As I have explained in posts one and two, our present brief (13,000-year) warm interglacial and even briefer (9,000-year) period of extreme climate stability will end. Another ice age is coming. Though for a number of reasons (as I will explain) we cannot prevent the onset of an ice age, there are some things we can do to delay it.

Primary Natural Drivers of the Ice Age Cycle
As I describe in some detail in my book, Improbable Planet, the primary natural drivers of the ice age cycle are (1) cyclical variations in Earth’s rotation axis tilt (aka obliquity), and (2) cyclical variations in the elliptical shape or eccentricity of Earth’s orbit about the Sun.¹

Earth’s obliquity varies from 22.1° to 24.5°. The predominant periodicity of this variation is 41,000 years. Presently, Earth’s obliquity = 23.439281°. It is decreasing at a rate of 47 arc seconds per century (0.0130° per century). Lower obliquity favors ice ages because summers are cooler and seasonal differences at high latitudes (where ice resides) are less pronounced, reducing the amount of winter snow and ice that melts. Earth’s obliquity is projected to reach its minimum value around 10,000 AD.

The eccentricity of Earth’s orbit varies from 0.000055 to 0.0679^2, where a value of 0.0 equals a perfect circle and 1.0 describes an orbit where the maximum orbital diameter divided by the minimum orbital diameter = infinity (that is, the minimum orbital diameter = 0.0). The predominant periodicities are 413,000, 125,000, and 95,000 years. Presently, Earth’s orbital eccentricity = 0.01670986, and it is decreasing. The last maximum (0.019) was about 10,000 years ago, and the previous minimum was 40,000 years ago (0.010). Lower eccentricity favors ice ages and a minimal value of Earth’s eccentricity is projected to occur roughly around 60,000 AD.

Delaying the Next Ice Age
If the primary natural drivers of the ice age cycle were the only significant factors driving the cycle, we should be in an ice age right now. Both Earth’s obliquity and orbital eccentricity are declining. Both are operating to cool our global climate. If Earth’s obliquity and orbital eccentricity were the only significant factors, the next ice age should have begun roughly 5,000 years ago.

Figure 1 shows the global mean temperatures over the past 300,000 years. Some unknown event or unique combination of obliquity and eccentricity cycles, circa 5,000 years ago, prevented the global mean temperature from rising high enough and long enough to melt the polar ice cap and bring on a subsequent ice age.

Figure 1: Global Mean Temperatures for the Past 300,000 Years. The temperature scale (y-axis) is in degrees Centigrade relative to the present global mean temperature. Image credit: Adapted by author from image produced by Robert A. Rohde, Global Warming Art Project, CC by SA.

The domestication of cows began about 10,500 years ago but remained a small component of animal husbandry until 7,000–6,000 years ago.³ The dramatic rise in the domesticated cow population that began during the sixth millennium BC substantially enhanced the emission of greenhouse gases into Earth’s atmosphere. This emission compensated for the cooling generated by Earth’s declining obliquity and orbital eccentricity.

Additional compensation for the cooling arising from Earth’s declining obliquity and orbital eccentricity came from the domestication of rice and the deforestation of Eurasia to make room for intensive crop cultivation and pasture land.⁴ Before the advent of the industrial revolution, the combination of the growth of animal husbandry, irrigation for rice farming, and the transformation of forests into cultivated fields and pasture lands raised the atmospheric carbon dioxide level from 245 parts per million to 285 parts per million, and the atmospheric methane level from 450 parts per billion to 700 parts per billion.

These three features of anthropogenic activity (human activity that affects nature) operating over the past 7,000 years played a major role, not only in delaying the onset of the next ice age, but also in producing an unprecedented period of extreme global climate stability. As figure 2 shows, the global mean temperature throughout the past 9,000 years has not varied by more than 2°Celsius (3.5°Fahrenheit). As I explained in Improbable Planet,⁵ it is due in large part to this brief period of extreme climate stability that humanity has been able to launch and sustain global, high-technology civilization and grow a human population numbering in the billions.

Figure 2: Global Mean Temperatures during the Last 80,000 Years. The blue lines show the global mean temperature as determined from the GRIP Greenland deep ice core while the purple lines show the global mean temperature as determined by the NGRIP Greenland deep ice core. Image credit: adapted by author from image produced by Leland McKinnes/Wikipedia Commons, CC-by-3.0.

Since the advent of the industrial revolution and especially during the explosion of human wealth and technology that has occurred since the end of World War II, anthropogenic activity has overcompensated for the global cooling arising from the currently ongoing decline in Earth’s obliquity and orbital eccentricity. As I explained in my previous two blogs, it is this overcompensation that is threatening to accelerate the onset of the next ice age.

Many scientists and many more politicians are calling for draconian economic sacrifices in order to rectify this overcompensation of human activity. These scientists and politicians, in my opinion, are failing to fully consider the biblical principle of the universality of human sin and selfishness. In light of this biblical principle, as I explained in Hidden Treasures in the Book of Job,⁶ the only practical remedies for reducing the overcompensation are remedies that simultaneously boost peoples’ economic well-being and lower the impact of human activity. I discussed several such remedies in Hidden Treasures in the Book of Job, including restoring the whale populations,⁷ reducing the Sahara and Gobi deserts to the sizes they manifested two millennia ago,⁸ and substituting ostrich meat for beef.⁹

In addition to remedies achievable with existing resources and technology, there are a number of foreseeable technological advances that promise to reduce the over-compensation and restore the extreme climate stability we have been enjoying for the past 9,000 years. A prominent example is nuclear fusion. For several decades, physicists around the world have been working hard to develop nuclear fusion (as opposed to fission) reactors. If such reactors could be developed and produced in quantity, we would no longer need to use fossil fuels to generate energy to sustain the global economy.

While we can take steps to significantly delay the onset of the next ice age and restore extreme climate stability, such steps could have a severe impact on agricultural productivity. One reason why we are able to grow enough food to feed 7.5 billion humans, plus all the world’s domesticated animals, is that we depend on the melting of glaciers left over from the last ice age to provide the necessary water to irrigate our vast cultivated fields. Thus, a substantial delay in the onset of the next ice age could confront us with another potentially catastrophic problem—the complete melting away of the glaciers that currently are supplying water to our agricultural plains.

Preparing for the Next Ice Age
I am not saying it is infeasible for humanity to find a way to delay the onset of the next ice age by one or two millennia. Nuclear fusion reactors, for example, conceivably could provide a means to desalinate huge quantities of ocean water. However, to cite another biblical principle and a famous Christian hymn, this world is not our home.

In chapters 15 and 16 of Improbable Planet, I explain how the ice age cycle is a marvel of divine design. It is designed to enable our planet to sustain several billion people at one time. It is designed to enable these several billion humans to develop the wealth and technology to make possible the completion of the Great Commission (Matthew 28:18–20) within the next few decades.

I describe how it is possible—with existing resources—for Christians today to take the good news of salvation through Jesus Christ to all the people groups of the world where, within each people group, a large minority of them would become disciples of Jesus Christ. With sufficient motivation on the part of existing evangelical Christians, I demonstrate in Improbable Planet how the task of “making disciples of all nations” could be completed in less than a few decades.¹⁰

The Bible promises (Romans 8, Revelation 20–22) us that when the full number of human beings that God intends to redeem is in fact redeemed, the universe and our planet Earth will have fulfilled the purpose for which God created them. God will then replace them with a brand new creation—the new heavens and the new earth, a realm where “the old order of things” will pass away and where God says about the new creation, “I am making everything new.” As I explain in Beyond the Cosmos¹¹ and in Why the Universe Is the Way It Is,¹² the new creation will be governed by completely different laws of physics and dimensions. In the new creation we will not need to be concerned about the ice age cycle, global warming, or climate stability. God has promised to make the new creation a perfect realm for all eternity.

To be clear, I am not saying that because it appears the Great Commission can be fulfilled within a few decades, that we can ignore the climate problems we currently face. Many Christians, including myself, believe that the Bible teaches a literal reign of Jesus Christ here on planet Earth for a one-thousand-year period following the completion of the Great Commission. For Christians who do not hold to a millennial reign of Christ on Earth, there are still the exhortations from our Savior to “occupy until I come” (Luke 19:13) and the creation care mandate described in Genesis 1:28–30 and Job 37–39.

What I am saying is that God generously granted us an extremely beneficial ice age cycle and a brief period of extreme climate stability within that cycle so that we could not only enjoy a brief period of unprecedented wealth and technology but also, far more importantly, to use that wealth and technology to fulfill an eternal spiritual destiny. Yes, let’s do everything we can to wisely and economically sustain this remarkable period of terrestrial blessing in which we currently reside. However, let us do much more to partner with God to bring about the redemption of untold human beings, the eradication of all evil, and our preparation for eternal life and our careers in the new creation.