ONCE UPON A TIME there was a little planet that, over billions of years, had all the right things happen to it to bring forth life. This was not just any life, but life capable of understanding some small portion of the forces that brought it into existence. The little planet had a very hot, liquid core that produced thermal vents on its ocean floors, which likely served as the original womb where life came into being.

 

Once that early microbial life was present, it acted on its surrounding environment and through its metabolism produced oxygen as a byproduct, enriching the atmosphere and allowing the early microbes to join together in communities of multicellular life. Simple, archaic forms like sponges eventually evolved into complex ones like quadrapedal apes and then upright walking apes, or hominids. The first hominids known as humans arrived on the scene some two million years ago, while the human beings from which all of us are directly descended populated all of Africa and from there the rest of the continents less than 100,00 years ago. That process was finally completed less than 50 years ago, when a mother gave birth to the first baby ever born in Antarctica.

 

During the period of modern humans populating the world and for hundreds of thousands of years prior to that, the little planet’s atmosphere kept its surface warm enough to avoid the plunge into ice from poles to equator that it had experienced earlier in its history, but cool enough to avoid the expansion of its tropics to Antarctica and to the lands above its arctic circle that it had also experienced earlier during its long history. Between these larger extremes, which also involved plate tectonics and other forces that change over much longer periods of time than the two million years humans have been here, the planet experienced a relatively stable climate. Its primary stabilizer was its atmosphere’s R-value, which stands for Resistance to conductive flow. The atmosphere acts like a huge down comforter, wrapping up the planet and keeping much of the heat generated from sunlight striking its surface at the surface and in the lower atmosphere. Without the atmosphere, or with a very thin atmosphere like the one on Mars, nearly all that heat would radiate, or flow, back out into space, rendering the planet inhospitable to life. The atmosphere is able to resist this conductive flow of solar radiation back out to outer space partly because of three greenhouse gases that in its mix. Those gases are carbon dioxide, methane, and nitrous oxide.

 

Increasing the concentration of those three gases in the atmosphere is the equivalent of wrapping the planet in a higher quality down comforter. But because this is the story of a goldilocks planet, it’s not so simple as to say that is purely bad. As everyone knows, the real Goldilocks liked everything just right—not too big and not too small, not too hard and not too soft, and not too hot and not too cold.

 

But setting aside those climate extremes of palm trees in Antarctica and ice on the beach in Equador, this little planet has very much leaned toward the frosty side of things during the 100,000 years or so that it took modern humans to populate all seven continents, and for hundreds of thousands of years before that too. The planet spent over 90% of that time locked in ice ages averaging over 100,000 years each, separated by brief interglacial periods averaging a little over 10,000 years each. Human civilization has arisen entirely in the 10,000 years or so that the current interglacial period has been going on, a geological epoch known as the Holocene.

 

The Holocene began at the end of the last ice age, about 11,700 years ago. If humans hadn’t started adding massive amounts of carbon dioxide to the atmosphere (its concentration is measured in parts per million in the atmosphere) and smaller amounts of methane and nitrous oxide (their concentrations are measured in parts per billion), the little planet would either have already or would very soon be returning to another 100,000 year ice age, carrying humanity right along with her into the ice. Instead we inadvertently created a true Goldilocks moment for her, putting enough carbon dioxide in the atmosphere to avoid another ice age, but not so much as to heat her up to the point of driving many species into extinction, including potentially our own. The problem though is that the human-caused Goldilocks moment took place about a hundred years ago, but we didn’t then stop adding heat trapping gases to the atmosphere. Instead we’ve kept our foot on the gas so to speak ever since, holding down that pedal to the metal
with all of our ever-increasing industrial might.