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Climate Change Over the Last 200 Years (Part 2).docx

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Department
Life Sciences
Course
LIFESCI 2H03
Professor
Luc Bernier
Semester
Winter

Description
Climate Change Over the Last 200 Years (Part 2) Pacific Decadal Oscillation: - Reversal in Pacific Ocean temperatures o Positive “warm” phase (name based off of the temperatures of American water) o Negative “cool” phase (name based off of the temperatures of American water)  This is associated with winter conditions over the great lakes A Probable Cause of the Little Ice Age? - Could be related to long-term changes in the North Atlantic Oscillation (NAO) o Wet and warm conditions are seen on the coast on N.A. when it is positive and vice versa when it is in the negative phase Modern Climate Change: - Only anthropogenic forcing of climate can explain recent anomalous large- scale warming in the late 20 century o Could be due to the amount of aerosols in the atmosphere Natural Variations: - Changes that occur over long timescales cannot explain current warming - All natural scales show us that the earth should be cooling o The contribution that the collision of India and the rest of Asia has is 0.00001 degrees Celsius of cooling per century o About 0.016 degrees Celsius of cooling per century, is due to the orbital-scales Solar Radiation and Sunspots: - Because of short duration means cooling and warming of <0.1 degree Celsius in Earth’s mean temperature o We can see that the correlation between the amount of solar radiation received and the amount of sunspots is high!  Changes of 0.15% in solar irradiance during cycle (11-year cycle)  Could explain ~0.07 degree Celsius of the warming El Nino and Southern Oscillation: - Short length of some records leaves possibly that natural oscillations in climate could have contributed to some of the observed trends - ENSO: the most prominent short-term oscillation o The highest temperatures are associated with El Nino years o Decrease in sea level pressure o Precipitation decreases over Northern Australia Pacific Decadal Oscillation (PDO) - Similar distribution of ENSO but can last for decades o This cycles about every 15 years o The trends are not as strong since the 1980s - Prominent change from cool to warm in the mid-1970s - Record too short to determine role of current trend North Atlantic Oscillation (NAO) - Fluctuation in atmosphere pressure between two pressure centers o Warmer and wetter Europe in the positive phase - Has varied in strength over decadal scales, more positive in the early 1900s and 1990s but negative during the 1950s El Nino and Volcanic Eruptions - El Nino sea surface warms by 2-5 degrees Celsius o 0.1 – 0.2 degree Celsius of the global warming could be due to El Nino - Eruption a function of sulfur content in emissions o 0.1-0.3 degree Celsius of the global cooling could be due to eruptio
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