Section 3 Section 3 Remote sensing of global changeRemote sensing of global change

3. Greenhouse gasses3. Greenhouse gasses

Global ChangeInstructor: Dr. Cheng-Chien LiuDepartment of Earth SciencesNational Cheng Kung UniversityOffice: Building of Earth Sciences, room 30206Voice: +886-6-2757575 ext. 65422E-mail: ccliu88@mail.ncku.edu.tw Office hours: Monday 14:00 – 17:00, Wednesday 9:00 – 12:00URL: http://mail.ncku.edu.tw./~ccliu88/

Last updated: 27 April 2004

4.1 Introduction4.1 Introduction

Definition of greenhouse gassesDefinition of greenhouse gasses• The gasses that prevent heat energy given off

by the sun from leaving our atmosphere back into space

Greenhouse effectGreenhouse effect• See §4.2

4.1 Introduction (cont.)4.1 Introduction (cont.)

A list of greenhouse gassesA list of greenhouse gasses• Carbon dioxide CO2

• Methane CH4

• Chlorofluorocarbon CFC• Ozone O3

• Water vapor H2O• Nitrous oxide N2O• Soot • …

4.2 Mechanism of Greenhouse effect 4.2 Mechanism of Greenhouse effect

Black body radiationBlack body radiation Selective absorption of energy by Selective absorption of energy by

greenhouse gassesgreenhouse gasses• Long wavelength radiation preferred• Daytime absorption (long : short = 89:50)• Nighttime release long radiation

ConsequencesConsequences• Make the Earth warmer• Reduce the diurnal variation of temperature

Fig. 4.2.1 The electromagnetic spectrum after and before penetrating the atmosphere. Source: http://www.ccrs.nrcan.gc.ca/ccrs/learn/tutorials/fundam/chapter1/chapter1_4_e.html

Fig. 4.2.1Fig. 4.2.1

4.3 Emission of Greenhouse Gases4.3 Emission of Greenhouse Gases

Slowdown Slowdown • International cooperation

CFC use (Phase-out) (Montreal Protocol )Slower growth of CH4

A steady rate of CO2 emissions

Significance of CHSignificance of CH44

• The warming effect CH4:CO2 = 1:2 • CH4 tropospheric O3

Tropospheric O3 is a principal ingredient in "smog," which is harmful to human health and reduces agricultural productivity

4.3 Emission of Greenhouse Gases 4.3 Emission of Greenhouse Gases (cont.)(cont.)

A cheaper and faster way A cheaper and faster way reduce CH reduce CH44Reduction of CH4 emissions and soot could yield a major near term

success story in the battle against global warming, thus providing time to work on technologies to reduce future CO2 emissions.

• A short video about CH4 and climate change http://svs.gsfc.nasa.gov/stories/greenhouse_20020103/MethPackage_QTbigprogress.mov

Long-term goal Long-term goal reduce CO2reduce CO2• Limiting CO2 will still be needed to slow global

warming over the next 50 years. If the same fossil fuel consumption rate with CH4 and pollution halted

for the next 50 years 0.70C If “business-as-usual” 1.40C the specter of imminent disaster

Fig. 4.3.1Fig. 4.3.1

Fig. 4.3.1 changes in 12 climate "forcings" or factors that have contributed to climate change since 1850Source: http://svs.gsfc.nasa.gov/stories/greenhouse_20020103/figure1m.gif

Fig. 4.3.2Fig. 4.3.2

Fig. 4.2.2 Growth rate of climate forcings by greenhouse gasesSource: http://svs.gsfc.nasa.gov/stories/greenhouse_20020103/figure2m.gif

4.4 Questions4.4 Questions

Ozone is one of the greenhouse gases. Ozone is one of the greenhouse gases. Does the depletion of ozone cause the Does the depletion of ozone cause the global warming directly? global warming directly?