But I don't want to be political here. I'm interested in what the real science says. For the first time, I've actually begun to investigate it that way. So here, I'm sharing what I have learned about the scientific evidence for and against global warming. If you happen to see that I'm missing some vital information, please share it, but do so in the spirit of scientific truth and discovery, and not in a political, angry or mean way.
As far as I understand it, the advocates of doing something about human-caused-global warming (for brevity HCGW) offer this basic thesis:
Human beings have increased the amount of carbon dioxide (C02) in the atmosphere. C02 is a “greenhouse gas” (it retains a portion of radiation from the sun in the atmosphere). This extra C02 is causing the world to get warmer. Soon, because of human-generated C02, the world will warm so rapidly and so much that we will experience disastrous, catastrophic climate change. We might be able to avert this by controlling emissions of C02 into the atmosphere.
I am interested in this: what is the scientific evidence that pertains to this theory? Is the hypothesis theoretically and experimentally sound?
I have a Bachelor of Science degree – but that only means I had more science classes than liberal arts classes for my undergraduate degree. My Master's Degree is not in a scientific field. I am not a scientist. But I am a reasonably intelligent person. What follows is my understanding of the SCIENCE behind “Global Warming.” I gathered a lot of this from “Environmental Effects of Increased Atmospheric Carbon Dioxide” by Arthur B Robinson, Noah E Robinson and Willie Soon. This paper is a review and summary of a great deal of peer-reviewed scientific literature available about the history of global climate change. Over 31,000 trained scientists have signed a petition which states they generally agree with the conclusions of this review. It's worth your own time to read it, but in case you don't, I'll offer the main points (in simplified form) here.
First, my own disclaimer. Scientists on both sides of the debate must rely on secondary data. In other words, when studying climate change three thousand years ago, they rely on things like ice cores and the relative biomass found on sea floors and things like that. They also take into account historical records of crop production in various areas of the world, but these records are incomplete. My point is, no one had thermometers back then, and no one was recording specific temperatures or ice thicknesses or sea levels. So, all of this should be taken, at some level, as “informed guessing.” But both sides of the debate have this same liability.
I have had several questions about the science of global warming. First, is the world in a long term trend of warming? If so, is there anything unusual about a long warming trend? Second, is that warming trend (if it exists) the result of increased carbon dioxide in the atmosphere? Can Carbon dioxide really do that? Third, does the evidence show a connection between human activity and the alleged warming trend? Although I am suspicious of people who want more power and money to fix problems I can't see, I am open to be convinced by the science. I'll take each of these three questions, one at a time.
PART I: IS THE WORLD GETTING WARMER?
According to the data that are testable, verifiable and available, over the past three-thousand years, the temperature of the earth has varied within a range of about 3°C. If you drew a horizontal line to represent the average temperature, and then drew a graph over it to represent actual temperature, the graph would vary between 2° above average to 1.5° below the average. These variation trends occurred over periods of hundreds of years. The warmest times during the past three thousand years were around 1000 BC, and again around 500 BC.
When we are talking about the worldwide average temperature, this is actually a fairly large variation, with definite implications for climate change, though not catastrophic climate change. For instance, in 1000 AD (1000 years ago) the average world temperature was about 1° warmer than it is today. At that time, Europeans settled Greenland (and named it "Green-land") growing crops and keeping cattle and other livestock. That type of agriculture is not possible in Greenland today, though the average global temp is just 1° cooler. On the other hand, the polar bears survived that warm period just fine, as did all the other creatures on earth.
Looking at the past 3,000 years, our global temperature today would be marked right on, or slightly below, the “average” line, two degrees cooler than the warmest time periods.
The data show that three or four hundred years ago, the Northern Hemisphere experienced a “little ice age.” We have been climbing out of that unusually cool period now for about two hundred years. The rate of temperature increase has been, on average, about 0.5°C per century. Within that steadily increasing trend, are shorter, wider fluctuations (lasting a few years or decades) of both cooling and warming. For example, there were some very warm years in the 1920s and 1930s, and some very cool ones in the 1910s and 1970s, but when it is all averaged out, the trend is steady and unchanging at about 0.5° per 100 years.
Remember, this two-hundred year warming trend is in itself, an ordinary part of a larger trend of centuries-long fluctuations within a range of 3°C. We would have to climb an additional 2°C before equaling the warmest temperatures during this 3,000 year period. The current average rate of warming (0.5° per century) is not, by any measure, the steepest rate of temperature change during the period.
The conclusion: For the past two hundred years, the world has been gradually warming. In the context of the past 3,000 years, this warming is not unusual in its rate of increase, in its short term fluctuations or in actual temperatures.
NEXT TIME: CAN C02 CHANGE THE WORLD'S TEMPERATURE?