In the face of the cold sciences and heated debates about climate change, we should remember first and foremost that climates do indeed change. Do not assume that the seasonal patterns humans have adapted to and enjoyed around the world for the last 10,000 years are a permanent fixture. Climates change and civilization needs a back-up plan.
During the Pleistocene, the last 2.5 million years of evolution, Earth has been visited by as many as forty ice ages, each dramatically reshaping ecosystems and selective environments of the planet. Walking around the streets of Manhattan, I like to remind myself that not so long ago this island was under a mile of moving ice and will be again some day.
Climate change can happen gradually or quickly. The cyclical pattern of ice-ages during the Pleistoceneâ€”occurring every 10,000 to 12,000 yearsâ€”are possibly caused by wobbles in the Earthâ€™s orbit or variations in the Sunâ€™s furnaces. Sudden climate changes, on the other hand, are generally caused by catastrophic events, especially the eruption of supervolcanos. The last such eruption was Mount Tuba in Indonesia some 74,000 years ago which not only covered South Asia with many meters of volcanic ash, but also brought on a sudden ice age. Genetic analysis suggests that the explosion of Mt. Tuba was a major bottleneck in human evolution, reducing our common ancestor to perhaps as few as 10,000 souls.
There are a dozen potential supervolcanos around the world that could erupt at any moment in the deep time of geology. One of the largest calderas in the world is Yellowstone, which has blown-up about 100 times over the last 16 million years. For instance, 2.1 million years ago Yellowstone covered what was then New York State under twenty meters of volcanic ash and plunged the globe into an instant ice age.
Slow or fast, without these dramatic geological changes occurring throughout the long history of our planet, Earth would be a pretty boring place. No mountains, no canyons, no parries, no deserts, no tropical islands, not very interesting flora and fauna, and certainly no humans.
Before we can profitably discuss anthropogenic climate change, we need to recognize that most of the people in the world know nothing of these facts. Many of our fellow citizens and elected officials willfully reject the science(s) of climates changing based on competing religious historical narratives. This is why we need to start with the simple fact that climates change and the complex sciences behind these remarkable and quite recent discoveries.
When it comes to anthropogenic climate change, we also need to chill out. The burning of fossil fuels, the exponential growth in methane producing livestock, as well as methane producing termites in recently deforested lands, all contribute to increasing greenhouse gases in the atmosphere. No question but that humans are changing the planet in profound ways, including changing the atmosphere of the planet. Greenhouse gases are only the tip of the melting iceberg. We change the Earth with myriad methods, literally moving mountains and jumbling up ecosystems with invasive weed species. Perhaps we will melt the polar ice caps, perhaps sea levels will rise and destroy the costal cities around the world. Perhaps this will happen quickly or slowly. It is hard to actually know until it happens, because there are so many positive and negative feedback loops involved in climates. Regardless of what our amazing computer models predict, we really canâ€™t know. This inability to predict the future, however, is not something that should put you at ease. It could all be much, much worse, if negative feedback loops are unleashed. Indeed, it may already be too late.
Late or slow, even if there were no threat of human-caused climate change, the policies and practices recommended to deal with global warming would be good for us economically and environmentally. Reducing energy inputs is a way of increasing economic productivity and our trade balance. Reducing fossil fuel consumption improves local environments. By way of example, about a third of the nitrogen pollution that is destroying the Chesapeake Bay and other bodies of water around the world comes from the burning of fossil fuels. There are more than enough economic, environmental, and geopolitical reasons to reduce fossil fuel consumption, so lets get on with it.
That being said lets not be naive about the Second Law of Thermodynamics. Our species recent success, our growth in numbers, and the luxuries of the modern world are directly correlated with a dramatic increase in energy consumption. This holds not just for humans, but for the evolution of life. Measured in ergs per second per gram, plants have an energy density flow estimated about a 1000 times that of an average star. Animals have an energy density flow about 20,000 times that of a star. The human brain achieves an energy density flow about 150,000 times that of a star and modern human civilization is estimated at 500,000 times that of a star. These rough estimates are indicative of something vitally significant. If human civilization is going to advance, we will need more energy per capita, not less. If our civilization is to survive and thrive, we are going to need to grow in a manner that reduces entropy, even as we maximize complexity. Again, the policies and transformations recommended by climate change activists make good sense, even if there were no threat of anthropogenic climate change.
Someday, climates will change with or without our distributed tinkering. Civilization needs a backup plan. Of all of the large mammals, humans will be the best able to survive dramatic climate change, whether it be sudden or slow, natural or anthropogenic. Humans are the only large mammal that has successfully inhabited almost every bioregion of the planet. We have incredible cognitive, cultural, and technological plasticity, which the survivors would put to good use in the challenges of adapting to a much-changed planet. This does not mean this would be a happy event for humanity. Billions would die in the resulting chaos and dislocation with the collapse of agriculture and our global economy, but there is no reason to think that humanity would thereby go extinct.
The more interesting question is what of human civilization would survive on a much-transformed planet, as some day it surely will be. Here, our best strategy is to distribute the hard won discoveries and inventions of science, technology, history, and culture as broadly as possible throughout the world. Doing so requires that Big History be taught and studied throughout the world today, because as humanity only recently learned climates indeed do change.