8,000 Years in Retrospect
One of the more confounding phenomena in climate science is the rise in global temperatures that ended the last ice age 11,000 years ago. Previously, it was assumed that this rise in temperature was mainly due to changes in the Earth's orbit around the Sun (called Milankovitch cycles) rather than an increase in carbon dioxide, which - in the vast historical accumulation of climate data - appears to have been the result of rising temperatures rather than the cause; counter to what the current climate is doing. This phenomena is one that climate change denialists tend to fervently cling to as a counter-argument to human-induced climate change.
And in fact, it looks as if the Milankovitch cycle may have truly been the trigger behind the forces that brought Earth out of the last ice age, as suggested by a recent NPR news article. However, as the article discusses beyond it's ambiguous and uninteresting title, there's a lot more to the story. Unfortunately, it also fails to offer a link to the actual published scientific paper, which can be found here.
In a nutshell, the rise in global atmospheric carbon dioxide levels that we once thought occurred after the temperature rise that ended the last ice age, actually occurred before. Furthermore, it set the stage for what eventually became a global meltdown of the enormous ice sheets: Initially starting in the Northern hemisphere as a moderate warming due to more sunlight reaching the north pole (the Milankovitch cycle), it sent large amounts of freshwater into the oceans (called a Heinrich event) thus halting the global thermohaline circulation (regularly cycling warm/cold ocean currents that soak up carbon dioxide from the air and store it the deep ocean). In turn, this allowed warm water to pool around the Southern hemisphere, releasing a majority of Earth's carbon dioxide that was locked up in the Southern ocean. After that, temperatures spiked with the release of so much carbon dioxide into the air, that it ended the ice age and brought about the current climate regime that allowed human civilization to prosper.
This new study does several things: (1) It removes ammunition from the machine gun of anti-science that climate change deniers use to misrepresent global warming science, (2) further establishes that carbon dioxide has been a primary driver of the Earth's climate in the geologic past, and (3) shows that the sciences - unlike dogmatic ideology, polemic demagogy, or stubborn politicians - evolve over time based on updated data and a better understanding of how the cosmos functions.
A few things bother me about how this new study will be reported in the news: (1) The media will always add some minor or irrelevant counter-source of information to make it appear as if there's a large controversy about the science, (2) they will make the subject matter seem so dry and obscure that virtually no one will bother reading the whole article and assume that the title tells the whole story (in NPR's case, "Shake It Off: Earth's Wobble May Have Ended Ice Age"), and (3) the manufactured doubt industry cronies will hijack the comments section and lead astray the entire discussion with recycled arguments that have long-since been proven false.
Regardless, the NPR article ended on a note that I think drove the point home (emphasis mine):
"'The CO2 increase turned what initially was a (localized) Southern Hemisphere warming into a global warming...' But that's a process that has taken about 8,000 years... the amount of CO2 it took to end the ice age is about the same amount as humans have added to the atmosphere in the past century."
8,000 years. Think about that. What's happened in 8,000 years of human history? Extrapolating back from today, that was roughly the year 6000 BCE. Humans were just beginning to adopt agriculture, cutlery, and wine. The entire world population was estimated at 5 to 7 million people, smaller than the population of New York City all by itself. Christianity, Judaism, and Islam have their earliest creation scriptures reaching back to this period, not the least of which being the Great Flood. Countless empires have risen and fallen since this time, all seven Wonders of the World have been constructed, and every piece of modern technology since the Stone Age has been invented, developed, and incorporated into our civilization.
All because the level of carbon dioxide in the air went from 180 to 260 parts-per-million over the preceding eight millennia, thus ending the last ice age and stabilizing our climate.
How can we NOT be humbled by this process? How can we NOT take pause knowing that the carbon dioxide level in the air has changed from 285 to 392 parts-per-million since the year 1850 (i.e. more than the amount that caused the last ice age to end)? How can we be justified in continuing the status quo of burning fossil fuels without restraint when we KNOW with absolute certainty that this is what's causing the carbon dioxide levels to rise?
With this knowledge, how can we NOT act when we know that the climate of the past 8,000 years - the one that gave birth to our entire civilization - might not be here in less than 100 years?