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Section 1 Background

December 2002. Section 1 Background. GLOBAL CLIMATE CHANGE:. What’s Happening, and What Can We Expect. What is ‘climate’?. Climate is ‘average weather’ - and its variability - for a particular region - over a period of time Includes many different elements. What is ‘climate change’?.

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Section 1 Background

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  1. December 2002 Section 1Background

  2. GLOBAL CLIMATE CHANGE: What’s Happening, and What Can We Expect

  3. What is ‘climate’? • Climate is ‘average weather’ • - and its variability • - for a particular region • - over a period of time • Includes many different elements

  4. What is ‘climate change’? • Climate change is a shift in ‘climate’ relative to a given reference time period • It is caused by: Natural factors -Solar variability -Volcanic dust levels -Internal variability -Geological change Human factors • - Greenhouse gases • - Aerosols • -Ozone depletion • -Land use change

  5. The earth’s atmosphere consists of multiple layers

  6. …and provides several important life supporting services • Suitable, stable climate • and weather Protection from solar uv-b (stratospheric ozone) stratosphere surface thunderstorm troposphere The air we breath (21% oxygen)

  7. The atmosphere’s energy budget is determined by net heat flow Outgoing Heat Energy Reflected Energy ~31% Incoming Solar Energy Energy Trapped By Greenhouse Gases • CO2 0.028% • CH4 0.0007% • N2O 0.0003%

  8. Estimating the Magnitude of the Natural Greenhouse Effect Net Incoming Solar Energy Outgoing Heat Energy = (S0 (1-A) R2) (4R2kTe4) where S0 is the solar constant A is average albedo, or reflectivity R is the radius of the earth k is Boltzmann’s constant Te is earth’s apparent temperature (seen from space) Te equals -19C  However, average global surface T is + 14C Natural greenhouse effect warms the surface by 33C 

  9. Primary Contributors to the Natural Greenhouse Effect ~10% ~25% ~65%

  10. Atmosphere: mass 90x earth’s GH Gases: >90% CO2 Sfc. Temp.: 477C GH Effect: 523C FAR TOO HOT! Venus • GH Gases: ~0.04% CO2 • ~ 1% H2O • Sfc. Temp.: 15C • GH Effect: 33C • NOT BAD! Earth Atmosphere: mass <1% earth’s GH Gases: >80% CO2 Sfc. Temp.: -47C GH Effect: 10C FAR TOO COLD! Mars Other planets also have Greenhouse Effects, but these are unsuitable for life Sun

  11. Latitudinal differences in net energy balance cause atmosphere and ocean circulation

  12. However, the climate system is also influenced by many other complex interactions and feedbacks

  13. Denser waters in high latitude oceans create a thermohaline circulation system that has a major impact on regional climates

  14. Highlights of historical research into the natural greenhouse effect • 1827: Fourier – theorized that greenhouse gases warm the planet • 1896: Arrhenius - proposed that changes in atmospheric CO2 concentrations due to volcanic eruptions can cause climate change • 1938: Callendar – first noted that human emissions of CO2 may add significantly to natural concentrations in the atmosphere • 1957: Revelle et al. – first warned that human emissions have started a global scale geophysical experiment and initiated an atmospheric CO2 concentration monitoring program

  15. An Early Warning About Climate Change “Many important economic and social decisions are being made today on long-term projects…based on the assumption that past climate data…are a reliable guide to the future. This is no longer a good assumption…” UNEP/WMO/ICSU Conference Villach, Austria 1985

  16. “Humanity is conducting an unintended, uncontrolled, globally pervasive experiment whose ultimate consequences could be second only to a global nuclear war.” World Conference on The Changing Atmosphere: Toronto, June 1988

  17. Everyone seems to be talking about climate change - but confusion reigns! Kyoto Framework Convention on Climate Change Greenhouse Effect Junk Science! IPCC I Love Global Warming! Disaster

  18. The IPCC is the principal source of sound advice on climate change science 1990 1992 1995 1997 2001 First Report RIO Second Report Kyoto Third Report Increasing Confidence Bonn & Marrakesh Cautious

  19. The IPCC process for providing science advice • Selection of lead authors • based on internationally recognized expertise • Assessment based on published literature • invited contributions from other experts • Contents peer reviewed twice • Second draft also reviewed by governments • Final contents are responsibility of lead authors • accepted (not approved) by IPCC • SPM developed and • approved collaboratively • by IPCC and lead authors • 2001 WGI report • involved 1078 experts

  20. The IPCC progression in confidence FAR: "Our judgement is that the size of [global] warming is broadly consistent with predictions of climate models but it is also of the same magnitude as natural climate variability“ SAR: "The balance of evidence suggests a discernible human influence on global climate.“ TAR: "There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activities."

  21. Some Contrarian Viewpoints: “I have never witnessed a more disturbing corruption of the peer-review process than the events that led to this IPCC report.” Dr. Fred Sietz, Former president, US NAS Wall Street Journal 12/6/96 “By failing to convey a balanced presentation of the science presented in the detailed reports, the SPMS, along with the IPCC press releases, have become a tool to drive public hysteria.” Chris De Freitas, U of Auckland climatologist Bull. Can. Petroleum Geologists, June 2002 • “When it to comes to climate change, humans aren't the culprits.” • Dr. Sally Baliunas, Harvard-Smithsonian astrophysicist; • Dr. Tim Patterson, Carleton geologist; • Allan McCrae, PEng G&M 19/11/02

  22. U.S. NRC Committee advised President Bush that IPCC reports were well done It noted that: • Full IPCC TAR WGI report is “an admirable summary of research activities in climate science” • The full report is adequately summarized in the Technical Summary • The SPM puts stronger emphasis on concerns, less emphasis on uncertainties than full report • all changes were made with consent of convening lead authors • most changes had little impact on contents

  23. Joint statement by Academies of Science from 17 other countries – May 2001 “The work of the…IPCC represents the consensus of the international science community on climate change science. We recognize IPCC as the world’s most reliable source of information…and endorse its method of achieving this consensus.”

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