Why the Anthropocene has divided the scientific community

The term is every­where: from the École de l’Anthropocène in Lyon to a ded­i­cat­ed IGN atlas¹ and even two ded­i­cat­ed sci­en­tif­ic jour­nals², every­one – sci­en­tists includ­ed – is using the con­cept of the Anthro­pocene. This new geo­log­i­cal era is char­ac­terised by a sig­nif­i­cant glob­al human foot­print on the plan­et. But the term is not offi­cial­ly recog­nised. In March 2024, the Inter­na­tion­al Com­mis­sion on Stratig­ra­phy – the organ­i­sa­tion respon­si­ble for defin­ing the geo­log­i­cal time scale – reject­ed the offi­cial addi­tion of a new geo­log­i­cal era³. We are there­fore still offi­cial­ly in the Holocene era, as we have been for the past 11,700 years. Nonethe­less, this deci­sion has not put an end to the debate with­in the sci­en­tif­ic community.

True: Part of the scientific community recognises its existence.

Erle Ellis. The Anthro­pocene, as defined in dic­tio­nar­ies, exists and is wide­ly used in sci­ence to define a time when humans are trans­form­ing the plan­et. How­ev­er, there is no offi­cial era in the geo­log­i­cal timeline.

Michel Mag­ny. A large part of the inter­na­tion­al sci­en­tif­ic com­mu­ni­ty recog­nis­es the term. When it was first pro­posed in our team, which works on the recon­struc­tion of past envi­ron­ments in rela­tion to soci­eties, we had the impres­sion that all our work incor­po­rat­ed the con­cept of the Anthro­pocene! We have seen the major impact of humankind on ecosys­tems since the first agri­cul­tur­al soci­eties. Many geol­o­gists also recog­nise the exis­tence of the Anthropocene.

With­out dis­put­ing the fact that rapid and far-reach­ing cli­mate changes may have occurred in the past, the Anthro­pocene marks a sud­den change in the cli­mate pat­tern. Where­as for a mil­lion years, cli­mat­ic oscil­la­tions were main­ly dri­ven by the Earth’s orbital fac­tors, now it is the rate of human green­house gas emis­sions that is caus­ing the cli­mate to warm up by a sim­i­lar amount.

False: The International Committee for Stratigraphy has rejected the adoption of the Anthropocene as a geological epoch.

Jan Piotrows­ki. There is no jus­ti­fi­ca­tion for end­ing the Holocene. The end of the last Ice Age – rough­ly coin­cid­ing with the begin­ning of the Holocene – was marked by envi­ron­men­tal changes that were sig­nif­i­cant­ly greater than those that would have marked the begin­ning of the Anthro­pocene. For exam­ple, the tem­per­a­ture rose by 1°C per decade in Wales 15,000 years ago; 11,700 years ago in Green­land, a warm­ing of 7°C occurred in just 50 years; and 14,000 years ago, the doc­u­ment­ed rise in sea lev­el in Bar­ba­dos was 40 mm/year. These rates of change are greater than those our plan­et has expe­ri­enced since 1950.

Unclear: There are other alternatives for characterising humanity’s footprint on the planet.

JP. The only valid alter­na­tive to the Anthro­pocene is to describe it not as an epoch but as an event. Events are ele­ments that are well estab­lished in stratig­ra­phy: we find, for exam­ple, the Great Oxi­da­tion 2.4 bil­lion years ago, or the Ordovi­cian bio­log­i­cal explo­sion 500 mil­lion years ago. An event can be diachron­ic, as is the case with the Anthro­pocene. [Edi­tor’s note: The Anthro­pocene work­ing group says it has con­sid­ered this pos­si­bil­i­ty in detail, and con­cludes that it is incom­pat­i­ble with the strati­graph­ic data⁴.]

True: Scientists have defined a marker for the start of the Anthropocene.

MM. A work­ing group ded­i­cat­ed to the Anthro­pocene was set up in 2009 at the request of the Inter­na­tion­al Union of Geo­log­i­cal Sci­ences. In 2019, this group pro­posed adopt­ing the term Anthro­pocene. In 2023, it even defined a gold­en spike in the sed­i­ments of Lake Craw­ford, in Cana­da. Here, and across the globe, there has been a rapid increase in the con­cen­tra­tions of two iso­topes of plu­to­ni­um, cor­re­spond­ing to the first nuclear tests on land. The begin­ning of the Anthro­pocene would thus be defined in 1952. Apart from the nuclear mark­er, many oth­er indi­ca­tors show an abrupt change at this time: green­house gas lev­els ris­ing, bio­di­ver­si­ty falling, pol­lu­tion pil­ing up, man-made waste (such as plas­tic) accumulating.

Some have crit­i­cised the choice of Lake Craw­ford to define the gold­en spike mark­ing the begin­ning of the Anthro­pocene, main­ly because of its lack of acces­si­bil­i­ty. But what about the site offi­cial­ly cho­sen for the Gold­en Spike at the start of the Holocene? It’s a bore­hole in the Green­land ice cap, which is in dan­ger of dis­ap­pear­ing because of glob­al warming…

False: It is not possible to precisely define the beginning of the Anthropocene.

JP. There are geo­log­i­cal traces of human pres­ence well before the pro­posed start of the Anthro­pocene (begin­ning of agri­cul­ture, set­tle­ment of the Amer­i­c­as, indus­tri­al rev­o­lu­tion, etc.). Among the argu­ments against recog­nis­ing the Anthro­pocene as a geo­log­i­cal epoch, sev­er­al con­cern the begin­ning of the Anthro­pocene. It can­not be pre­cise­ly defined because it began at dif­fer­ent times and in dif­fer­ent places on Earth. What’s more, the pro­posed date (1952) makes no sense, as humanity’s impact on the Earth goes back much fur­ther than that. This would make the Sec­ond World War pre-Anthro­pocene! Final­ly, the pro­posed gold­en spike – Lake Craw­ford – does not meet the stan­dards of the geo­log­i­cal time­line: it is not very acces­si­ble and geo­log­i­cal­ly unstable.

EE. It’s poten­tial­ly pos­si­ble to pre­cise­ly define a date and mark­er for the Anthro­pocene, but there’s no obvi­ous sci­en­tif­ic point to it, espe­cial­ly if it’s recent. There are bet­ter ways of under­stand­ing the Anthro­pocene as an ongo­ing process and event, rather than an abrupt glob­al change that occurred in 1952.

Uncertain: Conflicting positions remain, not always based on scientific evidence.

MM. The deci­sion by the Inter­na­tion­al Com­mis­sion on Stratig­ra­phy to refuse to recog­nise the Anthro­pocene may seem sur­pris­ing. In fact, in 2023, the ded­i­cat­ed work­ing group had rec­om­mend­ed the adop­tion of the Anthro­pocene and pro­posed a gold­en spike.

But I under­stand the geol­o­gists’ mis­giv­ings. First, it should be remem­bered that the Anthro­pocene epoch was pro­posed in 2000 by Paul Josef Crutzen. This chemist, who works on stratos­pher­ic ozone, is recog­nised by the inter­na­tion­al sci­en­tif­ic com­mu­ni­ty and has been award­ed the Nobel Prize for Chem­istry. But he is not a geol­o­gist. The fact that a chemist is propos­ing to revis­it the geo­log­i­cal time­line can be a source of dif­fi­cul­ty. Final­ly, geo­log­i­cal time­lines are very long, often mil­lions of years. The change of scale here is rad­i­cal, with the Anthro­pocene start­ing in 1952, i.e. only 72 years ago!

True: The term unites many scientists.

MM. The inter­na­tion­al sci­en­tif­ic com­mu­ni­ty seized on the term as soon as it was pro­posed. There are ded­i­cat­ed jour­nals, and major sci­en­tif­ic jour­nals such as Nature and The Holocene have devot­ed spe­cial issues to the Anthro­pocene. The term brings togeth­er sci­en­tists from the nat­ur­al and human sci­ences, and it is a ban­ner that car­ries weight with the author­i­ties that gov­ern us, and we will con­tin­ue to use it. In my view, refus­ing offi­cial recog­ni­tion sends out a neg­a­tive sig­nal to sci­en­tists, but above all to polit­i­cal and eco­nom­ic lead­ers and to pub­lic opin­ion. I fear that it will serve as an ali­bi for inac­tion in the face of cli­mate change. It’s a real source of con­fu­sion, which is to be deplored.

EE. I think that sci­en­tists will con­tin­ue to dis­cuss the mean­ing of the “human era” using the term Anthro­pocene, and prob­a­bly oth­ers. Human soci­eties are not the first or only glob­al change to the plan­et caused by organ­isms, but it is the most recent and is dif­fer­ent from pre­vi­ous ones in many ways. There is no need to for­mal­ly define the Anthro­pocene epoch for the dis­cus­sion to continue.

Uncertain: Debate is part of the scientific method, and this decision is not final.

MM. Despite the deci­sion of the Inter­na­tion­al Com­mis­sion on Stratig­ra­phy, the debate con­tin­ues. As sci­en­tists, we are used to see­ing nar­ra­tives and inter­pre­ta­tions evolve as the data pro­gress­es, and I think that as the eco­log­i­cal cri­sis inten­si­fies, the break marked by the Anthro­pocene will become more and more obvious.

JP. There’s noth­ing wrong with using the Anthro­pocene as a sci­en­tif­ic term, but it should be called an event rather than an epoch. If the Anthro­pocene start­ed only 70 years ago, then its future impact is based on pre­dic­tions and not on avail­able geo­log­i­cal data. Con­se­quent­ly, its sta­tus should be con­firmed by future gen­er­a­tions of geologists.

Anaïs Marechal