ATMO 336 1st EditionExam # 4 Study Guide Lectures: 1 - 12Lecture 1 - Climate model forecasts= simulate earth’s climate changes including changes due to increased greenhouse gas concentrations. Do not make accurate predictions. Fail to repoduce temporal (time) and spatial (position) variability.Reproduce short term and natural fluctuations in climate due to historic events (i.e. volcanic eruption). o The observed changes in climates at the scale of a regional climate zone has notbeen reproduced by any climate modelo Increasing greenhouse gases= slows down rate earth emits IR radiation to space (as long as energy in exceeds energy out, planet warms= surface temp warms) as earth temp warms, it emits more radiation, and warming contintues until energy out equals the energy inputo Earths surface= 70% covered by oceans. Oceans have high thermal interial so warming of ocean is slow (because water has high specific heat, and addition ofheat must be abe to mix through the entire depth of ocean). As a result, there is a delay in temperature increase which is induced by oceans.- Model predictions of temp for 21st centuryo Even if all concentrations of greenhouse gases are kept constant to 2000 levels, warming of about 1degree C would still be expected due to ocean delayo Most climate models predicted far too much warming in global average surface temp. this is because there was a lack of warming since 2002 due to natural variability, energy or heat is being currently stored in deep oceans, or the models are wrong; real climate is not as sensitive to changes in CO2 (may be dominated by positive feedbackso Currently, IPC predicts warming of .3-4.8 degrees C in average temp for the last two decades of this centure (2081-2100) relative to average temp for 1985-2005o Information on IPCC reports regard: total # of frost days, intra annual extreme temp range (difference between highest and lowest temps in a year), growingseason length, heat wave duration index, warmth of daily lows, wet days, dry days, wet stretches, and average daily precipitation intensity. IPCC predicts it is very likely to have increase in extreme precipitation events over most mid-latitude land masses as well as wet tropical arLectuer 2- Climates were not the same as they were todayo Glaciers currently cover 10% of earths surface, if melted, sea level will rise 213 feeto Proxy records= records of past climate that are not based on direct measurments, include archaoloical info about past human civilizations, written accounds, and environmental indicators. Shows decent reconstruction of medieval time and back a few thousand years)- The Pleistoceneo Before= global climate much warmer than now (no ice in polar regions) until glaciation period interrupted this o Pleistocene was the most recent glaciation period where glaciers advanced andretreated over north America and Europe. This was the most important environmental event that happened since human species been on earth (20 interglacial/glacial cycles recorded). Glaciers never met the tropics (tropics still warm), bering shelf exposed where humans crossed over into north America. Reached its max when two large ice sheets were in northern hemisphere (laurentide ice sheet in easter North America, Scandinavian ice sheet in northern Europe) and sea level dropped by 85 meterso We are currently in an interglacial period (holocene epoch). Peaks of glaciates occure every 100,000 yearso Evidence sugguests that temperature causes carbondioxide and methane concentrations to change (not the other way around) discovered using ice cores. This is because as oceans warm, they cant hold as many dissolved gases, and therefore release CO2 and methane into the atmosphereo Paleoclimate perspective= cimate change is normal and part of the earths natural variability related to interactions among the atmosphere, ocean, and land, as well as changes in the amount of solar radiation reaching earth- Variations in earths orbital patterns:o Eccentricity= variations in shape of the orbit from less elliptical to more elliptical (period of about 100,000 yrs) The more elliptical, the larger the difference in solar radiation between farthest and closest approach of the sun Varies between circular to 6% elliptical (currently 1.7%) This has nothing to do with the year to year seasonal changeso Obliquity= changes in tilt of earths axis (period of 41,000 years) When the orbit is more vertical compared to the plane of the earths orbit, seasonal variations in incoming sunlight are less Ranges from 22.0 degrees- 24.5 degrees (we are currently 23.5 degrees)o Precession= slow turning, or wobbling of earths axis Currently the earths axis points towards the north star (changes over time) Completes cycle in 23,000 years Combined with eccentricity of orbit, cause northern hemisphere and southern hemisphere to experience greater seasonal changes Currently we are closest to sun during northern hemisphere winters, leading to slightly milder winter and summers but harsher winters and summers in southern hemisphere.Lecture 3- Observed temperatures since 1850o More urban areas= influence idea of heat island effect= building materials and human activity create more warms in a particular locationo Estimates state that temp has risen 5 degrees C since 1850 o Large warming that occurred from 1910-1940 (warming too rapid and hard to explain with little greenhouse gas inputs= natural change in global average temp)o Cooling trend from 1940-1970 (cooling even though greenhouse gas concentrations were increasing= natural fluctuations were larger influence than greenhouse gases)o Global average temp has not increased since 2002o Concentrations of CO2 higher now than any other time in US historyo Researchers say we will have period of cooling due to recent low solar activityLecture 4- Strongest influencing factor on climate= yearly variation in amount of solar energy received from sun (varies with latitude and seasonal changes). Small seasonal changes at lower latitudes and stronger at higher latitudes.- Largest seasonal changes @ poles- Elliptic plane= trace of the path that earth orbits the sun- Axis of rotation= imaginary line which extends through the earth’s north and south poles. Current xis is 23.5 degrees away from perpendicular. Seasons occur because axisof rotation is not perpendicular to elliptic plane since this causes the distribution of solar energy around the globe to change during the yearo