Climate Change and the Oceans

Transcription

1 Climate Change and the Oceans Topics: Composition of atmosphere Climate Change Global Warming Greenhouse effect Carbon cycle Composition of Atmosphere Distribution of Earth s CO 2 99% of the atmosphere = N 2 + O 2 + H 2 O + CO 2 H 2 O & CO 2 are variable in atmosphere. More CO 2 in oceans than in the atmosphere. Global Warming Global Warming = World wide increase in average Temp. Cause = greenhouse effect 1

2 Global Warming= World wide increase in average Temp. Recent criminal hacking of server at Climate Research Unit, East Anglia Statistical Trick = neat, simple method of comparing two records - this is a proven statistical method The records are of the tree-ring temperature proxy divergence : far northern forest tree rings don t show effects of warming since 1950s Why: don t know, could be too few data. Importance: little. southern forest data do show reflect the warming trend Point learned: if tree-ring proxy for time before thermometers diverges from another proxy, we should question the tree-ring data CRU suggested certain Editors and Journals published research that contradicted climate science consensus with poor data and weak arguments. So what? These particular s were basically a few scientists complaining about other scientists. There is real concern about a couple of journals (e.g. Climate Research) publishing poorly reviewed papers. Global Warming= World wide increase in average Temp. Recent criminal hacking of server at Climate Research Unit, East Anglia Investigative results: Factcheck and Associated Press concluded: s do not call into question scientific results, and consensus on human induced climate change is unchallenged. House of Commons Technology Subcommittee and the Assessment Panel of U of EA concluded: No scientific malpractice s do not challenge scientific consensus on climate change Scientists in question could ve behaved better. UEA, CRU has a practice of withholding data from climate science detractors - this should end. The criticisms of CRU detractors have been selective and uncharitable U.S. Dept. of Commerce Inspector General s investigation (2/2011) determined No scientific data were manipulated by NOAA scientists No inappropriate review procedures conducted by NOAA scientists A fourth review form House of Commons is pending. There is a criminal investigation ongoing into the hacking of the server Some 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. Mideval 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. 2

3 Some 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 Pleistocene Ice Age) However, this is not true of today s warming trend - Temperature changes today are 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. So, if not solar fluctuation or orbital variation, then what? The only other means of warming Earth s surface are: the Greenhouse effect Changing Earths albedo (more or less ice): really this results from climate change and serves as a feedback Changing ocean currents: again a result of climate change that feeds back into climate change The cause of today s climate change is the greenhouse effect! None of the other mechanisms can be shown to operate today. This is the overwhelming consensus of the scientific community. Greenhouse Effect: Simply put Greenhouse Effect: Anomalous heating of atmosphere Energy radiated from surface absorbed by GH gas in atmosphere GH gases re-radiate the Energy, heating atm. & surface Natural process! W/out it, Earth would average 30ºC (86ºF) cooler! Goldie Locks effect Earth is just right 3

4 Goldie Locks: The Movie 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 an ice house like Mars. Greenhouse Gases Naturally occurring: CH 4, CO 2, H 2 O, N 2 O Anthropogenic: AGU s position CH 4, CO 2, H 2 O, CFC, N 2 O Global Warming 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! Similar concentration trends for all anthropogenic green house gasses: SO 4, N 2 O, CH 4 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 Recall, the ocean is a huge sink for CO2 What are possible results of global warming? Think about it, discuss it with your neighbor You have a couple of minutes I will ask you to share with the class 5

6 Observed Results of climate change (CC) Global Warming by ºC (avg surface T)! 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 East coast US: SL expected to rise twice as fast as global levels (>18 in by 2100) due to slowing of Atlantic circulation b/c of warming high latitude (Geosci. Nature, 2009) Mostly from thermal expansion of ocean, not added melt water Observed Results of climate change (CC) Sea level increasing 1.8 mm/y and <50% of that is from melting glaciers. Recent studies show that rates of glacial melting are increasing relative to rates from the 1990s. Antarctic ice sheet melting Eastern Ice Sheet began melting in 2006 Unexpected find and likely will see accelerated rise in sea levels. Nature Geosci, 2009 Observed Results of climate change (CC): Loss of Sea Ice Median Sept. ice edge Sept 2010 ice Decreasing > 11%/decade 2007 minimum recorded sea ice extent 2010 sea ice extent is >2.5 x 10 6 km 2 below the average for 1980 Cause: Changes in Atmospheric Circulation due to Climate Change Result: increased climate warming (heat transfer to atm. from oceans in winter). This is a Negative feedback. Warming causes warming. Warming in arctic is linked to 2010 massive snow events in NE North Am., N. Europe and Asia Dramatic change in ecosystem both on and below the ice. (we will discuss this later) 6

7 Observed results of CC: Loss of Sea Ice Effects polar bears: 2006 study showed predation and cannibalism within Beaufort Sea population. In past 5 years, 43% of cubs survive compared to 65% between Blonde Grizzlies observed in arctic Effects walrus : 2010 walrus populations coming aground on North Slope of Alaska This is not supposed to happen! Not enough sea ice to support the population near their summer feeding grounds Now cows must swim miles from Alaska coast to reach feeding ground. Observed results of CC: Increased hydrologic cycle Nature, 05 North Atlantic Cyclone activity Increase in number of category 4 and 5 cyclones over past 35 yrs. Increase in the duration of cyclones over past 35 yrs. No trend in number, or intensity has been detected in the S. Pacific or S. Indian Ocean (Kuleshov et al, JGR 115, 2010). Extreme rain events during Indian Monsoon between % Increase in frequency of intense rain events (>10 cm/day) Increasing magnitude of intense rain events Total amount of precipitation may be decreasing (Naidu et al., JGR 114, 2009) Global Dimming - may have muted the effects of global warming Aerosols in atmosphere increase Earth s albedo Particles reflect sunlight Between 1960 and ~1985, increase in aerosols caused dimming of ISR by ~3 to 6% Total aerosol ~1985 to early 90s Earth began to brighten again (increase ISR) Decreasing aerosol emissions Improved air-quality regulations Reduced Pinatubo (volcanic) aerosols eruption 7

8 Brightening and Global Warming ~1985 to early 90s Earth began to brighten again This correlates with the rapid increase in temperature during the 1990s Predicted Effects of human induced Climate Change Increasing Global Temperatures Stabilizing our climate will require near-zero emissions (GRL, 2008) Model result GH gasses remain in atm for centuries Must stop emissions to prevent warming beyond today s temperatures Not possible given energy needs and sources Predicted Effects: Shifts in climate zones How might this effect US economy and lifestyles? 8

9 Predicted Effects: Increasing SST average of >20 climate model predictions Warming in tropics relative to subtropics Tropical atmosphere has lighter winds relative to Trade winds, and have higher humidity. Thus, less evaporative cooling of sea surface water This may negatively impact coral (due to coral bleaching) Clement et al., Nature Geosci. 3, 2010; Xie et al., 2009 Predicted Effects: Local climate will change, e.g., Chicago Chicago: 1st city to produce local climate change projection Lead Authors include Don Wuebbles Conservative Projections (by the end of the century): Summers like Atlanta Ga Higher heat index ( ºF) Recall, when T exceeds 100 in Chi, people start dying. Winters - not much change Same amount of snow and ice So, expect wide variation in annual temperatures Early spring, late fall and cold winters Predicted Effects: Continued rise in sea level Consider how this will effect coastal communities. Maldives < 2m above sea level Population density of Bangladesh ~ 1000 people / km 2 Nile Delta: by 2050 expect displacement of 1-5 million people 9

10 Predicted Effects: Extreme Weather Heightened hydrologic cycle (greater rainfall and snowfall events) Recall Current Observations of Cyclones and Monsoon events above. Resent computer models indicate that increased moisture in atmosphere over Atlantic may decrease the frequency of hurricanes, while increasing the frequency of Category 4 and 5 hurricanes. Science, v. 327, Predicted Effects: Negative impact on marine ecosystems Increasing CO 2 atm increases amount of CO 2 in oceans. This decreases ph of oceans (making them more acidic) Harmful to Plankton and Coral These form the base of the marine food web! These are one of Earth s main sources of atmospheric Oxygen! Prediction - Harmful conditions will develop first in southern ocean within decades. (Nature, 2006) A recent study in Science (2008) found that coccolithophors were not adversely effected by moderately low ph - unexpected result. Demo HCl + cc Predicted Effects: Negative impact on marine ecosystems Measured decline in productivity of all oceans Area of low productivity (<0.07 mg chlorophyll/m 3 ). Area is expanding in all oceans. Area expanding fastest in North Atlantic. Productivity migrating to high latitude. Direct effect on food webs, especially large mammals and fish who feed on zooplankton 10

11 Predicted Effects: Negative impact on marine ecosystems Patagonian (Magellanic) penguins Survival of chicks threatened Parents must swim further to forage (>60km) compared to decade ago Return with fewer nutrients Southern colonies fair better than northern colonies due to shorter foraging distances. Why? Oceans are warming Prey follow productivity, productive regions shifting further from penguin breading grounds Warm oceans somehow result in more male prey-fish offspring, thus fewer females and prey-fish populations declining. P. Dee Boersma: 2008, BioScience, 58(7) , Ecological Monographs, 79(1), , Marine Ecology Progress Series, 375, Predicted Effects: Negative impact on marine ecosystems Coral is a symbiotic relationship between the coral polyp and algae Global warming and resulting changes in ocean chemistry (increasing acidity) lead to negative effects on Coral This negatively impacts the vitality of the reef community. E.g., Coral Bleaching - coral expel their algae due to change in environment. Causal correlation with warming temperatures (exacerbated by El Niño). Damages the reef by decreasing ecosystem structure and habitat 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. Individual corals can recover Baker et al., 2008 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. Science, 2008: Yosemite - ecosystems migrating ~500 m up elevation. Alpine communities are contracting. Tropical frogs - fungus growing on skin is killing them. Increased humidity is favoring the growth of fungus. Polar Bears in competition with Grizzly Bears around Hudson Bay - Polar Bears don t hibernate. Will they eat sleeping grizzly cubs? Polar bears eat seals, will they adapt? Will polar bears and grizzly s mate? These are just a few examples of many - we are currently experiencing the greatest rate of extinction in Earth history (i.e., we are in the midst of the most rapid mass extinction in Earth history). 11

12 Have I taught you anything? A. Yes B. No Have I challenged you to rethink a previously held notion? A. Yes B. No We Can Fix it! We only need to try! US GDP=13.8 Trillion in 08. Projected loss ~ Billion Previously, the 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 >1000 year atmospheric residence time. So, by the time market forces cause change it will be TOO LATE to effect change! Who will this hurt first? Third world - poor people that can t spend their way out of trouble. Note it is a falsehood to argue that limiting GHG emissions will harm GDP (we learned this is not true when implementing the Clean Air Act) New technologies will be developed New industries will arise to produce the new technologies that will accomplish the reductions New jobs will be created to implement and maintain the technologies that accomplish the reductions 12

13 We Can Fix it! We only need to try! Currently, the US has begun to follow other nations by addressing the issue in serious ways: By 2016 all new cars must get > 35 mgp Fall, 09 House passed American Clean Energy & Security Act or the cap-ntrade / carbon offset bill Senate tabled the bill till next session. Future legislation on Building Standards etc. The global community is beginning to address the issue in a serious way. Copenhagen Summit this past December - agreement to keep Temp Change to below 2ºC, but no agreement on emission reductions to meet this goal! Keep watch on US, China, India and Brazil US and China disagree again at Tianjin talks and kill efforts to reach Copenhagen agreement (Fall 2010) China wants only wealthy nations to cut emissions, US wants all large emitters to make cuts. US + China = 40% of GH emissions We Can Fix it! Mitigating Climate Change Reduced production of GH gasses does not do enough because of the long residence time of CO 2 in Atm. Kyoto Agreement (reduce emissions to 5.2% below 1990 levels) Copenhagen and Tianjin talks were to re-address GH production - basically a bust We must find ways to Sequester CO 2 or Consume CO 2 Why was the Future Gen project stopped? Do we want to concede this technology to another nation? Oops, it was started again We Can Fix it! Mitigating Climate Change Ethanol does little to reduce CO 2 - some estimate it increases concentrations: depends on biomass used to produce ethanol If US crop land is used (e.g. corn), then rainforest is cleared to replace the cropland. Current research is looking for grasses that can grow in areas between crops Looking at bacteria and waste materials Recent research Synthetically photosynthesis ethanol Input solar and wind power U of I researchers recently found a catalyst making the reactions efficient. 13

14 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 Current stage: Investigating ways to reduce CO 2 emissions Investigating climate Engineering Investigating clean energy What you can do Be politically active and vote with this issue in mind Find ways to diminish your consumption of fossil fuels. Eat Locally Grown Food The single most effective mitigation effort a population can make! Mitigating Climate Change The Carbon Cycle 14

15 The Carbon Cycle: flux of a greenhouse gas and one way to cool Earth Let s look only at Carbon in the oceans. Dissolved In Organisms Buried This will be grossly oversimplified Note: this is not in your textbook (p ) as I present it here. Consider simple ocean circulation & life North Atlantic Equator Cooling photosynthesis 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 respiration North Atlantic Effect of climate change 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 15

16 If no sinking cold oxygen rich water, then no respiration on seafloor and no CO 2 pumped back into the atmosphere North Atlantic Equator Cooling photosynthesis Heating What is the result if CO 2 return is cut-off? Possible Global Cooling Also, this is how some Oil originates! This may have happened 55 Ma, Resulted in mass extinctions on land and in the sea Conclude: Climate change is intimately linked to ocean circulation, heat transport and life No decomposition (respiration) on seafloor! Burial of C (No CO 2 released) How might you shut off Cooling surface water at high latitude? Global Warming Move continents to open warm water circulation paths A similar event with extreme consequences Review Questions What are the exogenic reservoirs of CO 2 and which contains the most CO 2? Why can t you call on variations in solar radiation or variations in Milankovitch cycles to explain the current global warming trend? Explain the Greenhouse Effect. What is the Goldie Locks Effect? How do you know that anthropogenic forcing of the greenhouse effect is responsible for the current global warming trend? If global warming continues at the same rate, do you expect sea level to rise at the current rate, or faster? How does loss of sea ice feedback into global warming? What are some expected consequences of continued warming and CO 2 production? Describe the Carbon Cycle and how Global Warming impacts the cycle. 16