|Climate Change III : Why the Enemy Is Us
||[Oct. 28th, 2009|09:06 am]
The arguments against a human cause of a) the increased carbon dioxide and b) global climate change rest on several false assumptions. First, that because there are other sources of CO2, the human contribution must be so paltry as to be insignificant. Second, that CO2 isn't a major component of greenhousing--it's all sun cycles or something.
But there again the evidence is on the side of the original thesis...that this round of global climate change is being accelerated by human activity. In the paleoclimate record, high levels of carbon dioxide and methane are associated with warmer climates. These are not the only "greenhouse gases" or the only contributors to the atmospheric change, but they are easy to measure. Carbon dioxide was recognized as a greenhouse gas long before the climate-change hypothesis was raised--in fact, it was because it is a known greenhouse gas that rising carbon dioxide created an interest.
With increasing precision, it's possible to know how much geologic and other processes contribute to the levels of CO2 in the air. It's possible to track entire air masses, with their associated chemical components (satellites are a big help.) Samples of air at various altitudes allow comparison of the carbon isotope ratios in the carbon dioxide both vertically and across time. So the human contribution to the atmosphere--across many atmospheric components, not just carbon dioxide--can be traced. That contribution has increased rapidly in the past two centuries, both because of the increased population but also because of activities that decrease carbon uptake (reduction) via photosynthesis and increase carbon oxidation.
It does not matter that there are non-human-derived sources of CO2 and methane, such as volcanoes. What matters, in terms of the anthropogenic component, is whether it's enough to tip the scales. After all, if you're in a rowboat with a lot of water in it, just barely floating, and you reach over the side and dip another bucketful into the boat--you can indeed sink your own boat. The last bucketful--the one that sinks the boat--may be a small fraction of what's in the boat, but it's a critical fraction. If you're smart, you'll be dipping water from the boat and pouring it into the ocean.
Humans have impacted this planet in many ways for tens of thousands of years, but that impact has accelerated as a) the population increased (it has about tripled in my lifetime) and b) developed more effective technology for changing the topography, vegetation, watercourses, etc. and using more resources per capita. Population growth by itself would create changes in the surrounding ecosystems--could not help doing so. But combined with the technology that developed during and since the Industrial Revolution, humans have made visible, unmistakable changes to the landforms, water supplies, and distribution of species. Human activity has nearly always (and always in "civilizations") been aimed at short-term human benefit: this year's food supply, this year's water supply, this year's ease of transportation, etc.
That's natural--but the ways we go about it are not natural, and have demonstrable long-term negative consequences, even not considering global climate. A few thousand years ago, forest clearing in both Greece and China prompted a few to recognize that clear-cutting on slopes led to erosion, silty rivers (with more erosion downstream from the increased cutting power of soil particles in the water), flooding, and so on. Farming practices that were easy, but depleted soil fertility, have been common worldwide until farmers were forced to recognize the long-term futility of short-term exploitation. Many such practices still exist, and have recurred in areas where the need to make a money profit (rather than feed one's own family or village) pushes farmers to try for maximum gain every year.
Urbanization and uncontrolled urban sprawl damaged ecosystems before anyone thought of global warming: industrial pollution of waterways was a subject of legal interest as early as 1250 in England, when butchers were constrained from throwing offal in the Thames (if they could be caught.) Polluted water supplies--polluted by humans--still cause illness and disability, and degraded food supplies (fish too toxic to eat safely) around the world today. The loss of productive farmland to development raised food prices (food had to be transported from farther away) in the 19th and 20th centuries, and still continues. Damming of rivers interrupts migration of fish (and thus limits the fish species found above the dams and sometimes below) and in hot climates results in net loss of water through evaporation, while the stored water leaches salts (some even toxic) from the ground it sits on.
Air pollution of human origin has caused--and continues to cause--human disease and disability. Asthma is the most obvious--but not the only--metric for the human cost of air pollution. Agricultural, industrial, and home sources of air pollution markedly increase the risk of asthma and other conditions of the lung. But air pollution does not limit itself to the lower levels of the atmosphere. I remember flying to Chicago to a friend's wedding in 1970. At that time, the air back home was still clear, seen from an aircraft. But flying along the industrial northeast, we saw brown smog everywhere and came down through layers of yellow, orange, and brown--the mess extended to 20,000 feet. The chemicals that gave the colors created acidic conditions leading to acid rain (acid rain that fell hundreds or thousands of miles away, damaging the lakes and rivers and their fish...) It was already known that cities created their own weather...that the air in the most rural areas, though purer than in cities, was not as pure as it had been.
Given that human activity was already having regional effects on the atmosphere, there's no reason to balk at the idea that human activity, if increased, could have global effects on the atmosphere, or that atmospheric and ground-level changes affect climate. Beyond theory, those effects can now be demonstrated--as discussed in Climate Change I and II.
Of course, no one has to accept the evidence. You can play King Canute battling the tide if you want to. Unfortunately, we don't have a way to offer each position in this a separate planet on which to play out their particular viewpoint and see who does best. We have one planet, and one human race; all of us are in the boat together. When there were only a few millions of us--even a couple of billion--we could play with putting more water in the boat and tossing water out--the boat was riding higher in the water. Now--mistakes will be very costly indeed, costly not just in money, but in human lives. You may think yours is safe...you may even dream of building a spaceship and going somewhere else...but right now, this is the boat we have. Bailing it out seems better to me than sinking it.