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