Lecture 38: Global and Regional Environmental Issues - Global Warming

[Music] so [Music] [Applause] [Music] [Applause] [Music] hello friends you may recall that these days we are discussing about global and regional environmental issues and in this series we have already discussed about ah ozone layer depletion and today we will cover the global warming related issues so in this particular presentation or lecture first of all we will you know very briefly discuss about what is global warming and the indicators which are related to global warming which represent it in a better way so that we can measure it track it what are the greenhouse gases although you

know about this but briefly we will touch and then we will see how much you know growth rate or contributions of different greenhouse gases is there and then what is the global warming potential of the greenhouse gases and the radiative forcing which is caused by solar insulation and then what is the status of you know this global warming in terms of the temperature global temperature and impacts of different impacts of global warming because it is not only the global temperature increase but other also like climate change related issues which ah ok we will see in

brief and then we will look into like what are different mitigation measures which can ah you know work for reducing the greenhouse gas emissions and we can curb this global warming related effects and we will conclude so when we talk about global warming basically it is nothing but the long term you know heating kind of process of the earth's climate system which has been observed since the pre-industrial period like ah from 1815 to 1900 or so because before industrialization ah you know this global average temperature was more or less up to a particular you know

degree celsius and it was for centuries altogether but now we have seen that since when this industrialization has occurred so after this james what developed the steam engine and then coal burning and other fossil fuel related burning activities we started so you know the greenhouse gases that means carbon dioxide etcetera they were pumped into the atmosphere and at the same time temperature of the global ok the planet temperature increased and we can see ok you can see here from 1880 to ah you know this up to for this present times so the global temperature is

ah basically increasing right and of course there are different schools of thoughts sometimes i discuss with you that some people say that this is because of just natural phenomena but now we have this internal international government panel of climate change and they produce a lot of scientific evidences which gives this evidence based conclusion that of course the man made or anthropogenic contributions are much more predominant in in in this particular global warming related issue so the since you know this pre-industrial era when human activities started to contribute into global warming because of greenhouse gases emissions

so the average temperature has increased about 1 degree celsius right it looks very small but basically in the earth system it means a lot it can change many things basically so the human activities which are basically related to fossil fuel burning ah you know this has increased emissions of greenhouse gases like co2 etcetera and they trap the ah you know heat which is outgoing from the planet we will see how does this happen so as i said that there are indicators like to measure the intensity and impact of global warming like global warming potential gwp

or radiative forcing or annual greenhouse gas index so we will discuss about these things later on and they are needed because we want to study long term relationships between greenhouse gases and their impact in terms of temperature or the heating kind of contribution so we need to measure those global warming potential etcetera well when we look into greenhouse gases so you know about this particular phenomenon of the green house effect in the sense because you know it covers ah the planet this greenhouse gases like co2 methane etcetera they are in the atmosphere and they basically

ah don't allow the infrared radiation or long wave radiation which goes out of the earth planet into the atmosphere into the space because lot of ultraviolet rays or solar insulation comes to the earth surface and some part of it is reflected some part of it is you know absorbed and then it is emitted like a long wave radiation so this heating effect occurs because that long wave radiation is basically absorbed by greenhouse gases into the atmosphere and it acts like a blanket it does not allow it goes to pass and then heating effect occurs in

the atmosphere right and you you know this ah although naturally greenhouse gas effect is very much required because ah due to this effect only we have you know certain temperature of the planet like around 15 degree celsius ok and this makes the life possible otherwise it will freeze and it will like mass ok it will be completely frozen kind of planet which is not good for you know ecosystems which supports lot of varieties of life like us so we need this effect but beyond certain limit it is not good for us we which we will

see how does that happen basically so when we talk about greenhouse gases there are several gases which are ah having this kind of effect to absorb the infrared radiation or long wave radiation and causing the ah heating effect basically and these are like carbon dioxide methane or nitrous oxide and two then there are certain you know fluorinated gases or ozone and even water vapor the these all these you know gaseous components you can say compounds they contribute into greenhouse gas effect basically when we talk about co2 so it is basically the primary ah greenhouse gas

and it is emitted in a very huge quantity whenever we burn ah you know fossil fuels whether it is coal or whether it is you know diesel or gasoline because these are hydrocarbons basically ok and when we burn it so this carbon content is oxidized into co2 and it goes into the atmosphere right and because the lifetime of co2 is for centuries and that you know forcing the positive forcing means increasing the temperature that kind of forcing occurs and the reason is like it comes not only from natural sources like volcanic eruptions or even forest

fire but lot of human activities ah including land use chains when we go for deforestation or urbanization and various industrial ah related activities they emit lot of co2 like you can see you know this atmospheric content or abundance of co2 has increased around an average around 1.85 ppm per year ah in the past 41 years from 1979 to 2020 this has been observed basically and if you look into you know the last decade like 2009 to 2020 then it becomes rather more ah predominant like 2.4 ppm per ah year basically and this anthropogenic activities which

are you know increasing this c two concentration ah they are like contributing ah in a large way and you can see this ah huge steep increase of the co2 concentration in recent years basically so that is very problematic and 50 percent since the industrial revolution became so that way you can see the in a very small period lot of concentration of co2 has increased and that is the worrisome because that has ah intensified this global warming phenomena because of greenhouse gas effect well when we i look into the co2 contribution from different segments or domains

so like fossil fuel and industrial processes they contribute around 65 percent and the carbon dioxide from forestry and other land use like deforestation or etcetera that is around 11 percent so total 76 percent you know from these kind of activities ah goes to the atmosphere basically and this fossil fuel burning industrial you know processes ah where they consume lot of you know coal or gasoline diesel etcetera and they contribute lot of co2 when we talk about methane so methane comes from ah you know even natural sources like wetlands etcetera plus these human activities like livestock

and then ah you know these landfills where anaerobic digestion occurs or agriculture practices even rice cultivation etcetera they ah manual management all these activities contribute to methane emissions into the atmosphere and this is responsible around 40 percent of the human caused warming ah you know means after co2 you can say this is very important greenhouse gas in terms of global warming effect when we talk about its growth rate basically from 1750 again we will see lot of activities are there of human nature so you can see this there was of course some constant or little

bit decrease you can say in the increased rate but again from 2007 you know emissions of methane are increasing so they they are related to several kind of human activities and technologies basically now if you talk about you know contribution so 16 percent of global greenhouse gases ah you know this comes in terms of methane basically right so 76 percent ah is this greenhouse gas emissions in terms of gaseous components is co2 and 16 percent is methane basically and then we will see other contributions of like nitrous oxide so nitrous oxide also comes from different

kind of activities like organic fertilizers or fossil fuel combustion nitric acid production and also agriculture related activities basically it comes from ah you know these kind of activities and this is also very potent greenhouse gas and it contributes although only around you know 2 percent but as i said because this is also predominant after the methane so the growth rate you can see it is increasing because lot of human activities are of that nature which contributes into the emissions of n2o and it is around 1 ppv per year over the past decade it is increasing

so lot of quantity of n2 is coming out of these activities and 6 percent around 6 percent of the greenhouse gases and is because of entry this is the third you know largest ah contribution you can say ah co two methane and ah nitrous oxide basically nitrous oxide is also problematic because it may reach to the statosphere and it can contribute to the ozone layer depletion you might recall that kind of thing then there is this fluorinated gases they are very small in quantity but their potency is very high we will see how potent they

are thousands time than the co2 so even though their quantity is very small but because of their global volume potential is very high it is a kind of worrisome and also they contribute into this ozone layer depletion so ah it is good that through montreal protocol we are reducing their ah you know production and that way we are going to control it so you can see the decline trend after 2020 because of montreal protocol so that is a good thing well the growth rate ah only this 2 percent was the contribution and it is declining

because we are replacing it with the better you know chemicals when we talk about the ozone as you know ozone in troposphere acts like a greenhouse gas although in stratosphere it is good because it protects us from ultraviolet rays but in troposphere it is not only toxic gas but also having the greenhouse gas effect in terms of that increasing the temperature so basically it is not emitted directly as you know this is the secondary pollutant and the precursors of ozone are like vocs volatile organic compounds or the nox emissions ok hydrocarbons etcetera and because of

in the presence of sunlight due to this photochemical reaction ozone is produced so if we can control the precursors we can control the ozone basically and these vocs knocks etcetera they come from again several kind of human activities like industrial boilers refineries chemical plants etcetera well ah you can see this ah the effect of the ozone as i said this is shown here it it gives the warming effect in the ah you know this troposphere because of absorbing the solar radiation well ah not the solar radiation exactly the outgoing radiation basically then we talk about

the water vapor water vapor is you know this is a kind of feedback effect so as such because of global warming vapor occurs you know vapor is produced and it goes to the atmosphere and then it also absorb the outgoing radiation ok outgoing radiation so basically ah you know it is a kind of vicious cycle you can say because as it goes it contributes to the global warming effect or because of greenhouse gas effect so that way means more temperature more vapor and more again the this greenhouse gas effect so feedback mechanism is there and

then the forcing of these co2 etcetera we can look into well global warming potential if we talk about so this is one indicator which can you know compare which can help us to compare the potential of the different greenhouse gases like if you talk about like carbon dioxide for 100 years or so if it is the unit 1 then the methane is 25 times than the carbon dioxide nitrous oxide is around 300 times so c means like unit potential of carbon dioxide of the same quantity is 400 years is around 1 then 300 times is

the meth this ah nitrous oxide and these fluorinated gases they are you know 10 000 times even 1000 to 10000 depending upon different these planet gases but thankfully they are reducing in quantity ok then we talk about this global warming potential basically as you as you know because different lifetime span is there for different gases so it will depend it will depend upon the ah these kind of ah two things like the ah trapping of the heat ah how long this stage in the atmosphere ok and how much intensity it captures that potency ok so

those things are there to decide whether it is ah you know very going it is going to intensify the global warming effect or not like you can see methane ah stays around 12 years in the atmosphere where co2 can ah you know go for for centuries you can say right so that will be effect but because of their you know phenomena of capturing the heat ah as we have seen it is 25 times methane so even like a smaller in quantity it will have more effect you can see well when we talk about you know

different kind of scales so you can see emission reducing strategies are needed ah for that particular purpose and ah if we talk about this gwp hundred so total warming of greenhouse gas compared to co2 after 100 years you can say so this one is the most widely used kind of thing so if you compare like ah you know different kind of studies have been there through ipcc so you can see this methane only 21 or so and the n2o is 296 or 310 in different reports the quantities is varying because scientific evidences are refining their

potential that way you can see the variation well when we talk about global warming potential again you can see the co2 and methane around 28 times so 25 times you can say and this ah n2o this can have ah different like 20 years or 100 years so different values may be there well fluorinated gases we have seen like 100 years its potential may vary from 5000 to around 23000 depending upon different fluorinated gases well radiative forcing is ah like how much you know positive or negative effect is there for example clouds are reflecting ah the

solar insulation which is coming so it will reflect so it is causing cooling effect you can say so its value is negative when black carbon or some aerosols which capture the ah you know radiation then we call it positive forcing so that way greenhouse gases are having positive forcing you can see carbon dioxide methane ok all these nitro nitrous oxide they are having positive forcing although you know this negative radiic forcing is ah because of these gases destroy the ozone so that is why some part of these ah halogenated gases is having the negative impact

because of contribution in destroying the ozone otherwise it is having the positive forcing similarly you can see these aerosols like sulphate etcetera they are ah you know reflecting kind of nature so they have this negative and the black carbon aerosols they are having positive right so but the net effect is positive forcing basically we which we if we add everything then we we get that all these things add up into the positive forcing that means they will increase the temperature because they will capture the heat ok then if you see these radiative forcing because of

you know in terms of annual greenhouse gas index so see over the years like 1990 if we take as one then in comparison to that ah you know in 2019 it became around 1.4 so that way because their concentrations are increasing their index related values are also increasing and you can see you know these various like co2 ch4 all these are having ah because of human activities they are coming and then the aerosols are also being emitted and it is said that because of health related issues we are you know reducing emissions of these particulate

matter like pm 2.5 pm10 so there are some studies which say that because these aerosols much part of these aerosols are having cooling effect so if we reduce them then maybe more warming effect may be observed in future well if you talk about the status of the global temperature you know ah it is increasing ah in 20th century it is you know increasing and in 21st century you can see the hottest you know these years have been observed like in 2016 the hottest day have been observed or the highest temperature have been observed the temperature

you can see so in 2020 it ranks around second hottest year right 2016 was the the first one sixth is twenty twenty one so after two thousand you can see the temperature is rather very high so it's a very very some phenomena we have to really capture it or you know control it otherwise it would be difficult then there are several impacts of the global warming ah which has been discussed like in lecture 37 you can recall like it will not only increase the average temperature but it will also increase into like heat waves or

flood related phenomena drought related phenomena precipitation variation extreme events of the precipitation or then the storms etcetera sea level rise ok ecosystem will be disturbed because temperatures are increasing in certain ecosystems then it will disturb is complete ah you know that balance and then the health and society are affected because suppose in higher ah you know latitudes if temperature is increasing then malaria related ah problems may also increase in thought those regions well if you talk about the mitigation then ah the best way is to reduce greenhouse gas emissions so that means we have to

change our energy sources so that is why lot of efforts are being made at the global level different countries are you know going for different kind of renewable energy sources in india you you might have seen lot of emphasis is there on solar radiation or other kind of renewable resources even mobility like we are going for e mobility in a big way so that way you know we are going for reducing the emissions of greenhouse gases although there are issues like some people talk that if we go for you know in a life cycle assessment

then situations may be kind of different but it is still in the mode of the research and there are two schools of thought but at least when urban emissions are reduced then health effects related issues will not be there but from global warming point of view we have to see only those kind of technologies which really help us in reducing the greenhouse gas emissions so that is we have to go for and you can see like the concentrations have been rising since the pre-industrial era and they are increasing because of population is increasing urbanization is

increasing in industrialization is increasing so if we have to reduce you know these emissions of the greenhouse gases then we have to go for better energy sources which are not dependent upon fossil fuels or we have to capture them like carbon sequestration phenomena you might have heard so we have to avoid them to go to the atmosphere that is the key thing and several agreements have been there at the global scale you know like earth summit kyoto protocol paris agreement etcetera so therefore you know ah capturing ah or reducing the greenhouse gas emissions so that

we do not have this global warming effect or we do not have the climate change related issues so thank you for your kind attention and these are the references for additional reading for you you can read it at leisure and let us meet in the next lecture thanks again thank you [Music] [Applause] [Music] [Applause] [Music] hey [Music] you