Trego's Mountain Ear

The question is not whether human activities have altered the planet’s climate.  The map below, gives a pretty decent interpretation of how wintry the planet looked 20,000 years ago – and glancing at my own little part of Montana shows a spot much less suitable for agriculture or gardening.

In high school, I heard of the cyclic nature of ice ages – the explanations weren’t there, but evidence of the cycles was apparent. History.com provides this commentary:

“There have been at least five significant ice ages in Earth’s history, with approximately a dozen epochs of glacial expansion occurring in the past 1 million years. Humans developed significantly during the most recent glaciation period, emerging as the dominant land animal afterward as megafauna such as the wooly mammoth went extinct.”

Nothing personal – but I like living in a world that is 6 degrees Celsius warmer – as I write this, with the summer solstice due tomorrow, the temperature is 38 degrees Fahrenheit.  Six degrees Celsius is 10.8 degrees Fahrenheit – you can push the numbers and figure out the growing season 20,000 years back.  Climate change can be a good thing.  On the other hand, if you had owned oceanfront property in Florida 20,000 years ago, it’s ocean today.  Climate change is a matter of location and perspective.  My perspective if I lived in Paramaribo would likely differ – 6 feet above sea level is very different from 3,000 feet above sea level.  There is a difference between 49 degrees of latitude and 6 degrees.

“Over at least the past million years, glacial and interglacial cycles have been triggered by variations in how much sunlight reaches the Northern Hemisphere in the summer, which are driven by small variations in the geometry of Earth’s axis and its orbit around the Sun. But these fluctuations in sunlight aren’t enough on their own to bring about full-blown ice ages and interglacials. They trigger several feedback loops that amplify the original warming or cooling. During an interglacial,

• sea ice and snow retreat, reducing the amount of sunlight the Earth reflects;
• warming increases atmospheric water vapor, which is a powerful greenhouse gas;
• permafrost thaws and decomposes, releasing more methane and carbon dioxide; and
• the ocean warms and releases dissolved carbon dioxide, which traps even more heat.

These feedbacks amplify the initial warming until the Earth’s orbit goes through a phase during which the amount of Northern Hemisphere summer sunlight is minimized. Then these feedbacks operate in reverse, reinforcing the cooling trend.”

Climate.gov

Humans work best in the interglacial periods.  Mammoths and mastodons are better adapted to interglacials.  Here, where the continental glaciers hit, warming is not so much a threat as cooling.  Climate change is something we need to understand – and the first thing to understand is what the alternatives are.  Then, we can make decent decisions.