[2] Based on the magnetic susceptibility of Miocene sedimentary stratigraphic sequences in the Huatugou section in the Qaidam Basin, the MMCO lasted from 17.5 to 14.5 Ma; rocks deposited during this interval have a high magnetic susceptibility due to the production of superparamagnetic and single domain magnetite amidst the warm and humid conditions at the time that defines the MMCO.
[7] During orbital eccentricity maxima, which corresponded to warm phases, the ocean's lysocline shoaled[clarification needed] by approximately 500 metres.
[10] Central Europe's annual precipitation range was 1050–1600 mm, based on data from Hevlín Quarry in the Czech Republic.
[12] Dense, humid rainforests covered much of France, Switzerland, and northern Germany, while southern and central Spain were arid and contained open environments.
[21] Northern South America developed increased seasonality in its precipitation patterns as a consequence of the ITCZ's northward migration during the MMCO.
[23] The Cape Peninsula in South Africa was significantly warmer than today, and its environment fluctuated between open riparian forest and swampland.
[31] The global warmth of the MMCO resulted from its elevated atmospheric carbon dioxide concentrations relative to the rest of the Neogene.
[36] The activity of the Columbia River Basalt Group (CRBG), a large igneous province in the northwestern United States that emitted 95% of its contents between 16.7 and 15.9 Ma, is believed to be the dominant geological event responsible for the MMCO.
Carbon dioxide was released both directly from volcanic activity as well as by cryptic degassing from intrusive magmatic sills that liberated the greenhouse gas from existing sediments.
[39] Albedo decrease from the reduction in Earth's surface area covered by deserts and the expansion of forests was an important positive feedback enhancing the warmth of the MMCO.
[18] Terrestrial mammals in the tectonically active region of western North America experienced a surge in species originations.
[57] The genus Procervulus was able to diversify its dietary habits as a result of the MMCO's effects on vegetation and ecosystem structure in Europe.
[59] The MMCO may have favoured the spread of pongines into Asia by creating continuous stretches of subtropical forest that enabled the migration of these apes from Africa into Eurasia.
[65] In Africa, rapid speciation in Bicyclus representing the continent's largest radiation of satyrine butterflies occurred amidst the climatic changes of the MMCO.
[66] The MMCO's temperature estimates of 3–4 °C above the preindustrial mean are similar to those projected in the future by mid-range forecasts of anthropogenic global warming conducted by the Intergovernmental Panel on Climate Change (IPCC).
[1] Arguably, it is the best of all possible analogues; the pCO2 of the cooler Pliocene has already been exceeded, while the warmer Eocene had global temperatures and carbon dioxide levels so high that reaching them would require scenarios that are no longer considered realistic or likely to occur.