Climate Change. Greenhouse Effect & Global Warming

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1 Climate Change What is climate change Greenhouse Effect & Global Warming Global Warming = World wide increase in average Temp. Cause = greenhouse effect 1

2 Some would argue the Global Warming trend is natural - not forced by human activity. Some argue that solar activity is linked to global warming. In the geologic past this is true: Global trends in temperature proxies sometimes correlate with solar activity and cosmogenic nuclide abundances (e.g. 36 Cl) E.g. Midieval Warm period ( A.D.) and the Little Ice Age ( A.D.) However, this is not true of today s warming trend: there is no measurable increase in 36 Cl abundance over the past century. Measurable variability in solar activity after 1978 accounts for ~0.01% of total irradiance. Some would argue the Global Warming trend is natural - not forced by human activity. Long-term trends in temperature proxies sometimes correlate with Earth orbital cycles called Milankovitch cycles (e.g. the last ice age) However, this is not true of today s warming trend - it is much to rapid to correlate with variations in Earth s orbit The cause of today s climate change is the greenhouse effect! This is the overwhelming consensus of the scientific community. AGU s position 2

3 Greenhouse Effect: Simply put Greenhouse Effect: Anomalous heating of atmosphere Energy radiated from surface absorbed by GH gas in atmosphere GH gas re-radiates the Energy, heating atm. & surface Natural process! W/out it, Earth would average 30ºC (86ºF) cooler Goldie Locks effect Earth is just right Goldie Locks Effect If Earth was 17% closer to sun, then liquid water would not form on surface. Thus no CO 2 dissolved in oceans and E would be hot enough to melt Lead.Like Venus is. If Earth was further from sun, then solar radiation would be lower and E would be and ice house like Mars. 3

4 Greenhouse Gases Naturally occurring: CH 4, CO 2, H 2 O, N 2 O Anthropogenic: CH 4, CO 2, H 2 O, CFC, N 2 O Problem b/c of anthropogenic increase Not a single refereed journal article (peer-reviewed) has argued the contrary since prior to 1995! In other words, the scientific consensus is that anthropogenic forcing of the greenhouse effect is causing global warming! Observed increase in Greenhouse gases 4

5 Very strong argument for anthropogenic forcing Sources of GH gas increase CO2: Fossil fuel & cement, Volcanism, weathering CH4: Decomposition in Wetlands, Fossil fuel, Land fill & Animal husbandry CFC: industry & consumer 5

6 Global Dimming - may have muted global warming Aerosols in atmosphere increase Earth s albedo Particles reflect sunlight Between 1960 and ~1985, increase in aerosols caused dimming of ~3 to 6% ~1985 to early 90s Earth began to brighten again Decreasing aerosol emissions Improved air-quality regulations Reduced Pinatubo (volcanic) aerosols eruption Total aerosol Brightening and Global Warming ~1985 to early 90s Earth began to brighten again Decreasing aerosol emissions Improved air-quality regulations Reduced Pinatubo (volcanic) aerosols eruption This correlates with the rapid increase in temperature during the 1990s 6

7 Observed Effects of GH Global Warming by ºC! Receding Glaciers & Ice caps - past 100 yr Rising Sea level - 18 cm in 100 yrs (greatest rate in E history)! Mostly from thermal expansion of ocean, not added melt water Predicted Effects of Global Warming Increasing Global Temperatures A change of 5ºC = ~9ºF 7

8 Predicted Effects: Shifts in climate zones Predicted Effects: Continued rise in sea level Rising Sea level - >20 cm in 100 yrs (greatest rate in E history)! Averaging ~1.8 mm/y from 1950 to 2000 Rising faster today Mostly from thermal expansion of ocean, not added melt water Consider how this will effect coastal communities. 8

9 Predicted Effects: Extreme Weather Heightened hydrologic cycle (greater rainfall and snowfall) Observations: Increase in number of category 4 and 5 cyclones over past 35 yrs. Increase in the duration of cyclones over past 35 yrs. Predicted Effects: Negative impact on marine ecosystems Increasing CO 2 atm increases amount of CO 2 in oceans. This decreases ph of oceans Harmful to Plankton and Coral Prediction - Harmful conditions will develop first in southern ocean within decades. Observed change in phytoplankton productivity with latitude in both N. Atlantic and E. Pacific Productivity migrating to high latitude. Direct effect on food webs, especially large mammals and fish who feed on zooplankton A recent study in Science (2008) found that some plankton were not adversely effected by moderately low ph - unexpected. 9

10 Predicted Effects: Negative impact on marine ecosystems Measured decline in productivity in all oceans Area of low productivity (<0.07 mg chlorophyll/m 3 ). Area is expanding in all oceans. Area expanding fastest in North Atlantic. Predicted Effects: Negative impact on marine ecosystems Global warming and resulting changes in ocean chemistry (increasing acidity) lead to negative effects on Coral Coral is a symbiotic relationship between the coral polyp and algae Coral Bleaching - coral expel their algae due to change in environment. This negatively impacts the vitality of the reef community. Recent results suggest this may not lead to the death of coral. It is suggested that this, in-fact, opens a niche for another algae more capable of surviving. 10

11 Predicted Effects: Negative impact on terrestrial ecosystems Alpine Frogs - as climate warms, they must migrate up-mountain to reach cooler climate. Thus, the available habitat is decreasing. Tropical frogs - fungus growing on skin is killing them. Increased humidity is favoring the growth of fungus. These are just two examples of many - we are currently experiencing the greatest rate of extinction on Earth (i.e., we are in the midst of the most rapid mass extinction in Earth history). Predicted Effects: Negative impact on marine ecosystems Observed change in phytoplankton productivity with latitude in both N. Atlantic and E. Pacific Productivity migrating to high latitude. Direct effect on food webs, especially large mammals and fish who feed on zooplankton 11

12 We Can Fix it! We only need to try! Reduce production of GH gasses (Kyoto Agreement = reduce emissions to 5.2% below 1990 levels) Sequester CO 2, Consume CO 2 - how? Recent direction of US: let market forces drive remediation. So, when things get bad enough, we will want to change. The problem with this is that CO 2 has a 100 year atmospheric residence time. So, by the time market forces cause change it will be TOO LATE to effect change! CO2 credits - individuals pay for remediation to offset their pollution. This does nothing to help, emissions continue and individuals feel good about it. Further, some remediation efforts never materialize - e.g. plug-ins for truckers s.t. they don t have to idle rigs overnight for heat. Not a single one built yet, but many have paid for them. Who will this hurt first? Third world - poor people that can t spend their way out of trouble. Predicted cost of continued warming: We will begin to fix the problem when the cost to developed nations becomes harmful to GDP. 12

13 Mitigating Climate Change Tree plantations decrease CO 2 atm However, studies suggest they may decrease stream flow and increase soil acidification Aerosols & dimming Large volcanic eruptions cause dimming and decrease heat content of oceans and drop in mean sea level Suggested that injections of SO 2 into the stratosphere could dampen warming trend This requires Pinatubo sized injections biannually Side-effects: stratospheric ozone depletion We will solve this problem: It will require multiple mitigating methods. The solution will combine international efforts and cooperation between governments, research, engineering, and economic efforts on a scale that has never before been necessary. The Carbon Cycle: Geologic Perspective Carbon is cycled between mantle, crust and atmosphere: CO 2 emissions: Volcanoes release mantle CO 2 Fossil fuels, respiration, decomposition Dissolution of limestone, metamorphism CO 2 sinks: oceans, CaCO 3 sediments, chemical Weathering, photosynthesis 13

14 Consider simple ocean circulation & life North Atlantic Cooling photosynthesis Equator Heating CO 2 from atmosphere dissolves in N Atlantic surface water Photosynthetic organisms use CO 2 to make sugar/tissue When they die the tissue (organic C) collects on seafloor. scavengers consume it (respiration) and release CO 2 to ocean & atmosphere Question: what happens if no cold, oxygen rich water circulated to the seafloor? respiration Effect of climate change North Atlantic Equator Cooling Heating Question: what happens if no cold, oxygen rich water circulated to the seafloor? Recent studies suggest that this circulation pattern in the Atlantic diminished by 30% between 1957 and 2004 Likely due to warmer temperatures in North America 14

15 If no sinking cold oxygen rich water North Atlantic Cooling Equator Heating What is the result if CO 2 return is cut-off? Possible Global Cooling Also, this is how Oil originates! This may have happened 55 Ma, causing a shift from N- to S-flowing circulation Resulted in mass extinctions on land and in the sea Conclude: Climate change effects ocean circulation, heat transport and life photosynthesis No decomposition (respiration) on seafloor! Burial of C (No CO2 released) How might you shut off Cooling surface water at high latitude? Global Warming Move continents to open warm water circulation paths 15