Earths Climate System Dr. R. M. MacKay. Natural and Anthropogenic Climate Forcing

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Earths Climate System Dr. R. M. MacKay Slide 2 Slide 3 Slide 4 Natural and Anthropogenic Climate Forcing Slide 5 Slide 6 Slide 7 Slide 8 Slide 9 Slide 10 Slide 11 Carbon Dioxide in Prehistoric times Slide 12 Slide 13 Plate tectonics can remove CO2 from the atmosphere Slide 14 Slide 15 Milankovitch Theory of Ice Age Cycles Past 1,000,000 years Changes in Earths orbit about the sun results in changes in High latitude NH summer sunlight. When summer sunlight is low ice sheets can slowly grow from year to year. Orbital factors include: Changes in Earth axial tilt (now 23.5 degrees) Changes in the eccentricity of Earths orbit. And the precession of perihelion. Slide 16 Earths Axial Tilt No Tilt no seasons Extreme tilt extreme seasons Slide 17 Orbital Eccentricity Slide 18 What does Precession of perihelion mean? Today we are actually closer to the sun during winter and farthest during summer. Earth is at its perihelion position (position of closest approach) on January 4. This make for cooler summers and warmer winters. These conditions would promote glacial growth from year to year. Slide 19 Slide 20 Slide 21 ~20,000 Years ago Slide 22 18,000 years Slide 23 Slide 24 Slide 25 Climate of the last 1000 yr Slide 26 Slide 27 Slide 28 Slide 29 Slide 30 Slide 31 Greenhouse Gases Slide 32 Slide 33 Slide 34 Slide 35 Slide 36 Climate of the last 1000 yr Slide 37 Slide 38 1000 years Slide 39 Volcanoes Slide 40 Volcanic aerosol loading Slide 41 Pinatubo Slide 42 Aerosol lifetime Slide 43 Last 50 years Slide 44 Troposphere and Stratospheric Response Slide 45 Tropospheric Sulfate Aerosols Slide 46 Cooling to offset warming Slide 47 Estimated Sulfur Emissions Slide 48 Ozone and Climate Change Slide 49 Increased greenhouse gases result in warmer surface temperatures and Cooler cooler stratospheric temperature. This results in increased abundances of Polar stratospheric clouds which enhance Ozone destruction. Thus despite the phase out of CFC production the healing of the ozone hole will likely be delayed by increases in CO2. Slide 50 Ozone and Climate Change Less ozone in the stratosphere can cause a decrease in the global greenhouse effect. This likely offset global warming from 1980 to 2000 masking the true effect of increased atmospheric CO2. Slide 51 Slide 52 Slide 53 Slide 54 Slide 55 Greenland Ice Sheets Slide 56 Latest satellite data on Greenland mass change I've just updated the Greenland is losing ice page as a new paper analysing satellite data on Greenland mass change has been released (Wouters 2008). The Gravity Recovery and Climate Experiment (GRACE) measures changes in the Earth's gravity field and found that from February 2003 to January 2008, Greenland lost mass at a rate of 179 Gigatonnes per year. This is equivalent to a global sea level rise of 0.5mm per year. The rate is also increasing over time, suggesting an acceleration of mass loss.Greenland is losing ice pageWouters 2008 Gravity Recovery and Climate Experiment Slide 57 Artic Sea Ice Slide 58 Slide 59 Slide 60 Slide 61 Slide 62 Slide 63 Climate Models Slide 64 1-D Radiative convective models Slide 65 2-D Models Slide 66 3-D Atmosphere Ocean General Circulation Model Slide 67