Past climates Past climates were different than today. Global climate change. Climate change

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1 Past climates Past climates were different than today Warmer: Europe AD (Medieval Times) Cooler: Northern Hemisphere - Little Ice Age AD Wetter: North Africa 1 million+ y.o.: savanna Drier: American West AD Global climate change Global warming increase in average global temperature Climate change alteration of global climate Climate average weather conditions; i.e. what is expected Climate change Global issue bigger than atmospheric or water pollution Will affect most of world s population, but differently Climate is changing never static Our culture built on life today, not life tomorrow Extremely controversial issue due to potential influence of humans on climate

2 Long term coral temperature record from tropical Pacific and Indian Oceans derived from oxygen isotope data shows warmest temps in 20 th century X ray of a coral core, Global sea level has risen almost 20 cm during past century Arctic Sea Ice earthobservatory.nasa.gov

3 Full flowering date of cherry trees in Kyoto (days from Jan 1) Estimated March mean temperature Average global temperature C.R. Scotese PALEOMAP Temperatures do fluctuate 150 mya 200 mya 550 mya 2 3 mya 14 C 22 C Antarctica, Isthmus of Panama, Arctic Ocean, Tibetan Plateau, North Atlantic deepwater production 17 C 12 C Alligators swam in swamps near the North Pole, palm trees grew in southern Alaska, Greenland, and Patagonia. 65 mya

4 Glacial = when ice advances Interglacial = when ice retreats 2-3 mya 12 C 17 C 14 C Precession Precession has a 21,000 year cycle that determines the distance of northern hemisphere from summer sun Changes the locations in the Earth's orbit at which the equinoxes and solstices occur.

5 Axial Tilt Tilt of Earth is 23.5º Tropics of Cancer and Capricorn are 23.5º N and S to mark the furthest extent of direct sunlight Polar circles are 66.5º, marking the edge of total darkness and light Axial tilt Axial Tilt If tilt of Earth changes, these lines change Parts of Earth gets less or more sunlight Tilt of axis varies from 21.5º to 24.5º over a period of 42,000 years. Eccentricity Shape of earth s orbit (eccentricity) varies from elliptical to almost circular over period of 96,000 years Causing changes in the amount of insolation Earth receives

6 Milankovitch Cycles Using the three cycles, Milankovitch created a mathematical model explaining variations in temperature and insolation for 600,000 BP Seeks to explain long term climate change A closer look at the last 150,000 years shows variations related to Milankovitch cycles tilt eccentricity? precession Global Conveyer Belt Increased rainfall in the North Atlantic, and the melting of glaciers and sea ice, or the influx of warm freshwater onto the sea surface could disrupt the conveyor belt, changing climates

7 Other influences Volcanic eruptions Sun activity Natural vs. anthropogenic effects Natural factors are warming earth, but humans are warming it more Earth Atmosphere Radiation Budget Absorbed by the atmosphere ~19% Direct 25% Indirect 25%

8 Similar effects Atmospheric gases act in similar ways to clouds blocking sunlight and blocking longwave radiation from leaving the atmosphere Greenhouse Effect A natural effect that warms the atmosphere Longwave (outgoing) radiation blocked by atmospheric gases Atmosphere delays transfer of heat from Earth into space Without effect: Average world temperature would be approx. 5 F Average world temperature actually approx. 59 F Greenhouse Effect Energy is trapped by greenhouse windows or atmosphere Gases in the atmosphere absorb radiation and emit the energy Carbon dioxide, nitrous oxide, and methane most important called the greenhouse gases Anthropogenic addition of greenhouses gases to the atmosphere may enhance the Effect

9 Major Greenhouse Gases Gas Carbon dioxide (CO 2 ) (fossil fuel) Carbon dioxide (biological sources) CFCs/HCFC Methane Nitrous oxide Current contribution 44% 13% 25% 12% 6% Influx of plant based CO2 Simulations agree that a new glaciation would be underway if greenhouse gases had behaved as they did before humans became active players.

10 Kyoto Protocol Treaty adopted in Kyoto, Japan in 1997 Effective 2005: 191 countries signed & ratified US signed but did not ratify protocol Aimed at reducing levels of GHG Green: countries that have ratified the treaty; Dark green: Annex I and II countries that have ratified the treaty; Grey: not yet decided; Brown: no intention of ratifying; Red is Canada, which announced its intention to withdraw in Dec 2011 Kyoto Protocol 37 countries committed (under Annex I of protocol) to reduce four greenhouse gases (CO 2 methane, nitrous oxide, and sulphur hexafluoride) and two groups of gases in atmosphere Flexible protocol can meet GHG emission limitations by buying GHG emission reduction credits elsewhere (financial exchanges, projects that reduce emissions in non-annex I countries, other Annex 1 countries) Kyoto Protocol Most countries experienced increased emissions since ratification (Japan and US included) UK, France, and Germany have successfully reduced emissions Will take time and greater regulations

11 Intergovernmental Panel on Climate Change (UN) Group of over 1300 wellrespected scientists who are experts in the field Predict rise of global average temperature of 2.5 to 10 F over the next 100 years (IPCC 2007) IPCC Effects of climate change Climate change occurring at different rates and at different times, depending on the location Poorer countries feel affect more tied to climatesensitive economies (agriculture) Use computer models to predict changes on a worldwide and smaller scale Some effects already occurring: Rising sea levels Warmer temperatures (summer, winter, and overall) Changing rainfall patterns 30-year moving average for climate Summation

12 Effects of climate change 70 to 75% of world s population live within 75 miles of coastline; life and livelihood at risk IPCC predicts: Rising sea level from melting ice: predicted average sea level will rise between 0.6 and 2 feet (0.18 to 0.59 meters) in next 100 years Increase in tropical storm intensity and frequency Warmer temperatures Result: loss of land, increased flooding, loss of fresh water, economic loss, saltwater intrusion into groundwater Muir Glacier, Alaska, August 13, 1941, by William O. Field. Photo August 31, 2004, by Bruce F. Molnia of the United States Geological Survey. Glacier retreated more than twelve kilometers (seven miles) and thinned by more than 800 meters (875 yards).

13 If sea level rises more Two One meters meter (~3.2 (~6.4 ft) ft) Sea level rise Maldives 1,200 islands with approx land size of 115 mi 2 Average elevation of 1.5 m, 80 % land >1 m Effects of climate change Water access: 1 billion do not have access to safe drinking water now IPCC predicts: Increased droughts Decreased western US snowpack Warmer temperatures Increase in heat waves Result: less access to water in some regions: greater water stress (i.e. less fresh water available), increased evaporation (=less water), less water for irrigation

14 Effects of climate change Increases in temperature = increases in the use of electricity, increase energy costs, puts greater demands on environment IPCC predicts: Warmer temperatures More heat waves Result: greater expenditure on energy, more demand on environment Effects of climate change Other predicted impacts: Edges of Amazon forest replaced with tropical savannah Increased erosion from increased frequency of storms Increase and decrease of rain-fed agriculture depending on region Increased flooding from increased intensity of rain events Unknowns Positive and negative feedback mechanisms Speed of change forcing of some mechanism could cause climate to change faster than expected Oceans a major sink for CO 2 Warmer sea water (a result of warmer temperatures) would hold less CO 2, resulting in greater CO 2 in atmosphere None of the unknown predict a stop in sea level rise