Milankovitch Theory of Climate Change The Earth changes its: a)orbit (eccentricity), from ellipse to circle at 100,000 year cycles, b)wobble (precession),
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Presentation on theme: "Milankovitch Theory of Climate Change The Earth changes its: a)orbit (eccentricity), from ellipse to circle at 100,000 year cycles, b)wobble (precession),"— Presentation transcript:
Milankovitch Theory of Climate Change The Earth changes its: a)orbit (eccentricity), from ellipse to circle at 100,000 year cycles, b)wobble (precession), affects timing of seasons with respect to perihelion, at 23,000 year cycles c) tilt (obliquity), from 22° to 24.5° at 41,000 year cycles. THESE FACTORS AFFECT GLOBAL CLIMATE BECAUSE OF GREATER LAND AREA IN THE NORTHERN HEMISPHERE
* Climate Change is Nothing New TODAY *NB: The temporal scale used to examine climate change is very important, as different patterns are revealed, depending on the timescale used. The rate of climate warming projected by the IPCC is believed to be very rapid compared to past climate changes
[insert fig 16-6] Temperature variation during the past two millenia
Berner RA and Kothavala Z. 2001. GEOCARB III: A revised model of atmospheric CO2 over Phanerozoic time. American Journal of Science. 301: 182-204 Climate and CO 2 Concentrations: 2 to 590 million years BP Current Global Mean Temperature & [CO 2 ] vap
Climate Change Carbon dioxide absorbs outgoing longwave radiation emitted by the Earth This causes temperature to rise on a global scale CO 2 -induced global warming first predicted by Arrhenius (1896) Concentrations have increased from 280ppm (preindustrial) to 390 ppm (2011) http://www.glumbert.com/media/globalwarming1958
Source: NOAA ABSORPTION K TO SPACE=31 L <K !! Heat transfer 7+24=31 Compensates for radiation imbalance at surface L 46+19+4=69 L TO SPACE=69 100 46-15=31 100-31-69=0 GREENHOUSE EFFECT HERE
Future Scenarios Temperature Increase +2.5 to + 5.7 C above 1971-2000 climate normals (McGinn and Shepherd, 2003) THE YEAR 2050 IN SOUTHERN ALBERTA
Growing Degree Days Barrow and Yu (2005) In: Sauchyn (2007 ), with permission
Future Scenarios Precipitation Increase +3 to +36 % above 1971-2000 climate normals (McGinn and Shepherd, 2003) More rain and less snow from autumn to spring (Lapp et al., 2005) THE YEAR 2050 IN SOUTHERN ALBERTA
Annual Moisture Index: ET > P Barrow and Yu (2005) In: Sauchyn (2007 ), with permission
SEASONAL FLOWS (2039-2070) Annual flow projected to vary from -13 to +8% (mean -4%). Increased winter rain:snow ratio and above-freezing temperatures will increase winter runoff Earlier spring melt and increased evapotranspiration will decrease summer runoff CURRENTECHHADNCAR m 3 s -1 Pietroniro et al. (2006) In: Sauchyn (2007) OLDMAN RIVER FLOW PROJECTIONS
Carbon ‘Enrichment’ MORE EFFICIENT PLANTS? Faster growth rates Increased water-use efficiency lower stomatal conductance required to maintain c i Increased nitrogen-use efficiency? Impact of global change on WUE depends on net result of opposing effects of increased T a and VPD vs. elevated [CO 2 ] vap Will the same species be dominant in a 2xCO 2 environment?
Future Scenarios NET PRIMARY PRODUCTIVITY OF ALBERTA GRASSLANDS Ecosys Model accounts for both climate change and CO 2 enrichment (Li, Grant and Flanagan, 2004) Input Canadian Regional Climate Model II climate change projections (IS92a emissions scenario). Results Lengthened growing season Transpiration increases from higher temperatures were offset by increasing plant water-use efficiency caused by rising CO 2 Increased net primary productivity offset by increasing respiration, so that carbon sequestration only increased very slightly (2 g C m 2 y 1 ) under climate change N.B.: Climate change may alter interspecies competition/dynamics and cause migration. Rapid change may also reduce biodiversity.