Yet another storm hit Wellington; this time winds were a mere maximum of 165 k/h (about 100 mph). Is this climate change? Whatever, it is interesting that climate change is now a major concern, which raises the question, what can we do about it? Suppose we answer, “Stop burning fossil fuels,” what would the effect be? Currently, the atmospheric concentration of carbon dioxide is about 400 parts per million (compared with about 280 ppm at the beginning of the Industrial Revolution). If we are concerned about the effects of such atmospheric carbon dioxide, then if we stop producing it right now, the 400 ppm remain. Now, as noted in the last post, the climate shows strong signs of what physicists call hysteresis. This is when the effect is something depends on how you got there, where the system has “memory” of previous times. In this aspect, the Greenland ice sheets are actually the last remnants of the last great Ice Age. As we heat the planet, all that happens first in some places is that ice melts, the extra heat being absorbed by the melting ice without any temperature increase. In other words, for a while what you see is not what you are going to get!
In my opinion, the major problem civilization is going to face is rising sea levels. If the Greenland Ice Sheet melts, then the sea will rise about 7 meters. Take a look at Google Earth and see what goes. Amongst other places, a significant fraction of Bangla Desh, and essentially all Pacific islands based on coral reefs (as opposed to the volcanic basalt peaks, but you cannot live on the side of them). So, how do you defend against that?
One suggestion is to build sea walls. These would have to be around all the land, including alongside riverbanks, and they may have to last tens of thousands of years. And, of course, while you are making all the required concrete and moving rock, you are probably generating massive amounts of further carbon dioxide, which will lead to more of the Antarctic ice melting, thus cancelling any value from your efforts. You could build walls of up to fifty meters high, and that would certainly be adequate for as long as the walls last.
You could try removing the carbon dioxide from the environment. At first sight this seems futile; there is just too much there. However, at least some can be removed without much effort if we regrow forests. You would have to start planting them, but once underway, they would happily consume carbon. Even more spectacular would be to grow marine algae. The kelps such as Macrocystis pyrifera are extremely fast growing, and you can harvest them by mowing them. I rather fancy collecting such kelp and using it to make either biofuel or other chemicals. The key is to ensure that the carbon is removed from the ocean.
Currently, we produce about 10 billion tonne per annum of carbon dioxide. That means we have to remove 10 billion tonne per annum just to break even. It is unlikely we can do that, although what we can do, we should, so what other options are there? A massive deployment of nuclear power would slow the fossil fuel burning, but it would not remove any of the current 400 ppm, and who wants nuclear power?
The simplest answer is for every tonne of water melted by the ocean currents, we deposit a tonne of snow into the ice sheets. That involves geoengineering, and the problem is, when you interfere like that with nature, the effects are probably not that readily calculated. Such proposals in the past have been met with opposition. The problem is, some countries are going to be adversely affected by the geoengineering, and these are the ones that, in the first place caused the problem. Of course if we do nothing, it is the Pacific Islanders and the Bangla Deshis who pay. Do we know what will happen if we intervene? No, we do not, but we know what will happen if we do not. Of course there is another problem: how do we decide, and who decides?