by Adam Frank

About 12,000 years ago (give or take a thou­sand) the glac­i­ers cov­er­ing much of the north­ern hemi­sphere dis­ap­peared and an ice age grip­ping the Earth ended. The planet became warmer, wet­ter and entered the geo­log­i­cal era sci­en­tists call the Holocene. Marked by a sta­ble cli­mate, the Holocene has been good to humans. The entire his­tory of our civ­i­liza­tion (agri­cul­ture, city build­ing, writ­ing etc.) is bound within the Holocene and its bounty of pro­duc­tive land and oceans.

Now, it appears, the Holocene is over.

Recently The Econ­o­mist reported on a rad­i­cal idea that has been float­ing around in the geo­log­i­cal com­mu­nity for last few years: we are enter­ing a new era in the his­tory of the planet dom­i­nated by human “forc­ing.” As the arti­cle aptly puts it: “Wel­come to the Anthro­pocene.”

I’ve been intro­duc­ing the Anthro­pocene con­cept for the last few years in my “Astro­physics of Plan­ets” course. It such a deep perspective-shift that it always soaks up an entire class-hour’s worth of discussion.

The first point to absorb is that there are no pol­i­tics in the des­ig­na­tion. It is nei­ther a value judg­ment nor a cri­tique. Instead, it is sim­ply a recog­ni­tion that human activ­ity has now come to be the most sig­nif­i­cant “forc­ing” dri­ving the var­i­ous inter­lock­ing sys­tems that define the cur­rent “state” of the planet.

Sci­en­tists dig­ging through sed­i­ments mil­lions of years from now should eas­ily be able to iden­tify the tran­si­tion from the Holocene to the Anthro­pocene. From the fos­silized remains of our cities to changes in the car­bon­ate con­tent in sea-floor sed­i­men­ta­tion, the Anthro­pocene may appear as clearly to future sci­en­tists as the Cre­ta­ceous appears to us.

And before we begin the usual tired argu­ment about cli­mate change, it’s impor­tant to under­stand that cli­mate is just one part of this tran­si­tion. Along with unin­ten­tional changes in the carbon-cycle, humans have also inten­tion­ally altered the nitrogen-cycle as well. With the inven­tion of the Haber process we fig­ured out how to extract more nitro­gen from the atmos­phere and use it to cre­ate fer­til­izer to grow more plants. The dead zones increas­ingly com­mon in costal regions where algae blooms feed off fertilizer-rich run-off are one result of an epic alter­ation of the planet’s nitro­gen cycle. The pres­ence of so many of us eat­ing all that fer­til­ized food is another.

To see how recog­ni­tion of the Anthro­pocene is rel­a­tively free of pol­i­tics, con­sider the responses var­i­ous com­mu­ni­ties have had to the con­cept. For some the advent of the Anthro­pocene is recog­ni­tion of our greed and igno­rance. With the birth of indus­tri­al­iza­tion we failed to rec­og­nize the forces we were unbal­anc­ing and now a planet “tipped” into another, per­haps harsher, regime rel­a­tive to human habi­ta­tion is the fate await­ing us. For oth­ers our entry into the Anthro­pocene is the ulti­mate acknowl­edge­ment of our priv­i­leged sta­tus in the hier­ar­chy life. It was exactly through the intel­li­gence that forged indus­try that this planet was shaped in our image. In response, it will be through intel­li­gence that we will engi­neer our way through the Anthro­pocene to a planet that can han­dle our ever-growing numbers.

Thus one response sees the Anthro­pocene as the advent of an eco-apocalypse. It is a dis­as­ter that can only be averted through a draw down of the tech­nolo­gies that brought us here and the devel­op­ment of smaller scale human foot­prints on the planet.

The other response sees global-scale tech­no­log­i­cal responses as the only effec­tive solu­tion. “Geo-engineering” projects — such as alter­ing the chem­istry of the oceans to increase car­bon uptake — rep­re­sent one pro­posed mech­a­nism to a human friendly Anthro­pocene (with genetic engi­neer­ing per­haps design­ing new forms of car­bon eat­ing algae).

Regard­less of your phi­los­o­phy, the recog­ni­tion that we have entered a geo­logic age of human­ity raises the obvi­ous ques­tion of just how long such an age will last.

In the infa­mous KT bound­ary geol­o­gists can see evi­dence for a rather short-lived event that also reshaped the planet. Sixty five mil­lion years ago an aster­oid struck the Earth, dri­ving one of only five mass extinc­tions in the planet’s his­tory. The loss of the dinosaurs turned out to be an oppor­tu­nity for our mam­mal ances­tors and led directly to our own age.

Since the Anthro­pocene appears to mark a sixth great extinc­tion, one has to won­der what it will take for us to make it out of own era with civ­i­liza­tion intact.