Could Global Warming Jumpstart Another Ice Age?

I’m sitting on a bench in Fort Lee historic Park and I notice that something is wrong. Oh yes, I’ve got it: I’m under nearly a half mile of ice. The date is August 27, 20,000 BC. We’re still in the most recent ice age. Luckily, I’m only here in my imagination or I would be squashed like a bug.

It’s hard to believe that New Jersey and New York were under so much ice just yesterday, as measured in geologic time. Geologists estimate that a half million years ago, the ice sheet was between 2,000 and 10,000 feet deep at what is now High Point, New Jersey. The most recent glacial period in our state occurred 21,000 years ago. Is another coming soon?

What is an Ice Age?

An ice age is a long period of low ocean and atmospheric temperatures. It causes continent-sized ice sheets and alpine glaciers to form and to migrate. Our planet’s climate alternates between cold ice ages and warm greenhouse periods. During the latter, there are few if any glaciers and ice sheets on the planet. Glaciation has happened many times, the most recently ending about 10,000 years ago. As the ice melted, the Earth returned to its normal climate.

The last Ice Age had an important role in the development of our species. About 2.5 million years ago, our distant ancestors were driven south by the encroaching ice. As they migrated in its shadow, life became more dangerous. They had to work harder to find food and shelter. Paleontologists hypothesize that in response to this stress, their brains grew larger and more complex, growing from 600 cc (cubic centimeters) to about 1000 cc, making us the largest brained species on the planet.

What Causes Glaciation?

It’s not just cold weather. Rising atmospheric temperatures increase evaporation from the warming oceans. More water vapor in the atmosphere causes more rain, which in mountainous regions becomes snow. Major ocean currents, such as the gulf stream transport cold water southward and transport warm water northward.

Disruptions in this flow causes planetary temperatures to decrease. Solar radiation, which can vary with solar cycles, has a much smaller effect on our climate. But together, these factors have caused six major ice ages over the last few hundred million years.

Mountain glaciers appear when snowfall continues to build up at high elevations over long periods. The amount of water vapor in the atmosphere increases rainfall, which on mountainous terrain becomes snow. After about 50 feet of snow depth, its weight crushes the snow crystals at the bottom into a form of ice substance that moves like taffy.

This mass begins to flow like a viscous fluid, scouring everything in its path and reshaping the land. Glaciers have long lifetimes and travel great distances. They concentrate and store fresh water and carve out river valleys.

Ice sheets, by comparison, form on level land. When the snow gets deep enough the mass begins to plasticize and flow, very much like honey poured on a countertop. Ice sheets can become the size of continents. In the last ice age, 5-mile-thick ice sheets caused a global sea level drop of about 400 feet.

Will Global Warming Cause Another Ice Age?

The climate of the Earth is controlled by many forces: The Sun’s changing luminosity; the Earth’s wobble in its orbit; volcanic eruptions; ocean currents; and changes in greenhouse gas concentrations, primarily carbon dioxide and methane. And now human behavior has entered the equation.

Disruptions in major ocean currents, such as the Gulf Stream, can have a massive impact on the climate. The Gulf Stream is a current of water that originates in the Gulf of Mexico and stretches across the eastern coastlines of the United States before entering the Atlantic Ocean as the North Atlantic Current.

A stream of warm water travels north from Antarctica on the Gulf Stream, releases its heat and then sinks to the bottom of the ocean and travels back south. Global warming stalls this process, causing the currents to slow down. This can seriously disrupt the weather. Scientists have previously linked disruptions to Atlantic currents from heat waves in Europe to rising sea levels in coastal US cities.

The Greenhouse Effect

We have become the leading cause of the Earth’s rapidly changing climate, by increasing the strength of the “greenhouse effect.” This is a natural process that warms the Earth’s surface.

When the Sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. The absorbed energy warms the atmosphere and the surface of the Earth. When there is a greater concentration of greenhouse gases, they trap heat that would normally leave the atmosphere and rise into space.

We generate enormous amounts of greenhouse gases. In moderate quantities, greenhouse gases help us: they keep the planet warm enough for human habitation. However, according to the 2019 Intergovernmental Panel on Climate Change (IPCC), “concentrations of carbon dioxide, methane, and nitrous oxides have increased to levels unprecedented in at least the last 800,000 years.”

Our industrial activity has caused greenhouse gases to increase dramatically since pre-industrial times. And the many billions of bovines we maintain for food constantly emit methane at levels that cause atmospheric heating. Some scientists have argued that eating less meat would reduce the bovine effect on the climate. Nowadays, having recently lost more than 100 glaciers with only 50 remaining, we appear to be quickly heading in the wrong direction.

An August 14, 2020 publication from Climate.gov states that …

“Through 2019, the warming influence of all major human-produced greenhouse gases has increased by 45%. Carbon dioxide and methane account for just over 80% of the total. As natural carbon “sinks,” oceans and forests that absorb greenhouse gases, can’t handle our rising emissions. The planet is warming at an alarming rate. The earth’s average temperature rose by about 1° Fahrenheit during the last century.

If this trend continues, sea levels will rise from 1 to 8 feet by 2100. This will cause worldwide loss of land, widespread famine, a shortage of clean water, more intense storms and heat waves, and other devastating financial and cultural effects.

A 2003 publication from Yale University quotes Wallace Broecker, an ocean circulation researcher at the Lamont Doherty Earth Observatory in New York:

“Climate is an angry beast and we are poking at it with sticks.” A 2020 NASA publication entitled “There Is No Impending ‘mini Ice Age’” states that the warming caused by increased levels of carbon dioxide in the atmosphere will in the near future cause average temperatures to rise by about 5°C. This will cause “devastating effects for us earthlings, such as rising sea levels and dramatic changes in weather patterns… but even that warming will not stave off the eventual return of huge glaciers.”

The article reminds us that our supply of fossil fuel will be consumed in 300 years. At that point we will be vulnerable to another Ice Age.

Nature is an unforgiving mistress. Our survival requires that we control the increase in greenhouse gases by stopping our use of fossil fuels and developing nuclear, solar and other clean energy sources. Humanity has never faced so dire an accelerating threat. We need a planetary wide response, which given our political climate of distrusting science, seems unlikely to happen.

From the perspective of a father and grandfather with a loving family, I cannot comprehend how anyone in power can turn a blind eye to the unassailable evidence of climate change. They are condemning their own descendants to living in a hostile and dangerous world. My children and grandchildren are depending on us to leave them a world in which they will not just survive, but thrive. We cannot let them down.