AP Enviro -- Chapter 18

Tree Rings

tree rings — the width of each ring of a tree trunk cut in cross-section reveals how much the tree grew in a particular growing seasons — a wide ring means more growth, generally indicating a wetter year — long-lived trees such a bristlecone pines can provide records of precipitation and drought going back several thousands years — tree rings are also used to study local fire history, since a charred ring indicates that a fire took place in the region in that year

climate

- describes an area's long-term atmospheric conditions, including temperature, moisture content, wind, precipitation, barometric pressure, solar radiation, and other characteristics - climate differs from weather in that weather specifics conditions at localized sites over hours or days, whereas climate describes conditions across broader regions over seasons, years, or centuries

Transportation choices

- some people are choosing to live nearer to their workplaces — other use mass transit such as buses, subway trains, and light rail — still other bike or walk to work or on errands - unfortunately, reliable and convent public transit is not yet available in many U.S. communities — making automobiles-based cities and suburbs more friendly to pedestrian and bicycle traffic and improving people's access to public transportation stand as central challenges for city and regional planners

Electricity generation is the largest source of U.S. greenhouse gases

- the generation of electric produced the largest portion (40%) of U.S. carbon dioxide emissions — fossil fuel combustion generates 70% of U.S. electricity, and coal alone accounts for 50% along w/ most of the emissions from electrical generation — there are two ways to reduce the amount of fossil fuel we burn to generate electricity: 1. encouraging conservation and efficiency and 2. switching to cleaner and renewable energy sources

Solar output

- the sun varies in the amount of radiation it emits, over both short and long timescales - scientists are concluding that the variation in solar energy reaching our planet in recent centuries has simply not been great enough to drive significant temperature change on Earth's surface

Automotive technology

- the technology exists to make our vehicles far more fuel-efficient than they current are - raising fuel efficiency for American-made vehicles will require government mandate and/or consumer demand, and as gasoline prices rise, demand for more fuel-efficient automobiles intensify - advancing technology is also bringing us alternatives to the traditional combustion-engine automobile — these include hybrid vehicles that combine electric motors and gasoline-powered engines for greater efficiency — they also include fully electric vehicles, alternative fuels such as compressed natural gas and biodiesel, and hydrogen fuel cells that use oxygen and hydrogen and produce only water as a waste product

What is climate change?

- when people speak of climate change and global warming, they generally are referring to the trends taking place right now — scientists may also sometime sure these terms to refer to trends in the geologic past - the climate changes unfolding today are proceeding at an exceedingly rapid rate — scientists agree that human activities, notably fossil fuel combustion and deforestation, are largely responsible

Ice Cores

Ice caps, ice sheets, and glaciers hold clues to climate history — over the ages, these huge expanses of snow and ice have accumulated to great depths, preserving within layers tiny bubbles of the ancient atmosphere — scientists can examines the trapped air bubbles by drilling into the ice and extracting long columns, or cores — the layered ice, accumulating season after seasons over thousands of years, provides a timescale — by studying the chemistry of the ice and the bubbles in each layer in these ice cores, scientists can determine atmospheric composition, GHG concentrations, temperature trends, snowfall, solar activity, and even frequency of forest fires and volcanic eruptions during each time period

Carbon dioxide is the greenhouse gas of primary concern

although carbon dioxide is less potent on a per-molecule basis than other greenhouse gases such as methane and nitrous oxide, it is far more abundant in the atmosphere so it contribute more to the anthropogenic greenhouse effect, b/c our greenhouse gas emissions consists mostly of carbon dioxide — that is, even after accounting for the greater global warming potential of molecules of the gases, carbon dioxide's abundance in our emissions make s it the major contributor to anthropogenic global warming

Climate change affects people

damage from drought, flooding, storm surges, sea level rise, and other impacts of climate change has already taken a toil on the lives and livelihoods of millions of people — climate change will have still more consequences for human populations, including impacts on agriculture, forestry, economics, and health

Global climate change

describes trends in Earth's climate, involving aspects such as temperature, precipitation, and storm frequency and intensity

Forestry

enriched atmospheric carbon dioxide may spur greater growth in the near term, but other climatic effects such as drought, fire, and disease may eliminate these gains

packrat middens

in arid regions packrat middens are a valuable source of climate data — packrats are rodents that carry seeds and plant parts back to their middens, or dens, in caves and rock crevices sheltered from rain — in arid locations, plant parts may be preserved for centuries, allowing researchers to study the past flora of the region

fee-and-dividend

in the fee-and-divided approach, funds form the carbon tax, or "fee", paid to government by polluters are transferred as tax refund, or "dividend", to taxpayers — this way, if polluters pass their costs along to consumers, those consumers will be reimbursed for those costs by the tax refund they receive — the system should provide polluters a financial incentive to reduce emissions, while imposing no financial burden on taxpayers

Coral Reefs

researchers gather data on past ocean conditions from coral reefs — living corals take in trace elements and isotopes ratios from ocean water as they grow, and they incorporate these chemical clues to ocean conditions, layer by ayer, into growth bands in the reefs they build

Transportation is the second largest source of U.S. greenhouse gases

- 1/3 of the average American city — including roads, parking lots, garages, and gas stations — is devoted to use by the nation's 220 millions registered automobiles - the typical automobile is highly inefficient — over 85% of the fuel you pump into your gas tank does something other than move your car down the road - more aerodynamic designs, increased engine efficiency, and improved tire design can help reduce these losses, but gasoline-filed automobiles may always remain somewhat inefficient

Precipitation is changing, too

- A warmer atmosphere holds more water vapor, but changes in precipitation patterns have been complex, w/ some regions of the world receiving more rain and snow that usual and others receiving less - future changes in precipitation and predicted to vary among regions in ways that parallel regional differences seen over the past century — in general, precipitation will increase at high latitudes and decrease at low and middle latitudes, magnifying differences in rainfall that already exist and worsening water shortages in many developing countries o the arid subtropics

Proxy indicators tell us about the past

- Evidence about paleoclimate, climate in the geologic past, is vital for giving us a baseline against which to measure changes happening in our climate today — environmental scientists have developed a number of ingenious method so decipher clues from the past, taking advantage of the record-keeping capacity of the natural world - Proxy indicators: ice cores, sediment cores, tree rings, packrat middens, and coral reefs - proxy indicators often tell us information about local or regional areas — to get a global perspective, scientists need to combine multiple records from various areas — b/c the number of available indicators decreases the further back in time we go, estimates of global climate conditions for the recent past tend to be more reliable than those for the distant past

Temperatures continue to rise

- In IPCC's 2007 report concluded that average surface temperatures on Earth increased by an estimated in the century from 1906 to 2005, w/ most of this increase occurring in that last few decades — the numbers of extremely hot days and heat waves have increased globally, whereas the number of cold days has decreased - In the next 20 years, we can expect average surface temperatures on Earth to rise, according IPCC analysis — even if we were to cease GHG emissions today from fossil fuel use and deforestation, temperatures would still rise b/c of a time lag: some gases already in the atmosphere have yet to exert their full influence — unusually hot days and heat waves will become more frequent — future changeless in temperature are predicted to vary from region to region in ways that parallel regional differences already apparent - sea surfaces temperatures are also increasing as the oceans absorb heat from the atmosphere — recent analyses of storm data suggest that warmer seas may not be increasing the number of tropical storms but may be increasing their power and their duration

The IPCC summaries evidence and predicts impacts

- Intergovernmental Panel on Climate Change (IPCC) — consists of many hundreds of scientists and government officials — established in 1988 by the United Nations — UNEP & WMO, the IPCC was awarded the Nobel Peace Prize in 2007 for its work in forming the world of the trends & impacts of climate change - IPCC released its Fourth Assessment Report, which represented the current consensus of scientific climate research from around the world — summarized many thousands of scientific studies, & it documented observed trends in surface temperature, precipitation, patterns, snow and ice cover, sea levels, storm intensity, & other factors — it also predicted future changes in these phenomena after considering a range of potential scenarios for future GHG emissions — the report addressed impacts of current & future climate change on wildlife, ecosystems, & society — it discussed possible strategies we might pursue in response to climate change - the IPCC report deals in uncertainties — its authors therefore took great care to assign statistical probabilities to its conclusions & predictions — in addition, its estimates regarding impacts on scouts are conservative, b/c its scientific conclusions had to be approved by representatives of the world's national governments, some of which are reluctant to move away from a fossil-fuel-based economy - climate scientists at the WMO & many other institutions, agencies, & universities around the world are continuing to monitor our changing climate

Will emissions cuts hurt the economy?

- The U.S. Senate has steadfastly opposed emissions reductions out of fear that they will dampen the U.S. economy — industrializing nations such as China and India have so far resisted emissions cuts under the same assumption — this assumption is understandable, give that so much of our economy depends on fossil fuels — yet other nations have demonstrated that economic vitality does not require ever higher emissions - b/c resource use and per capita emissions are high in the U.S. and other industrialized nations, governments and industries there often feel they have more to lose economically from restrictions on emissions than developing nations do — industrialized nations are also the ones most likely to gain economically from major energy transitions, b/c they are best positioned to invent, develop, and market new technologies to power the world in a post-fossil-fuel era

The Copenhagen conference failed to produce a treaty

- an international conference in Copenhagen, Denmark, in Dec. '09 was intended to design a successor treaty to the Kyoto Protocol — initially, hopes were high b/c the new administration of U.S. President Obama favored international climate negotiations, & other nations hoped this would lead to U.S. participation in a full international agreement — Obama chose not to promote the international community more than the U.S. Congress had already agreed to — although the House had passed legislation to mandate emissions reductions, the Senate had not, & Senate approval is needed for U.S. ratification of any treaty - w/ no agreements reached by the final day of the Copenhagen conference, Obama & a handful of other leaders of major nations put together a last-minute accord that fell far short of most nation's hopes — the most notable aspect of his Copenhagen Accord was an offer from developed nations to pay developing nations to help w/ their mitigation and adaptation efforts — the accord also reflected widespread intent during the conference to begin counting deforestation in emissions calculations & rewarding nations that reduce forest loss — non of the accord's langue was legally binding, & the conference ended w/o specific targets being set or solid commitments being made - several nations denounced the accord, so that the conference could not even formally adopt it by consensus & had to merely "take note" of it

Health

- as climate change proceeds, we will face more heat waves — heat stress can cause death, especially among older adults - a warmer climate also exposes us to other health problems: respiratory ailments from air pollution, as hotter temperatures promote formation of photochemical smog, expansion of tropical disease, such as dengue fever, into temperate regions as vector of infectious disease move toward the poles, disease and sanitation problems when floods overcome sewage treatment systems, injuries and growing if storms become more frequent or intense - health hazards from cold weather will decrease, but most researchers feel that increase in warm-weather hazards will more than offset these gains

Greenhouse gases warm the lower atmosphere

- as earth's surface absorbs solar radiation, the surface increases in temperature & emits infrared radiation — infrared radiation has longer wavelengths than the visible & ultraviolet light that had arrived from the sun & passes through the atmosphere — atmospheric gases having three or more atoms in their molecules tend to absorb this infrared radiation very effectively — include: water vapor, ozone, carbon dioxide, nitrous oxide, & methane, as well as halocarbons, a diverse group of mostly human-made gases that includes CFCs — greenhouse gases — after absorbing radiation emitted from the surface, greenhouses gases subsequently re-emit infrared radiation in all directions, some of this energy is lost into space, but some travels back downward, warming the atmosphere & the planet's surface in a phenomenon known as the greenhouse effect - the greenhouse effect is a natural phenomenon & greenhouse gases have been present in our atmosphere for all of Earth's history — w/o the natural greenhouse effect, our planet would be too cold to support life — it is not the natural greenhouse effect that conner scientists today, but rather the anthropogenic intensification of the greenhouse effect — by adding novel greenhouse gases to the atmosphere, & by increasing the concentration of several natural greenhouse gases over the past 250-300 years, we are intensifying our planet's greenhouse effect beyond what our species has ever experienced - greenhouse gases differ in their ability to warm the troposphere & surface - global warming potential refers to the relative ability of one molecule of a given greenhouse gas to contribute to warming - Values are expressed in relation to carbon dioxide, which is assigned a global warming potential of 1 — thus, a molecule of methane is 25 times as potent as a molecule of carbon dioxide, & molecule of nitrous oxide is 298 times as potent as a carbon dioxide molecule

Rising sea levels will affect hundreds of millions of people

- as glaciers and ice sheets melt, increased runoff into the oceans causes sea levels to rise — sea levels are also rising b/c ocean water is warming, & water expands in volume as its temperature increases — recent sea-level rise has resulted primarily from the thermal expansion of seawater - higher sea levels lead to beach erosion, coastal flooding, intrusion of salt water into aquifers, & other impacts - a storm surge is a temporary & localized rise in sea level brought on by the high tides & winds associated w/ storms -- the higher the sea level is to begin w/, the further inland a destructive storm surge can reach - if sea levels rise as predicted, hundred of millions of people will be displaced or will need to invest in costly efforts to protect against high tides & storm surges — densely populated regions on low-lying river deltas would be most affected — storm-prone regions & areas where land is subsiding would need to be evacuated —already some nations fear for their existence — in the meantime, island nations are likely to suffer form shortages of fresh water as rising seas bring salt water into aquifers — the contamination of groundwater & soils by seawater also threatens coastal areas that depend on small lenses of fresh water that float atop saline groundwater

Melting ice and snow have far-reaching effects

- as the world warms, mountaintop glaciers are disappearing; many glaciers on tropical mountaintops have disappeared already - mountains accumulate snow in the winter & release meltwater gradually during the summer — over 1/6 of the world's people live in regions that depend on mountain meltwater — as wearing temperatures continue to diminish mountain glaciers, this will reduce summertime waters supplies to millions of people, likely forcing whole communities to look elsewhere for water or to move - warming temperatures are melting vast amts of ice in the arctic — recent research levels that the immense ice sheet that cover Greenland is melting faster and faster — at the other end of the world, Antarctic, costal ice shelves the size of Rhode Island have disintegrated as a result of contact w/ warmer ocean water, although increased precipitation is suppling the continent's interior w/ extra snow, making its ice sheet thicker even as it loses ice around its edges - one reason warming is accelerating in the Arctic is that as snow & ice melt, darker, less-reflective surfaces are exposed, & Earth's albedo, or capacity to reflect light, decreases — pools of meltwater are darker than ice or snow, & bare ground is darker still — as a result, more of the sun's rays are absorbed at the surface, fewer reflect back into space, & the surface warms — in a process of positive feedback, this warming causes more ice & snow to melt, which in turn causes more absorption of radiation & more warming - scientists predict that snow cover & ice sheets will decrease near the poles & that sea ice will continue to shrink in both the Arctic & Antarctic — some emission scenarios show Arctic sea ice disappearing completely by the late 21st century, creating new shipping lanes for commerce & a rush to exploit underrated oil & mineral reserves - warmer temperatures in the Arctic are also coating permafrost to thaw — as ice crystals within permafrost melt, the thawing soil settles, destabilizing buildings, pipelines, & other infrastructure — when permafrost thaws, it also can release methane that has been stored for thousands of years — b/c methane is a potent GHG, this acts a positive feed mechanics that intensifies climate change — large amt of methane is in permafrost

Feedback compliances our predications

- as tropospheric temperatures increases, Earth's water bodies should transfer more water vapor into the atmosphere, but scientists aren't yet sure how this will affect our climate — more atmospheric water vapor could lead to more warming, which could lead to more evaporation and water vapor, in a positive feedback loop that would amplify the greenhouse effect - more water vapor could give rise to increased cloudiness, which might, in a negative feedback loop, slow global warming by reflecting more solar radiation back into space — depending on whether low- or high-elevation clouds result, they might either shade & cool Earth or else contribute to warming & accelerate evaporation & further cloud formation

Shall we pursue mitigation or adaption?

- both adaptation and mitigation are necessary — adaption is needed b/c even if we were to halt all our emissions now, global warming could continue until the planet's systems reach a new equilibrium, w/ temps rising an estimated more by the end of the century - mitigation is necessary b/c if we do nothing to diminish climate change, it will eventually overwhelm any efforts at adaptation we might make — to leave a sustainable future for our civilization and to safeguard the living planet that we know, we will need to pursue mitigation — the faster we begin reducing our emissions, the lower the level at which they will peak, and the less we all alter climate

You can reduce your carbon footprint

- carbon taxes, offset emissions trading schemes, national policies, international treaties, and technological innovations will al play roles in mitigating climate change — the most influential factor may be the collective decisions of million of regular people — in our everyday lives, each one of us can take steps to approach a carbon-neutral lifestyles by reducing GHG emissions that result from our decisions and activities - we have a carbon foot-print that expresses the amount of carbon we are responsible for emitting

Carbon taxes

- carbon trading markets show mixed results early in their growth, a number of economists, scientists, and policymakers are saying that cap-and-trade systems are not effective enough, don't work quickly enough, or leave too much to change — many of these critics would prefer that governments enact a carbon tax - the carbon tax approach, governments charge polluters a fee for each unit of GHGs they emit — gives polluters a financial incentive to reduce emissions — carbon taxes have so far been established in several European nations - the downside: most polluters simply pass the cost along to consumers by charging higher prices for the products or services they sell — proponents of carbon taxes have responded by proposing an approach called fee-and-dividend

Climate change affects organisms and ecosystems

- changes in earth's physical systems often have direct consequences for living things — organisms adapted to their environments, so they are affected when the environments are altered — as global warming proceeds, it is modifying all manner of biological phenomena that are regulated by temperature — altering shifts can create mismatches in seasonal timing - biologists also record spatial shifts in the ranges of organisms, w/ plants & animals moving towards the piles or upward in elevation as temperatures warm — as these trends continue, some organisms will not be able to cope, & the IPCC estimates that as many as 20-30% of all plant & animal species could be threatened w/ extinction - trees many not be able to shift their distributions fast enough — rare species may be forced out of preserves into developed areas, undercutting the effectiveness of refuges as tools for conservation — animal & plants adapted to montane environments may be forced uphill until there is nowhere left to go - effects on plant communities comprise an important component of climate change, b/c by drawing carbon dioxide for photosynthesis, plants air as reservoirs for carbon — if higher carbon dioxide concentrations enhance vegetative growth, this could hep mitigate carbon emissions in a process of negative feedback — however, if climate change decreases plant growth, then positive feedback could increase carbon flux to the atmosphere - Free-Air Carbon Dioxide Enrichment (FACE) experiments are revealing complex answers, showing that extra carbon dioxide can bring both positive & negative results for plant growth - in regions where precipitation & stream flow increase, erosion & flooding will pollute & alter aquatic systems — in regions where precipitation decreases, lakes, ponds, wetlands, & streams will shrink, affecting aquatic organisms, as well as human health & well-being — will diminish the ecosystems goods & services we receive from nature & that our societies depend on, from food to clean air to drinking water

Coral reefs are threatened by climate change

- coral reefs are critical for economy — coral reefs provide habitat for important food fish that are consumed locally and exported — they offer snorkeling and scuba diving sites for tourism — reefs also reduce wave intensity, protecting coastlines from erosion — rising seas are eating away at the coral reefs, mangrove forests, and salt marshes the serve as barrier protecting coasts - destruction of coral reefs would reduce marine biodiversity and fisheries significantly, b/c so many organisms depend on living coral reefs for food and shelter

Agriculture

- earlier springs require earlier crop planting — for some crops in the temperate zones, moderate warming may slightly increase production b/c growing seasons become longer - additional carbon dioxide being available to plants for photosynthesis may also increase yields, but elevated carbon dioxide can have mixed results - some research shows that crops become less nutritious when supplied w/ more carbon dioxide - if rainfall shifts in space and time, intensified droughts and flood will likely cut into agricultural productivity - IPCC predicts global crop yields to increase, but beyond 3 degrees C, it expects crop yields to decline - in seasonally dry tropical and subtropical regions, growing seasons may be shortened, and harvests may be more susceptible to drought — product that crop production will fall in these regions even w/ minor warming — would worsen hunger in many of the world's developing nations

Carbon offsets are popular

- emissions trading programs generally allow participants to buy carbon offsets, voluntary payments intended to enable another entity to rescue emissions that one is unable to reduce oneself — the payment just offsets one's own emissions - carbon offsets have fast become popular among utilities businesses, universities, governments, & individuals trying to achieve carbon-neutrality, a state in which no net carbon is emitted — for busy people w/ enough wealth, offsets represent a simple & convenient way to reduce one's emissions w/o investing in efforts to change one's habits - in principle, carbon offsets seem a great idea, but w/o rigorous oversight to make sure that the offset money actually accomplishes what it is intended for, carbon offset risk being little more than a way for wealthy consumers to assuage a quality conscience — offsets are effective only if they find emissions reductions that would not occur otherwise — & b/c trees can sock up only so much carbon dioxide, at some point our ability to reduce emissions by funding reforestation could each its limit — efforts to create a transparent & enforceable system for verifying the effectiveness of offsets are ongoing — if these offsets succeed, then carbon offsets could become an important means of mitigating climate change

climate change poses threats to coral reefs

- first, warmer waters contribute to coral bleaching, which kills corals - enhanced carbon dioxide concentration in the atmosphere are altering ocean chemistry — as ocean water absorbs atmospheric carbon dioxide becomes more acidic — this increases acidity impairs the ability of corals and other organisms to build exoskeletons of calcium carbonate — ocean acidification and the potential loss of cereal reefs worldwide threaten to become one of the most serious and far-reaching impacts of global climate change

Impacts will vary regionally

- future impacts of climate change will be subject to regional variation, so the way each of us experience these impacts over the decades will vary depending on where we live - temperature changes have been greatest in the Arctic, & scientists are still debating why - here, ice sheets are melting, sea ice is thinning, storms are increasing, & altered conditions are posing challenges for people & wildlife — as sea ice melts earlier, freezes later, & recedes from shore, it becomes harder for Inuit people & for polar bears alike of hunt the seals they each rely on for food - thin sea ice is dangerous for people to travel and hunt upon, & in recent years, polar bears have been dying of exhausting & starvation as they try to swim long distance b/w ice flows - permafrost is thawing in the Arctic, destabilizing countless building — the strong Arctic warming is melting ice caps & ice sheets, contributing to sea level rise - in the U.S., potential impacts are analyzed & summarized by the U.S. Global Change Research Program, which Congress created in 1990 to coordinate federal climate research — in 2009, scientists for this program reviewed current research & issued a comprehensive report to highlighting the effects of climate change on the U.S. & issuing predictions of future impacts - the report predicted that some impacts would be felt across the nations — average temps in most of the U.S. have already increased since the 1960s-70s & they will rise by another by the end of this century - plant communities will likely change in all areas of the country, in generally shifting northward & upward in elevation - other impacts will likely vary by region, w/ each region of the U.S. facing its own challenges — winter & spring precipitate is projected to decrease across the South but increase across the North — Drought may strike in some regions & flooding in others — Sea level rise may affect the East Coast more than the West Coast — Agriculture may experience a wise array of effects that will vary from one regions to another — as climate models improve, scientists become able to present graphical change on particular geographic areas - all these impacts of climate change are projects consequences of the warming effect of our GHG emissions — we are bound to experience further consequences, but by addressing the roost causes of anthropogenic climate change now, we may still be able to prevent the most severe future impacts

Other greenhouse gases add to warming

- human activities have increased earth's atmospheric concentration of carbon dioxide - methane concentrations are also rising — we realize methane by tapping into fossil fuel deposits, raising livestock that emit methane as a metabolic waste product, disposing of organic matter in landfills, & growing certain crops, such as rice - human actives have also enhances atmospheric concentrations of nitrous oxide — a by-product of feedlots, chemical manufacturing plants, auto emissions, & synthetic nitrogen fertilizers - ozone concentration in the troposphere have rise b/c of photochemical smog — the contribution of halocarbon gases to global warming has begun to slow b/c of the Montreal Protocol & subsequent controls on their production & use - water vapor is the most abundant GHG in our atmosphere & contributes most to the natural greenhouse effect — vary locally, but its global concentration has not changed over recent centuries — so it is not viewed as having driven industrial-age climate change

Milankovitch cycles

- in the 1920s, Milankovitch described three types of periodic changes in Earth's rotation & orbit around the sun — over thousands of years, our planet wobbles on its axis, varies in the title of the axis, & experiences change in the shape of its orbit, all in regular long-term cycles of different lengths — Milankovitch cycles, alter the way solar radiation is distributed over Earth's surface - by modifying patterns of atmospheric heating, these cycles trigger long-term climate variation — includes periodic episodes of glaciation during which global surface temperatures drop & ice sheets advance from the poles toward the midlatitudes, as well interglacial periods

Fossil fuel use and deforestation release carbon dioxide

- most carbon is stored for long periods in the upper layers of the lithosphere - the deposition, partial decay, & compression of organic matter that grew in wetland or marine areas hundreds of millions of years ago led to the formation of coal, oil, & natural gas in buried sediments — in the absence of human activity these carbon reservoirs would remain buried for many millions more years — we have extracted these fossil fuels from the ground & burned them in our homes, factories, & automobiles, transferring large amounts of carbon from one reservoir to another — this sudden flux of carbon from lithospheric reservoirs into the atmosphere is the main reason atmospheric carbon dioxide concentrations have increased so dramatically - people have clerked & burned forests to make room for crops, pastures, villages, & cities — forests serve as reservoir for carbon as planets conduct photosynthesis & then store carbon in their tissues — when we clear forests it reduces the biosphere's ability to remove carbon dioxide from the atmosphere

Ocean circulation

- ocean water exchanges tremendous amts of heat w/ the atmosphere, & ocean currents move energy from place to place - in equatorial regions, the oceans receive more heat from the sun & atmosphere than they emit - near the poles, the oceans emit more heat than they receive — b/c cooler water is denser than warmer water, the cooling water at the poles tends to sink, & the warmer water from the equator moves to take its place - the oceans' thermohaline circulation system has influential regional effects — it moves warm tropical water northward toward Europe, providing that continent a far milder climate than it would otherwise have - El Nino, which involves systematic shifts in atmospheric pressure, sea surface temperature, and ocean circulation in the tropical Pacific Ocean — these shifts overlie longer-term variability from a phenomenon known as the Pacific Decadal Oscillation — El Nino and La Nina events alter weather patterns from region to region in diverse ways, often leading to rainstorms and foods in dry areas and drought and fire in moist areas

we can response to climate change in 2 fundamental ways

- one is to pursue actions that reduce GHG emissions, so as to lessen the severity of climate change — mitigation b/c the aim is to mitigate, or alleviate, the problem — examples include improving energy efficiency, switching to clean an renewable energy sources, preventing deforestation, recovering landfill gas, and encouraging farm practices that protect soil quality - the second type of response is to pursue strategic to minimize the impacts of climate change on us — adaptation b/c the goal is to adapt to change by finding ways to cushion oneself from its blows — examples including restricting coastal development; adjusting farming practices to cope w/ drought; and modifying water management practices to deal w/ reduced river flows, glacial outburst floods, or salt contamination groundwater

Economics

- people will experience a variety of economic costs and benefits form the many impacts of climate change, but on the whole researches predict that costs will outweigh benefits, especially as climate change grow more severe - climate change is also expected to widen the gap b/w rich and poor, both within and among nations — poorer people have less wealth and technology w/ which to adapt to climate change, and poor people rely more on resources that are sensitive to climatic conditions - the IPCC estimated that climate change will cost 1-5% of GDP on average globally, w/ poor nations losing proportionally more than rich nations — economists are trying to quantify damages from climate change by measuring its external costs have proposed costs of anywhere from $10 to $350 per ton of carbon — shows that climate change could cost us roughly 5-20%of GDP by the year 2200, but that investing just 1% of GDP starting now could enable us to avoid these future costs - many economists and policymakers are concluding that spending money now to mitigate climate change will save us a great deal more money in the future

Market mechanisms are being used to address climate change

- permit trading programs aim to harness the economic efficiency of the free market to achieve public policy goals while allowing business, industry, & utilities flexibility in how they meet those goals — supports of this argue that they produce the fairest, least expensive, & most effective method of reducing emissions — polluters choose how to cut their emissions & are given financial incentives for reducing emissions below the legally required amt - once used, it is hoped that the system will be self-sustaining — the price of the permit is meant to fluctuate freely in the market, creating the same kinds of financial incentives as any other commodity that is bought & sold in our capitalist system - first — Chicago Climate Exchange — voluntary, but legally binding trading system has imposed a 6% reduction on overall emissions by 2010 - largest — European Union Emissions Trading Scheme — got off to a successful start in '05, but once investors discovered that national governments has allocated too many emissions permits to their industries, the price of carbon fell — the overallocation gave companies little incentive to reduce emissions, so permits lost their value, & prices in the market tanked to 1/100th of their high value — in '08, Europeans tried to correct these problems by making emitters pay for permits & setting emissions caps across the entire European Union while expanding the program to include more GHGs, more emissions sources, & additional members — in '09, it expanded, but prices fell — the long run, permits will be valuable & the market will work only if government policies are in place to limits emissions

climate models

- programs that combine what is known about atmospheric circulation, ocean circulation, atmosphere-ocean interactions, & feedback cycles to simulate climate processes — requires manipulating vast amounts of data w/ complex mathematical equations — a task not possible until the advent of modern computers - climate modelers provide starting information to the model, set up rules for the simulation, & then let it run — researchers strive for accuracy by building in as much information as they can from what is understood about how they climate system functions — they then test the efficacy of model by entering past clime data & running the model toward the preset — if a model accurately reconstructs current climate, based on well-established data from the past, then we have reason to believe that it simulates climate mechanisms realistically & that it may accurately predict future climate - plenty of challenges remain for climate modelers, b/c the climate systems is so complex & b/c many uncertainties remain in our understanding of feedback processes — yet as scientific knowledge of climate process improves, as computing power intensifies, & as we glean enhanced data from proxy indicators — they are improving in resolution & are beginning to predict climate change region by region for various areas of the world

We will need to follow multiple strategies

- reducing emissions will require many steps by many people & institutions across many sectors of our economy — good news: most reductions can be achieved using current technology & that we can begin implementing these changes right away - environmental scientists Stephan Pacala & Robert Socolow advise that we follow some age-old wisdom: when the job is big, break it into small parts — Pacala & Socolow propose that we adopt a portfolio of strategies that together can stabilizes our carbon dioxide emissions at current levels - Pacala & Socolow w/ graphs that predicted a doubling of emissions over the next 50 years and asked: what would we need to do to hold our emissions flat instead & avoid the additional future emissions represented by the triangular area of the graph above the flat trend line? the researchers subdivided their so-called stabilization triangle into seven equal wedges, like slices of a pie — to eliminate one wedge, a strategy would need to reduce emissions equivalent to 1 billion tons of carbon per year 50 years in the future - in the long term, the stabilization-wedge approach will not be enough — to stop climate change, we will need to reduce emissions, not just stabilize them — & this may require us to develop new technology, modify our lifestyles, reduce our consumption, &/or reverse our population growth — there is plenty we can do in the meantime to mitigate climate change simply by scaling up technologies & approaches we already have developed

Are we responsible for climate change?

- scientists agree that most or all of today's global warming is due to the well-documented recent increase in GHG concentrations in our atmosphere — also agree that his rise in GHGs results from our combustion of fossil fuels for energy & secondarily from land use changes, including deforestation & agriculture - by the time of IPCC's fourth assessment report came out, many scientists had already become concerned enough about the consequences of climate change to put themselves on record urging governments to address the issue - yet despite the overwhelming evidence for climate change & its impacts, many people, especially in the U.S., long tried to deny that is was happening — may of these naysayers now admit that the climate is hanging but doubt that we are the cause — will most of the mold's nations moved forward to confront climate change through international dialogue, in the U.S. public discussion of climate change remained mired in outdated debated over whether the phenomenon was real & whether humans were to blame — these debates were fanned by spokespeople from conservative think tanks & a handful of scientists, many funded by corporations in the fossil fuel industries — these people aimed to cast doubt on the scientific consensus, & their views were amplified by the American news media, which seeks to present two sides to every issue, even when the sides argument are not equally supported by evidence - awareness of climate change grew as the 2007 IPCC report was made publicly available on the Internet & was widely covered in the media, & later as Gore and the IPCC were jointly awarded the Nobel Peace Prize - most of the world's people accept that our fossil duel consumption is altering the planet that our children will inherit -- as youth & grassroots activities spread this message, & as political leaders begin to respond, everyday people are searching for solutions — as a result of this shift in public perception, & in response to demand from their shareholders, many corporations & industries are looking for ways to reduce their GHGs emissions & are supporting policies to reduce them

The Kyoto Protocol sought to limit emissions

- since climate change is a global climate — global commitment is needed to forge effective solutions — why the world's policymakers have tried to tackle climate change by means of international treaties - in 1992 @ the U.N. Conference on Environmental & Development Earth Summit in Rio de Janerio, Brazil, most of the world's nations signed the U.N Framework Convention on Climate Change (FCCC) — this agreement outlined a plan for reducing GHG emissions to 1990 levels by the 2000 through a voluntary, nation-by-nation approach - by the late 90s, it was clear that a voluntary approach was not succeeding — nations of the developing world helped create a biding international treaty that would require emissions reductions — an outgrowth of the FCCC drafted in '97 in Kyoto, Japan, the Kyoto Protocol mandates signatory nations, by the period 2008-2012, to reduce missions of six GHGs to levels below those of 1990 - the U.S. refused to ratify the Kyoto Protocol & remains the only developed nation not to join this international effort — U.S. leaders who oppose the Kyoto Protocol call the treaty unfair b/c it requires industrialized nations to reduced emissions but does not require the same of rapidly industrializing nations such as China & India, whose GHGs emissions have risen over 50% in the past 15 years — the U.S. emits 1/5 of the world's GHGs, so its refusal has generated widespread resentment & has undercut the effectiveness of global efforts

States and cities are advancing climate change policy

- state and local governments across the country are responding to popular sentiment and advancing policies to limit emissions — by 2010, mayors from over 1,000 cities from all 50 states had signed on to the U.S. Mayors Climate Protection Agreement, initiated by Seattle Mayor Greg Nickels — under this agreement, mayors commit their cities to pursue policies to "meet or beat" Kyoto Protocol guidelines - at the state level — the boldest actions so far has come in Cali, where in 2006 that state's legislature worked w/ Schwarzenegger to pass the Global Warming Solution, which aims to cut Cali's GHG emissions 25% by the year 2020 — this law was the first stage legislation w/ penalties for noncompliance and followed earlier efforts in Cali to mandate higher fuel efficiency for automobiles

The sun and atmosphere keep Earth warm, while other factors regulate climate

- w/o the sun, earth would be dark and frozen - w/o atmosphere, earth would be as much as 33 degrees C colder on average, and temperature differences b/w night and day would be far greater than they are - the sun and the atmosphere keep our planet warm enough to sustain life - the oceans shape climate by soaring and transporting heat and moisture, and cycles in the ways our planet spins, tilts, and moves through space influence how climate varies over long periods of time - the sun suppose most of our planet's energy — earth's atmosphere, clouds land, ice, and water together absorb about 70% of incoming solar radiation and reflect the remaining 30% back into space — the 70% that is absorbing power many of Earth's processes, from winds to waves to evaporation to photosynthesis

Conservation and efficiency

- we all can make lifestyle choices to reduce electricity consumption — for nearly all of human history, people managed w/o the countless electrical appliances that most of us take for granted today — each of us can choose to use fewer GHG-producing appliances and technologies and to take practical steps to use electricity more efficiently - new energy-efficient technologies make it easier to conserve — the U.S. Environmental Protection Agency's Energy Star Program

Sources of electricity

- we can also reduce GHG emissions by switching to clean energy sources - alternatives to fossil fuels include nuclear power, biomass energy, hydroelectric power, geothermal power, photovoltaic cells, wind power, & ocean sources — these energy sources give off no net emissions during their use - b/c our society is not ready to transition fully to these alternatives, we also need to consider the ways we use fossil fuels — switching from coal to natural gas is a step in the right direction, b/c natural gas produces the same amt of energy as coal, w/ roughly 1/2 of emissions - currently, interest in carbon capture & storage is intensifying. Carbon capture refers to technologies or approaches that remove carbon dioxide from power plant emissions — successful carbon capture would allow facilities to continued using fossil fuels while cutting GHG pollution - the next step is carbon sequestration or carbon storage, in which the carbon is sequestered, or stored, underground under pressure in rock formations where it will not seep out — depleted oil & gas deposits & deep salt mines are examples of the kinds of underground reservoirs being considered — however, we are still a long way from developing adequate technology & secure storage space to accomplish this w/o leakage

Direct measurements tell us about the present

- we measure temperature w/ thermometers - we measure rainfall w/ gauges - we measure wind speed w/ anemometers - we measure air pressure w/ barometers - using computer programs to integrate and analyze this information in real time - w/ these technologies & more, we document in detail the fluctuations in weather day-by-day & hour-by-hour across the globe — we have gained an understanding of present-day climate conditions in every region of our planet - we measure chemistry of the atmosphere & the oceans w/ a range of equipment — direct measurements of carbon dioxide concentrations in the atmosphere began in 1958 when Keeling started analyzing hourly air samples from a monitoring station at the Manua Loa Observatory in Hawaii — these data show that atmospheric carbon dioxide concentrations have increased — as scientists continue these measurements today, they build upon the best long-term dataset we have of direct atmospheric sampling of a GHG - direct measurement of climate variables such as temperature & precipitation extend back in time somewhere further — precise & reliable thermometer measurements cover more than a century — people have also kept records of economically important impacts of climate that allow scientists to infer climate conditions of recent centuries: Fishers have recorded the timing of sea ice formation, & winemakers have kept meticulous records of precipitation & the length of the growing seasons — accurate records of thee types extend back at mostly only a few hundred years — to truly understand climate & how it behaves over time — & to predict future change — scientist must learn what climate conditions were like thousands & millions of years ago

Most aerosols exert a cooling effect

- whereas GHGs exert a warming effect the atmosphere, aerosols, microscopic droplets & particles, can have tier a warming or cooling effect - soot particles, or black carbon aerosols, generally cause warming by absorbing solar energy, but most other tropospheric aerosols cool the atmosphere by reflecting the sun's rays - sulfate aerosols produced by fossil fuel combustion may slow global warming, at least in the short term — when sulfur dioxide enters the atmosphere, it under goes various reactions, some of which lead to acid precipitation — these reactions, along w/ volcanic eruptions, can form a sulfur-rich aerosol haze in the upper atmosphere that reduced the sunlight reaching Earth's surface — aerosols released by major volcanic eruptions can exert cooling effects on Earth's climate for up to several years

Several factors influence climate

Our climate is influenced by cyclic changes in Earth's rotation and orbit, variation in energy released by the sun, absorption of carbon dioxide by the oceans, and ocean circulation patterns:

Sediment Cores

Researchers drill cores into beds of sediment beneath bodies of water — sediments often preserve pollen grains and other remnants from plants that grew in the past — b/c climate influences the types of plants that grow in an area, knowing what plants were preteen can tell us a great deal about the climate at that place and time

global warming

refers specifically to an increase in Earth's average surface temperature — only one aspect of global climate change, although warming does in turn drive other components of climate change

Ocean absorption

the oceans hold 50 times more carbon than the atmosphere holds — they absorb carbon dioxide from the atmosphere when the gas dissolves directly in water and when marine phytoplankton use it for photosynthesis — however the oceans are absorbing less carbon dioxide than we are adding to the atmosphere — thus, carbon absorption by the oceans is slowing global warming but is not preventing it — recent evidence indicates that the rate of absorption is now decreasing — as ocean water warms, it absorbs less carbon dioxide b/c gases are less soluble in warmer water — a positive feedback effect that accelerations warming of the atmosphere

Studying climate change

to comprehend any phenomenon that is changing, we study its past, present, and future — scientists monitor present-day climate, but they also have decides means of inferring past change and have developed sophisticated methods to predict future conditions

Radiation forcing expresses change in energy input

to measure the degree of impact that any given factor exert on Earth's temperature, scientists calculate its radiative forcing — radiative forcing: the amount of change in thermal energy that a given factor causes — positive forcing warms the surface, whereas negative forcing cools it

Models help us predict the future

to understand how climate systems function and to predict future climate change, scientists simulate climate processes w/ sophisticated computer programs

Proxy indicators

types of indirect evidence that serve as proxies, or substitutes, for direct measurements and that shed light on past climate