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Global Warming

Global Warming. Dennis Silverman Physics and Astronomy U C Irvine. Global Warming . Greenhouse gases: CO 2 , methane, and nitrous oxide Already heat world to average 60° F, rather than 0° F without an atmosphere How greenhouse gases work Increased CO 2 has raised temperature 1.2° F

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Global Warming

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  1. Global Warming Dennis Silverman Physics and Astronomy U C Irvine

  2. Global Warming • Greenhouse gases: CO2 , methane, and nitrous oxide • Already heat world to average 60° F, rather than 0° F without an atmosphere • How greenhouse gases work • Increased CO2has raised temperature 1.2° F • The present radiation imbalance will cause another 1° F heating by 2050, even without more greenhouse gas emissions. • Recent cleaning of air is causing the earth’s surface to be hotter and brighter. • Stabilizing the amount of CO2 would require a reduction to only 5% to 10% of present CO2 emissions

  3. Definitive Evidence of Rapid 1.2° F Temperature Rise over the Last Century

  4. Carbon Dioxide Concentrations are low in glacial periods and higher in warmer interglacial periods However, concentrations now are higher than at any time in the last 450,000 years. In the insert is the dramatic growth over the last 50 years.

  5. Temperature and CO2 Correlation

  6. 700 The last 160,000 years (from ice cores) and the next 100 years:temperature (red) tracks CO2 (green). CO2 in 2100 (with business as usual) 600 Double pre-industrial CO2 500 Time (thousands of years) Lowest possible CO2 stabilisation level by 2100 400 CO2 concentration (ppm) CO2 now 300 10 Temperature difference from now °C 200 0 –10 100 160 120 80 40 Now

  7. Adding Climate Model Projections for the next hundred years (new analysis expected in Feb.)

  8. Q: What is today’s anthropogenic Radiative Forcing ?

  9. Temperature comparison with and without greenhouse gases and sulphur (NCAR/DOE)

  10. NCAR/DOE conclusions on temperature models • “Solar activity contributed to a warming trend in global average temperature from the 1910s through 1930s. • As industrial activity increased following World War II, sun-blocking sulfates and other aerosol emissions helped lead to a slight global cooling from the 1940s to 1970s. • Since 1980, the rise in greenhouse gas emissions from human activity has overwhelmed the aerosol effect to produce overall global warming. “

  11. Global Warming Effects • Predicted Global Warming of 5°F will affect everyone in most structural aspects of society and in their costs. • We don’t realize how our present housing, business, and supply nets are closely adapted to our current climates. • The major increase in temperature and climate effects such as rainfall, drought, floods, storms, and water supply, will affect farming, year round water supplies, household and business heating and cooling energy. These may require large and costly modifications. • Some cold areas may benefit, and some hot areas will become unfarmable and costly to inhabit. • Recent projection: US agriculture would go up 4%, CA down 15%. • Methane production seems to have stabilized (UCI result) • It is very misleading to portray the problem as a purely environmentalist issue which affects only polar bears, a few Pacific islanders, and butterflies.

  12. What can be said about the controversy?Here are some comments. • 17 national science academies have endorsed the conclusion of global warming and its man-made causes. • The Intergovernmental Panel for Climate Change (IPCC, www.ipcc.ch ), consulting 2,500 scientists from 130 countries, will issued a new report on Feb. 2, after six years, which states a 90-99% probability that warming since 1950 is human caused. • It has also concluded a >90% probability that temperatures will continue to rise.

  13. What can we reasonably say about fossil fuels and global warming? • Global warming of 1° F has occurred in the past century. • CO2 is a greenhouse gas and is way higher than it has historically been. • This is generated by human burning of fossil fuel, but fortunately, half of that generated has been absorbed in the carbon cycle. • Common sense, models of earth systems, and the correlation of warming with CO2 in ice ages, indicate a direct effect between the two. • Clearly, funding much more research on this is clearly justified. • Since we are going to run out of cheap fossil fuel this century, research on new energy sources, and plans to develop them are clearly called for.

  14. Arguments against global warming and its man-made causes • 1. Global warming doesn’t exist • There is one location which hasn’t warmed • The Antarctic ice is growing in thickness • Michael Crichton’s State of Fear • 2. Global warming is a natural cycle and not caused by humans (and will go away?) • Answer: But temperature changes must have a cause. All of the known causes are included in the models, and human made causes dominate. Users of this symantic out never propose a “natural” cause. • 3. Other objections to man-made origins: • The dip in the 50s in the temperature curve • How can ppm of CO2 have any effect • Breathing creates CO2 • The temperature always fluctuates • You can’t predict next week’s weather, so how can you … • Water vapor is more important

  15. Global Warming and Publicity • 4. “Global warming is the greatest fraud perpetrated against the U.S.” • Sen. Inhofe, previous head of the Energy Committee • It is used by climate scientists so we will fund them • Please refer to www.realclimate.org for detailed scientific discussions of these challenges and of recent research publications. • Oil and energy companies are using the same organization to lobby against global warming as brought you the cigarettes do not cause cancer campaign. They are also funding the dissident scientists. See Union of Concerned Scientists report at www.ucusa.org.

  16. Greenhouse Gases and the Kyoto Treaty • The treaty went into effect in Feb. 2005 to reduce greenhouse gas emissions of developed countries to 5% below their 1990 level. • The U.S., as the largest CO2 emitter in 1990 (36%), will not participate because it would hurt the economy, harm domestic coal production, and cost jobs. • China has signed the protocol, but as a developing country, it does not have to reduce emissions, and burns lots of coal. • In China’s defense: • it only has ¼ the emissions of the US per capita; • ¼ of its GDP is for export; • it has significantly lowered its birth rate to one child per couple; • it is planning a large nuclear reactor program (20-30 or more); • it only has one private car per hundred inhabitants; and • half of its population earns less than $2 per day; • the new three gorges dam is equivalent to several nuclear reactors in hydropower; • they are asking for a 4% reduction per year in greenhouse gases but probably will not obtain it; • they are trying to get sources of natural gas to use instead of coal.

  17. Comparative World CO2 Emissions

  18. World Greenhouse Gas Emissions

  19. Effects of the Doubling of CO2 • Doubling of CO2 projected by end of century, causing approximately a 5° F increase in average temperature (most rapid change in over 10,000 years) • ~1.5 foot maximum sea level rise • More storms and fiercer ones as illustrated by Atlantic hurricanes in 2005 with 10° hotter Caribbean sea temperatures • Loss of coral reefs • Increase in tropical diseases since no winter coolness to kill insects • 25% decline in species that cannot shift range • Warming expected to be greater over land • Hot areas expect greater evaporation from hotter winds causing drought • In the past, half of produced carbon has gone into storage as in the oceans. • Heating of the surface ocean layer could stop ocean mixing and absorption into lower layers, thus shutting off carbon absorption.

  20. Global Warming Effects • Global Warming is an average measure • Local warming or climate fluctuations can be very significant • Arctic is 5° warmer • Ice cap is ½ the thickness of 30 years ago • Partly due to natural cycle, partly man caused global warming • Antarctic is 5° warmer • Ice shelves over the sea are melting and breaking off and may allow the 10,000 foot thick ice sheet over Antarctica to slide off the continent faster • This would cause a sea level rise • Rainfall is hard to predict. It could be increased or decreased. • Drought can partly be caused by increased evaporation at the higher temperature.

  21. Global Warming Predictions for 2100 for business as usual. The average increase is 5°F. Since we don’t live over the oceans, warming will be larger.

  22. Worldwide Glacial Melting, causing 2/3 of sea level rise of an inch a decade.

  23. Global Warming effects in California • Summer temperatures rise by 4-8° F by 2100 for low emission scenario: 8-15° F for higher emissions. • Heat waves will be more common, more intense, and last longer. • Spring snowpack in the Sierra could decline by 70-90%, as winters will be warmer. • Agriculture, including wine and dairy, could be affected by water shortages and higher temperatures. • More forest fires. • Tree rings show that in eras of global warming, megadroughts of decades hit the southwest US.

  24. CO2 Effects to Increase Over Centuries

  25. Hasn’t yet added in Hurricane Katrina in 2005

  26. Depending on high or low emissions model, most of permafrost in Canada, Alaska, and Russia melt by 2050 or 2080. Permafrost melting by 2050 or 2080

  27. Worldwide increases in the average number of frost-free days by 2080

  28. Sea level rise has been 2 mm/yr for 50 years, but 3 mm/yr for the last decade

  29. Florida with a 1 meter sea level rise or storm surge

  30. Nile and Sea Level Rise • At 0.5 m, 3.8 million population displaced (intermediate blue). • At 1 m, 6.1 million population displaced (light blue). • The protective 1-10 km sand belt is eroding due to the Aswan dam.

  31. Ganges River delta and 1m sea level rise in Bangladesh. 13 million displaced and 16% of rice production lost. • Similar 1 m sea level rise in China would displace 72 million people.

  32. Increase in Droughts (red) from 1948 to 2002.The fraction of global land experiencing very dry conditions (-3) rose from about 10-15% in the early 1970s to about 30% by 2002. Almost half of that change is due to rising temperatures rather than decreases in rainfall or snowfall.

  33. IPCC 2007 Summary Graphs

  34. Historical Changes in Greenhouse Gases over 10,000 years • CO2 • Methane • NO2

  35. Blue shaded bands show the range from climate models using only the natural forcings due to solar activity and volcanoes. Red shaded bands show the range from climate models using both natural andanthropogenic forcings.

  36. Global Surface Warming for This Century

  37. Economic Climate Models, Roughly in Order of Temperature Increases, High to Low • A2 Growing population, regional inequities • A1 Peaking then declining population, world equity, high tech growth • A1FI Fossil fuel intensive • A1B Balance of sources • A1T Non-fossil fuel sources • B2 Increasing population, regional inequities, lower population growth than A2 and tech development than A1 • B1 Peaking then declining population, world equity, non-material economy, clean solutions

  38. U.S. Carbon emission sources

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