Global Warming – one engineers viewpoint.

If you attempt to figure out what the global warming problem is you might find it more difficult than you thought. I have come to realize that it is a rather complex topic, and requires a lot of investigation to understand the issues. There are a lot of opinions, hearsay, and considerable misinformation. Please recognize that these comments are only my own draft engineering analysis of the problem. I do not suggest that I am expert at global warming modeling and control, and may revise my suggestions in the future in case I missed some important considerations. I have modeled and controlled many complex processes before, so I at least have some basic technical idea of how such problems can be approached. I have done considerable work in the oil, gas, and energy sectors and to a large extent have helped us get into problems with CO2, so it would seem responsible to understand the nature of the problem and make suggestions on how to help society deal with this problem.

The Problem: The place to start is to ask “What exactly is the problem here?” The problem seems to be that global temperatures are rising sharply in the past few decades, especially at the poles, and this environmental shift is and will continue to present a lot of problems for a lot of people, and other living things. We have all heard of the problems that global warming has already caused and will likely cause in the future. Problems like more severe weather, melting glaciers, rising sea level, impacts of forests, farming, and wildlife. In the process of trying to get educated on this topic I found the environmental models overwhelmingly complex, but the Wikipedia description seems to provide a fairly complete description that gets updated as new information is available:

The climate models of our planets environment are rather complicated. Global warming is only one part of the model. The only practical way to make predictions is to make detailed math models. As sunlight is a key variable that clearly affects our environment, the models must also include a model of how the sun works (it has a cyclical and burst outputs), the air, wind, the clouds, the land and all of it’s life forms, organic, and inorganic materials, the core of the earth, and the oceans. A few key observations:

• Without natural global warming due to greenhouse gases, the earth would be some 59 DegF cooler, and not so friendly to life as we know it.
• The average global air temperature near the Earth's surface increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the past 100 years and the IPCC concludes this is mostly due to CO2 produced by human activity. It would be hard for any individual scientist/engineer to make their own calculations on this. The IPCC (Intergovernmental Panel on Climate Change) does not do research themselves, but bases it's results on peer reviewed scientific literature and would appear to be the primary authority representing the worlds scientists as a whole. It would seem that worldwide scientist believe it is unlikely that our current rise in global temperatures is primarily due to natural causes
• The present atmospheric concentration of CO2 is about 385 parts per million (ppm) by volume. The atmospheric concentrations of CO2 and CH4 have increased by 31% and 149% respectively since the beginning of the industrial revolution in the mid-1700s.
• An enormous part of our economy is based on energy. Most of our energy sources have CO2 production as a byproduct. This includes Coal, Hydrocarbons, and BIOMass. Significantly reducing CO2 production or increasing CO2 capture is a big problem, as reducing CO2 production is likely to require completely rebuilding our energy economy. Increasing CO2 absorption from the atmosphere would also seem to require a enormous changes in forest management or development of other means to reduce CO2.
• All models are wrong, but some are useful. Climate Models are best tested by comparing predictions to actual data. Assuming we give the climate modeling experts adequate funding and competent management, we will continue to refine these models, and they will get better. We must make estimates of model accuracy, and work hard to get the best models that we know how. All serious objections to the model assumptions, methodologies, or results should be evaluated and used to improve the models. Detailed first principle climate models are very useful, and are likely the best possible method of predicting our impact on the environment.
• You cannot control what you cannot measure. We can measure CO2 and global temperatures, although I expect we could make more and better measurements to improve our accuracy. Good measurements alone do not mean we can control them, but we can monitor our progress relative to our target.
• To develop a global temperature control strategy, we must understand the processes we are trying to control and the impacts of any proposed control actions. We must determine the setpoint(s) for our controlled variables and make sure that our manipulated variables have sufficient effect (gain). In other words we should decide what is the best earth temperature and how do we achieve this. Perhaps this is a bold goal, but simply changing global CO2 without concern of the consequences is stupidity.
• We are looking beyond earth for new frontiers, It would appear that there are approximately 0 frontiers we can reach if we traveled for a lifetime. We have arrived at our only home at planet Earth with 6 billion people. We are the caretakers of our planet. Future generations will live with our decisions.
• From a controlled variable perspective, the global temperature appears to be primarily a self regulating process. Note: this does not mean, the problem will go away itself. That is for a given concentration of greenhouse gases (all other variable constant) the Earths temperature will reach a steady average temperature. The time constant is determined primarily the sensible heat of the earths surface I.e. the oceans temperature. If we were to have a step change in CO2 concentration (hypothetical) this large thermal mass would result in an exponential delay to the new steady state. We have roughly been ramping up the CO2 concentration each year, especially over the past 50 years. The CO2 concentration itself is a measure of the inventory of CO2 in the atmosphere. The inventory this year is the inventory last year plus the net accumulation (inflow - outflow) over the past year.

The basic mass balance equation for CO2 in the atmosphere is:

Accumulation = Inflow – Outflow

Our problem is Inflow has become higher than Outflow. To reduce inventory we must make Outflow higher than Inflow for a period of time, and once the concentration is where we want it we can adjust to a balanced Inflow and Outflow. So far we have only continued to increase the Inflow and through deforestation have reduced the Outflow. We continue to watch the CO2 rise, and have not seriously tried to control CO2. Even if CO2 inflow from human-induced CO2 were stopped completely temperatures would continue to rise until the CO2 concentration falls back to normal levels. We would hope that increased CO2 would increase plant life and help to stabilize the CO2, but it is not clear that this is the way it actually works, and it may take a century for this effect. So even it humans left the planet, it could take a very long time for CO2 concentrations to return to pre-industrial levels.

Overall this is just a very rough model. It does not include various positive feedback systems that might result if for example higher temperatures cause an unexpected increase of greenhouse gases by some natural process. There is much to learn about this process and my highly simplified model only gives a basic feel for the nature of the control problem.

The Solutions:

See the overall energy solutions that are on the Energy Options Page. These give specific recommendations for the problem of energy supply and the related global warming. www.GO_TO_Energy_Options_Page.htm

If we look at the CO2 footprint of our various energy options we can see that Electric Vehicles (and Hydrogen) actually have a higher CO2 footprint than conventional hydrocarbons.

Now lets look at the net CO2 of actual vehicles taking into account their thermal efficiency. I.e. taking into account how good the engines are at converting energy to shaft work.

With our current CO2 intensive energy grid there is a virtual tie except the lower engine efficiencies of the solid fuels penalize them. This says that steam engines are not the solution (unless they can be much more efficient than 10%). It also says that neither electric cars nor hydrogen cars offer much savings in CO2 with our current power grid. Now the cost to operate might encourage drivers to do the wrong thing, as hydrogen and electric vehicles appear to be cheaper to operate. This graph is $ per million BTU equivalent of shaft work. This is the work that can propel the vehicle. Now obviously, small, aerodynamic, vehicles driven as little as practical will take less work to propel them. Other technologies such as regenerative braking, or engine idle cut-off can reduce the energy. The other conclusion is the diesel looks like it has nearly the best combination of economy and CO2 footprint. The new TDI diesels in a small car can really make a dent in the problem without breaking the bank. Natural Gas looks good here but the advantage on price is mostly due to regulated prices and the figures used for the prices are based on home use and do not include any road taxes.

Send mail to rys@R2Controls.com with questions or comments about this web site.
Last modified: July 21, 2008