In reality every bit of evidence for Global warming is hypothetical, or inconclusive. There are also recent discoveries that make it's fears look a joke:
For example, consider this:
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Considering the titanoboa was twice the size of today’s largest snake, the anaconda, the scientists estimated that the average temperature of its ecosystem would have been about 91 degrees Fahrenheit, 10 degrees warmer than the tropical forests which cover South America today.
"This temperature estimate is much hotter than modern temperatures in tropical rainforests anywhere in the world,” said Carlos Jaramillo, a paleobotanist at the Smithsonian Tropical Research Institute. “The fossil floras that the Smithsonian has been collecting in Cerrejon for many years indicate that the area was a tropical rainforest. That means that tropical rainforests could exist at temperatures 3-4 degrees Celsius hotter than modern tropical rainforests experience."
Such a discovery may have widespread implications as scientist attempt to predict how tropical forests will change in face of global warming. Many have feared the forest would become savannah due to higher temperatures, but if the climate of 60 million years ago is any indication some of tropical plants could survive temperature increases.
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So even if global warming is happening faster than it naturally happens(the earth cools and warms periodicaly), we still may be in the safe area for a long time.