Climate Change Part 2
Updated: Nov 18, 2019
The Current Global Warming Situation Explained
So why are the air temperatures climbing so fast over the last fifty years? There are basically two suspects, water vapor and CO2. Water vapor is a more potent greenhouse gas but its residence time in the atmosphere is very short (measured in days to weeks), so even though the amount of water vapor in the air increases slightly with air temperature, it is impossible to show that water vapor could cause the recent spike in temperatures. This leaves CO2 which has a residence time in the atmosphere measured in decades and has almost doubled its fraction in the atmosphere over the period of interest. There are also some positive feedback taking place since rising temperatures melt glaciers and icecaps which increase the amount of solar radiation absorbed, and rising temperatures melt permafrost which releases methane gas another greenhouse gas.
I do believe CO2 is the primary change agent today, because the situation has greatly changed from historical times. In the last five thousand years humans have developed large scale farming and metallurgy which destroyed much of the ancient forests. This was followed by the industrial age over the last two hundred years where massive amounts of fossil fuels (coal, petroleum, and natural gas) were burned to power growing economies. This has benefited humanity with better and longer lives but the loss of forests combined with burning fossil fuels has raised the amount carbon dioxide in the air from about 270 ppm in 1850 to over 400 ppm in 2019.
Figure 6 on the right shows the yearly amounts of CO2 that humans from various countries have dumped into the atmosphere in recent history. The Earth’s atmosphere currently holds just over 3.2 x 10^12 metric tons (3200 gigatons) of CO2. As you can see in from figure 6 humans are currently dumping roughly 40 gigatons of CO2 into the atmosphere each year (2019). While CO2 levels have been as high as 4000 ppm during the Cambrian period about 500 million years ago, the current 400 ppm is the highest level of CO2 in the atmosphere in the last 20 million years.
The current high CO2 emissions are caused by the enormous amount of fossil fuels burned for energy and somewhat by the increase in the cement and smelting industries to support the current worldwide building boom. This energy has been vital to the advancement’s humanity has made over the last 170 years and any reduction in energy per capita is going to reflect badly in average standard of living. This is especially important to developing countries because they want to achieve a livable Gross National Product (GDP) infrastructure before carbon taxes close the door on further economic development. So, as can be seen in Figure 6, they are building fossil fuel power plants as rapidly as they can to power the infrastructure they need catch up with the developed countries. This situation is almost untenable since parts of Asia and most of Africa have no hope of developing modern cities and industries without an abundant source of base energy and that is not going to happen in the near future without fossil fuel power plants.
So, how do we reduce greenhouse emissions without destroying current and future economic progress? It is going to be very difficult, require decades of worldwide effort, and be insanely expensive. Figure 7 below shows the magnitude of the problem and which emissions are going to be the hardest to eliminate.
As I am writing this the radio is telling me that a presidential candidate just introduced their new Green Energy plan that will eliminate all fossil fuels by 2050. Evidently this politician has never seen figure 7 because it will be almost impossible to eliminate fossils fuels from long-haul trucking, the airline industry, long-distance ocean shipping, remote power generation, cement manufacturing, and steel production within that time frame. The best we can hope for is to continue to use fossil fuels for these industries and focus on economically eliminating fossil fuels for the remaining ¾ of the energy users. However, my personal observation is that politicians are not embracing the necessary technologies. Renewable Green Energy (i.e. windmills and solar panels) provide power only part of the time, and on occasion, renewables produce no power at all. The average solar power available at any site in the U.S. is shown in figure 8 below. Assuming a standard summer radiance of 1.0 kW/m2 this figure shows that, in Seattle where I live, a photo-voltaic array rated at ten kWe would produce on average 10 * 3.5/ 24 = 1.45 kWe-hrs/day. That’s why I don’t have solar panels on my house.
Figure 8 - Average Light Resources reaching Surface in the United States
On the other hand, if I lived in Death Valley, California, my average power from a 10-kW array would be 10*8/24 = 3.33 kWe-hrs per day, much better, but still not very useful after dark. Wind power is more available as shown in figure 9 below. As can be seen in the figure, the wind power capacity can vary seasonally from about 40% to 25% with an average power output of approximately 33% of design. The lack of availability for “Renewable Power” somehow never gets mentioned by our leaders, and as we will see, plays a major role in comparing costs for fossil fuel power-plant replacement. The Green Revolution would supplement their renewable power-plants with batteries, but that is not a cost viable solution either.
The point I’m trying to make is that it is critical to have reliable base-load electric power that can provide up to 100% of the possible power draw. In the US we currently provide this with coal-fired power plants backed up the natural gas-fueled turbines to handle the variable loads. These will have to go in order to go green. Hydroelectric power plants supply the base-load and variable power in the Pacific Northwest where I live, but we are blessed with abundant rain and snow, and all economic hydroelectric sites have already been developed. Base load energy is probably the key issue in solving Global Warming and I will cover my proposed solution in the next section.
The other major source of greenhouse gas emissions we can solve is short-to-medium-haul car and truck emissions. In theory, all-electric cars and trucks can handle the 16% that is short and medium distance road transport, but I drive an electric car, so I know that once I leave my major city (Seattle), and if I’m visiting a small town, it is almost impossible to find an unoccupied charging station to get home. Therefore, if we look at the automobile and truck drive train options in Figure 10 below, there is a progression from all-fossil fuel to all-electric. From my viewpoint we can still probably eliminate 90% or more of all auto and truck emissions by switching to plug-in hybrid electrics where the battery provides all the normal motive power, but a small fossil-fuel engine is available to allow the vehicle to return home or make the next available charging station when things don’t go as planned. In my opinion this a necessary provision to insure our transportation system is fully operational. It will add some cost and complexity to the transportation system, but you know there will always be a few die hards who will hang onto their gas-powered-cars no matter what, so refueling stations will have gasoline and diesel for a long time.
The real issue here is predicting how the climate is going to change with the various reductions’ in fossil fuels humanity could manage from the present forward. Assuming we want to maintain the levels of energy consumption and life styles we currently enjoy, we’re going to have to make some hard choices. We have lots of options, but fossil fuels are not limitless and will be become increasingly expensive relative to renewables and nuclear as they become scarcer. To make these hard decisions we need to understand what we’re facing and how soon and how bad it is going to get.
For the final installment of this story, go to Climate Change Part 3.