I tackle this subject with some trepidation, mainly because it’s such a complicated topic and I’m not a climate scientist, so I’m bound to miss something. So please don’t consider this an in-depth discussion coming from an expert active in the field. I’m merely a (non-practicing at this point in time) environmental scientist. What I can try to do is explain what climate change is, why it’s happening, why it’s important, a little bit about how it works and maybe try and highlight why climate change is such a controversial topic. In other words, I’m going to cover the basics to give you an idea of what is happening and why, and then you can take it from there.
In order to have a meaningful discussion about climate change, we must first understand global warming.
In its most basic form, global warning means “the increase in Earth's average surface temperature due to rising levels of greenhouse gases.”
Note that it says “average surface temperature”. That pretty much means exactly what it says. You all know how averaging works. If you have a column of twenty figures, and you add them all up, and divide by twenty, then you have the average. It’s one of the most basic statistical functions.
This means that, over time, the measured average temperature at the surface of the planet have been increasing. In terms of science, this is our observation. This is what scientists saw happening, and they saw it by the simple expedient of measuring the temperature over time, taking the yearly average and then plotting it out on a graph to see how the temperature changed over time.
The scientists saw this happening, and, being scientists, they naturally asked a question: “Why?” Why do we see this rise in global temperature over time?
The answer, they finally concluded, was rising levels of greenhouse gasses. We’ll leave how they arrived at that conclusion for a follow-up article. For now, the important thing is that that was the conclusion.
So what is global warming? The measured increase in the average surface temperature due to an increase in greenhouse gasses.
Why is this important? Why should anyone care? The global increase isn’t that big. It’s only about one degree Celsius over the last hundred and ten years? Surely that’s nothing to be alarmed about?
Well, yes and no. The main thing to consider isn’t our experience of temperature on the ground. To us as humans, a slight increase in temperature isn’t going to matter much. Who can really tell the difference between twenty and twenty-one degrees Celsius, after all? No. The temperature in and of itself isn’t the problem. It may become so, but I’ll save that for a follow-up article. The main problem is in how that one degree Celsius increase in temperature affects global climate patterns.
Yes. Climate change. That is the big kahuna. The IPCC (Intergovernmental Panel on Climate Change) defines climate change as “...a change in the state of the climate that can be identified (e.g., by using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer.”
In simpler terms, it’s the long-term change in the expected weather at any given location. For example, down there in the Western Cape, you expect summers to be dry and winters wet. Up on the Highveld, you expect the opposite. You expect a dry cold with average lows of about freezing to highs of mid to high teens in the winter and wet summers with lows in the mid to high teens and highs of into the thirties. Climate has to do with long-term expected weather patterns. Climate change would therefore be changes in those patterns. Climate can be very specific. It’s not just expected temperatures, but also prevailing wind direction, expected amounts of rain at various points in time etc.
Think for a moment about the implications. What would happen should those patterns change over time? Here’s an easy one: farming. Farmers gamble a lot on the weather. They rely on long-term climate stability to predict when they should plant and what they should plant. Mielies is a good crop to put into the ground in spring on the Highveld because the plant is suited to the climate: it likes spring and summer rains, but no rain the winter because that’s when it dries. The farmers know they can put the mielies in the ground at a certain month because it will rain. Now go ahead and change that pattern to a less predictable one, or one in which the rainy season shifts just a few months later or earlier. Suddenly your planting season is gone. Should it rain at the wrong time your crops can either drown or rot in the field. Not good for the profits of the farmer or food security for the country.
This is just one practical example of why climate change is important. There are many other reasons too, and I’ll get to those in later articles.
What though, is the link between global warming and climate change? How can one degree Celsius have that big an effect?
Well, that’s where it gets complicated, and I’ll expand on it later. The simple answer is this: an increase in energy.
Increase the energy in a system, and the system will become more chaotic. Global weather patterns are driven by energy. Mostly energy from the sun, but also energy from within the earth. It not only heats the atmosphere, but also the oceans. There’s a very complicated interplay between the oceans and the atmosphere that contributes greatly to global weather patterns. It’s the differences in temperature (the difference in energy) between ocean and atmosphere and between different parts of the atmosphere that drives our weather, and the overall climate. Add more energy to that system, and the pattern will change. Not only will it change, it will become more chaotic.
Still don’t see the big deal? How can one degree Celsius be that much energy? Enough energy to disrupt the global climate?
Well...the world is a big place. The atmosphere is approximately twenty-two kilometres thick from top to bottom. That’s twenty-two kilometres straight up to get completely clear of the atmosphere. The earth is approximately twenty-one-thousand kilometres in circumference. That’s...a lot of air. How much energy will it take, do you think, to raise the average temperature – globally – by one degree Celsius? Imagine the amount of energy it takes to heat your home in the winter? Air isn’t that easy to heat. Then we haven’t even started talking about the ocean. It takes a lot more to heat the ocean. That’s billions of cubic meters of water. That’s a lot of water too. That’s a lot of energy added to the overall system, and that energy isn’t just expressed in an increase in temperature. It also drives changes in the climate through shifting air currents and the like.
So how is all this happening? We humans simply aren’t putting out that much energy. How could we possibly cause this problem? Simple answer? Greenhouse gas. We don’t have to output that much energy by ourselves in order to have that kind of effect. All we need to do is create conditions in which more energy from the sun enters the system than energy leaving the system. We do this by outputting greenhouse gasses that trap solar heat inside the atmosphere. The sun’s energy output is more than enough to drive climate change, and it would just take a small intervention from us to change conditions sufficiently to cause a global increase in energy.
That’s global warming and climate change in a nutshell. It is, quite literally, a lot of hot air.