Several organizations help private landowners create legal protections against commercial development on their lands, which aren't just those our housesare onbut includecommercial, industrial and agricultural lands, too. Pictured: The Gwynedd Wildlife Preserve in Ambler, Pennsylvania. It's fields are being restored and protected after overa century of agricultural use. (Photo courtesy amdougherty/Flickr)

Earth Day is an occasion for us to reflect on the dependence of humans upon the attributes of Earth that sustain human life.

For 10,000 years prior to the Industrial Revolution, Earth’s climate was at a “sweet spot,” conducive to the development of agriculture and with agriculture, civilization. An optimal concentration of carbon dioxide in Earth’s atmosphere created this temperature range favorable to human habitation and progress.

Carbon dioxide in Earth’s atmosphere is a “greenhouse gas” that traps heat energy radiated away from the Sun-warmed Earth. Some of that trapped heat energy radiates back to Earth, causing Earth to be warmer than it would be if greenhouse gases did not exist. The combined heat energy from the Sun plus greenhouse gases resulted in global temperatures ideal for human life.

During the past two centuries, humans have been disturbing the equilibrium that existed for 10,000 years prior to the Industrial Revolution between carbon dioxide emitted into Earth’s atmosphere and carbon dioxide absorbed by Earth’s living vegetation. When humans began burning fossil fuels we started emitting more carbon dioxide into Earth’s atmosphere than Earth’s living vegetation could absorb, causing the concentration of carbon dioxide in Earth’s atmosphere to increase. As we burn fossil fuels at accelerating rates, we accelerate the rise in Earth’s average temperature.

Human-caused global heating is causing hundreds of billions of dollars worth of damage to Earth’s life-sustaining resources, including crop loss due to heat-induced drought, increasing storm damage due to the higher heat energy content of Earth’s atmosphere and sea level rise caused by thermal expansion of the worlds oceans and melting of ice caps on Greenland and Antarctica. Earth’s temperature increases cause forty thousand heat-related deaths worldwide annually.

Most ominously, the Arctic tundra, which contains vast quantities of frozen methane, is beginning to thaw. During the first twenty years of its existence in the atmosphere, a molecule of methane traps and re-radiates to Earth eighty times as much heat energy as a molecule of carbon dioxide. If we continue burning fossil fuels at current high rates we will cause uncontrollable thawing of the Arctic tundra. Then we will have started a “positive feed back loop” in which methane released into Earth’s atmosphere by the thawing tundra causes acceleration in Earth’s global temperature increases, which causes acceleration in the Arctic tundra thaws and releases more methane into Earth’s atmosphere. At this point, humans will have lost control of Earth’s temperature and climate. Earth’s global temperature will continue rising for centuries. Melting ice sheets on Greenland and Antarctica will pour water into the oceans causing sea levels to rise 200 feet, inundating most of the world’s major cities. Most of Earth’s land surfaces will be too hot for human habitation.

We do not need to allow this worst-case scenario to occur. We have the technical capability to generate most of the world’s energy needs with “renewable” energy sources, principally solar and wind, which do not emit carbon dioxide into Earth’s atmosphere. With effective economic incentives, we can transition to renewables in time to allow Earth’s temperature and climate to remain life sustaining for our descendants.

The most effective way to provide the economic incentive to transition away from fossil fuels and towards renewables is to impose a revenue neutral tax on fossil fuels at the point of sale. The tax initially would be low enough to avoid abrupt economic disruption, and would be raised periodically to make renewable energy technologies increasingly attractive to energy suppliers and consumers. The tax would be revenue neutral because it would be returned to households on a per capita basis. The majority of households would receive more than enough revenue to compensate for any initial increases in the cost of energy. Some of the revenue could be used to provide re-training and income supplements for coal miners and other fossil fuel workers whose jobs would be phased out when we implement the revenue neutral carbon tax.

We owe future generations the chance to live in a world as supportive of human life as the one we have lived in. We are at a major crossroads in the life of humans on planet Earth. For the Earth and all future generations we must make the right decision. We must act on our commitment to protect Earth for future generations by asking our legislators to impose a revenue-neutral carbon tax on the fossil fuels that are harming planet Earth.

– Al Barrett is a Santa Monica resident