Farmlands, Petroleum and Global Warming

A simple calculation shows that all the carbon generated by 100 million cars across North America operating at the same time generates about as much carbon as that absorbed by a patch of land measuring approximately fifty by fifty miles. As North America is the leading consumer of gasoline for automobiles, this is a reassuring statistic.

Fly an airplane over the American Midwest. The land is not covered with cities or forests, it is farmland. Farmlands are near carbon equilibrium, they absorb it in the summer when crops are growing and release it when they are harvested. Centuries ago, the countryside consisted of natural habitats, including forests and grasslands. Not only did we release carbon forests into the atmosphere by logging and burning over the last few centuries, but we replaced them with land that is dark and barren sunlight-absorbing dirt during the spring and fall when crops are not growing. What is the heating effect of all that farming and how does it compare to, say, petroleum usage?

In the winter, some of the fields are snow-covered, but not entirely and not all winter. The snow-covered fields reflect more sunlight than their forest counterparts, where the barren trees absorb more heat from sunlight. This leads to cooler temperatures in the winter.

Planting takes place in the spring, but for several weeks, the fields are essentially barren. The dark soil thus absorbs more heat than a natural green habitat. How much heat from sunlight are we talking about?

Calculation
If the sun is directly overhead and all the light is absorbed, the earth receives nearly 1400 watts per square meter or 100 watts per square foot. An incandescent light bulb per square foot. That translates to 2.7 gigawatts per square mile. If solar panels were 100 percent efficient instead of 10 percent, that would be enough power to run 270,000 electric cars at highway speeds (at 10 KW average), for each square mile of land.

That is a staggering amount of energy from sunlight. It would only take a square of sunlit land 19 by 19 miles to equal the power of 100 million cars on the road at the same time across the entire North American continent.

While the above calculation was based on an electric car, that is the same energy output required to operate a petroleum powered car of equal size. However, an internal combustion engine is not 100% efficient. It is about 15% efficient (By comparison, commercial solar cells are only around 10% efficient). 15% efficiency corresponds to 6.6 times more energy generated by the engine than it uses. This is released in the form of heat. How much total energy us used by internal combustion? Our 19 mile square grows to 6.6 times the area to a square that is 50 miles on a side.

The heat of 100 million internal combustion cars all operating equals the heat of the sun, directly overhead, falling on a dark square surface only 50 miles on a side, a miniscule fraction of the Earth's surface. The sun does not always shine but neither do that many cars always run. There is a peak at rush hour in each time zone and a minimum overnight.

Environmentalists are not concerned about the puny amount of heat produced from petroleum fuel, they are worried about the carbon in the form of CO2. How much carbon is that? Let us compare it with carbon grown on land. A rough calculation follows.

If plant life is fifteen percent efficient at absorbing sunlight and turning it into carbon capture [CD: this will be checked], that would again require a square of land 50 by 50 miles to match the carbon output of 100 million cars. The interesting thing here is that a lot of cars on the road do not produce a lot of carbon.

Barren farmland does not absorb 100% of sunlight because it is not black. The dark brown color does absorb well over half, which is more than green plant life in the forests. And while that warming is not year-round and in the northern United States it happens at a time of year when the sun's rays are slanting more, it does mean a definite warming of farmlands must be tolerated if we are to have agriculture. And it does seem to be completely tolerated, I do not see anybody arguing against farming.

The good news is the worldwide logging of forests has slowed to a near standstill as replacement trees are planted at about the same speed they are cut down. If any global warming has been due to farming, the rise has occurred over the last few centuries and has recently leveled off. The majority of the planet's surface is neither farmland nor forest, but oceans, mountains, deserts and other terrain.

Most of the earth's surface is capable of absorbing carbon: Mountains absorb it when rain and CO2 react with the rocks. In oceans, sea creatures grow, producing shells made primarily of carbon, which eventually turn into limestone. Once formed, limestone does not readily re-enter the atmosphere. Limestone cliffs are one dramatic example of these gigantic land forms. The stone quarries found all across the Midwest hint at the underground vastness of land-based limestone.

Whereas a 50 by 50 mile square of the ecosystem can absorb the same carbon as 100 million cars, the earth's total area is so large that it contains 78,000 such squares. The total area may not be able to absorb seventy eight thousand north Americas full of cars, but it will never have to. The carbon contribution of all the present and projected future cars is insignificant compared to the natural carbon processes found in the world. In short, we don't have to worry about it.

Every time we cut down a 50 by 50 mile area of forest for cities and highways, do we risk an equal effect? Every time we irrigate that much new land, do we relieve the pressure? In fact, these patches of land are small potatoes compared to the rest of the earth. The rest of the world is busily absorbing CO2 as it always has. If there is a bit more available, it will absorb a bit more, adding up over time, as evidenced by the enormous size of limestone deposits.

The question then remains is why was everyone so worried about petroleum producing high CO2 levels? There are 78,000 reasons not to worry.