What is climate change?

1. What is climate change? • Climate change is the fastest-developing area of environmental science • Climate = an area’s long-term atmospheric conditions • Temperature, moisture, wind, precipitation, etc. • Weather = short-term conditions at localized sites • Global climate change = describes trends and variations in Earth’s climate • Temperature, precipitation, storm frequency • Global warming and climate change are not the same

2. Global warming • Global warming = an increase in Earth’s average temperature • Only one aspect of climate change • Climate change and global warming refer to current trends • Earth’s climate has varied naturally through time • The current rapid climatic changes are due to humans • Fossil fuels and deforestation

3. The sun and atmosphere keep Earth warm • Four factors exert most influence on climate: • The sun = without it, Earth would be dark and frozen • Supplies most of Earth’s energy • The atmosphere = without it, Earth’s temperature would be much colder • The oceans = shape climate by storing and transporting heat and moisture • How Earth spins, tilts, and moves through space influences how the climate varies over long periods of time

4. The fate of solar radiation • The atmosphere, land, ice, and water absorb 70% of incoming solar radiation – 30% is reflected back

5. Greenhouse gases warm the lower atmosphere • Earth’s surface absorbs solar radiation, warms up, and emits infrared radiation • Greenhouse gases = atmospheric gases that absorb infrared radiation • Water vapor, ozone, carbon dioxide, nitrous oxide, methane, halocarbons [chlorofluorocarbons (CFCs)] • Greenhouse gases then re-emit infrared energy, to earth and space • Greenhouse effect = greenhouse gases keeping the surface warm

6. The greenhouse effect is natural • Greenhouse gases have always been in the atmosphere • We are not worried about the natural greenhouse effect (we need it) • Anthropogenic increase is worrisome

7. Carbon dioxide is of primary concern • It is not the most potent greenhouse gas, but there is a lot of it • The major contributor to the greenhouse effect • CO2 exerts six times more impact than methane, nitrous oxide, and halocarbons combined

8. What caused levels of CO2 to increase? • Burning fossil fuels moves CO2 from underground stores into the atmosphere • The main reason for increased atmospheric CO2 • Deforestation contributes to rising atmospheric CO2 • Forests serve as reservoirs for carbon • Removing trees reduces the carbon dioxide absorbed from the atmosphere • Humans have increased atmospheric CO2 from 280 parts per million (ppm) to 389 ppm • The highest levels in more than 800,000 years • OMG right?

9. Fluxes of carbon dioxide

10. Other greenhouse gases add to warming • Methane = fossil fuels, livestock, landfills, crops (rice) • Nitrous oxide = feedlots, chemical manufacturing plants, auto emissions, and synthetic nitrogen fertilizers • Ozone levels have risen 36% due to photochemical smog • Halocarbon gases (CFCs) are declining due to the Montreal Protocol • Water vapor = the most abundant greenhouse gas • Contributes most to the natural greenhouse effect • Concentrations have not changed

11. U.S. emissions of major greenhouse gases

12. Feedback complicates our predictions • Tropospheric warming will transfer more water to the air • But the effects are uncertain • A positive feedback loop? = more water vapor … more warming … more evaporation … more water vapor … • A negative feedback loop? = more water vapor … more clouds … shade and cool Earth • Minor modifications of the atmosphere could lead to major effects on climate

13. Most aerosols exert a cooling effect • Aerosols = microscopic droplets and particles • Can have either a warming or a cooling effect • Soot (black carbon aerosols) causes warming by absorbing solar energy • Most tropospheric aerosols cool the atmosphere by reflecting the sun’s rays

14. Milankovitch cycles influence climate • Milankovitch cycles = periodic changes in Earth’s rotation and orbit around the sun • Alter the way solar radiation is distributed over Earth • Modify patterns of atmospheric heating • Triggering climate variation • For example, periods of cold glaciation and warm interglacial times

15. Solar output and ocean absorption influence climate • Solar output = the sun varies in the radiation it emits • Variation in solar energy (e.g., solar flares) has not been great enough to change Earth’s temperature • Ocean absorption=the ocean holds 50 times more carbon than the atmosphere • Slowing global warming but not preventing it • Warmer oceans absorb less CO2 • A positive feedback effect that accelerates warming

16. Proxy indicators tell us about the past • Proxy indicators =indirect evidence • Ice caps, ice sheets, and glaciers: • Trapped bubbles in ice cores provide a timescale of: • Atmospheric composition, greenhouse gas concentrations, temperature trends • Snowfall, solar activity, and frequency of fires

17. Ice cores from Antarctica • Ice cores let us go back in time 800,000 years

18. More proxy indicators • Cores in sediment beds preserve pollen grains and other plant remnants • Tree rings indicate age, precipitation, droughts, and fire history • In arid regions, packrats carry seeds and plants to their middens (dens) • Plant parts can be preserved for centuries • Researchers gather data on past ocean conditions from coral reefs • Scientists combine multiple records to get a global perspective

19. Models help us predict the future • Climate models = programs combine what is known about: • Atmospheric and ocean circulation • Atmosphere–ocean interactions • Feedback mechanisms • Etc... Models simulate climate processes to predict climate change

20. Results from three simulations • Figure (a) shows natural climate factors only • Figure (b) shows only human factors • Greenhouse gas emissions • Figure (c) shows both factors • (Red line is observed climate data)

21. Current and future trends and impacts • Evidence that climate conditions have changed since industrialization is everywhere • Fishermen in the Maldives, ranchers in Texas, homeowners in Florida, etc. • Scientific evidence that climate has changed is overwhelming and indisputable • Intergovernmental Panel on Climate Change (IPCC) was established in 1988 • Composed of hundreds of international scientists and government officials

22. The IPCC’s fourth assessment report (2007) • The IPCC reports on the synthesis of scientific information concerning climate change • Global consensus of scientific climate research • Summarized thousands of studies • Evidence is overwhelming

23. Temperatures continue to increase • Average surface temperatures increased 0.74 °C since 1906 • Most of the increase occurred in the last few decades • Number of extremely hot days have increased • The 16 warmest years on record have been since 1990

24. The future will be hotter • In the next 20 years, temperatures will rise 0.4°C • At the end of the 21st century, temperatures will be 1.8–4.0 °C higher than today’s • We will have more unusually hot days and heat waves • Polar areas will have the most intense warming • Sea surface temperatures will rise • Hurricanes and tropical storms will increase in power and duration

25. Temperatures will rise globally Projected increases in surface temperature for 2090–2099 relative to 1980–1999

26. Precipitation is changing, too • Some regions are receiving more precipitation than usual, and others are receiving less • Droughts have become more frequent and severe • Harming agriculture, increasing soil erosion, reducing water supplies, and triggering fires • Heavy rains contribute to flooding • Killing people, destroying homes, and inflicting billions of dollars in damage

27. Projected changes in precipitation Precipitation will increase at high latitudes and decrease at low and middle latitudes

28. Melting snow and ice • Glaciers are disappearing • Glaciers on tropical mountaintops have disappeared • The remaining 26 of 150 glaciers in Glacier National Park will be gone by 2020 or 2030 • Reducing summertime water supplies • Melting of Greenland’s Arctic ice sheet is accelerating • Warmer water is melting Antarctic coastal ice shelves • Interior snow is increasing due to more precipitation • Melting ice exposes darker, less-reflective surfaces, which absorb more sunlight, causing more melting

29. 2007 vs 2005

30. Melting ice... • Nations are rushing to exploit underwater oil and mineral resources made available by newly opened shipping lanes • Permafrost (permanently frozen ground) is thawing • Destabilizing soil, buildings, etc. and releasing methane http://www.worldviewofglobalwarming.org/pages/glaciers.html

31. Rising sea levels • Runoff from melting glaciers and ice will cause sea levels to rise • As oceans warm, they expand • Leading to beach erosion, coastal floods, and intrusion of salt water into aquifers

32. Coastal areas will flood • Storm surge = temporary, localized rise in sea level • Caused by the high tides and winds of storms • Cities will be flooded • 53% of people in the U.S. live in coastal areas

33. Rising sea levels will devastate coasts • 1 million acres of Louisiana’s wetlands are gone • Rising sea levels eat away vegetation • Dams upriver decrease siltation • Pollution from the Deepwater Horizon • Millions of people will be displaced from coastal areas

34. Coral reefs are threatened • Coral reefs are habitat for food fish • Snorkeling and scuba diving sites for tourism • Warmer waters contribute to coral bleaching • Which kills coral • Increased CO2 is acidifying the ocean • Organisms can’t build their exoskeletons • Oceans have already decreased by 0.1 pH unit • Enough to kill most coral reefs

35. Climate change affects organisms and ecosystems • Organisms are adapted to their environments • Global warming modifies temperature-dependent phenomena (e.g., timing of migration, breeding) • Animals and plants will move toward the poles or upward in elevation • 20–30% of species will be threatened with extinction • Droughts, fire, and disease will decrease plant growth

36. Animals and plants have nowhere to go • Animals and plants adopted to montane environments will be forced uphill until there is no place to go

37. Climate change affects people • Societies are feeling the impacts of climate change • Agriculture: shortened growing seasons, decreased production, crops more susceptible to droughts • Increasing hunger • Forestry: increased fires, invasive species • Insect and disease outbreaks • Health: heat waves and stress can cause death • Respiratory ailments, expansion of tropical diseases • Disease and sanitation problems from flooding • Drowning from storms

38. Climate change affects economics • Costs will outweigh benefits of climate change • It will widen the gap between rich and poor • Those with less wealth and technology will suffer most • External costs of damages will be $10–350/ton of carbon • It will cost 1–5% GDP on average globally • Poor nations will lose more than rich ones • The Stern Review predicts it will cost 5–20% of GDP by 2200 • Investing 1% of GDP now could avoid these costs

39. Impacts will vary regionally • Where we live will determine how we experience the impacts of climate change • Temperature changes have been greatest near the poles • Melting ice sheets, thinning ice, increasing storms, etc. • Harder for people and polar bears to hunt • U.S. temperatures will continue rising • Plant and animal communities will shift north and upward • More intense extreme weather events • The southern U.S. will get drier, the northern wetter • Sea levels will rise and may be worse in the East

40. Impacts of climate change The Arctic has suffered the most so far U.S. temperatures will continue to rise

41. Impacts of climate change will vary

42. Are we responsible for climate change? • Scientists agree that increased greenhouse gases are causing global warming • Burning fossil fuels is increasing greenhouse gases • In 2005, scientists from 11 nations issued a joint statement urging political leaders to take action • There is a broad and clear scientific consensus that climate change is a pressing issue • But many people deny what is happening • People will admit the climate is changing • But doubt we are the cause

43. The debate over climate change is over • Conservative think tanks and industry-sponsored scientists cast doubt on the scientific consensus • The news media tries to present two sides to an issue • But the sides’ arguments are not equally supported by evidence • Most Americans accept that fossil fuel consumption is changing the planet

44. Electricity generation A coal-fired, electricity-generating power plant • The largest source of U.S. CO2 emissions • 70% of electricity comes from fossil fuels • Coal causes 50% of emissions • To reduce fossil fuel use: • Encourage conservation and efficiency • Switch to cleaner and renewable energy sources

45. Conservation and efficiency • We can make lifestyle choices to reduce electricity use • Use fewer greenhouse-gas-producing appliances • Use electricity more efficiently

46. Sources of electricity • We need to switch to clean energy sources • Nuclear power, biomass energy, solar, wind, etc. • We need to consider how we use fossil fuels • Switching from coal to natural gas cuts emissions 50% • Cogeneration produces fewer emissions • Carbon capture= removes CO2 from power plant emissions • Carbon sequestration (storage) = storing carbon underground where it will not seep out • We can’t store enough CO2 to make a difference

47. Transportation • 2nd largest source of U.S. greenhouse gases • Cars are inefficient • Ways to help: • More efficient cars • Drive less and use public transportation • Ride a bike! • U.S. public transportation saves 4.2 billion gallons of gasoline and 37 million metric tons of CO2 emissions per year

48. Conventional cars are inefficient

49. We can reduce emissions in other ways • Agriculture: sustainable land management lets soil store more carbon • Reduce methane emissions from rice and cattle • Grow renewable biofuels • Forestry: reforest cleared land, preserve existing forests • Store carbon in trees and soil • Waste management: treating wastewater • Generating electricity by incinerating waste • Using the methane from landfills • Individuals can recycle, compost, reduce, or reuse goods

50. We need to follow multiple strategies • There is no magic bullet for mitigating climate change