Geology lecture 9b and 10
Geology lecture 9b and 10 Geol101
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This 15 page Class Notes was uploaded by Shelby Green on Monday February 22, 2016. The Class Notes belongs to Geol101 at Clemson University taught by Dr. Coulson in Spring 2016. Since its upload, it has received 31 views. For similar materials see Physical Geology in Geology at Clemson University.
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Date Created: 02/22/16
3/1/16 Lecture 9b Climatology Geology in the News • New Study suggests oxygen buildup on earth might have started during the Archean eon instead of the Proterozoic eon • 1.8 billion years earlier What affects Climate? 1. The Hydrosphere: Water has a high heat capacity (heat energy store), the heat stored in the water moves north and south through currents to distribute the heat Gulf Stream: a stream of warm water that originates in the gulf of Mexico that supplies a warmer climate towards Europe, red in top photo Thermohaline Cirulation: the red pathway, shows how water moves at the surface of the ocean, and the blue shows how the water moves at the bottom of the ocean All one big current , moves like a conveyor belt moves warm salty water around. Key to keep belt moving: the water sinks in the north atlantic Ocean Heat Transport: why does water sink in the north Atlantic? o Water gets cooler/saltier/denser as it travels north and begins to sink. Ocean Heat Transport: o Slowing of ocean heat transport in recent decades because.. The oceans are warmer now days, so there isn’t much cooling in the process Glaciers are melting and adding fresh water into the ocean and dilutes the slat content Negative feedback loop: the area where warm water is being brought to has gotten warmer, causing belt to slow down, which brings less warm water in the area, that area then cools, so the belt speeds up again, and as it speeds up, warm water is brought to the area, then slows down again, repeat… 2. The Biosphere Plants o Draws down CO2 for photosynthesis which warms temp o Affects albedo or the measure of reflectivity (how much sunlight will be reflected vs. absorbed) Animals o Release CO2 and methane CO2/methane increase, temp increases Biological Pump o Interaction of biosphere, atmosphere, hydrosphere, and lithosphere Organisms in the ocean cause CO2 to be stored long term in the lithosphere (kinda like photosynthesis in the oceans) Crysphere o The amount of snow and ice o Ice covers ca ~9% of land surface Antarctica has more ice during winter than summer o Ice coverage albedo: reflects 40-90% of the sunlight Hard to warm area back up if its reflecting that much light o Land surfaces albedo: reflects 14-25% of the sunlight 3. The Lithosphere Tectonics affect climate in several ways o Continental position: whether its near/far from equator o Continental size: the bigger continents tend to have desert like interiors b/c they’re so far from coast line, smaller continents have more weather climates b/c they’re closer to coastline o Collision zone uplift: rain shadows, mountain blocks one side of mountain from getting rain Land Bridges o Control where the ocean currents can move which play a big role in heat energy Land bridge formed between north and south America keeping the current from going between them and changed the climate o Land bridge broke down between south America and Antarctica and changed the Antarctic climate Recording Climate Instrument and historical records only go back so far **Studying previous climates and comparing it to our climate now, helps us understand how climate can change in the future 1. Air trapped in glacial ice: o Air bubbles are pockets of atmosphere that has been preserved since the was ice formed (so it could be over 50 thousand years old) Can see how much CO2 was in the atmosphere at that time vs. now ** Note: NOT A PROXY actually studying samples from ancient atmosphere so there is no substation involved o Ice cores Like an oil rig for ice (digging for old ice in ice cores to study the air bubbles) Ice cores in Greenland and Antarctica >2 miles (3300 m) Scientists haven’t even reached the bottom of these cores yet and they already represent >1 million years 2. Proxies: Substitute to get the info you want o Lots of things that form in nature are sensitive to different aspects of climate that can be studied to tell us about those parts in the climate o Can also tell us different time scales o Always consider the nature of proxy Tree Rings: Tree ring width tells us how healthy that tree was during that year (healthy=good climate) Hard to decide what made the tree unhealthy/healthy though between the diff aspects of climate Biogeography: The study of where different plants and animals live (species distributions) Many species only live in different climate conditions Fossils of those organism tells us about the climate at different points in the path o Not going to find crocodile fossils in a cold climate area Crocodile fossils from 90 million yrs ago found in Canada climate in Canada must have been warm 90 million year ago Stable Isotopes Measure as ratio: ex) 18O/ O Diff atomic weights = diff amounts of each isotope get incorporated into molecules Ratio: always bigger #/smaller # Key: the ratio in some materials changes with climate variables Ex: at one temperature, you add a certain ration of 18 16 O/ O to a growing shell…. …But at a different temperature, you add a different ratio of 1O/ O6 Stable Oxygen Isotopes Ex: many invertebrate & plankton shells Can provide quantitative paleotemperature data Oxygen in shells can be used to calculate the water temp when that animal was alive Ex: 1O/ O (stable isotopes of oxygen) in fish bone reflects water temperature when the fish was alive T = 111.4 – 4.3*(Df – Dw) Df = ratio in fish bone Dw = ratio in seawater (assume= 1.0) T = water temp (Celsius) Measured ratio in a fossil fish is 20.1, what was the water temp? T= 111.4-4.3*(20.1-1)=29.27 Other Temp Proxies Some Trace Metals in Shells Ex: Magnesium/Calcium in shells also tell what temp the ocean was at that point Q: Why do we want multiple temp proxies? The more ways to find temp, the more accurate the guess If same answer found of water temp with three different proxies proves it is an accurate reading Stable 13rb12 Isotopes C/ C both stable isotopes of carbon Both isotopes form CO in2the atmosphere 13 12 Ex: CO 2 , CO 2 Plants take in both types of CO f2r photosynthesis The 13C/ C ratio in each plant depends on the plant’s photosynthetic style C3 plants vs C4 plants **Note: the names ‘C3’ and ‘C4’ do not refer to carbon isotopes; they refer to types of plants Groups of plants that photosynthesis with slightly different weights (Like a Ford vs. Chevy truck: same type of car, different parts) Each type of plant represents two diff types of habitats 13 12 • The C/ C ratio in animals’ skeletons thus reflects the type of plants in the ecosystem • Provides clues to climate 3/3/16 Lecture 10 Global Warming Global Warming (GW) • This is a big topic in society, and debates can get quite heated – Sorry, bad pun intended J • Everyone has an opinion, but remember the difference between opinions & hypotheses? – Hypotheses require facts to support them – Opinions do not (Ex:) IMO sushi is terrible. • This is just my opinion, and it’s not even based on many facts: • I’ve only tried sushi 1-2x • There are a lot of types I’ve never tried • So why should you believe me if I tell you sushi is yucky? • Remember: – People are always trying to convince you to agree with their opinion • “Vote for this candidate, he/she’s the best!” • “Buy this product, it’s better than other products!” – But what are their opinions based on? – Think about the issue for yourself & develop your own, informed opinion One big source of confusion w/ GW is that there are 2 separate questions: 1. Is the Earth warming up? 2. If so, why is it warming up? **We have to address these issues separately. o If Earth is not warming up, we don’t even have to worry about #2 Is Earth Warming up? • It sounds simple, but temp calculations can get confusing – You have to consider different locations, whether you’re measuring daily, weekly, monthly, or seasonal temp, are you going by daytime highs or daytime lows, what statistical and graphing methods to use….yikes! • Instead, let’s use a simple proxy glaciers – If Earth is warming up, then glaciers should be getting smaller. That’s a simple hypothesis to test… • To test the hypothesis, all we have to do is see if glaciers are getting smaller. • All pictures on the next pg show the same location in the same season Based on Glaciers shrinking, we must conclude that yes, lots of places are getting warmer over the past several decades So now we can start to figure out WHY the Earth is warming up…. Why is Earth Warming? 1. Earth is currently naturally warming after coming out of the most recent ice age – Natural processes (ex- Milankovich cycles) account for ~ 50% of warming over the past few centuries 2. Unusual Warming Pattern: – But the warming is occurring faster and has a greater magnitude than other warming trends we have data for in recent history – The temps are higher now than at any time within the past 2,000 years and they’ve risen very quickly since ~1850 Greenhouse Gases and Global Warming • Humans have added a lot of greenhouse gases (GGs) to the atmosphere since the Industrial Revolution began in the 1800s • Remember: – Greenhouse Effect: GGs trap insolation, keeping more heat energy at Earth’s surface Question: Is the amount of GG in the atmosphere increasing? These 3 GGs have become much more abundant in the atmosphere, and the timing coincides with the Industrial Revolution Question: Are the GGs really decreasing the amount of insolation that escapes from Earth? Yes. Satellites measure exiting insolation. o It’s been steadily decreasing for decades. o The energy wavelengths that GGs trap are exactly the wavelengths that are escaping less and less easily. Conclusion: Based on these facts, scientists calculate that ~ 50% of the temp increase of the last ~ 200 years is due to greenhouse gas buildup. Humans and Greenhouse Gases Are human-made GGs responsible, for the warming? i.e., is the GG buildup anthropogenic (man-made)? • World population is now > 7 billion – Up almost 3 billion since 1970 – That’s a lot of people emitting a lot of GGs, but is it really enough to alter global climate? • Let’s look at the atmospheric GG buildup closer… – This data (the Mauna Loa Curve) clearly shows that carbon dioxide levels in the atmosphere have been rising – Levels are higher now than any time for the past 1,000 years – But neither graph can tell us where the CO2 coming from CO2 Buildup (400k yr record) **Modern Levels have no equal in the past 400,000 years, still haven’t proved where CO2 came from The CO2 Buildup • So we have plenty of data demonstrating that CO levels 2re higher now than at any point in the past 400,000 years • Next, we need a way to figure out where all this extra CO h2s come from • For that, we’ll examine carbon isotopes again 12 – Note: C-12 and C mean exactly the same thing; the notations are used interchangeably in this lecture Finding the Carbon Source • Different sources produce diff isotopic mixes of carbon – Ex: volcanoes release C-13, forest fires release C-12 & C-14, etc 14 12 • Seuss Effect: a decline in the atmospheric C / C ratio – Why would that ratio decrease? • There are two ways to make a ratio smaller: • 1: make the numerator smaller to decrease the amount of C-14 in the air • 2: make the denominator bigger to increase the amount of C-12 in the air – Think of the isotope ratio like a mixed drink… • C-14 = rum and C-12 = Coke • You put one shot of rum in each glass, so they have the same amount (= the numerator is the same) • Next, fill the glasses with Coke. • The small glass has a higher rum/coke ratio than the big glass b/c the big glass has more Coke (the denominator is larger) – So which happened, less C-14 or more C-12? • Remember that C-14 is created in the atmosphere (we covered this during lecture 8) at a pretty constant rate • Thus, the amount of C-14 in the atmosphere has not significantly changed • So there must be more C-12 in the air than they’re used to be – So what can add C-12 to the air without adding any C-14 or C- 13? • It wasn’t discussed herein, but the amount of C-13 has not changed • Volcanoes would add C-13 to the atmosphere • Other sources (ex- forest fires, cellular respiration) would add some C-14 12 • Fossil fuel burning adds lots of C to atmosphere and adds no 14C – Why doesn’t fossil fuel burning produce C-14? 14 • Remember: It takes ~ 57,300 yrs for all the C to decay after an organism dies • But It takes millions of years for organic remains to become fossil fuels • So, fossil fuels contain no C-14, just C-12 – Thus, the Seuss Effect strongly supports the anthropogenic hypothesis b/c burning fossil fuels is the only thing that accounts for the drop in the 14/12 ratio. • Note: it’s fine if people want to challenge the GW hypothesis, but that requires finding a better explanation for the Suess Effect, which GW skeptics have not been able to do. • Remember: to challenge scientific ideas, you have to work with facts, not just some group’s opinion • Fact: humans are increasing atmospheric CO 2 • Fact: CO 2elps increase temperature • Conclusion: humans are responsible for some of the current warming • Even if someone remains unconvinced that humans are the cause of GW, remember that we have to deal with the changes GW causes regardless of what’s causing it – Possible effects of GW: • Ice sheet melting • Rising sea levels • Aridity in mid latitudes • Stronger hurricanes and El Ninos • Extinctions due to ecosystem changes – These are all things that will adversely affect our society Seven Global Warming Myths ***Both sides exaggerate & twist the facts 1. “The Coasts are about to flood!” a. As glaciers melt, much of the water will flow into the oceans, so sea level will rise b. Some GW advocates claim coastal cities and beaches thus are in imminent danger of flooding c. Consider the timescale of the change i. Significant sea level will occur, but on decadal-century timescale ii. Thus, the threat is Not imminent 2. “The Planet is burning up!” a. The map below was included in Al Gore’s movie, An Inconvenient Truth, to make people realize how much GW is occurring b. The data is real, but about that map has some issues… i. When you project a 3-D world onto a flat map, things can get distorted. ii. This type of map makes things near the poles look really big iii. Thus, the worst warming appears to cover a bigger area iv. Also, the color scheme intentionally uses colors that we associate with danger signs/warnings c. This map shows the same type of data in a less alarming manner d. Earth tone color scheme e. Different type of map that doesn’t stretch the area near the poles i. Again, the data on the other map is fine, but that map was designed specifically to get you to agree with their message 3. “Record Low temps disprove GW” a. GW skeptics often make statements like this one: i. “1,100 record low temperatures were recorded in the US during summer ‘09… so much for Global Warming!” b. Many people listen to this point b/c it sounds like a fact with lots of data supporting it… but often these people are talking about weather, not climate c. The data are accurate, but the data do not support the conclusion i. The temps may be from just one small area ii. They may reflect only one small length of time d. Data on record highs and norms is lacking e. We don’t base climate trends on data from just one area (Ex) Spring semester 2011 was very cold around Clemson i. We even missed the first day of class due to snow! 1. GW skeptics were quick to use this as anti-GW fodder, 2. But it was just one cold month in one place- that’s not a global climate trend, that’s just unusual local weather ii. Spring semester 2012 we had unusually WARM conditions all semester J 4. “It’s only 3 degrees, who cares?” a. Skeptics dismiss GW b/c scientists predict global temps will increase about 3 over the next century, and that seems like a tiny temp change b. Scientists use Celsius, but most people use Fahrenheit i. 3 C = ~ 5.4 F, that’s a bigger change ii. ****Always check your units! c. That number is a global average; temps will vary a lot form place to place i. During the last Ice Age: global average temp was only ~ 4.5o C lower than today d. So drop the temp 4.5o C and we get an ice age, so what will a 3o C increase do? L i. Many organisms can’t tolerate temp shifts of even a few degrees ii. We rely on many species for food, medicine, etc. 5. “Scientists Can’t Decide between Global Warming and Cooling!” a. This point goes back to 1975… i. National Academy of Science Report stated that global warming or cooling was possible ii. Data was inconclusive, so they could not determine how temperature would change b. Also published in 1975: i. Newsweek- "The evidence in support [of global cooling] has now begun to accumulate so massively that meteorologists are hard-pressed to keep up with it.” ii. Reporters often make mistakes when trying to explain scientific studies iii. Skeptics still use this 37 year-old Newsweek issue to try and discredit scientists, even though it is clearly outdated AND make a huge reporting error in the first place c. Lesson: Always consider the source & check the date! i. We often get our ‘facts’ from unreliable sources ii. Ex: I can post a blog on the internet describing my life as a roadie for Metallica who has 3 arms… but that’s not even remotely true d. If you want reliable info, talk to experts… e. Tooth aches? Talk to a dentist. Car won’t start? Talk to a mechanic. Unsure about GW? Talk to scientists. Bloggers post anything to get your attention Politicians say anything to get your vote. 6. “Scientists Profit from Global Warming a. Scientists are telling us climate is changing just so they can have “lavish laboratories“ and fund their “Arctic vacations” (quotes from a Senator speaking out against global warming research a couple of years ago) i. When a scientist gets a grant, it does NOT go into their pockets. ii. The money is closely controlled by the university/company they work for. iii. They must justify and document every expense they want to make 7. Professionals a. Many anti-global warming politicians have recently started using this tactic: “I’m not a scientist.... but I don’t trust what climate scientists tell me because they are paid to study climate for a living”. b. Think about that… they’re saying you shouldn’t listen to the professionals who know the most about the subject c. So who would they recommend we listen to…. amateurs who don’t really know much about the subject? That doesn’t make any sense
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