Baxter Pharr: Climate change is human-caused |

Baxter Pharr: Climate change is human-caused

Baxter Pharr

In a recent letter to the editor, Dr. Martin Hertzberg stated that the main driver for global climate were changes in the Earth’s orbit around the Sun and the Earth’s tilt on its axis. This theory is called the Milankovitch theory named after the Serbian mathematician Milutin Milankovic. It states that there is a 100,000 year cycle in the Earth’s eccentricity, a 41,000 year cycle in the Earth’s axial tilt, and a 23,000-year cycle in the Earth’s precession. In a landmark paper in the journal Science in 1976, Hays, Imbrie and Shackleton showed that glacial and interglacial periods for the last 450,000 years coincided almost perfectly with their predicted occurrence by the Milankovitch theory. The problem is that, according the Milankovitch cycles, incoming solar radiation has been decreasing for the last 9,000 years. In other words, according to these orbital cycles, the Earth should have been cooling rather than warming for the last 8,000 years or so. The article predicted increased glaciation in the Northern Hemisphere, ignoring anthropogenic (human-caused) effects, over the next 7,000 years.

Dr. Hertzberg also cites an ice core study that shows that temperature increases precede carbon dioxide increases in the Earth’s atmosphere by 500 to 1,000 years. The scientific explanation for this is that, as the Earth was emerging from the last Ice Age about 18,000 years ago driven by the Milankovitch cycle, more carbon dioxide began escaping from the ocean in the Southern Hemisphere. As the CO2 moved into the atmosphere, it trapped more incoming solar radiation, further warming the planet. However it was not until the Industrial Revolution around 1750 that CO2 levels began to rise exponentially from around 275 ppm to its current level of around 390 ppm.

According to Wikipedia: “The overwhelming scientific evidence is that anthropogenic global warming is occurring. Nevertheless political and public debate continues.” As the catastrophic events along the Gulf Coast states demonstrate, we must break our addiction to the burning of fossil fuels and transition to the cleaner and greener renewable energy sources such as solar, wind, biofuels, geothermal, nuclear, and hydroelectric. The American Power Act, currently being debated in the U.S. Senate, aims to do just that by creating up to two million new jobs. Please support this bill by contacting the National Resources Defense Council at and the Environmental Defense Fund at

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