biology project work

8/14/2019 Biology Project Work

1/16


2/16

lobal warmingis the increase in the average temperature of Earth's

- -near surface air and oceans since the mid 20th century and its projected

continuation. Global surface temperature increased0.74 0.18 C(1.33 0.32 F) between the start and the end of the20th century. The Intergovernmental Panel on Climate Change (IPCC)concludes that most of the observed temperature increase since themiddle of the 20th century was very likely caused by increasingconcentrations of greenhouse gases resulting from human activity such

as fossil fuel burning and deforestation. The IPCC also concludes thatvariations in natural phenomena such as solar radiation and volcaniceruptions had a small cooling effect after 1950. These basic conclusionshave been endorsed by more than 40 scientific societies andacademies of science. including all of the national academies of scienceof the major industrialized countries.

Climate model projections summarized in the latest IPCC report indicatethat the global surface temperature is likely to rise a further 1.1to 6.4 C (2.0 to 11.5 F) during the 21st century. The uncertaintyin this estimate arises from the use of models with differing sensitivityto greenhouse gas concentrations and the use of differing estimates offuture greenhouse gas emissions. Most studies focus on the period

leading up to the year 2100. However, warming is expected to continuebeyond 2100 even if emissions stop, because of the large heat capacity


3/16

An increase in global temperature will cause sea levelsto rise and will change the amount and pattern of

precipitation, probably including expansion ofsubtropical deserts. Warming is expected to bestrongest in the Arctic and would be associated withcontinuing retreat of glaciers, permafrost and sea ice.Other likely effects include changes in the frequencyand intensity of extreme weather events, species

extinctions, and changes in agricultural yields.Warming and related changes will vary from region toregion around the globe, though the nature of theseregional variations are uncertain.

Political and public debate continues regarding globalwarming, and what actions to take in response. Theavailable options are mitigation to reduce furtheremissions; adaptation to reduce the damage causedby warming; and, more speculatively, geo engineeringto reverse global warming. Most nationalgovernments have signed and ratified the KyotoProtocol aimed at reducing greenhouse gasemissions.


4/16

urechanges

The most common measure of global warming is thetrend in globally averaged temperature near theEarth's surface. Expressed as a linear trend, thistemperature rose by 0.74 0.18 C over the period19062005. The rate of warming over the last half ofthat period was almost double that for the period as a

whole (0.13 0.03 C per decade, versus 0.07 C 0.02 C per decade). The urban heat island effect isestimated to account for about 0.002 C of warmingper decade since 1900. Temperatures in the lowertroposphere have increased between 0.13 and0.22 C (0.22 and 0.4 F) per decade since 1979,according to satellite temperature measurements.

Temperature is believed to have been relatively stableover the one or two thousand years before 1850, withregionally varying fluctuations such as the MedievalWarm Period and the Little Ice Age.

Estimates by NASA's Goddard Institute for Space Studiesand the National Climatic Data Center show that 2005was the warmest year since reliable, widespread

instrumental measurements became available in thelate 1800s, exceeding the previous record set in 1998by a few hundredths of a degree. Estimates preparedby the World Meteorological Organization and theClimatic Research Unit show 2005 as the secondwarmest year, behind 1998. Temperatures in 1998were unusually warm because the strongest El Nio inthe past century occurred during that year. Globaltemperature is subject to short-term fluctuations that


5/16

Temperature changes vary over the globe. Since1979, land temperatures have increased abouttwice as fast as ocean temperatures (0.25 C perdecade against 0.13 C per decade). Oceantemperatures increase more slowly than landtemperatures because of the larger effective heatcapacity of the oceans and because the oceanloses more heat by evaporation. The NorthernHemisphere warms faster than the SouthernHemisphere because it has more land andbecause it has extensive areas of seasonal

snow and sea-ice cover subject to ice-albedofeedback. Although more greenhouse gases areemitted in the Northern than SouthernHemisphere this does not contribute to thedifference in warming because the majorgreenhouse gases persist long enough to mix

between hemispheres.

The thermal inertia of the oceans and slowresponses of other indirect effects mean thatclimate can take centuries or longer to adjust to

changes in forcing. Climate commitment studiesindicate that even if greenhouse gases were


6/16

Greenhouse gases h e gr e en h o u se e f fe ct is t he pr o ce ss by wh i c hbs or p ti on an d e mi s s io n o f i nf r ar e d r a di a ti on byas es i n t h e at m os p h er e w a rm a pl a n et ' s l ow er.tm os ph e re an d s ur f a ce It was discovered by Joseph

Fourier in 1824 and was first investigated quantitatively by

Svante Arrhenius in 1896. Existence of the greenhouseeffect as such is not disputed, even by those who do notagree that the recent temperature increase is attributableto human activity. The question is instead how the strengthof the greenhouse effect changes when human activityincreases the concentrations of greenhouse gases in theatmosphere.

Naturally occurring greenhouse gases have a mean warmingeffect of about 33 C (59 F). The major greenhouse gasesare water vapor, which causes about 3670 percent of thegreenhouse effect; carbon dioxide (CO2), which causes 926 percent; methane (CH

4

), which causes 49 percent; andozone (O3), which causes 37 percent. Clouds also affect


7/16

CO2 concentrations are continuing to rise due toburning of fossil fuels and land-use change. Thefuture rate of rise will depend on uncertaineconomic, sociological, technological, and naturaldevelopments. Accordingly, the IPCC SpecialReport on Emissions Scenarios gives a wide rangeof future CO2 scenarios, ranging from 541 to 970ppm by the year 2100 (an increase by 90-250%since 1750). Fossil fuel reserves are sufficient to

reach these levels and continue emissions past2100 if coal, tar sands or methane clathrates areextensively exploited.

The destruction of stratospheric ozone by

chlorofluorocarbons is sometimes mentioned inrelation to global warming. Although there are afew areas of linkage, the relationship between thetwo is not strong. Reduction of stratosphericozone has a cooling influence, but substantialozone depletion did not occur until the late

1970s. Ozone in the troposphere (the lowestart of the Earth's atmos here does


8/16

Climate models

The main tools for projecting future climate changes aremathematical models based on physical principlesincluding fluid dynamics, thermodynamics and radiativetransfer. Although they attempt to include as manyprocesses as possible, simplifications of the actual climatesystem are inevitable because of the constraints ofavailable computer power and limitations in knowledge ofthe climate system. All modern climate models are in fact

combinations of models for different parts of the Earth.These include an atmospheric model for air movement,temperature, clouds, and other atmospheric properties; anocean model that predicts temperature, salt content, andcirculation of ocean waters; models for ice cover on landand sea; and a model of heat and moisture transfer fromsoil and vegetation to the atmosphere. Some models alsoinclude treatments of chemical and biological processes.Warming due to increasing levels of greenhouse gases isnot an assumption of the models; rather, it is an endresult from the interaction of greenhouse gases withradiative transfer and other physical processes in themodels. Although much of the variation in modeloutcomes depends on the greenhouse gas emissions usedas inputs, the temperature effect of a specific greenhouse

gas concentration (climate sensitivity) varies dependingon the model used. The representation of clouds is one of-


9/16

Global climate model projections of future climate mostoften have used estimates of greenhouse gasemissions from the IPCC Special Report on EmissionsScenarios (SRES). In addition to human-causedemissions, some models also include a simulation ofthe carbon cycle; this generally shows a positive

feedback, though this response is uncertain. Someobservational studies also show a positive feedback.Including uncertainties in future greenhouse gasconcentrations and climate sensitivity, the IPCCanticipates a warming of 1.1 C to 6.4 C (2.0 F to11.5 F) by the end of the 21st century, relative to19801999.

Models are also used to help investigate the causes ofrecent climate change by comparing the observedchanges to those that the models project from variousnatural and human-derived causes. Although thesemodels do not unambiguously attribute the warmingthat occurred from approximately 1910 to 1945 toeither natural variation or human effects, they do

indicate that the warming since 1970 is dominated byman-made greenhouse gas emissions.

The physical realism of models is tested by examiningtheir ability to simulate current or past climates.Current climate models produce a good match toobservations of global temperature changes over thelast century, but do not simulate all aspects of climate.Not all effects of global warming are accuratelypredicted by the climate models used by the IPCC. For


10/16

-Environmental

It is usually impossible to connect specificweather events to global warming. Instead,global warming is expected to causechanges in the overall distribution andintensity of events, such as changes to thefrequency and intensity of heavyprecipitation. Broader effects are expected

to include glacial retreat, Arctic shrinkageincluding long-term shrinkage of Greenlandice sheet, and worldwide sea level rise.Some effects on both the naturalenvironment and human life are, at least inpart, already being attributed to globalwarming. A 2001 report by the IPCCsuggests that glacier retreat, ice shelfdisruption such as that of the Larsen IceShelf, sea level rise, changes in rainfallpatterns, and increased intensity andfrequency of extreme weather events areattributable in part to global warming. Other

expected effects include water scarcity insome regions and increased precipitation in


11/16

Social and economic effects of global warming maybe exacerbated by growing population densities inaffected areas. Temperate regions are projected toexperience fewer cold-related deaths but manymore deaths from heat exposure. A summary ofprobable effects and recent understanding can be

found in the report made for the IPCC ThirdAssessment Report by Working Group II. The newerIPCC Fourth Assessment Report summary reportsthat there is observational evidence for an increasein intense tropical cyclone activity in the NorthAtlantic Ocean since about 1970, in correlationwith the increase in sea surface temperature (seeAtlantic Multidecadal Oscillation), but that the

detection of long-term trends is complicated by thequality of records prior to routine satelliteobservations. The summary also states that thereis no clear trend in the annual worldwide numberof tropical cyclones.

Additional anticipated effects include sea level rise of0.18 to 0.59 meters (0.59 to 1.9 ft) in 20902100relative to 19801999, new trade routes resultingfrom arctic shrinkage, possible thermohalinecirculation slowing, increasingly intense, in somelocations, (but less frequent) hurricanes andextreme weather events, reductions in the ozonelayer, changes in agriculture yields, changes in the

range of climate-dependent disease vectors, whichhave been linked to increases in the prevalence of


12/16

MitigationThe IPCC's Working Group III is responsible for crafting reports onmitigation of global warming and the costs and benefits ofdifferent approaches. The 2007 IPCC Fourth Assessment Reportconcludes that no one technology or sector can be completelyresponsible for mitigating future warming. They find there are key

practices and technologies in various sectors, such as energysupply, transportation, industry, and agriculture that should beimplemented to reduced global emissions. They estimate thatstabilization of carbon dioxide equivalent between 445 and 710ppm by 2030 will result in between a 0.6 percent increase andthree percent decrease in global gross domestic product.

Mitigation of global warming is accomplished through reductions inthe rate of anthropogenic greenhouse gas release. The world'sprimary international agreement on reducing greenhouse gasemissions, the Kyoto Protocol, now covers more than 160countries and over 55 percent of global greenhouse gasemissions.As of February 2010, only the United States, historicallythe world's largest emitter of greenhouse gases, has refused toratify the treaty. The treaty expires in 2012. International talksbegan in May 2007 on a future treaty to succeed the current one.

The 2009 United Nations Climate Change Conference met inCopenhagen in December 2009 to agree on a framework for


13/16

Adaptation

A wide variety of measures have beensuggested for adaptation to globalwarming, from the installation of air-conditioning equipment, to majorinfrastructure projects, such as

abandoning settlements threatenedby sea level rise.Measures including water

conservation, water rationing,adaptive agricultural practices

including diversification, constructionof flood defenses, changes tomedical care, and interventions toprotect threatened species have allbeen suggested. A wide-rangingstudy of the possible opportunities

for adaptation of infrastructure hasbeen published by the Institute of


14/16

Geo-engineeringGeoengineering is the concept of planetaryengineering applied to Earth: The deliberate

modification of Earth's natural environmenton a large scale to suit human needs. Anexample is greenhouse gas remediation,which removes greenhouse gases from theatmosphere, usually through carbon

sequestration techniques such as carbondioxide air capture. Solar radiationmanagement reduces absorbed solarradiation, such as by the addition ofstratospheric sulfur aerosolsor cool rooftechniques. No geoengineering projects ofsignificant scale have been implemented,and detailed study has largely been thework of small numbers of scientists; butvarious significant institutions such as theRoyal Society and IMechE have recentlysuggested that further study is warranted.

Their various externalities and other costs

are seen as major issues, and the idea orconcern that one country could act


15/16

CONSEQUENCES


16/16

THANK YOU

biology project work

Documents