What Can Dinosaurs Tell Us About Global Warming

From a scientific perspective, the extinction of the dinosaurs 65 million years ago and the potential extinction of humanity due to global warming within the next 100 to 200 years might seem to have little to do with one another. Certain details have yet to be settled, but the main reason the dinosaurs went kaput at the end of the Cretaceous period was the impact of a comet or meteor on the Yucatan peninsula, which raised huge amounts of dust, blotted out sunlight worldwide, and caused the slow withering of terrestrial vegetation--leading first to the demise of plant-eating hadrosaurs and titanosaurs, and then the death of the tyrannosaurs, raptors and other meat-eating dinosaurs that preyed on these unfortunate leaf-munchers. Human beings, on the other hand, find themselves facing a much less dramatic, but equally serious, predicament. Pretty much every reputable scientist on the planet believes that our relentless burning of fossil fuels has caused a spike in global carbon dioxide levels, which in turn has accelerated the pace of global warming. Carbon dioxide, a greenhouse gas, reflects sunlight back to earth rather than allowing it to dissipate into space. Over the next few decades, we can expect to see more, more widely distributed, and more extreme weather events (droughts, monsoons, hurricanes), as well as inexorably rising sea levels. The complete extinction of the human race is unlikely, but the death and dislocation caused by severe, unchecked global warming could make World War II look like an afternoon picnic. How Global Warming Affected the Dinosaurs So what do the dinosaurs of the Mesozoic Era and modern humans have in common, climate-wise? Well, no one claims that rampant global warming killed the dinosaurs. In fact, Triceratops and Troodons that everyone loves thrived in 90- to 100-degree, lush, humid conditions that not even the worst global-warming alarmists foresee existing on earth anytime soon. Why was the climate so oppressive 100 million years ago? Once again, you can thank our friend carbon dioxide: the concentration of this gas during the late Jurassic and Cretaceous periods was about five times current levels, an ideal level for dinosaurs but not for humans. Weirdly enough, its the existence and persistence of the dinosaurs over tens of millions of years, not their extinction, that has been seized on by some in the global warming is a hoax camp. As the (admittedly wacky) reasoning goes, at a time when carbon dioxide levels were truly alarming, dinosaurs were the most successful terrestrial animals on earth--so what do human beings, who are much smarter than the average Stegosaurus, have to worry about? Theres even convincing evidence that a surge of severe global warming 10 million years after the dinosaurs went extinct--at the end of the Paleocene epoch, and probably caused by a giant methane burp rather than carbon dioxide--helped to stimulate the evolution of mammals, which up until that time were mostly small, timid, tree-dwelling creatures. The problem with this scenario is threefold: first, dinosaurs were clearly better adapted than modern humans to living in hot, humid conditions, and second, they had literally millions of years to adjust to rising global temperatures. Third, and most important, while dinosaurs as a whole survived the extreme conditions of the later Mesozoic Era, not all of them were equally successful: hundreds of individual genera went extinct during the Cretaceous period. By the same logic, you can argue that human beings will have survived global warming if some human descendants are still alive a thousand years from now--even if billions of people perished in the interim from thirst, floods, and fire. Global Warming and the Next Ice Age Global warming isnt only about higher global temperatures: theres a very real possibility that the melting of the polar ice caps will trigger a change in the warm-water circulation patterns of the Atlantic and Pacific oceans, resulting in a new Ice Age across North America and Eurasia. Once again, though, some climate-change deniers look to dinosaurs for false reassurance: during the late Cretaceous period, a surprising number of theropods and hadrosaurs thrived in the north and south polar regions, which werent nearly as cold as they are today (the average temperature back then a was a moderate 50 degrees) but were still substantially cooler than the rest of the worlds continents. The problem with this type of reasoning, once again, is that dinosaurs were dinosaurs and people are people. Just because big, dumb reptiles werent particularly bothered by high carbon-dioxide levels and regional plunges in temperature doesnt mean that humans will have a comparable day at the beach. For instance, unlike dinosaurs, humans depend on agriculture--just imagine the impact of a prolonged series of droughts, wildfires and storm surges on global food production--and our technological and transportation infrastructure depends, to a surprising extent, on climatic conditions remaining roughly the same as they have been for the last 50 to 100 years. The fact is that the survival or the ability to adapt of dinosaurs offers virtually no useful lessons for a modern human society that is just beginning to wrap its collective mind around the fact of global climate change. The one lesson we can indisputably learn from the dinosaurs is that they went extinct--and that hopefully, with our bigger brains, we can learn to avoid that fate.