Climate change Prepared by: Sana Salah AbdulkareeemSupervised byMrs. Sanar fawziDate of Submission: Jan 16, 2018 Contents Introduction. 3 Causes.
4 Internal forcing mechanisms. 4 External forcing mechanisms. 6 Physical evidence.
9 Temperature measurements and proxies. 9 Ice cores. 9 Animals. 10 Arctic sea ice loss. 10 Historical and archaeological evidence. 11 Vegetation. 11 Pollen analysis.
12 Sea level change. 12 What can we do to stop climate change?. 13 Conclusion. 14 References. 15 IntroductionClimate change is a change in the statisticaldistribution of weather patterns when this change lasts forextended period of time (i.e.
, decades to millions of years). Climate changemay refer to a change in average weather conditions, or in the time variationof weather within the context of longer-term average conditions. Climate changeis caused by factors such as biotic processes, variations in solar radiation received by Earth, plate tectonics, and volcaniceruptions. Certainhuman activities have been identified as primary causes of ongoing climatechange, often referred to as global warming.
1Scientists actively work to know and understandpast and future climate by using observations and theoretical models. A climaterecord—extending deep into the Earth’s past—has been assembled, and continuesto be built up, based on geological evidence from borehole temperature profiles, cores removed from deep accumulations of ice, floral and faunal records, glacial and periglacial processes, stable-isotope and other analysesof sediment layers, and records of past sea levels. More recent data areprovided by the instrumental record. Generalcirculation models, based on the physicalsciences, are oftenused in theoretical approaches to match past climate data, make futureprojections, and link causes and effects in climate change.
Weatherand climate are not the same thing. weather is what is happening outside yourwindow right now. Weather is short term, limited area, can change rapidly, difficultto predict.
Climateis the average of many years of weather observation. Climate is long term, widearea, seasonal change, measured over long spans of time.Causes Factors that can shape climate are called climateforcings or “forcing mechanisms”.
Forcingmechanisms can be either “internal” or “external”. Internalforcing mechanisms are natural processes within the climate system itself(e.g., the thermohaline circulation).
External forcing mechanisms can be eithernatural (e.g., changes in solar output, the earth’s orbit, volcano eruptions)or anthropogenic (e.g. increased emissions of greenhouse gases and dust). Internal forcing mechanisms Scientists generally define the fivecomponents of earth’s climate system to include atmosphere, hydrosphere, cryosphere, lithosphere (restrictedto the surface soils, rocks, and sediments), and biosphere. Natural changes inthe climate system (“internal forcings”) result in internal”climate variability 1.Ocean-atmospherevariabilityThe oceanand atmosphere can work together to spontaneously generate internal climatevariability that can persist for years to decades at a time.
These variations can affect global average surfacetemperature by redistributing heat between the deep ocean and the atmosphere and/orby altering the cloud/water vapor/sea ice distribution which could affect thetotal energy budget of the earth.centennial Theoceanic aspects of these circulations could produce variability on timescalesdue to the ocean having hundreds of times more mass than in the atmosphere, and so very high thermal inertia. For example, alterations to ocean processes like thermohalinecirculation play a key role in redistributing heat in the world’s oceans. 2.LifeLife affectsclimate through its role in the carbon and water cycles and through such mechanismsas albedo, evapotranspiration, cloud formation, and weathering.23 Examples of how life may haveaffected past climate include: glaciation 2.
3 billion years ago triggered by the evolution of oxygenic photosynthesis, which depleted the atmosphere of the greenhouse gas carbon dioxide and introduced free oxygen. 4 another glaciation 300 million years ago ushered in by long-term burial of decomposition-resistant detritus of vascular land-plants (creating a carbon sink and forming coal) 4 termination of the Paleocene-Eocene Thermal Maximum 55 million years ago by flourishing marine phytoplankton5 reversal of global warming 49 million years ago by 800,000 years of arctic azolla blooms5 global cooling over the past 40 million years driven by the expansion of grass-grazer ecosystems6 External forcing mechanisms 1.Orbital variationsSlightvariations in Earth’s motion make to changes in the seasonal distribution ofsunlight reaching the Earth’s surface and how it is distributed across theglobe. There is very little change to the area-averaged annually averagedsunshine; but there can be strong changes in the geographical and seasonaldistribution. The three types of kinematic change are variations inEarth’s eccentricity, changes in the tilt angle of Earth’s axis ofrotation, and precession of Earth’s axis. Combined with eachother, these make Milankovitchcycles whichhave an influence on climate and are notable for their correlation to glacial and interglacialperiods, theircorrelation with the advance and retreat of the Sahara, and for their appearance in the stratigraphic record.7 2. Solar outputThe Sun isthe predominant source of energy input to the Earth.
Othersources include geothermal energy from the Earth’s core,tidal energy from the Moon and heat from the decay of radioactive compounds.Both long- and short-term variations in solar intensity are known affect globalclimate. 7 3.VolcanismThe eruptions considered to be large enoughto affect the Earth’s climate on a scale of more than 1 year are the ones thatinject over 100,000 tons of SO2 into the stratosphere. This is due to the opticalproperties of SO2 and sulfate aerosols, that strongly absorb orscatter solar radiation, creating a global layer of sulfuric acid haze. On average, sucheruptions occur several times per century, and cause cooling (by partiallyblocking the transmission of solar radiation to the Earth’s surface) for aperiod of a few years.
8 4.PlatetectonicsOver thecourse of millions of years, the motion of tectonic plates reconfigures globalland and ocean areas and generates topography. This can affect both global andlocational patterns of climate and atmosphere-ocean circulation.
The positionof the continents affects the geometry of the oceans and therefore influencespatterns of ocean circulation. The locations of the seas are important incontrolling the sending of heat and moisture across the globe, and therefore,in determining global climate. Arecent example of tectonic control on ocean circulation is the formation ofthe Isthmusof Panama about5 million years ago, which shut off direct mixing between the Atlantic and Pacific Oceans. This strongly affectedthe ocean dynamics ofwhat is now the Gulf Stream and may have led to NorthernHemisphere ice cover.8 5.HumaninfluencesIn thecontext of climate change, anthropogenic factors are human activities which influencethe climate. The scientific consensus on climate change is “that climate ischanging and that these changes are in large part caused by human activities,” andit “is largely irreversible.
“”Sciencemade enormous inroads in understanding climate change and its causes, and is startingto help develop a strong understanding of current and potential impacts thatwill affect people today and in coming decades. This understanding is crucialbecause it allows decision makers to place climate change in the context ofother large challenges facing the nation and the world. 8 6.GreenhousegasGreenhousegases are those that absorb and emit infrared radiation in the wavelengthrange emitted by Earth.8 In order, the most abundantgreenhouse gases in Earth’s atmosphere are: Water vapor (H2O) Carbon dioxide (CO2) Methane (CH4) Nitrous oxide (N2O) Ozone (O3) Chlorofluorocarbons (CFCs) Hydrofluorocarbons (incl. HCFCs and HFCs) Atmosphericconcentrations of greenhouse gases are determined by the balance betweensources (emissions of the gas from human activities and natural systems) andsinks (the removal of the gas from the atmosphere by conversion to a differentchemical compound). The proportion of an emission remaining in theatmosphere after a specified time is the “airborne fraction” (AF).
The annual airbornefraction is the ratio of the atmospheric increase in a given year to thatyear’s total emissions. As of 2006 the annual airborne fraction for CO2 wasabout 0.45.
The annual airborne fraction increased at a rate of0.25 ± 0.21% per year over the period 1959–2006.8 Physicalevidence Temperature measurements and proxies The instrumental temperature record from surface stations wassupplemented by radiosondeballoons, extensiveatmospheric monitoring by the mid-20th century, and, from the 1970s on,with global satellite data as well. Taking the record as a whole, most of the 20thcentury had been unprecedentedly warm, while the 19th and 17th centuries werequite cool.9 GlaciersGlaciers are among the most sensitiveindicators of climate change.
Their size is determined by a mass balance between snow input and meltoutput. As temperatures warm, glaciers retreat unless snow precipitationincreases to make up for the additional melt; the converse is also true.9 Ice cores Analysis ofice in a core drilled from an ice sheet such as the Antarcticice sheet, can beused to show a link between temperature and global sea level variations. Theair trapped in bubbles in the ice can also reveal the CO2 variationsof the atmosphere from the distant past, well before modern environmentalinfluences. 9 Animals Remainsof beetles are common in freshwater andland sediments.
Different species of beetles tend to be found under differentclimatic conditions. Given the extensive lineage of beetles whose geneticmakeup has not altered significantly over the millennia, knowledge of thepresent climatic range of the different species, and the age of the sedimentsin which remains are found, past climatic conditions may be inferred. Thestudies of the impact in vertebrates are few mainly from developing countries,where there are the fewest studies; between 1970 and 2012, vertebrates declinedby 58 percent, with freshwater, marine, and terrestrial populations decliningby 81, 36, and 35 percent, respectively. 10 Arctic sea ice loss The declinein Arctic sea ice, both in extent and thickness, over the last several decadesis further evidence for rapid climate change. Sea ice is frozen seawaterthat floats on the ocean surface. It covers millions of square kilometers inthe polar regions, varying with the seasons.
In the Arctic, some sea ice remains year afteryear, whereas almost all Southern Ocean or Antarctic sea ice melts awayand reforms annually. Satellite observations show that Arctic sea ice is nowdeclining at a rate of 13.2 percent per decade, relative to the 1981 to 2010average. 10 Historical and archaeological evidence Climatechange in the recent past may be noticed by corresponding changes in settlementand agricultural patterns. Archaeological evidence, oral history and historicaldocuments canoffer insights into past changes in the climate. Climate change effects havebeen linked to the collapse of various civilizations.9 Vegetation A change inthe type, distribution and coverage of vegetation may occur given a change inthe climate.
Some changes in climate may result in increased precipitation andwarmth, resulting in improved plant growth and the subsequent sequestration ofairborne CO2. A gradual increase in warmth in a region will lead toearlier flowering and fruiting times, driving a change in the timing of lifecycles of dependent organisms. Conversely, cold will cause plant bio-cycles tolag.9 Forest genetic resources Even though this is a field withmany uncertainties, it is expected that over the next 50 years climate changeswill have an effect on the diversity of forest geneticresources and thereby on thedistribution of forest tree species and the composition of forests. Diversityof forest geneticresources enables the potential for aspecies (or a population) to adapt to climatic changes and related futurechallenges such as temperature changes, drought, pests, diseases and forestfire.
Pollen analysis Palynology is the study of contemporaryand fossil palynomorphs, including pollen. Palynology is used to infer thegeographical distribution of plant species, which change under differentclimate conditions. Different groups of plants have pollen with distinctiveshapes and surface textures, and since the outer surface of pollen is composedof a very resilient material, they resist decay. Changes in the type of pollenfound in different layers of sediment in lakes, bogs, or river deltas indicatechanges in plant communities. 9 Sea level change Global sealevel change for much of the last century has usually been estimatedusing tide gauge measurements collated over longperiods of time to give a long-term average.
More recently, altimeter measurements — incombination with accurately determined satellite orbits — have provided animproved measurement of global sea level change. To measure sea levelsprior to instrumental measurements, scientists have dated coral reefs that grow near the surface ofthe ocean, coastal sediments, marine terraces, ooids in limestones, and nearshore archaeologicalremains. The predominant dating methods used are uraniumseries and radiocarbon, with cosmogenic radionuclides being sometimes used to date terraces that haveexperienced relative sea level fall.
10 What can we do to stop climate change? 1.Reducefossil fuel useBurning fossil fuels increases thelevels of greenhouse gases in the atmosphere. 2.Plant TreesBecause carbon dioxide is the mostimportant greenhouse gas, planting trees and other plants can slow or stopglobal warming. Plants take in carbon dioxide and release oxygen. 3.Reduce WasteThe production of garbagecontributes to global warming both directly and indirectly. Decomposing wastein landfills produces methane and other greenhouse gases.
4.Conserve WaterCities consume significant amountsof energy when purifying and distributing water, which contributes togreenhouse gas emissions. Saving water reduces the amount of energy used.
Conclusion – Climate change is a change which is attributed directly orindirectly to human activity. – It caused by internal andexternal forcing mechanism. – Evidence of climate change comes from different source such asincrease of temperature, move of animals, arctic sea ice loss, historical andarchaeological evidence, vegetation, forest genetic resources, pollen analysisand sea level change. – There are several ways to stop climate change like reduce fossilfuel use, plant trees, reduce waste and conserve water. References 1- America’sClimate Choices: Panel on Advancing the Science of Climate Change; NationalResearch Council (2010).
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