What is Climate Change?• Climate change is a significant and lastingchange in the statistical distribution of weatherpatterns over periods ranging from decades tomillions of years.
Weather vs. Climate Weather is the specific condition of the atmosphereat a particular place and time and is measured interms of things such as wind, temperature, humidity,atmospheric pressure, cloudiness and precipitation. Climate, on the other hand, is the average pattern ofweather for a particular region, usually taken over a30 year time period. Climate elements can includeprecipitation, temperature, humidity, wind velocity,fog, frost, hailstorms, and other measures of weather.
What factors determine Earth’s Climate?Influence of its own internal dynamics(Internal forcing)Changes in external factors that affect climate(External forcing).
Internal forcing mechanisms are naturalprocesses within the climate system itself (e.g.,the meridional overturning circulation).External forcing include natural phenomena suchas volcanic eruptions and solar variations, as wellas human induced changes in atmosphericcomposition.
Volcanic eruptions contain huge amounts of volcanic gas,aerosol droplets, and ash. Most of it is removed within several days to weeks -- andhas little impact on climate change. But volcanic gases like sulfur dioxide and carbondioxidetakes time to remove.
Solar variation is thechange in the amountof radiation emitted bythe sun and its spectraldistribution over yearsto millennia.
Energy from Sun The range of electromagnetic energy emitted by thesun is known as the solar spectrum, and lies mainlyin three regions: ultraviolet, visible, and infrared. While the sun does emit ultraviolet radiation, themajority of solar energy comes in the form of "light"and "heat," in the visible and infrared regions of theelectromagnetic spectrum.
Solar radiation in atmosphere The atmosphere may seem to be completelytransparent to solar radiation, but in fact there aredynamic interactions occurring constantly that resultin a complex and delicately balanced system crucialto the continuation of present life forms on Earth. two resulting phenomena that are crucial to themaintenance of life on Earth:1. The atmosphere acts as a filter, absorbing and reflectingportions of electromagnetic spectrum, such as the UVregion, that are harmful to humans and other life forms.2. The atmosphere provides a natural “Greenhouse effect”maintaining the temperatures and climates in which lifeforms on Earth have evolved to survive.
In red solar radiation spectrum at the top of the atmosphere In Blue solar radiation spectrum at the sea level
Solar Radiation Absorption, Balance,and the Natural Greenhouse Effect For every 100 units of solar radiation falling on theEarth and its atmosphere, 25 units are reflected bythe atmosphere, and 25 units are absorbed by theatmosphere. The remaining 50 units fall on thesurface of the Earth. Of these 50 units, 5 units arereflected by the surface of the Earth, and 45 units areabsorbed. Approximately 30% of the incident energy is reflectedby the atmosphere and the surface of the earth. The atmosphere absorbs approximately 25% of theradiation, and the earths surface absorbs 45%.
The phenomenon is responsible for keepingthe temperature of the Earth a full 33° Cwarmer than it would be otherwise.The reason the Earth’s surface is this warm isthe presence of greenhouse gases, which actas a partial blanket for the longwave radiationcoming from the surface. This blanketing isknown as the natural greenhouse effect.
Contribution of human activities onclimate change Human activities results in emissions of four principalGHGs:1. CO22. CH43. N2O4. Halocarbons (group of gases containing fluorine, chlorine andbromine) These gases accumulate in the atmosphere, causingconcentrations to increase with time.
CO2 CO2 has increased from fossil fuel use intransportation, building heating and cooling and themanufacture of cement and other goods. Deforestation
In terms of temperature, the move from the pre-industrial CO2 concentration to todays level (i.e. from280 ppm to 380 ppm) has resulted in a 0.5° C directincrease in the mean global temperature. Looking into the future, models used by the IPCCpredict that CO2 concentrations will rise to between500 ppm and 1000 ppm in 2100. It is estimated that between 1990 and 2100,temperatures will actually increase by between 1.4° Cand 5.8° C.
CH4 Agriculture and livestock farming are two of the principal humanactivities that produce methane. Another important factor in the emission of methane is theburning of vegetation leakage of this gas from coal, defective natural gas extractionsystems
Halocarbons Best known – CFC Accused of being the principal cause of a possibledepletion of stratospheric ozone, they also act asgreenhouse gases in the troposphere. Because they are man-made, there were barelypresent at all in the atmosphere until 1950. Since that time, they have been used extensively inrefrigeration systems
N2O N2O is emitted by use of fertilizer and fossil fuelburning. Natural process in soils and the oceans also releaseN2O.
Water vapor has very small direct influence of humanactivities. (human activities also influence CH4 undergoeschemical destruction in the stratosphere, producing a smallamount of water vapor. Ozone is continually produced and destroyed in theatmosphere by chemical reactions. In the troposphere,human activities have increased ozone through the releaseof gases such as CO, HC and Nox, which chemically reactto produce ozone. Halocarbons released by human activitiesdestroy ozone in the stratosphere.
US GHG Emission Flow ChartSource: World Resource Institute
country % of global totalannual emissionTones of GHG percapitaChina 17% 5.8United States 16% 24.1European Union 11% 10.6Nepal 0.09%
Impactsglobal temperature Instrumental observations over the past 157 yearsshow that temperatures at the surface have risenglobally. Expressed as a global average, surface temperatureshave increased by about 0.740C over the pasthundred years (between 1906 – 2005). For the last 50 years, the linear warming trend hasbeen 0.13 °C [0.10 to 0.16 °C] per decade accordingto AR4
The values in the tableabove are anomaliesfrom the 1901–2000global mean of13.9°C. For instance,the +0.55°C anomalyin 2007 added to the1901–2000 mean of13.9°C gives a globalaverage temperatureof 14.45 °C (58.00 °F)for 2007.year Global mean temperature(0C anomaly from 1901-2000)2005 0.61832010 0.61711998 0.59842003 0.58322002 0.57622006 0.56232009 0.55912007 0.55092004 0.54412001 0.51882008 0.48421997 0.47991999 0.42101995 0.40972000 0.3899
Snow and Ice is Decreasing Ice sheet and glaciers are melting due to increasingglobal temperature.
Greenland ice sheet is melting because of these risingtemperatures. Previously, NASA had estimated that Greenland’s ice sheetwould melt a meter every year. Now, it could be as much as ameter every month. In just the past 15 years, over 105 million acres of ice hasmelted and emptied into the oceans.
Annual average Arctic sea ice extent shrunk by 2.7 %per decade, decreases in summer 7.4 %Sept. 21,1979Sept. 16,2007Sea IceConcentration (%)0 15100
Sea level rising Global average sea level rose at an average rate ofaround 1.7 ±.3mm per year over 1950 to 2009 and ata satellite-measured average rate of about 3.3±.4mm per year from 1993 to 2009. Over the last 100 years, the global sea level hasrisen by about 10 to 25 cm. Cause: a) thermal expansionb) ice sheet / glacier melting
2 - 4C warming by ~2100 0.18 - 0.59 meter rise in sea level2 - 4C warming by ~2100 0.18 - 0.59 meter rise in sea level
Projected impacts Major cities like Los Angeles, London, and Tokyo willbe flooded as sea level rises. Already inhabitants of islands of Vanuatu have had toevacuate due to the rising water and some arealready underwater. Sea level rise could also displace many shore-basedpopulations: for example it is estimated that a sea level riseof just 200 mm could create 740,000 homeless people inNigeria. Maldives, Tuvalu, and other low-lying countries areamong the areas that are at the highest level of risk. The UNs environmental panel has warned that, at currentrates, sea level would be high enough to make the Maldivesuninhabitable by 2100.
Changes in extreme eventsHeat wavesDroughtsFloodsHurricanes
Extreme Heat WaveSummer 2003EuropeHeat waves are increasing
North Atlantic hurricanes have increased with SSTsSST(1944-2005)Marked increaseafter 1994Duration andstrength ofhurricaneshas increasedabout 50%over the last30 years
Regions of disproportionate changes in heavy(95th) and very heavy (99th) precipitationProportion of heavy rainfalls: increasing inmost land areas
Smoothed annual anomalies for precipitation (%) over land from1900 to 2005; other regions are dominated by variability.Land precipitation is changing significantly over broad areasIncreasesDecreases
If emission of the GHGs are reduced, howquickly do their concentration in the atmospheredecrease?GHG Life time at atm (Yrs)CO2 50 - 1000+CH4 10 +/- 3N2O 120CFC 45-100HCFC1-18PFC 1000HFC 1-270CO2CH4
Projections of Future Changes inClimateFor the next two decades a warming of about0.2°C per decade is projected.Even if the concentrations of all greenhousegases and aerosols had been kept constant atyear 2000 levels, a further warming of about0.1°C per decade would be expected.
Projections of Future Changes in ClimateBest estimatefor lowscenario (B1)is 1.8°C (likelyrange is 1.1°Cto 2.9°C), andfor highscenario(A1FI) is 4.0°C(likely range is2.4°C to6.4°C).
Projected warmingin 21st centuryexpected to begreatest over landand at most highnorthern latitudesand least over theSouthern Oceanand parts of theNorth AtlanticOceanProjections of Future Changes in Climate
Projections of Future Changes in ClimatePrecipitation increases very likely in high latitudesDecreases likely in most subtropical land regions
Projected impacts of climate change (Stern report, 2006)1°C 2°C 5°C4°C3°CSea level risethreatens major citiesFalling crop yields in many areas, particularlydeveloping regionsFoodFoodWaterWaterEcosystemsEcosystemsGlobal temperature change (relative to pre-industrial)0°CFalling yields in manydeveloped regionsRising number of species face extinctionSignificant decreases in wateravailability in many areas, includingMediterranean and Southern AfricaSmall mountain glaciersdisappear – watersupplies threatened inseveral areasExtensive Damageto Coral ReefsExtremeExtremeWeatherWeatherEventsEventsRising intensity of storms, forest fires, droughts, flooding and heat wavesPossible rising yields insome high latitude regions
Global WarmingSolutionsPrevention CleanupCut fossil fuel use (especially coal)Shift from coal to natural gasImprove energy efficiencyShift to renewable energy resourcesTransfer energy efficiency andrenewable energy technologies todeveloping countriesReduce deforestationUse more sustainable agricultureLimit urban sprawlReduce povertySlow population growthStore (sequester) CO2 byplanting treesSequester CO2 in the deep oceanRepair leaky natural gas pipelinesand facilitiesRemove CO2 from smokestackand vehicle emissionsSolutions to Global Warming