Clyde Burnett, Peak to Peak. A reminder of why it’s summer: The axis of our rotating earth is tilted 23 degrees from the orbit plane with the north pole now tilted toward the sun. The sun’s radiation is arriving nearly perpendicular to the northern hemisphere surface. We have maximum intensity and high temperature.

The axis and speed of rotation stays constant due to conservation of angular momentum. Six months later, it is tilted away from the sun and the same radiation is spread over a larger area; the intensity is less, and the temperature is lower - it’s winter.   

Because we have been burning fossil fuel, the atmospheric greenhouse effect of earth’s infrared trapping by CO2 is 48 percent greater than a few hundred years ago, with average global surface temperature about 1 degree Celsius warmer. We are getting triple digit midday temperatures with danger of heat prostration. Take care! 

The oceans have absorbed over 90 percent of the trapped heat. There is more evaporation and the transported water vapor is increasing our relative humidity. We have more rain and flooding.  It is costing more than if we had made the transition to renewable energy.

  The solar radiation is maximum intensity in the visible at 400 to 700 nanometers wavelength. It is the ultraviolet at about 300 nanometers where the high-energy photons most efficiently cause sunburn. Stratospheric ozone protects us from much of this. Seasonal ozone is low in summer; the absorbing slant path is short for four hours around midday, from 11 a.m. to 3 p.m., and the blue sky very efficiently scatters additional ultraviolet. Sunburn time with clear sky is only about 10 minutes, and teenage sunburn may cause skin cancer at age 90. 

Originally published in the July 18, 2019, print edition of The Mountain-Ear. Available in low resolution pdf format at https://themtnear.com/product/2019-07-18/