Climate Change Exam 2

Green Sahara

"Holocene wet phase" extended period from about 7500BCE-3000BCE (end of the last ice age) Wet and rainy conditions in Northern Africa, monsoon rains the earth's tilt was 24.1 degrees - warmer summers as more solar insolation hit north of the Equator preceded and followed by much drier periods supported a richer biota and human pop. * now a desert *radiocarbon dating culture produce rock art humans survived with large increase in marine life pottery lakes were 10 of meters higher than present moved back to the nile valley when monsoons stopped - due to the change in the Earth's Orbit which affects solar insolation what drives it? = becoming greener cyclically - walker cells influence it - the procession cycles (20 years ) make it cyclical *very powerful As the procession drove the northern hemi towards the sun making it much warmer, ever 20 years another warm period

H and B Events

* higher percentages of the polar species of foraminifera and larger concentrations of ice-rafted debris (rock matter that dropped to the seafloor) are an indication of the presence of colder North Atlantic waters carrying large numbers of icebergs *Such inputs of cold and fresh water may well have altered the density-driven thermohaline circulation patterns of the ocean, and often coincide with indications of global climate fluctuations.

Domestication in Ag

1. gathered preferred wild plant seeds, intentionally planting wild ones, selecting seeds of certain plants with preferred characteristics, gradual evolution of new species with more preference.

Holocene

11.5kya - present

Younger Dryas

12.8kya - 11.5kya

When was Bølling-Allerød interstadial (warm period)

14.5kya -12.8kya

When was OD?

19kya - 14.5kya

What has the rate of sea level rise been since the 1990s? What is the main cause?

2.5-3mm per year. Glacial melting & warming

late glacial maximum

22kya - 19kya

When was the Last Glacial Period

22kya-12kya

ITCZ

A belt of low pressure which circles the earth generally near the equator where the trade winds of the northern and southern hemispheres come together. It is characterised by convective activity which generate often vigorous thunderstorms over large area. Most active over continental land masses.

What is the AMO?

A near-global scale of observed multidecadal climate variability with alternating warm and cool phases over large part of the N. Hemisphere. Influence ITCZ by shifting the mean-> creating variation In the error range of a system because of the overlying factors.

Great plains

A period of severe dust storms that greatly damaged the ecology and ag of the US and Canadiam prairies. was forced by small change is the sst, several years of la nina like conditions in the Pacific and a warm subtropical North atlantic ocean. severe drought and failure to apply dryland farming methods to prevent wind erosion. lasted for 8 years, tens of thousands families abandoned their farms, some were homeless. migration west- largest in american history within a short time period. deep plowing of the topsoil turned into dust meaning less moisture. short term solution used to ogallala aquifer with fossil water

Cariaco Core

Based on the titanium found in the ocean sediments and oxygen isotopes. We use this because there is no bioturbation so each millimeter gives us records.

Heinrich and Bond Events

H Event: a natural phenomenon in which large armadas of icebergs broke off from glaciers and traverse the North Atlantic. B Event: north atlantic climate fluctuations occuring every 1470 (+-500) throughout the holocene H found episodes of unusually abundant ice rafting separated by as little as 7000 years to as much as 12000years. Later discovered by B even shorter terms (2000-3000) variations in 2 incidences.

PDO

Has a spatial distribution similar to ENSO. This Oscillation has patterns persist for intervals ranging from several years to decades. Positive phases: sea surface temperatures are warmer in the tropics along the pacific coast of W. North America. 1972 change from a negative phase of cooling and stability to rapid warming that continues today. The positive phase has been less persistent in the past 20-50 years, yet there is still warming.

Ruddiman Hypothesis

Himalayas rose and sucked up carbon dioxide which caused cooling in the early pleistocene, Early Anthropocene. European Conquest lead to population declines in the new world which led to forests growing back. agriculture influenced the the rise in temps due to rice irrigation farming, burning biomass, tending livestock, and organic waste, plus the methane from cows in the fertile crescent, china, and south american andes.

What caused the Sahel droughts?

Human desertification, global dimming, AMO, SSTS (changing sea surface temperature patterns, and a combo of natural variability superimposed upon anthropogenically force regional drying trend. (increased GHGs, aresols))

Diamonds 5 factors of collapse

Human impacts on the environment the vikings unintentionally cause erosion and deforestation by reckless farming and logging - this deprived them of both food and charcoal Climate Change colder weather Hostile Neighbors Inuit killed the Vikings Friendly Neighbors going relying on trade between motherland but when the seas iced up, ships from norway couldn't travel Dysfunctional political and cultural practices vikings refused to learn from Inuit who knew adaptations to colder weather

Help Remembering PDO

Pacific - so we're seeing activity in the pacific ocean. Specifically along the West Coast of North America & to the West, near Asia.

Medieval Climate Anomaly

Scattered evidence from Europe and high latitudes surrounding the North Atlantic suggests a time of relatively warm climate known as MCA or Medieval warm period (1000 to 1300) large scale warmth - followed by the little ice age Europe experience milder winters, and way drier summers nordic people settled southern greenland along the fringes of the ice sheet and managed to grow wheat heterogenous nature of climate warmer sea surface temperature very warm for the period, but not as warm as today why so hot? large-scale shifts in Northern Hemisphere Atmospheric circulation patterns winter = positive NAO sumer = reduced westerlies and anomalous advection from North Africa natural radiative forcing associated with volcanic activity relatively high solar output stronger mid latitude westerlies in winter

Region and Phenomenon tells us that El Nino only got "serious" again 5000 years ago?

The Atacama Desert. River flows carried sediment during MegaNinos. These seds were deposited along cutbanks in rivers. The higher energy seds are below the lower energy seds. A set of seds that goes from high to low energy is all from one MegaNino. this is because the MegaNino resulted in high energy river flow, and eventually, as it slowed down, the amount & size of sed the rivers could carry got smaller. Therefore you have large seds below small seds. :)

The Great Famine

The population explosion during the MCA caused this famine to be so significant. Population boomed during the MCA because previous, unfarmable land could now produce. Vineyards were 200-500 km north of their current limits The population pushed the agricultural sector to its limits. Only the maximum agricultural yield could feed everyone. Then, shit hit the fan in form of bad weather. Northern & Western Europe from 1315-1322 Torrential rains started around 1315, causing a shortage of food, hay, and salt. Lots. of. flooding. Continued the following year, these were unseen amounts of rains that went into winter, which would make us think it's a NAO+ Some people think that a volcanic eruption during the same time period may have also caused some of it, but at this point, there isn't concrete evidence of that eruption being large enough to do so. Most likely just the climate shifting from MCA to LIA. Destroyed the population (10-15% death in some areas). Guess what happened next? The black plague about 30 years later. This intense climate shift setback Europe for centuries to comes.

NAO

a fluctuation in atmospheric pressure between a subpolar low- pressure center near Iceland and a high pressure center in the Azores-Gibraltar region. as a result, the subtropical atlantic ocean is warmer in a large region extending from the mid-atlantic and southeast coast of the US eastward to the Azores Islands. largely atmospheric mode * very active form november to april - affecting wind speed and wind direction changes, changes in temperature in the North Atlantic region

holocence

a geological epoch beginning at the end of the pleistocence. climate has been fairly stable. large fauna have gone extinct due to human causes

4.2 Event

a phase on intense aridity - droughts regarded as one of the most severe climatic changes in the holocene exceeded to the plains of northwestern India evidence the kilimanjaro ice sheet, and Andean glacier -associated with the collapse of the Akkadian Imperial 2300 BC - invader plus drought archaeological documents widespread abandonment of the agricultural plains of northern Mesopotamia and dramatic influxes of refugees in the south

Refugia "Hideaway"

a place where species can exist during the ice ages in a refuge and then expand as the glaciers melt - since the plesitocene - southern alps contraction towards the tropics and expansion due to climatic changes, human activity (deforestation, over hunting) LGM refugia were places where people survived during the last glacial period in the N hemisphere around 20-25000 years ago.

Climate stabilization Wedge

an approach produced by Princeton University researchers.[1] looking at Climate change mitigation scenarios. The goal of the approach, Stephen Pacala and Robert H. Socolow, is to demonstrate that global warming is a problem which can be attacked using today's commercially available technologies to reduce CO2 emissions. The objective is to stabilize CO2 concentrations under 500ppm for the next fifty years, using wedges from a variety of different strategies which fit into the stabilization triangle. A new estimate[2] by the original authors indicates that nine wedges are now necessary, as emissions have continued to rise since the original paper on which the wedges was based was published.

Speleothems

are mineral deposits formed from groundwater within underground caverns. stalactites are pointed pendants hanging from the cave ceiling stalagmites are the "ground up" counterparts of stalactites *blunt mounds are rich archive of terrestrial climate information strength is age dating most commonly used methods are Uraniun-series dating then radiocarbon dating 14C show annual lamina which can be counted similar to tree rings carry greater uncertainty the sediments and tree rings our limited understanding of the true sensitivity of measured parametters (O18, C13) to climatic variables studies have focused on centennial- millennial scale climate variability

Ilopango Eruption

around 1,500 years ago ( AD. 535-536 ) in El Savador * now a lake * rated 6.9 on the scale caused extreme climate cooling and crop failure - ice core evidence for time period - radiocarbon dating of plant life was recorded by the Roman and Chinesse would have killed more than 100,000 people and displaced another 400,000 ash dust in the air for more than a year one of the largest in 10,000 years would explain the episode in Mayan history known as the Classic Period Hiatus, when the Maya stopped building stelae, decorative columns

8.2 Event

big flood, is colder but the earth is warming up. Following the end of the last glacial period about 11,500 years ago, the Earth's climate system began to look and behave more like it does today. The large continental ice sheets shrank, sea level rose, temperatures ameliorated, monsoons grew in strength. Around 8,200 years ago, however, a surprising event occurred. 4-8 degrees drop lasting 200 years CO2 decline of 25 ppm over 300 years aridification and cooling episode, which provided the natural force for Mesopotamian irrigation agriculture and surplus production sea level about .5 m sea rise

Chaco and the Anasazi "the ancient people"

chaco canyon host the densest and most exceptional concentration of pueblos in the American Southwest *New Mexico to Colorado "four corner area" * ancient ruins ancient pueblo pop "Anasazi" by 850 had rapidly expanded in the area tourquoise evidence drought beginning in 1130 lasted for 50 years = abandonment depended mostly on snow for their water sources agriculture in the spring wind and water erosion was an issue *Topsoil warfare due to stress of the environment they contributed a lot to the deforestation of the vast region

Paleoclimate Drought Atlas

dendro studies have been put together as an atlas to produce a climate for a whole region

Easterly Wave

driven by the pressure gradient force and coriolis the system that forms within the easterlies (trade winds) coming off of africa towards central america - where those easterlies increases in pressure into the subtropical high - hot areas of water squeeze together the isobars = parallel winds moving faster together then they converge - they go up and that lowers the pressure and lowers the temperature and creates more condensation = more latent heat energy is released = which causes air to rise more = more clouds the winds turning to the right creating these waves of rainfall over the ocean hurricanes if you have an area of hot water = AMO? a buildup of heat - low cloud cover, more absorption

Major Drivers of tropical climate

easterlies winds convection cycles MCCs

Atacama Deserts

el niño events from sediments evidence. el nino only starts *5000 years ago - holocene started to cool off - in the association with the seesaw of ENSO la ninas farther inward sediments

Clusters

elements the size of 10 or so km across with multiple elements together, 3/4/5/6 elements working together- rising off the same perfect surface condition, lot of convection occurring

Holocene temperature variations

from 8-6.5, 5.8-5.6, and 5-4.6 temp variations have been above the line. The lowest dip point was 500 years ago.

Greenland Norse

in 980s, the vikings took advantage of ice-free seas to colonize areas in Greenland and other outlying lands of the far north *evidence for the Medieval Warm Period raised cattle and sheep lasted for about 500 years 3000 to 5000 people why did they disappear from the area? - left in a hurry - left behind many important things cooling climate ice core evidence overgrazing decline in trade relationships emigration

MJO-Madden Julian Oscillation

is the largest element of the intraseasonal (30-90 day) variability in the tropical atmosphere, a not a seasonal pattern Rather than being a standing pattern like the El Niño Southern Oscillation (ENSO), the MJO is a traveling pattern that propagates eastward This overall circulation pattern manifests itself in various ways, most clearly as anomalous rainfall. The wet phase of enhanced convection and precipitation is followed by a dry phase where thunderstorm activity is suppressed. In the Pacific, strong MJO activity is often observed 6 - 12 months prior to the onset of an El Niño episode, but is virtually absent during the maxima of some El Niño episodes, while MJO activity is typically greater during a La Niña episode. Strong events in the Madden-Julian oscillation over a series of months in the western Pacific can speed the development of an El Niño or La Niña but usually do not in themselves lead to the onset of a warm or cold ENSO event.

Solar Cycles

is the periodic change in the Sun's activity (cycles average duration is about 11 years) levels of solar radiation and ejection of solar material appearance in changes in the number of sunspots, flares * Maunder Minimum Sunspots are cooler than the rest of the Sun, but many scientists think that when there are a lot of sunspots, the Sun actually gets hotter. This affects the weather here on Earth, and also radio reception. Without sunspots the Earth would probably be cooler. In the same way, if there were too many sunspots most of the radiation emitted from the Sun streams out from its polar regions and from bright rings surrounding the sunspots. During years when sunspots are abundant the amount of radiation emitted in solar flares is at a maximum -as a result the amount of solar radiation arriving at Earth during sunspot maxima is at a maximum rather than a minimum changes the amount of irradiation from the Sun

Dendrochronology & Kevin Anchukatis

is the scientific method of dating based on the analysis of patterns of tree rings, also known as growth rings *critical proxy can date the time at which tree rings are formed. it is possible to date back thousands of years chronologies can be built up by you sames trees in locale area one ring generally marks the passage of one year in the life of the tree the inner portion of the growth ring is formed early in the growing season (less dense) the outer portion is the "late wood" often produced in the summer more dense adequate moisture and a long growing season result in a wide right drought year may result in a very narrow one the rings are more visible in temperate zones where the seasons differ more how to use tree ring proxies? - use trees that will be affect on extreme conditions = slopes= because they dry out - drought atlases don't use tropical forrest trees know trees, some trees might only show results for certain season. Stressed trees are best for tree ring analysis. account for tree type - some have missing rings oak and elm trees rarely have missing rings can be used as a calibration and check of radiocarbon dating

Paleotempestology

is the study of past tropical cyclone activity by means of geological proxies as well as historical documentary records. recreating past hurricanes (geological and archival techniques) proxies include overwash deposits preserved in the sediments of coastal lakes and marshes, microfossils such as foraminifera, pollen, diatoms, dinoflagellates,phytoliths contained in coastal sediments, wave-generated or flood-generated sedimentary structures or deposits (called tempestites) in marine or lagoonal sediments, storm wave deposited coral shingle, shell, sand and shell and pure sand shore parallel ridges. *Speleothems and tree rings offer higher resolution records of long term tropical cyclones problem with dates because the error is 100 to 150 years radiocarbon dating problem with erosion flood plain tsunami (hard to differentiate) hurricanes are correlated with dead woods = fire can this tell us something about the fire return?

Mayan Drought

near the year 860, a sudden collapse of the mayan civilization on the Yucatan peninsula occurred. Lake sediments indicated that the worst part of this dislocation occurred during an interval drought and tree wings. (200 year drought AD800-100) associated with cold weather in N. Hemisphere. volcanic activity associated, excessive warfare, foreign invasion, peasant revolt, less trade, ag issues

Little Ice Age

occurred after the Medieval Warm Period - lasting from 1350-1850 cyclical lows in solar radiation heightened volcanic activity change in ocean circulation decreases in human population largely independent regional climate changes Northern Hemisphere cooling of less than 1 degrees c. difference Europe and North America - winter of 1794-95 was particularly harsh farms and villages in the Swiss Alps were destroyed by encroaching glaciers large amount of evidence from people documenting the encroachment canals and rivers in Great Britain and Netherlands were frozen deeply Freezing of the Golden Horn Norse Colonies in Greenland starved and vanished by early 15th century *Jared Diamond noted they had exceeded the agricultural carrying capacity before then textbook talked a lot about lichen evidence of the LIA, Lichen is a primitive moss-like for of vegetation grew on the Canadian Arctic region in halos dead halos were discovered as part of the LIA mostly likely buried beneath snowfields that completely blocked sunlight meaning that warm enough summers weren't happening to melt the snow radiocarbon dating shows that they Lichen started growing right before LIA evidence from ice cores and dust concentrations

ENSO- El Niño Southern Oscillation

refers to the effects of a band of sea surface temperature which are anomalously warm or cold for long periods of time that develops off the western coast of South America and cause climatic changes across the tropics and subtropics. The two variations are coupled: the warm oceanic phase, El Niño, accompanies high air surface pressure in the western Pacific, while the cold phase, La Niña, accompanies low air surface pressure in the western Pacific.

Drivers towards the change in climate

solar variation, variability of absorption, albedo of atmosphere, land and water distribution, THC

Late Victorian Holocaust

strong el nino = south india drier = causing mass famine = became a crisis for the british empire

Sea level rising

the most likely effect of sea level change on climate is linked to the very different thermal responses of land and water ice sheet melting and thermal expansion of sea water since the 1990s the rate of rise has accelerated to 2.5 -3mm/year. 1900s average of 1.7mm/year. glacier melt accounts for 5cm of the rise during the last century. Today, the Antarctic ice sheets hold the equiv of almost 60 meters of global sea level. land=low heat capacity water=high heat capacity

Maunder Minimum "Global Weirding"

the period between 1645-1715 when very few sunspots were observed the Maunder Minimum coincided in time with an era of colder weather, and that by implication the absence of magnetic activity was accompanied by a net fall in the total radiative output of the Sun. solar output might have been .25-.4 % weaker than today variation in the last 2 decades has been about .11% sunspot activity was concentrated in the southern hemisphere of the Sun coincides with the middle part of the Little Ice Age

Sahel

the region between savannah grassland and sahara desert. rainfall is concentrated in a very small period of the year. less that 100mm/year between a few weeks to 2 months. it experiences frequent droughts that have been thought to have increased since the late 19th century.

Drought Proxies

tree rings lake and dune sediments (pollen which reflect vegetation) records (diaries etc.) archeological remains

MCCs

usually the largest kind of system in tropics- systems maybe 50-100 km across- may pass for several hours at a time- a whole regional development of convection- Mesoscale convective complex

Tropical weather systems/drivers

· Convection at ITCZ- heats rising, creating constant cloud area, convection (hot towers) o Single elements- 1 tropical storm- thunderstorm, cumulonimbus clouds, hot towers (like ITCZ), developing throughout the day o Clusters-elements the size of 10 or so km across with multiple elements together, 3/4/5/6 elements working together- rising off the same perfect surface condition, lot of convection occurring o MCCs- usually the largest kind of system in tropics- systems maybe 50-100 km across- may pass for several hours at a time- a whole regional development of convection- Mesoscale convective complex