Only $2.99/month

AP Enviro -- Chapter 18

Terms in this set (61)

- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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
- 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