Paleoclimatology: Past Climates: Holocene (integrated)

Climate Change in Holocene 

(began approximately 11,700 BP): 

➽ General Characteristics of Holocene

➵ Can be considered an interglacial during the current ice age, when earth is in icehouse stage. 

➵ Due to interglacial, habitable zones in the north extended northwards, general decrease in ice volume, greater moisture in polar regions for participation in global hydrological cycle resulted in disappearance of the steppe-tundra climatic type. 

➵ Climate change is fairly stable during Holocene (On a side note, Glaciers are the most sensitive to climate change, ice core, which are core samples typically from ice sheets, can be obtained from drilling to examine climate change)
➵ During interglacial times, such as at present, drowned coastlines were common, mitigated by isostatic or other emergent motion of some regions (i.e. tectonic uplift)
➵ Primarily consists of two periods: Hypsithermal and Neoglacial period, while some scholars propose a new period called the Anthropocene, of which climate is heavily influenced by human advancement(s)

➽ Specific Periods within Holocene

➵ Holocene Climatic Optimum (HCO) (9000-5000 years BP) was a period of warming that was not uniform throughout the globe. This climatic event was probably a result of predictable changes in the Earth's orbit (Milankovitch cycles) and a continuation of changes that caused the end of the last glacial period

Link: Holocene Climatic Optimum

➵ Medieval Warm Period (950 to 1250) was a time of warm climate in the North Atlantic region that may also have been related to other climate events around the world during that time, including China^[1] and other areas.^[2][3] [4] It was followed by a cooler period in the North Atlantic and elsewhere termed the Little Ice Age. Some refer to the event as the Medieval Climatic Anomaly as this term emphasizes that effects other than temperature were important.^[5][6] Possible causes of the Medieval Warm Period include increased solar activity, decreased volcanic activity, and changes to ocean circulation. 

Link: Medieval Warm Period

➵ Little Ice Age (1300 to 1850) was a period of cooling after Medieval warm period. Several causes have been proposed: cyclical lows in solar radiation, heightened volcanic activity, changes in the ocean circulation, an inherent variability in global climate, or decreases in the human population. 

Link: Little Ice Age

➽ Summary

Climate has been fairly stable over the Holocene. Ice core records show that before the Holocene there was global warming after the end of the last ice age and cooling periods, but climate changes became more regional at the start of the Younger Dryas. During the transition from the last glacial to the Holocene, the Huelmo–Mascardi Cold Reversal in the Southern Hemisphere began before the Younger Dryas, and the maximum warmth flowed south to north from 11,000 to 7,000 years ago. It appears that this was influenced by the residual glacial ice remaining in the Northern Hemisphere until the later date. (note: more for pleistocene since it occurs before the holocene)

The Holocene climatic optimum (HCO) was a period of warming in which the global climate became warmer. However, the warming was probably not uniform across the world. This period of warmth ended about 5,500 years ago with the descent into the Neoglacial. At that time, the climate was not unlike today's, but there was a slightly warmer period from the 10th–14th centuries known as the Medieval Warm Period. This was followed by the Little Ice Age, from the 13th or 14th century to the mid-19th century, which was a period of cooling.

Compared to glacial conditions, habitable zones have expanded northwards, reaching their northernmost point during the HCO. Greater moisture in the polar regions has caused the disappearance of steppe-tundra.

The temporal and spatial extent of Holocene climate change is an area of considerable uncertainty, with radiative forcing recently proposed to be the origin of cycles identified in the North Atlantic region. Climate cyclicity through the Holocene (Bond events) has been observed in or near marine settings and is strongly controlled by glacial input to the North Atlantic.^[16][17]Periodicities of ~2500, ~1500, and ~1000 years are generally observed in the North Atlantic.^[18][19][20] At the same time spectral analyses of the continental record, which is remote from oceanic influence, reveal persistent periodicities of 1000 and 500 years that may correspond to solar activity variations during the Holocene epoch.^[21] A 1500-year cycle corresponding to the North Atlantic oceanic circulation may have had widespread global distribution in the Late Holocene.^[21]

Link: Holocene Climate

Note: In syllabus, it mentions that the Holocene includes the desiccation (i.e. state of extreme dryness) of pluvial lakes. Pluvial lakes were formed by continental glaciers scouring and eroding the surface, which created large depressions which stored water to form lakes. During Holocene (an interglacial), isostatic rebound or post glacial rebound, which is essentially the emergence of land masses previously covered by ice due to the ablation (i.e. removal of ice or snow by melting or evaporation or calving), resulted in the reversal of such depressions and therefore led to the desiccation of such lakes.