Global Warming 101

In a past life, somewhere back in the depths of the last millennium, I studied a science degree, and later did a Dip Ed. That makes me an expert on nothing, although years of teaching did help me refine the knack of explaining the complex as simply as possible.

After my millionth encounter (or so) with someone of the opinion that global warming is a conspiracy / not real / a matter of scientific dispute, I have decided to use my special power for good. Here, for your edification, entertainment, and as reference point in future encounters with climate skeptics, is Janet's basic guide to the science of global warming:

Carbon dioxide is produced during burning.

You may have learned a simple equation in school: organic material + oxygen -> carbon dioxide + water. This happens all the time in a slow "burning" called respiration, where we break down sugars to release energy for our bodies. (That's why we breathe out carbon dioxide). It also happens whenever an organic product is burned; wood, coal, oil, natural gas, toast. This reaction releases energy, which is why humans find it very useful.

Carbon dioxide levels are rising in the earth's atmosphere


Carbon dioxide levels in the atmosphere usually change very slowly from natural processes. However, carbon dioxide levels have changed significantly since people began large scale burning of fossil fuels (and clearing rainforests), especially in the last 50 years. See the diagrams here and here.

Carbon dioxide is a greenhouse gas


This means carbon dioxide helps to keep warmth in the atmosphere. This is a good thing: without carbon dioxide the earth would be freezing cold!

Direct radiation from the sun isn't absorbed by carbon dioxide: it passes straight through it, like light passes through glass in a greenhouse. However, radiation from the sun warms the earth, which then releases heat into the air (infrared radiation). That's why air temperatures rise when the sun comes up. Carbon dioxide helps to trap this heat in the atmosphere.

(For the technically minded, carbon dioxide strongly absorbs and re radiates infrared radiation of around 15 micrometres in wavelength.)

Increased carbon dioxide levels in the atmosphere lead to increased temperatures.


It is worth noting that average global temperatures vary from year to year as a result of a number of factors, such as how much radiation hits the earth (the activity of the sun), and how much radiation travels back into space. (This is impacted by many factors, such as cloud cover, dust, etc.) This is why average temperatures vary. However, higher levels of carbon dioxide lead to higher global temperatures that would otherwise occur.

Because carbon dioxide traps heat, you would expect to see a correlation between increasing carbon dioxide levels and increasing temperatures. This is exactly what has been occurring on earth. See one image here

In fact, Antarctic ice cores reveal higher carbon dioxide levels have been linked to higher global temperatures over thousands of years. (What is unique about the modern period is that the rise in levels has been very rapid due to human activity).

It is NOT in dispute that carbon dioxide traps heat, that humans are releasing large volumes of carbon dioxide into the atmosphere, that carbon dioxide levels are rising, and that average global temperatures are on a trended increase.

What is up for discussion, research and dispute is exact global temperatures in the future, and how global warming will impact life, sea levels, and local climates: the modelling for such things is very complex. But the basic pattern that higher carbon dioxide levels will lead to higher temperatures than would otherwise occur is not seriously disputed.

Incidentally, one of the first scientists to model the impact of carbon dioxide on global temperatures (in 1956!) was pretty much right on target with his predictions.

So... is that clear? Simple enough? Helpful?

Perhaps the next time someone suggests that global warming is "controversial" or "disputed" or "a conspiracy", and questions whether it has anything to do with human activity, you can send them here in the first instance!

And if you do read an article claiming this is a "controversial" area of science, find out in the first instance whether this is written by a climate scientist. It's easy. Google their name.

There are people writing about climate who are engineers, geologists, tv weathermen, English Lords, journalists, people paid by fossil fuel companies, and frankly... some total crackpots. If they're not involved in publishing climate research in scientific journals, please take what they say with a grain of salt.

Thank you.




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