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Essay:Global warming for beginners
Hopefully this is just overkill at this point, but if anyone stumbles on this page while trying to make sense of the whole climate change thing, maybe I can offer a few basic starting points.
If you have a math-related background (science, engineering, statistics, etc.), you probably feel like you understand logic and numbers, and if you could just see the evidence for yourself you would be able to make a reasonable assessment. Or maybe you just feel confused and can't make any sense of this whole thing: is it a worldwide conspiracy theory orchestrated by Big Science? are those damn tree huggers high again? can't these kids just get a job already?
Obviously I am not neutral about the issue, and I think I have good reasons, but that also applies to the "other side". Global warming is essentially a scientific question, and it calls for a scientific answer. I cannot recommend you enough to learn about the history of science, even if you think your experience entitles you to dismiss this old stuff (don't thank me, thank yourself for not missing this opportunity).
This being RationalWiki, at no point should you feel like you have to take anyone's word on faith. In addition, many articles and discussions here will persuade you to think about thinking, think about why you believe what you believe, think about why others believe what they believe.
However, when it comes to science, belief and overthinking won't help you. In a nutshell, science is a process by which we acquire knowledge about the physical world (hundreds of definitions exist, but that is the gist of it). If there is a closed box on your desk, and you are wondering what's in it, you can: (a) believe that it contains a gold ring, (b) open the box and look, (c) ask somebody to open the box and look. In this cheesy example, "opening the box" is the scientific process. The world is full of closed boxes, and no individual will ever be able to open them all: eventually, you need to trust somebody to open some for you, with the understanding that with enough time and resources you could do it yourself. This is why I use "trust" instead of "believe": it is safe to trust somebody to the extent that others can open the box and verify the findings.
In practice, scientists can be trusted because their work is reviewed by their peers. Mistakes are made all the time, there is the occasional fraud, but this system is designed to detect and fix those issues. As a result, scientific knowledge constantly improves. What we know today is better than what we knew yesterday, but not as good as what we will know tomorrow. This is exactly how it is supposed to be.
What is it?
Climate science is a horribly difficult subject (for a soft and quick preview, try this). In my opinion, unless you are ready to invest countless hours into studying physics, chemistry, geology, biology, statistics, and computer programming, you have no chance of being able to "decide from the evidence".
Scientists have measured that: (a) the planet has been warming at a relatively fast pace for the past 200 years, (b) in that period, human burning of fossil fuels (coal and oil) has increased the quantity of a gas called carbon dioxide (CO2) in the atmosphere. People quibble about temperature, but what matters is the accumulation of heat. Complex mathematical models based on the laws of physics allow scientists to deduce that the warming is mostly caused by humanity's CO2. How much is mostly? Somewhere around 100%.
Take a look at this chart from the 5th IPCC report. This is the conclusion obtained after studying hundreds of scientific reports. It compares human and natural radiative forcings, which is a measure of the accumulation of sun energy (as heat). The conclusion is that, relative to 1751 (early days of the Industrial Revolution), human-caused ("Total Anthrop.") radiative forcing in 2011 far exceeds the natural one. There is a precise mathematical meaning to the thin black bars, but intuitively they indicate that there is some uncertainty in the values. In this case, the uncertainty is not enough to seriously doubt the conclusion: to the best of our knowledge, AGW (Anthropogenic Global Warming) is a fact.
Does it matter?
Heat flows from where there is a lot to where there is little. Variations in heat distribution is what causes weather events (winds, rain, El Niño). The planet's interior does provide some heat, and the sun provides the rest. No amount of hand waving and philosophical wrangling will ever tell you which is doing what. You need solid physical theories, careful observations, elaborate mathematical models and powerful computers.
Our current scientific models give us a range of predictions taking into account various kinds of uncertainty. But these models get regularly updated, and scientific predictions are not prophecies. If scientists say "if we do nothing, bad things will happen", then it is the duty of policy makers to take the appropriate steps to make the predictions come false.
What about the other side?
The opposition to the science is so strong and diverse that it feels like there must be something wrong somewhere. In my view, the worst misinformation is coming from reputable scientists who do not specialize in climate science: it takes years of dedicated hard work and peer-reviewed publications to become an expert in climate science, and other scientists are simply not qualified to make sweeping statements aiming at discrediting a whole field.
Trying to understand the so-called "scientific" arguments against AGW requires a high-level mastery of a wide variety of theoretical concepts, the same as above actually: if you can't already understand the science, you will have a hard time assessing the counterarguments and their counter-counterarguments.
If you want to keep looking for sources in that direction, at the very least make sure that they use a polite, non-inflammatory language. Currently, tempers are flaring on all sides, but it would be a mistake to think that scientists are just another bunch of obnoxious political activists: to an outsider, peer reviewed science often generates the most neutral, boring, emotionally dry kind of literature you can possibly imagine. But reading and understanding this literature requires years of theoretical and practical training, and popularizers tend to dumb it down and spice it up in order to keep normal people awake.
I think that science should inform policy decisions according to the following diagram:
physical world -> scientific study -> policy -> action ^ | +-----------------------------------------+
Policy makers can ask for more studies, but nobody gets to accept or reject scientific conclusions based on personal opinion, ideology or religion. There is plenty of bickering to be done around the science, and that is the job of the scientists. For everyone else, the bickering should only start after accepting the scientific conclusions.