Geoengineering – to do or not to do?

Climate change remains an uncomfortable topic. Politicians continue to state it is such an important problem, and then fail to do anything sufficient to solve it. There seems to be an idea amongst politicians that if everyone drove electric vehicles, all would be well. Leaving aside the question as to whether over the life of a vehicle the electric vehicle actually emits less greenhouse gas (and at best, that is such a close call it is unlikely to have any hope of addressing the problem) as noted in my post https://wordpress.com/post/ianmillerblog.wordpress.com/885

the world cannot sustain then necessary extractions to make it even vaguely possible. If that is the solution, why waste the effort – we are doomed.

As an article in Nature (vol 593, p 167, 2021) noted, we need to evaluate all possible options. As I have remarked in previous posts, it is extremely unlikely there is a silver bullet. Fusion power would come rather close, but we still have to do a number of other things, such as to enable transport, and as yet we do not have fusion power. So what the Nature article said is we should at least consider and analyse properly the consequences of geoengineering. The usual answer here is, horrors, we can’t go around altering the planet’s climate, but the fact is we have already. What do you think those greenhouse gases are doing?

The problem is that while the world has pledged to reduce emissions by 3 billion t of CO2 per year, even if this is achieved, and that is a big if, it remains far too little. Carbon capture will theoretically solve some of the problems, but it costs so much money for no benefit to the saver that you should not bet the house on that one. The alternative, as the Nature article suggests, is geoengineering. The concept is to raise the albedo of the planet, which reflects light back to space. The cooling effect is known: it happens after severe volcanic eruptions.

The basic concept of sending reflective stuff into the upper atmosphere is that it is short-term in nature, so if you get it wrong and there is an effect you don’t like, it does not last all that long. On the other hand, it is also a rapid fix and you get relatively quick results. That means provided you do things with some degree of care you can generate a short-term effect that is mild enough to see what happens, and if it works, you can later amplify it.

The biggest problem is the so-called ethical one: who decides how much cooling, and where do you cool? The article notes that some are vociferously opposed to it as “it could go awry in unpredictable ways”. It could be unpredictable, but the biggest problem would be that the unpredictability would be too small. Another listed reason to oppose it was it would detract from efforts to reduce greenhouse emissions. The problem here is that China and many other places are busy building new coal-fired electricity generation. Exactly how do you reduce emissions when so many places are busy increasing emissions? Then there is the question, how do you know what the effects will be? The answer to that is you carry out short-term mild experiments so you can find out without any serious damage.

The other side of the coin is, if we even stopped emissions right now, the existing levels will continue to heat the planet and nobody knows by how much. The models are simply insufficiently definitive. All we know is that the ice sheets are melting, and when they go, much of our prime agricultural land goes with it. Then there is the question of governance. One proposal to run small tests in Scandinavia ran into opposition from a community that protested that the experiments would offer a distraction from other reduction efforts. It appears that some people seem to think that with just a little effort this problem will go away. It won’t. One of the reasons for obstructing research is that the project will affect the whole planet. Yes, well so does burning coal in thermal generators, but I have never heard of the rest of the planet being consulted on that.

Is it a solution? I don’t know. It most definitely is not THE solution but it may be the only solution that acts quickly enough to compensate for a general inability to get moving, and in my opinion we badly need experiments to show what can be achieved. I understand there was once one such experiment, although not an intentional one. Following the grounding of aircraft over the US due to the Twin Tower incident, I gather the temperatures the following two days went up by over a degree. That was because the ice particles due to jet exhausts were no longer being generated. The advantages of an experiment using ice particles in the upper atmosphere is you can measure what happens quickly, but it quickly goes away so there will be no long term damage. So, is it possible? My guess is that technically it can be managed, but the practical issues of getting general consent to implement it will take so long it becomes more or less irrelevant. You can always find someone who opposes anything.

Trump and Climate Change

In his first week in office, President Trump has overturned President Obama’s stopping of two pipelines and has indicated a strong preference for further oil drilling. He has also denied that climate change is real. For me, this raises two issues. The first is, will President Trump’s denial of climate change, and his refusal to take action, make much difference to climate change? In my opinion, not in the usual sense, where everybody is calling for restraint on carbon dioxide emissions. The problem is sufficiently big that this will make only a minor difference. The action is a bit like the Captain of the Titanic finding two passengers had brought life jackets so he confiscates them and throws them overboard. The required action was to steer away from a field of icebergs, and the belief the ship was unsinkable was just plain ignorant, and in my opinion, the denial that we have to do something reasonably dramatic about climate change falls into the same category. The second issue is how does science work, and why is it so difficult to get the problem across? I am afraid the answer to this goes back to the education system, which does not explain science at all well. The problem with science for most people is that nature cares not a jot for what you feel. The net result is that opinions and feelings are ultimately irrelevant. You can deny all you like, but that will not change the consequences.

Science tries to put numbers to things, and it tries to locate critical findings, which are when the numbers show that alternative propsitions are wrong. It may be that only one observation is critical. Thus Newtonian mechanics was effectively replaced by Einstein’s relativity because it alone allowed the calculation of the orbital characteristics of Mercury. (Some might say Eddington’s observation of light bending around the sun during an eclipse, but Newton predicted that too. Einstein correctly predicted the bending would be twice that of Newton, but I think Newton’s prediction could be patched given Maxwell’s electrodynamics. For Newton’s theory, Mercury’s orbit was impossible to patch.)

So what about climate change? The key here is to find something with the fewest complicating factors, and that was done when Lyman et al. (Nature 465: 334-337, 2010) measured the power flows across ocean surfaces, and found there was a net input of approximately 0.6 W/m2. That is every square meter gets a net input of 0.6 Joules per second, averaged over the 24 hr period. Now this will obviously be approximate because they did not measure every square meter of ocean, but the significance is clear. The total input from the star is about 1300 W/m2 at noon, so when you allow for night, the fact that it falls away significantly as we get reasonably away from noon, and there are cloudy days, you will see that the heat retained is a non-trivial fraction of the input.

Let us see what that means for the net input. Over a year it becomes a little under 19 MJ for our square meter, and over the oceans, I make it about 6.8 x 1021 J. There is plenty of room for error there (hopefully not my arithmetic) but that is not the point. The planet is a big place, and that is really a lot of energy: about a million million times 1.6 tonnes of TNT.

That has been going on every year this century, and here is the problem: that net heat input will continue, even if we totally stopped burning carbon tomorrow, and the effects would gradually decay as the carbon we have burnt gradually weathers away. It would take over 300 years to return to where we were at the end of the 19th century. That indicates the size of the physical problem. The fact that so many people can deny a problem exists, with no better evidence than, “I don’t believe it,” is our current curse. The next problem is that just slowing down the production of CO2, and other greenhouse gases, is not going to solve it. This is a problem that has crept up on us because a planet is a rather large object. It has taken a long time for humanity’s efforts to make a significant increase to the world’s temperatures, but equally it will take a long time to stop the increase from continuing. Worse, one of the reasons the temperature increases have been modest is that a lot of this excess heat has gone into melting ice. Eight units of water at ten degrees centigrade will melt one unit of ice, and we end up with nine units of water at nought degrees Centigrade. The ice on the planet is a great restraint on temperature increases, but once the ice in contact with water has melted, temperatures may surge. If we want to retain our current environment and sea levels, we have some serious work to do, and denying the problem exists is a bad start.

Climate Change

In the previous post, I showed why certain gases in the atmosphere acted as a blanket, and slowed down the cooling of the ground. The next question is, is there any observational evidence that this is happening? After all, there are a number of people who view statistics and argue that this is not happening because the temperatures are not rising the way you might expect from the models. So, what is the truth? The critical evidence is from the oceans, which have been measured as receiving 0.64 Watt per square meter. That may not seem to be much, but consider the number of square meters in the oceans. Without any doubt whatsoever, the planet is receiving a net heat input.

Some may protest that statistics show there has been none of the expected temperature raise since 2000 AD. This is difficult to account for with certainty. Temperatures fluctuate greatly from year to year, and arguments that there has been little net temperature rise since 2000 may simply mean that a negative fluctuation has been cancelled with net heat. The second reason might be that the ice caps are melting. If you heat a mix of ice and water, as long as you stir, there is no net rise of temperature until all the ice melts. The heat goes into melting the ice. The heat may be lost to the deep oceans. Finally, some places may get a significant rise in temperature but others do not, and statistics at one place may be misleading. It is very easy to get stupid answers from the misuse of statistics. It also may not matter. After all, if the Sahara or Death Valley get twenty degrees hotter and everywhere else stayed the same, would it matter? Even if the world got a few degrees hotter, would it matter? That depends on what happens to the spare heat.

So, the ground gets hotter, but what happens next? I mentioned in the previous post that the absorption of infrared radiation by greenhouse gases does not, in itself, heat the gas. There is an indirect method by which it can, though. If the excited state molecule undergoes a collision with another molecule, there can be an exchange of energy, and now neither molecule is in a stationary state, and this results in the energy being dissipated, usually as heat. Whether this happens depends on a quantum probability, and as far as I am aware, this probability is unknown, so I cannot answer whether this happens. The probability of a collision during the lifetime of the excited state depends on the overall gas pressure, and Earth’s pressure is such that whether a collision occurs is a bit of a toss-up. On the other hand, Martian pressure would be too low, and Venusian pressure would almost guarantee a collision. However, the reverse also happens. If a gas molecule collides with a molecule of greenhouse gas, heat may be converted to excited state vibrational energy, again with a certain quantum probability, and that may be radiated away. The very top of Earth’s atmosphere, called the thermosphere, has an absence of such molecules, and an effective temperature of something like 1400 degrees. The thermosphere of Venus, which is mainly made of carbon dioxide, and which receives twice the sunlight as Earth, has a temperature of a mild summer’s day.

Three are two mechanisms to warm the air. Contact between ground and air heats the air and cools the ground, whereupon the warmer air rises and mixes with the general air. A more effective mechanism is where ocean water cools by evaporating water, and when this condenses as clouds, heat is transferred to the air. It also tends to be dumped in one place, which raises the pressure of the local air, which in turn leads to air movement. The more water being condensed in a small volume, the more likely a storm will eventually result.

However, the biggest cause of temperature differences is ocean currents. Everybody knows that but for the Gulf Stream, Europe would be a miserable place, and ice ages are probably accompanied by a redirection of that Gulf Stream. And herein lies our real problem. The oceans are carrying sufficient heat to melt very significant amounts of polar ice, and this will led to major sea level rise. However, the issue regarding greenhouse gases now becomes more confused, because in the last four interglacials, there is clear evidence that without our industrial output of greenhouse gases, the Greenland ice sheet melted and sea levels were about 7 meters higher. Our problem is, if this is really inevitable this time, and with even more net heat input, more of Antarctic ice should melt. Now, look at Google Earth, and check the location of major coastal cities and see how much of their area is less than 10 meters above sea level. See how much prime agricultural land is less than ten meters above sea level. Now, work out how civilization can continue in our current ways if we continue to keep our population expanding the way it is?

See how difficult it is to get the future right in your novels?