Climate change is the reason for this project. We get most of our energy by burning hydrocarbons, and if it caused no harm to the planet we could carry on burning them. At present, fossil fuels are so cheap that the energy in the Thames cannot compete. 

We cannot go on as we are. There are already enough known reserves of fossil fuel that if it were all burned, the earth’s ecology would be damaged irreversibly. The earth would be able to support only a small fraction of the present population. 

There is endless debate out there about climate change. Each year the evidence grows stronger that we are changing the climate, but a vocal minority refuse to accept it. They cling on to arguments that an A-level student could demolish. For some it is because they sense an implied criticism of their life styles. Others have a blind faith in free markets and will not accept that governments need to act. Some insist that the climate is not changing, while others accept that it is but say human activity is not the cause. Yet others accept that it is but believe technology will save us. 

Will the 2014 floods challenge our complacency, in the same way as the flooding of New Orleans did in the US? Or will we just blame the Environment Agency, then forget it and go back to business as usual? The changes we are seeing globally are consistent with predictions: a warmer atmosphere can store more moisture and more energy, so there are more extremes and records being broken; wet areas getting wetter and dry areas drier, causing more floods and droughts.

The changing climate could affect Abingdon Hydro. Droughts are obviously bad news for us, but so are floods. That is because we need the water both to flow and to fall. When the flow is high the level rises downstream of the weir, so the water does not drop as far and the power is reduced. Effects like this are just small details within the big picture, but a little research has been done, that suggests that the loss of output when averaged over the next 20 years should be small.Warming earth graph

What causes climate change? 

It about something we cannot see - radiant heat. Everything radiates heat, and the hotter it is, the more it radiates. We can feel it from the sun, and also from much cooler objects such as a radiator. The earth receives heat from the sun and radiates it out into space. The two have to balance. If the atmosphere stops some of the heat being radiated away, then the earth warms up a bit to restore the balance. This is the “greenhouse effect”, except that a greenhouse traps warm air rather than radiant heat. 

The heat is trapped mainly by water vapour and carbon dioxide in the atmosphere. The result is that the earth’s surface is about 30 degrees warmer than it would be if the atmosphere did not trap any heat. The greenhouse effect is very basic physics, not in doubt. Our sister planet Venus has a dense carbon dioxide atmosphere, and because of the greenhouse effect its surface is hotter than molten lead. 

It follows that if you increase the amount of carbon dioxide, the amount of warming will increase. This is not new physics, the calculations were first done over 100 years ago. The only dispute can be over the amount of warming. The original estimates are not very different from the latest computer models: double the amount of carbon dioxide in the earth’s atmosphere, and the warming will rise from the present 30 degrees by roughly another 2 degrees. At present it is about 50% higher than the pre-industrial level, and rising. 

An extra 2 degrees does not sound like much, but the effects can be huge. The atmosphere is complex, and not very stable – that is why our weather is changeable. When you disturb an unstable system it can respond in unexpected ways. Circulation patterns are a delicate balance between different forces, and it does not take much to upset the balance. That is what we are doing to the atmosphere when we add carbon dioxide, by taking coal, oil, and gas out of the ground and burning them. 

The biggest concern is runaway climate change. For example, methane is a much stronger greenhouse gas than carbon dioxide, and there are huge amounts buried in the Arctic. As the Arctic warms, methane is being released, which will cause more warming. Could it become impossible to stop? It is hard to predict, but the extreme events we are already seeing may be just a foretaste.