testtestOctober 26 or October 28. You

chooseConsensus: Tuesday October 26.

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Paper topicsPaper topicsStill need to get your topics(only received one email from

Majd)

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topicstopicsLayal – Thursday (carbon dioxide in

the oceans – sink vs source; healthy components?) – October 14

Lilliane – Tuesday (Marine algae and dimethyl sulfide) – October 19

Majd – Thursday (gulf stream – what is happening and why?) – October 21

Choose dates 04/20/23 3

Living Planet Living Planet 20102010

EVSC 305: Climate Change – EVSC 305: Climate Change – the Science and Local Impact the Science and Local Impact on a Global Environmental on a Global Environmental CrisisCrisis

Climate Change: Chapter 1, Book 2History of Climate Science and Science of Climate History

Climate and BiologyClimate and BiologyClimate is a fundamental factor

influencing biologyThus…Can use biology to learn about

certain aspects of climateAndBiology can influence climate

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From cold climate…From cold climate…

For most of the past 2-3 million years, the Earth has been quite cold

Evidence from the distribution of oxygen isotopes in cores taken from deep ocean floor as many as 16 glacial cycles, each lasting up to 125,000 years with intervals of only 10,000 to 20,000 years

… … to a warmer climateto a warmer climate

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During the 20,000 years since the peak of the last glaciation, global temperatures have risen by ~ 8 C

Analysis of buried pollen can show how vegetation has changed during this period

Migrations of trees in eastern North America from 18,000 years ago to present are known from pollen grains deposited in bogs and lakes: the compositions of communities shifted as species

migrated across the landscape in particular, the composition of forests during the past

18,000 years has: included combinations of species that do not occur today lacked combinations of species that do occur at present

(c) 2001 by W. H. Freeman and Company

Changes in Climate 1Changes in Climate 1

Climate change…Climate change…

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Naturally – with the change in plants change in animals

Even in regions never glaciated, pollen deposits record complex changes in distribution In the mountains of Nevada – woody species show

different patterns of change in elevational range Species composition of vegetation is continually

changing – and is still changing So what could happen in the next 100 years?

Temperatures predicted to rise between 2 to 7 C in 100 years

Postglacial warming of 8 C occurred over 20,000 years

Now: trees will have to move at 300-500 km/100 years

Typically: trees move 20 – 40 km/100 years

“On every continent except Antarctica there are examples of deserted settlements and evidence of long-extinct civilizations. These are societies that once flourished but have now gone, due primarily to a change in climate.”

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Tyndall…Tyndall…1861 – described the greenhouse role of

some gases and he quantified their heat-absorbing properties

Also suggested what would happen if their [ ] in the atmosphere changed – if the greenhouse gases decreased

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Relationship between energy Relationship between energy and lightand lightMax Planck, 1902Simple equation:

◦ E = hv◦ E = energy measured in joules◦ V = frequency in hertz

◦ The energy of eletromagnetic radiation (light, thermal radiation and other rays) is proportional to its frequency (v) or color, with the constant of proportionality being Planck’s constant (h)

◦ Atmosphere is transparent to some frequencies of light but not others some higher-energy light is mixed into the blanket of atmosphere surrounding our planet, but lower-energy infrared wavelengths hindered from getting out

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Different warming Different warming contributions of each contributions of each greenhouse gasgreenhouse gasConcentrations and human additions

to the atmosphere of each gas are different (as discussed)

Each gas has a different global warming potential (GWP) ◦GWP: comparative index for a unit mass

of each gas measured against the warming potential of a unit mass of carbon dioxide over a specific period of time

◦Carbon dioxide: GWP of 1◦Need to take into consideration the

atmospheric residence times of each gas

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Atmospheric residence Atmospheric residence timetimeMethane: Atmospheric residence time

(ART): 12 years◦ All of a kg of methane will still be in the

atmosphere after 1 year◦ Half of it after 12 years◦ A quarter after 24 years

Nitrous oxide: ART – over a centuryComparing GWPs of methane and nitrous

oxide over 10 years will give different warming figures compared with the same comparison over 100 years

Plus: uncertainty (evolving..) of GWP estimates

Plus: IPCC – science by committee

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Carbon cycleCarbon cycle

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Carbon uncertaintiesCarbon uncertaintiesCarbon cycle: dynamicWhere does roughly half of the CO2

released into the atmosphere by human action end up?

Net imbalance: estimates of carbon dioxide entering and those accumulating and leaving the atmosphere (table 1.3)◦Has some route of carbon not been

identified?◦ Is one or more of the carbon-flow estimates

off the mark?

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Missing carbonMissing carbon Problem seems to be associated with one or more of

the other carbon sinks◦ Accumulation of carbon by terrestrial plants◦ By absorption into oceans

Estimates of deforestation – how accurate? Official estimates are typically under-estimates

Deforestation probably accounts for a greater contribution to atmospheric CO2 –not less

Could oceans be accumulating more carbon than we think? Could the increased atmospheric CO2 + increased temp ->

encourage terrestrial photosynthesis, drawing down carbon into plants?

What about carbon stored in soils and detritus?– currently – soil acts as a global net carbon sink

Driving force photosynthesis

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Missing carbonMissing carbon Isotopes of carbon may hold a key to

determining the source of the increased carbon in the atmosphere

Studies are based on the ratio of the three different carbon isotopes in atmospheric CO2. Carbon has three possible isotopes: - C-12, C-13, and C-14

C-12 - has 6 neutrons - most prevalent carbon isotope and is a stable isotope.

Carbon 13 also a stable isotope, but plants prefer Carbon 12 and therefore photosynthetic CO2 (fossil fuel or wood fuels) is much lower in C-13 than CO2 that comes from other sources (e.g.: animal respiration) ; ~ 1% C-13

Carbon-14 is radioactive.

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Rubsico enzyme evolved to handle the almost universal C-12 isotope

1% is C-13If photosynthetic activity increases

(each summer, or due to CC) then increase in atmospheric C-13 left behind can be measured

But: C-12 and C-13 dissolve =ly well in sea water; C-13 a bit better => so detecting atmospheric C-13

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2006 discovery2006 discoveryPlants in aerobic conditions

produce methaneAmounts detected small; globally

– can amount to a significant source

Could be between 1/12 and 1/3 of annual amount

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Research on carbon cycle to Research on carbon cycle to measure or infer carbon measure or infer carbon sinkssinks1. Global budgets based on atmospheric

data and models2. Global budgets based on models of

oceanic carbon uptake3. Regional carbon budgets from forest

inventories4. Direct measurements of carbon

dioxide above ecosystems5. Earth-system science modelling using

ecosystem physiology6. Carbon models based on changes in

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Pacemaker of the glacial-Pacemaker of the glacial-interglacial cyclesinterglacial cyclesThe Milankovitch or astronomical

theory of climate change is an explanation for the changes in the seasons which result from changes in the earth's orbit around the sun.

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Foraminifera found in deep-Foraminifera found in deep-sea sedimentssea sediments

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Evidence?Evidence?Not until the advent of deep-

ocean cores and a seminal paper, "Variations in the Earth's Orbit: Pacemaker of the Ice Ages", in Science 1976, did the theory attain its present state.

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EXCELLENT FIGURE! EXCELLENT FIGURE! FIGURE 1.8FIGURE 1.8

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1970s: ice cores revealed: last glacial lasted for 100,000 years; previous interglacial 10,000; change between the two was sudden. Current interglacial already lasted 100,000. new ice age?

1980s: facts revealed that planet was warming

?: how great a warming could we expect from our fossil-fuel generation of carbon dioxide and how would this compare against the current range of other climatic factors?

First IPCC report: 199004/20/23 46

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Ice cores – one toolIce cores – one tool

The great remaining ice sheets

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greenlandgreenland

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AntarcticaAntarctica

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Ice cores provided the Ice cores provided the evidenceevidenceThe great remaining ice sheetsIce cores

◦ Result of snow accumulation ◦ Snow contains air◦ Some air gets trapped in bubbles ◦ Bubbles then contain "fossil air." ◦ Ice contains water and water contains

isotopes of both hydrogen and oxygen ◦ Factors controlling the behavior of

hydrogen and oxygen isotopes ◦ Geographical distribution of dO18 ◦ Relation of dO18 values to temperature.

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Glacial/interglacial variations in atmospheric carbon Glacial/interglacial variations in atmospheric carbon dioxidedioxideNatureNature 407407, 859-869 (19 October 2000, 859-869 (19 October 2000

Twenty years ago, measurements on ice cores showed that the concentration of carbon dioxide in the atmosphere was lower during ice ages than it is today. As yet, there is no broadly accepted explanation for this difference. Current investigations focus on the ocean's 'biological pump', the sequestration of carbon in the ocean interior by the rain of organic carbon out of the surface ocean, and its effect on the burial of calcium carbonate in marine sediments. Some researchers surmise that the whole-ocean reservoir of algal nutrients was larger during glacial times, strengthening the biological pump at low latitudes, where these nutrients are currently limiting. Others propose that the biological pump was more efficient during glacial times because of more complete utilization of nutrients at high latitudes, where much of the nutrient supply currently goes unused.

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