We happen to be having a relatively mild winter this year. Last year was a different story. Next year may be the coldest ever recorded for all I know. But on the whole the trend seems to be towards warmer winters. I read once about the early settlers in the New England region ice skating on the Merrimack River from Newburyport up to Haverhill. The river in the stretch is tidal and brackish water. It’s hard for me to comprehend a winter, or a series of winters, when this stretch of river would freeze enough to safely skate. But then, our winters are different now than they once were.
I’ve contemplated the impact of obliquity on the winters over the last 300 years. If settlers were skating on a frozen Merrimack River in 1719, what is the impact of axial tilt on our ability to do the same in 2019? Don’t get me wrong, I’m a believer in the impact of mankind on climate change, but how much is that impact exacerbated by obliquity? I ran into this quote on NASA’s Earth Observatory site that describes the impact over time:
“As the axial tilt increases, the seasonal contrast increases so that winters are colder and summers are warmer in both hemispheres. Today, the Earth’s axis is tilted 23.5 degrees from the plane of its orbit around the sun. But this tilt changes. During a cycle that averages about 40,000 years, the tilt of the axis varies between 22.1 and 24.5 degrees. Because this tilt changes, the seasons as we know them can become exaggerated. More tilt means more severe seasons—warmer summers and colder winters; less tilt means less severe seasons—cooler summers and milder winters. It’s the cool summers that are thought to allow snow and ice to last from year-to-year in high latitudes, eventually building up into massive ice sheets. There are positive feedbacks in the climate system as well, because an Earth covered with more snow reflects more of the sun’s energy into space, causing additional cooling.” – NASA, referencing Milutin Milankovitch
The question I have is whether 300 years is enough time to have the dramatic impact, or whether we’ve sunk our own boat through carbon emissions? The impact of obliquity takes thousands of years. And yet there’s a significant difference in the types of winters we have today versus what we had roughly 15 generations ago. These are the questions that stir the inner scientist in me. Far more than whatever my teachers were dumping on me in school ever stirred me. It’s all about the questions you ask yourself when it comes to learning… or life.