Today’s post is about a speech Preston Manning gave to the Empire Club of Toronto on why we need to take action now on climate change.

No, really. It might seem like the answer is very complicated, but at some level it’s simple: sunshine. That’s actually an almost complete answer.

“What about hydro electricity”, you might ask, “doesn’t that come from falling water?” Yes, it does, but, to paraphrase Newton “what comes down must have gone up.” And what lifted the water, so that it could fall through the generator? The sunshine, which evaporated the water, lifting it into the air. As we look at other sources of energy, we come to the same conclusion. Oil, natural gas and coal are organic matter millions of years old. The energy in that organic matter is stored sunshine, captured by algae via photosynthesis. Windmills are turned by gusts that happen when sunshine warms the earth, in turn warming the air above it and causing that air to rise, creating air currents. Burning wood or other organics is liberating sunshine that was stored much more recently than that in fossil fuels.

There is an exception to the rule. Nuclear reactions also contribute to our energy supply. Nuclear fission reactors use radioactive elements created in the hearts of stars billions of years ago. Geo-thermal energy uses the heat released by natural nuclear decay inside the Earth.

What can we say about these sources? Well, nuclear fission energy relies on radioactive isotopes. These are found in the Earth’s crust and mantle in small amounts. We can only extract them from a certain depth, because it’s too hot if we dig farther. There is a limited supply within the crust, and there are different estimates of how long that supply will last, as well as how much energy we can get out, but the supply is certainly limited.

Sunshine has a similar limit. Quite a bit of it falls on the earth, but capturing it efficiently is difficult, so we are only able to obtain a very small percentage of the energy that reaches our planet. Most of the sunshine powers other processes that are useful to us, such as plants and animals in the biosphere, our own agriculture, the wind and rain, melting snow in the spring, making objects visible, etc. We wouldn’t want to use most of the sunshine to create energy even if we could.

It’s important to remember these limitations as we talk about alternative energy. Nothing produces limitless energy, so our planning for the future and our actions for today need to take into account the limits that we’re up against.