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Unformatted text preview: Global Change Global
Dr. Emily Berndt Fundamental of the Climate System EAS 253 Questions to Consider Questions What is meant by a “system approach” to What
Earth Science? Earth How does global warming differ from the How greenhouse effect? greenhouse Should we be concerned about the Should Antarctic ozone hole and tropical deforestation? deforestation? Can understanding Earth’s past give us Can clues about Earth’s future? clues Earth as a System Earth A system is a system
group of components that interact interact 4 Parts to the Parts Earth System Earth Atmosphere (air) Hydrosphere Hydrosphere (water) (water) Biota (life) Solid Earth (rock)
Fig 1-1 Earth as a System The components interact in response to The
external and internal forcings external External Forcings Changes in incoming solar radiation Changes in atmospheric composition Changes in earth’s surface Internal Forcings Changes in atmospheric circulation Changes in ocean circulation Earth as a System Earth Overview Overview Earth is being altered at an Earth unprecedented rate by human activity unprecedented
Greenhouse gases Depletion of the ozone layer Deforestation of the tropics and loss of Deforestation biodiversity How serious are these problems? How do these changes compare with past How
changes? changes? Global Change on Short Time Scales Scales Global Warming Difficult to separate the anthropogenic and Difficult natural influences natural Causes are deeply rooted in our global Causes industrial infrastructure industrial Most researchers agree the climate has Most warmed over the past century – not all agree it is the result of human activities it How is global warming different from the How greenhouse effect? greenhouse The Natural Greenhouse Effect The Greenhouse gases remit or trap longwave radiation from earth’s surface. This effect = 15oC-(-18oC)=33oC or 59°F Evidence of Global Warming Evidence Measurements of CO2 Observed Changes in Surface Temperature Temperature Historical data show surface temperature Historical
is on the increase. is The overall temperature increase during The the 20th Century was 0.8°C (1.4°F) the Problems with historical temperature Problems data? data? Is the warming trend really caused by Is human activities? human
http://earthobservatory.nasa.gov/IOTD/view.php?id=48574&src=eoa-iotd Changes in the Cryosphere Changes Temperature has been increasing more Temperature
rapidly in the polar regions rapidly Almost 4 times the global average in central Almost Alaska (3°C) Alaska http://earthobservatory.nasa.gov/IOTD/view.p hp?id=46282 Changes in the Cryosphere Changes Figure 5. September Arctic sea ice extent observed in 1979 (yellow line), and 2005 (white area). The predicted coverage of sea ice by Holland et al. et (2006) is shown for 2015 (red line) and 2040 (green line). Their model predicts that sea ice in summer by 2040 will occur only in narrow bands along the Canadian Arctic coast. However, there will still be about 50% sea ice coverage in winter. Original image taken from NASA. http://www.wunderground.com/climate/SeaIce_Fig05.asp Changes in the Cryosphere Changes Figure 4. Arctic sea ice extent since 1900, as estimated from satellite and ship reports compiled by Walsh and Chapman (2001). Image credit: University of Illinois cryosphere group. University http://www.wunderground.com/climate/SeaIce_Fig04.asp Changes in the Cryosphere Changes Figure 7. The change in age and thickness of sea ice between 1987 and 2005. In 1987, most of the Arctic sea ice was old and thick, generally more than ten years old. A period of strong positive Arctic Oscillation conditions between 1989 and 1995 created winds and currents that flushed most of this old ice out of the Arctic Ocean, through Fram Strait to the east of Greenland. The new ice that replaced the old ice is much thinner. Image credit: Rigor, I. G., and J. M. Wallace (2004), "Variations in the age of Arctic sea-ice and summer sea-ice extent," "Variations Geophys. Res. Lett., 31, L09401, doi:10.1029/2004GL019492. http://www.wunderground.com/climate/SeaIce_Fig07.asp Consequences of Global Warming Consequences Rise in sea level Melting of glaciers and ice Agricultural impacts Decrease in soil moisture Spread of tropical insect pests Ozone Depletion Ozone troposphere: layers of Earth’s atmosphere. Art. Encyclopædia Britannica Online. Web. 19 Jan. 2011. < http://www.britannica.com/EBchecked/topic-art/10857 Ozone Depletion Ozone Ozone Hole Nov 2009 Ozone http://ozonewatch.gsfc.nasa.gov/index.html http://earthobservatory.nasa.gov/IOTD/view.php?id=46704 Deforestation Deforestation http://earthobservatory.nasa.gov/IOTD/view.php?id=35891 Land Transformation Land Global Change on Long Time Scales Scales To understand the significance of changes To
we need to understand how the Earth system operated prior to humans system Geologic time scale Eons Eras Periods Epochs Glacial-Interglacial Cycles Glacial-Interglacial The glacial-interglacial cycles lasted from The
2.5 mya until about 10,000 years ago 2.5 During the Pliocene and Pleistocene epochs So how do we know about these cycles? Vostok Ice Core Dome C Ice Core Local change in temperature is estimated Local from the deuterium content of the ice from Glacial-Interglacial Cycles Glacial-Interglacial For the past 2.5 million years, Earth’s For
climate has fluctuated between cold (glacial) and warm (interglacial) periods. (glacial) 130,000 years ago interglacial period 130,000 21,000 years ago glacial conditions 21,000 11,000 years ago start of the current 11,000 interglacial period interglacial Ice Cores Ice Can we infer atmospheric CO2 Can
concentrations from the ice cores? concentrations 21,000 – 11,000 ya CO2 200 ppm to 280 ppm CO2 CH4 350 ppb to 650 ppb CH4 So does the increase in greenhouse So
gases correlate with increased temperature in the ice cores? temperature Temperature Anomaly & CO2 Temperature Questions to Consider Questions Why do CO2, CH4, and temperature covary? How did CO2 increase if there were no How Humans to pollute the atmosphere? Humans Ancient Ocean Circulation Ancient Ancient Ocean Circulation Ancient Ancient Ocean Circulation Ancient The sun’s brightness increases as it The
depletes it’s hydrogen fuel depletes Changes in Solar Luminosity Changes As H decreases in the core, there is less As pressure (core contracts and heats up) pressure A temperature rise increases the pressure As temperature increases, the rate of fusion As increases increases More energy and a brighter sun! http://www.physicsoftheunivers e.com/facts.html Changes in Solar Luminosity Changes The sun was 30% less luminous 4.6 bya Now the sun is brightening by about 1% Now
every hundred million years every What are the effects of Solar Luminosity What Changes? Changes? Early Earth should have been colder than it is Early today today Faint Young Sun Paradox – how did liquid Faint water exist if the sun was 70% as intense as today today Does Earth have a built in stability Does mechanism? mechanism? The Gaia Hypothesis The Earth is a self-regulating system in which Earth
the biota play an integral role. the Not totally true! Organisms do play a role in the overall Organisms functioning of the Earth system functioning Some form of self-regulation must exist for Some climate stability over long time scales climate End of Chapter 1 End ...
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This note was uploaded on 04/11/2011 for the course EAS 253 taught by Professor Dr.emilyberndt during the Spring '11 term at Saint Louis.
- Spring '11