Uh oh... Scientist have recently discovered an alarming piece of evidence that suggest that prehistoric mass extinctions in the past may be a warning that the same thing could easily happen again. And it is all due to greenhouse gases. Greenhouse gases are gases that cause infrared radiation in the lower atmosphere, which in turn causes a strong increase in temperature on earth (a WHOPPING 60 degrees Fahrenheit!). Global warming is caused by these dangerous temperature spikes. There are now so-called "greenhouse oceans" which have lower oxygen levels and higher carbon dioxide levels than they ever had before, and it's all because of greenhouse gases.
What does that have to do with mass extinction? As a matter of fact, a new development in core sample studies have shown that greenhouse oceans had (theoretically) a great impact on many prehistoric environments. Geologists off the coast of western africa studied layers of sediment from the late Cretaceous Period across a 400,000 year timespan. What they discovered is very alarming, considering the predicament we find ourselves in at the moment. They found a very large amount of marine life remains in the sediment. they were all buried within a layer of dangerously deoxygenated layers of the sediment.
The even scarier thing is that there are already many "dead zones" in the oceans, which are areas of water which have been deprived of oxygen and loaded with CO2, rising temperatures, and runoff from agriculture. This is a sign that the oxygen levels on earth are depleting. But it's not over! As you may know, the ocean is a very sensitive environment. Even the tiniest variation in temperature or vital gas levels can throw an entire ecosystem off-kilter. So when the oxygen decreases, millions of marine organisms die, and millions more are forced to new ecosystems.
On the brighter side, though, these periods of oxygen depravity (called hypoxic phases) seem to be temporary, and the oxygen levels improve. But this doesn't mean that these phases cannot be prevented, or at least made to happen less often. The only way to do that would be to treat the earth differently, and try to stop the advance of global warming.
http://www.sciencedaily.com/releases/2011/05/110517105812.htm
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