What is the Paleocene-Eocene Thermal Maximum? Describe this event including when it occurred and state the evidence.

The Paleocene-Eocene Thermal Maximum (PETM), alternatively "Eocene thermal maximum 1" (ETM1), and historically referred to as the "Initial Eocene" or "Late Paleocene Thermal Maximum" was a period of time with a global average temperature increase during the occurrence of more than 5-8 °C. This temperature occurrence occurred at the boundaries between the geological epochs of the Paleocene and Eocene. It is unclear about the precise age and period of the occurrence, but it is estimated that it happened about 55.5 million years ago. It has been estimated that the resulting duration of major carbon emission into the atmosphere has extended from 20,000 to 50,000 years. For about 200,000 years, the entire warm period continued. Increased global temperatures by 5-8 °C. Vulcanism and uplift associated with the North Atlantic Igneous Province have been associated with the beginning of the Paleocene-Eocene Thermal Maximum, causing extreme changes in the carbon cycle of the Earth and a major increase in temperature. The era is characterized by a major negative excursion from across the globe of carbon stable isotope (δ13C) records; more precisely, the 13C/12C ratio of marine and terrestrial carbonates and organic carbon has decreased dramatically. Paired results from δ13C, δ11B, and δ18O show that ~12000 Gt of carbon (at least 44000 Gt of CO2e) was emitted over 50,000 years, with an annual average of 0.24 Gt. Numerous other changes are uncovered by stratigraphic parts of rock from this time. Fossil data indicate large turnovers for many species. In the aquatic realm, for example, during the early stages of PETM, mass extinction of benthic foraminifera, worldwide proliferation of subtropical dinoflagellates, and the emergence of excursion, planktic foraminifera, and calcareous nanofossils occurred. Modern mammalian orders (including primates) are suddenly emerging on land in Europe and North America. On many outcrops and in many drill cores covering this time period, sediment deposition shifted dramatically. The Paleocene-Eocene Thermal Limit has been researched as an analogue in geoscience since at least 1997 to explain the consequences of global warming and significant ocean and atmospheric carbon inputs, including ocean acidification. Today humans emit about 10 Gt of carbon (about 37 Gt of CO2e) each year and at that point, they would have emitted a similar amount in about 1,000 years. A big contrast is that the earth remained ice-free during the Paleocene-Eocene Thermal Maximum, when the Drake passage had not yet opened and the Central American Seaway had not yet locked. Although PETM is now generally considered to be a "case study" for global warming and major carbon emissions, the event's cause, specifics, and ultimate importance remain unknown. During the early Paleogene, the arrangement of seas and continents was very different compared to the present day. North America and South America were not yet bound by the Panama Isthmus, and this permitted direct low-latitude circulation between the Pacific and Atlantic Oceans. The Drake Passage, which now divides South America and the Antarctic, was closed, which may have prevented the Antarctic from being thermally separated. Also the Arctic was more limited. While different proxies do not agree on absolute terms for past atmospheric CO2 levels in the Eocene, both indicate that levels were far higher then than at present. In either case, during this period, there were no major ice sheets. "Early Eocene Climatic Optimum "Early Eocene Climate Maximum (EECO). At least two (and perhaps more) "hyperthermal" were superimposed on the long-term, incremental warming. This can be described as geologically brief events marked by rapid global warming, significant environmental changes, and massive carbon addition (<200,000 years). PETM was the most serious of these, and perhaps the first (at least within the Cenozoic). Clearly, another hyperthermal occurred at about 53.7 Ma, and is now called ETM-22 (also referred to as H-1, or the Elmo event). Additional hyperthermal, though are likely to occur at about 53.6 Ma (H-2), 53.3 (I-1), 53.2 (I-2) and 52.8 Ma (informally called K, X or ETM-3). The number, nomenclature, absolute ages, and relative global effect of the hyperthermal eocene is the subject of considerable research at present. If they arose only during long-term warming and whether they are causally linked to seemingly identical phenomena in older geological record periods (e.g. the Jurassic's Toarcian turnover) are open problems. Spatial differences in carbonate dissolution can be explained by acidification of deep oceans, and later expansion from the North Atlantic. Model simulations show acidic water deposition at the start of the occurrence in the deep North Atlantic. Evidence for global warming. Normal global temperatures rose by about 6 °C (11 °F) within about 20,000 years at the start of the PETM. This warming was superimposed on early Paleogene "long-term" warming, which is based on many lines of evidence. In the δ18O of foraminifera shells, including those made in surface water and deep ocean water, there is a conspicuous (>1 ? ) negative excursion. Since in the early Paleogene, there was a scarcity of continental ice, the change in δ18O is most likely to indicate an increase in ocean temperature. Analyses of fossil assemblages, the Mg/Ca ratios of foraminifera, and the ratios of some organic compounds, such as TEX86, also help the temperature increase. During the PETM, exact constraints on the global increase in temperature and whether this varied substantially with latitude remain open issues. Measurements for reconstruction of past temperature are widely used for oxygen isotopes and Mg/Ca of carbonate shells precipitated in ocean surface waters; however these paleotemperature proxies can be undermined at low latitude sites, because re-crystallization of carbonate on the seafloor makes lower values than when formed. In the other hand, because of seasonality, these and other temperature proxies (e.g., TEX86) are affected at high latitudes; that is, the "temperature recorder" is skewed towards summer, and thus higher values when carbonate and organic carbon production occurred. Certainly, before after and during the PETM, the central Arctic Ocean was ice-free. This can be ascertained at 87 ° N on Lomonosov Ridge from the composition of sediment cores collected during the Arctic Coring Expedition (ACEX). In addition, as demonstrated by the brief presence of subtropical dinoflagellates and a marked rise in TEX86, temperatures rose during the PETM. However the above record is intriguing because it indicates an increase of 6 C (11 °F) during the PETM from ~17 °C (63 °F) before the PETM to ~23 °C (73 °F). Assuming that the TEX86 record represents summer weather, comparison to the present day it nevertheless suggests much colder temperatures on the North Pole, but no big latitudinal amplification relative to the current period. The above considerations are important because by ice-albedo feedback, high latitude temperatures rise even further at the poles in certain global warming models. However, it may be the case that this feedback was mostly absent during the PETM due to minimal polar ice, so temperatures on the Equator and at the poles rise accordingly. Evidence for carbon addition. Two findings offer compelling support for the massive inclusion of 13C-depleted carbon at the start of the PETM. First a major negative excursion from a variety of environments in the carbon isotope composition (δ13C) of carbon-bearing phases characterizes the PETM in various (>130) extensive locations. Second, in parts of the deep sea, carbonate dissolution marks the PETM. The basis of discussion remains the cumulative mass of carbon pumped into the ocean and atmosphere since the PETM. In principle, the volume of carbonate dissolution on the seafloor, or preferably, both, can be determined from the magnitude of the negative carbon isotope excursion (CIE). The δ13C change across the PETM, however, depends on the position and the studied carbon-bearing process. It is around 2% (per mil) in some bulk carbonate records; it reaches 6 %in some records of terrestrial carbonate or organic matter. The breakdown of carbonate often ranges across numerous ocean basins. In parts of the north and central Atlantic Ocean, it was extreme, but much less pronounced in the Pacific Ocean. Estimates of the inclusion of carbon vary from around 2000 to 7000 gigatons, depending on available knowledge.