In the first decade of the 21^st century evidence emerged from several scientific fields to clearly demonstrate that 55 million years ago a massive release of CO₂ abruptly raised earth’s temperature.

This event and its consequences is now commonly referred to as the Paleocene Eocene Thermal Maximum (or PETM for short).

This event happened at the end of a ten million year period of time known as the Paleocene. The gas release was initiated by an intense period of seafloor volcanic activity that stretched and thinned the seabed; forcing the American and Eurasian tectonic plates to spread further apart.

The North Atlantic had a violent birth; volcanic magma and superheated water flowed upwards through fissures in the earth’s crust; to first meet a vast store of hydrocarbon rich sediments in seabed basins, then sheets of methane hydrates on the seafloor of the continental margins. There was volcanic activity on the surrounding landmasses too. Flood basalts from this time are still widely exposed on the Faeroe Islands, Greenland and Baffin Island; whilst Iceland remains a volcanically active ‘hot spot’ to this day.

For over 10,000 years the combusted methane from volcanism, organic mudstones and methane hydrates combined with oxygen in the ocean to become CO₂, increasing the oceans acidity and quadrupling CO₂ concentrations in the atmosphere.

It's also thought that feedbacks (e.g. drying of shallow seas, peat fires) resulting from the initial warming would have contributed important feedbacks, contributing to the temperature rise.

So would have increased amounts of atmospheric water vapour, a greenhouse gas; a warmer atmosphere holds more vapour.

The seas became acidic with mass extinctions of phytoplankton.

The fossil record shows major migrations of flora and fauna into higher latitudes. Early primates, such as Teilhardina  migrated across land bridges from Eurasia to North America.

Mangroves and rain forests spread as far north as England and Belgium and as far south as Tasmania and New Zealand.

Turtles, hippo’s, alligators and palm trees graced Ellesmere Island in the Canadian Arctic; tropical algae, Apectodinium, spread northwards as far as the north pole.

As forests became more subtropical some animals adapted by becoming diminutive, fossils of horses the size of a Siamese cat (Hyracotherium Sandrae) have been found. 

Fossilized plant remains and soils show that the Bighorn Basin in Wyoming of 55 mya became a hot, humid subtropical forest, containing trees related to those found today in Panama and large Sequoias, related to those now found in California. The rich humid soils of that time are clearly shown on the exposed hillsides. e.g. below. More here.

Odd-toed ungulates such as horses and rhinoceroses and even-toed ungulates like sheep and antelope also migrated from Laurasia to America. After the onset of the PETM half of all fossils found there are of migrant species.

The struggle for life resulted in evolutionary adaptations that resulted in new mammal species appearing for the first time.

The ancestors of many modern mammals such as hoofed animals (pygmy horses and elk), tapirs, rodents, bats, owls, elephants and early whales also appeared during or shortly after the PETM.

So major were the changes this event generated that it is considered to have heralded a new period in earth’s history, the Eocene or 'Dawn of the New'.

Earth’s climate only cooled as atmospheric CO₂ concentrations fell after 100,000 years.

This period of abrupt warming is known as the Paleocene-Eocene Thermal Maximum (PETM).

Piecing together a jigsaw of research scientists now have evidence for the cause of the PETM’s abrupt increase in temperatures – the rise was both initiated and accompanied by the emission of massive amounts of CO₂ into the atmosphere from under the North Atlantic – together with how and why this event occurred together with the consequences it had for life at that time.

The PETM is CO₂’s smoking gun, a demonstration that atmospheric CO₂ concentrations directly influence the planet’s temperature.

This site is an overview of what is known and how evidence was recovered, based on peer reviewed research papers that have been published in scientific journals. It is divided into eight main sections, it is worth following these in the order they are presented; together they build the bigger picture.

At the bottom of each section I include links to the research papers & other literature I referred to when producing that section (Sources), in particular for sections 3, 4, 5, 6 & 7. This represents just a small amount of the literature.

Where a scientific paper is only available to a journal’s subscribers I put a link to an abstract (summary) so you can read that. One or two are not available, but you could refer to the journal in an academic library. Also included are links to articles from the popular science press, based on a paper’s results etc.

Where possible I have tried to connect links to either full copies or abstracts of the papers below. If links are broken try copying and pasting the title into Google or Google Scholar; that should help you locate an abstract at least. Also please let me know (I'll attempt to re-establish the links) at: climatehistory@googlemail.com

I also include boxed Notes: brief background information to help a general reader more fully understand terms used and provide background; in section three in particular. Also included are web-links to related information on other sites, should you wish to find out more.

The Web is a fluid medium; pages are moved, links become broken, servers go off-line etc. If this is the case, then try copying and pasting the paper’s title into a search engine.

I realise that we do not yet know all there is to know, but I hope to accurately reflect our present state of knowledge. I make no claims for this site other than I believe the information on it to be accurate.

Contribute to this site

If you can usefully contribute to this site please email me. If bringing information to my attention, I need paper / book / article - titles, author, publisher, date etc. A link to a PDF download or a scan of a relevant page is always useful. I prefer to read source material wherever possible. Other material can be sent as a PDF. Some types of files I won’t open due to virus concerns.

Please notify me know of broken URL links and I'll attempt to re-establish them. Possible omissions and corrections are always welcomed and duly considered. See also below.

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