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Lecture 22.docx

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John Stinchcombe

BIO220: Lecture 22: Greenhouse gases and climate change April 2, 2013  Earth has sthn many changes in climate, accompanied by drastic shifts in biota  Entered 5 major ‘ice age’ about 2.58 MYA  Since then, cycling between more and less ice (we’re supposed to be in a cooling phase)  The climate of the earth is cycled dynamically over history. These climate changes are dramatic  ice core data An ice age has alternating glaciai and interglacial periods  By reconstructing the isotoype ratios of gaps in frozen lakes, one can reconstruct what the past climate was.  All of them are separate cores. The vertical access is temperature (the change from a baseline) and you can see periodic warm bits and periodic cold bits What’s next?  But the short term prediction is very different, due to human activity  And how these long term natural scuycles interact with human processes that will change short term interactions Four pioneers of climate prediction  Tyndall: o Measured different gases absorbed radiation o How they absorbed and what happened to temperature o He discussed the greenhouse effect of water vapour o And how lots of water vapour as capble of absorbing radiation that raises average temperature o (Late 1800s- 1900s)  Arrhenius calculated overall effects of CO2 as a greenhouse gas o His projection at that time was doubling atmospheric [co2] should cause global temperature to increase 4C o Thought that they were due to fluctuations o Predicted coal burning was fending off the next ice age o At time this was rejected in favour of Milankovich cycles but now both are thought to be important o A lot of the newer models confirm his 4C  Bjerknes o Wrote the primitive equations for a model of weather including air movements, temperature and water content o Six coupled differential equations calculations overwhelmingly! o Can include radiation moving out, latitude, longitude o These equations at the time were impossible to solve  Richardson o Too k equations to calculate the first numerical weather prediction o So had the idea of how it could work. The technology wasn’t enough to make predictions yet EINAC’s breakthrough prediction, 1950, predicted 2 hours of weather in 24 hours. From weather to climate:  Can’t predict local weather far in advance because of its chaotic nature (and estimation/computing limitations)  But climate= statistics of weather, which is in fact predictable  But if you take a step back and think we’re not trying to predict the weather in April vs. April 3. (so when you aggregate things, averages, SD’s and son , it’s possible to make predictions)  So climate is the aggregations of statistics of weather  We can use our current knowledge, go back in time and make predictions to current time and compare to historical records Intergovernmental Panel on Climate Change:  This was happening by biologists, statisticians, and earth scientists, physicists. This was all happening somewhat independently  So government decides whose prediction is right?  Needed somewhere to synthesize this so the IPCC established. A group of scientists who go through all the literature on this and arrive t a consensus view  The very nature of it was to avert ‘alarmist’ projections by independent scientists o Designed to smooth out extremes of nothing was going to happen o You can think that as the international panel of climate change becomes more and more forceful, then evidence behind statements are that much stronger  THE IPCC doesn’t do its own research. It reads and says what the story is from the data. They don’t make policy recommendations. They just present the data  The 4 assessment in 2007 th  The 5 assessment in 2014  The IPCC (inc. Bob Jefferies) shared 2007 Nobel Peace Prize The basics of the Greenhouse Effect:  Incoming radiation from the sun, this is the source of all energy an d life on earth. About half of this is absorbed by Earth.. Some other fractions is reflected by atmosphere and into space. The earth is emitting heat and radiation into space (not just from human activities, but natural biological processes) . The thickness of the atmosphere (the amount of CO2, water, methane) is going to effect how efficiently radiation is leaving and coming in.  There are two effects: the albedo and greenhouse effect  The greenhouse effect: will warm the earth  Albedo: patterns of reflectance that will reflect heat back into space Albedo= reflectivity important to earth’s energy balance:  Fresh snow, reflects a lot of energy back into space  Open water, not very much. It absorbs heat and has a tremendous capacity in absorbing heat  The amount of greenhouse gases is going to determine how much heat is trapped in the atmosphere  Features of earth’s atmosphere is going to determine how much is going to reflect back out into space Charles Keeling: measured [CO2] at Mauna Loa, Hawaii  Periodic cycle of CO2 goes up and down in April – October. In N. hemisphere is that it’s at its growing season. So all the greening will happen in spring. Itll help lower it temporarily the global concentration of CO2 in atmosphere. Then frost in winter, not really any photosynthetic plants to take CO2 out.  Keeling first interested in annual cycle, but soon perceived upward trend  In early years, he thought it was measurement error (so he ignored upward trend) But then he compiled it all together. The red is the individual cycles where blue is the average Increases in Co2 concentration at different sites worldwide:  Really unlikely that Co2 concentration in Hawaii is going to go up while Alaska, American Samoa, South pole are unlikely to be. So effect will spre
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