Exam 4
9000 records were broken or tied in this month
July 2011
the prevailing atmospheric conditions at a particular place or region over a given time period
earths climates over the past 4.5 billion years
a substitute
Paleoclimate proxy
the study of natural phenomena (animal, vegtable or mineral) which are climate dependent and which incorporate into their structure a measure of this dependency
Proxy Climate Data
observational data used as surrogates for conditions not directly observable- tree rings, ice cores, fossil pollen, ocean sediments, corals, vertebrate remains
microscopic study of pollen remains, most widely used technique for paleoenvironmental analysis
elements having differing numbers of neutrons, these variations of the same element are called isotopes
Heavier than 16,O
during glacial periods, seawater is enriched in 18,O
16, O
Lighter than 18,O
usually evaporated
during glacial periods, large amounts of precipitated water is held in glaciers
Pleistocene Glaciations
by 2.4 mya, substantial ice sheets had developed across the northern hemisphere
at their maximum extent, 30% of Earths surface was covered by ice
Laurentide Ice Sheet
Over Canada
Cordilleran Ice Sheet
Below Alaska
Late Pleistocene (130-10 ka)
Earliest part is Sangaman Interglacial, the warmest period of the Quaternary, numerous paleosols developed, corresponds to oxygen isotope substage
numerous glacial advances and retreats
The Younger Dryas
Brief cold period 13-11 BP
Rapid cooling (1000years) followed by rapid warming (100years)
possibly caused by disruption of NADW ocean circulation pattern
Holocene Climate Change
Holocene begins 10,000 years ago
Considered an interglacial
Documented climatic oscillations
The Hypsithermal
Mid Holocene period of maximal warmth and dryness
ca 8000 to 4000 yr BP
warmest period of the Holocene, 2-4c warmer than at present
Pollen records provide best evidence
Medieval Warm Period
Roughly 700AD to 1300AD
during this time wine grapes were grown in Europe up to 300 miles north of their present northerly growing limit.
The Little Ice Age
A period of unusual cooling which began immediately following the Medievel Warm Period and lasted nearly until the present time (1300AD to 1900AD)
Reached its peak between 1550 and 1700AD
the average global temperature dropped between 1 and 2 degrees Celsius
Possible Causes for the Little Ice Age
increased volcanic activity
reduction in solar output:Maunder Minimum period of severely reduced sunspot activity
changes in the course of the Gulf Stream
Increase in the reflectivity of incoming solar radiation
The Anthropocene
most recent period in the Earth’s history during which humans have had a significant global impact, particularly on ecology and climate
James Watt’s invention of the steam engine in 1784
Early Anthropocene Hypothesis
William Ruddiman, greenhouse gas emissions began 8000 years before the industrial era when ancient farmers cleared forests to grow crops
Secundum Ruddiman I
beginning 8000 years ago humanss reversed an expected decrease in CO2 by clearing forests in Europe, China, and India for croplands and pasture
beginning 5000 years ago humans reversed an expected decrease in methane (CH4) by diverting water to irrigate rice and by tending large herds of livestock
in the last few thousand years the size of the climate warming caused by these early greenhouse emissions may have grown large enough to prevent a glaciation that climate models predict should have begun in the northeast Canada
Abrupt reversals of the slow CO2 rise caused by deforestation correlate with bubonic plague and other pandemics near AD200-600, 1300-1400 and 1500-1700
high mortality rates caused by the plague led to massive abandonment of farms causing them to regrow lowering CO2 levels
when the farms were reoccupied the forests were cut returning the CO2 to the atmosphere
Climate Forcing
an imposed change of earths energy balance( solar forcing, volcanic forcing, anthropogenic forcing
measured in Wattts per square meter (W/m2)
positive values are associated with temp increase and negative values with temp decrease
Climate sensitivity
a measure of how responsive the temp of the climate system is to a change in the radiative forcing
usually expressed as the temp change associated with a doubling of the concentration of carbon dioxide in earths atmosphere
Climate Response Time
the amoutn of time that it takes for the climate to respond to a climate forcing event
Solar Forcing
the change in the amount of radiation emitted by the Sun
variations have periodic components, the main one being the approximately 11 year solar cycle
Volcanic Forcing
volcanoes can propel enormous amounts of particulate matter high into the atmosphere
these aerosols are transported by strong upper-level, winds around the globe
aerosols reflect a significant amount of the sunlight, which results in a net cooling of earths surface
Mount Pinatubo Eruption, June 1991
Caused global temps to decrease 2.3C over a year
Anthropogenic Forcing
Human-induced effects on climate
Greenhouse gases, particularly carbon dioxide emissions, are the major culprit
Global Dimming
the reduction in incoming solar energy by as much as 10% caused by human induced increases in particulate matter in the atmosphere
Global dimming creates a cooling effect that is offsetting the effect of greenhouse gases on global warming by as much as 50%
Top 5 Greatest Effects of Global Warming
5. Spread of Disease-vector agent that transmits infections
4. Warmer Ocean Temperatures-stronger hurricanes
3. Economic Consequences- intense storms cause damage
2. Increase in frequency of heat waves and droughts
1.Melting of Polar Ice
Red Queen Hypothesis
a species must continually adapt to a dynamic environment or risk extinction
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