphere is becoming warmer. A long-term rise in the global climate could cause sea levels to rise around the world and bring a number of other adverse consequences (62). Reliance on fossil fuels as an energy source and the widespread destruction and burning of forests are chiefly responsible for the carbon emissions—the so-called greenhouse gases—that lie behind global warming (20,69,110,140,167,213,264).
One indication of global warming is that over the past 40 years the ocean surface (the top 1,000 feet) has warmed an average of half a degree Celsius (168, 209). The US National Oceanic and Atmospheric Administration (NOAA) has reported that tropical waters in the Northern Hemisphere have been warming up even faster—in fact, 10 times faster than the measured global rate—because tropical oceans retain heat more readily than other areas (168).
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