"It’s just a cycle, right?" 316

 "It’s just a cycle, right?" 

Have you heard this? It is a common response by many when I start a conversation about climate change. Many people “believe” we are at a hot point in a natural ice age cycle.

 

Before I launch into my explanation of why the current gnarly worldwide weather is not caused a cycles, let me acknowledge it is not easy to grasp the science. I am giving you my best shot.

 

 There is renowned scientist, Katherine Hayhoe, who has a science series on You Tube called, “Global Weirding”. She has been awarded for her communication skill so if you find her explanations easier to understand you cannot go wrong sticking with her. For a very thorough but straightforward presentation on why the climate is no longer the result of a natural cycles search: “Katherine Hayhoe.  This is all just a part of a natural cycle, right”. 

 

To be clear there are many cycles that influence us such as the solar and lunar cycles, the natural cycle of seasons, and the El Nino and La Nina cycles. There are hydrological cycles. In the longer term there are carbon cycles. If I missed your favorite cycle, please let me know! Many of these cycles do affect our weather but I guarantee you, none are responsible for the long-term warming we have experienced in the last 150 years.

 

Let’s examine the well-documented ice age cycles which are more appropriately called the Milankovitch Cycles.

Scientists have proven Milankovitch's theory valid by drilling into the thick Antarctic Ice Sheet, removing ice cores, and analyzing the trapped air. The cores go back 800,000 years. The orbital cycles cause the Earth to change the Greenhouse Gas composition (GHG). The primary GHG examined in ice core bubbles is carbon dioxide (CO2).

You can find the results of scientist hard work, the graphs, by searching, “carbon dioxide in ice core samples”.

 

Let's examine the consequences of the Milankovitch Earth Orbital Cycles.  The primary cause of massive buildups of glacial ice sheets, which have cyclically covered the northern hemisphere, is the lack of carbon dioxide in the air. The air analyzed in ice bubbles during the depths of an ice age show that the CO2 levels dipped to a low of 180 parts per million. (ppm). It got so cold up north that the compacted snow sliding down from the north covered the UP with two miles of ice!

 

As the Milankovitch orbital cycles shifted, the GHG concentration slowly changed. These shifts take 10s of thousands of years. As the GHGs gather in the atmosphere, the higher concentrations slow the heat escape and the Earth warms. When examining the ice core history, the normal high concentration of carbon dioxide is usually 280ppm CO2, only 100ppm more than the low concentration I mentioned previously at 180ppm.  One high excursion occurred about 300,000 years ago, reaching 300 ppm CO2. When reaching 280 to 300 ppm, the Earth has a warm, pleasant climate.

 

The complete cycle takes 100,000 years. The takeaway is twofold: First, the climate is extremely sensitive to the concentration of carbon dioxide, and second, the normal fluctuation takes thousands of years.  

 

Mankind fueled the Industrial Revolution by burning coal, oil, and gas. Industrialization via fossil fuels got rolling around 1880. In 1911, the greenhouse gas concentration blew through the previous maximum record of 300ppm CO2. This was a record held for 800,000 years. We have rapidly piled on the CO2 ever since. Today, we are at 419ppm.

 

When we blew through 300 ppm in 1911, the correlation between CO2 concentrations and the natural 800,000-year-old relationship of the Milankovitch Cycles ended. Thus, there is no cycle associated with what we are experiencing today.

 

You may have noticed that the difference between an ice age and a warm interglacial period is only 100 to 120 ppm. Since 1911, we have managed to inject an additional 119 ppm more CO2. We did in 100 years what Mother Nature does in 50,000 years.

 

Professor David McGee of the MIT Department of Earth, Atmosphere, and Planetary Sciences sums things up in more detail, "The cause of today's climate change is also different from the planetary forces that set off the breaks between ice ages. In past cycles, changes to the Earth's rotation kicked off warming by increasing the sunlight reaching icy parts of the Earth. As ice melted, the Earth became less reflective, and retained more of the sun's heat. That warming led carbon dioxide to move from the ocean into the atmosphere, prompting more warming.

 

But today, the cause is reversed: by burning fossil fuels, we have put large amounts of CO2 into the atmosphere very quickly, and that has spurred warming.

The speed of climatic change today is also more or less unprecedented. The amount of CO2 that humans have added over just the last hundred years is comparable to the amount that was added over 100 centuries after the last ice age. In other words, in the modern day, atmospheric carbon has risen about 100 times faster than when humans emerged from the last ice age. That difference is part of why current climate change is so alarming. 

 

At the end of the last ice age, ecosystems had a good deal of time to adapt to the warming as it occurred. Right now, they have much less time because warming is happening a lot faster."

 

There is no "cycle" which explains our current predicament. It is purely cause and effect. We are the cause, and if we do not act, our kids who are already feeling the effect are in for a massive amount of effect.

 

Reference: MIT's Climate Portal.

Search:  NASA Science, "Why the Milankovitch (Orbital) Cycles Can't Explain Earth's Current Warming  

There are many ice-core graphs. I like one by NOAA, "Carbon Dioxide over 800,000 years" by NOAAClimate.gov