1 Summary Environment Class 14 ## BRIEF OVERVIEW OF PREVIOUS CLASS (1:09 PM) ## CLIMATE CHANGE AND GLOBAL WARMING (1:13 PM) - **Climate:** - The **climate** refers to the atmospheric conditions of a place for a long period measured by a minimum of 30 years. - **UNFCCC** defines climate change as a change of climate attributed directly or indirectly to human activities that alter the composition of the global atmosphere and which is in addition to natural climate variability observed over a comparable period. ## CAUSES OF CLIMATE CHANGE (1:23 PM) - **Milankovitch cycles** result in changes in insolation, seasonal variations, etc. - Volcanic eruption - Thermodynamic circulation - Continental drift - **Anthropogenic Factor:** - Deforestation - Change in land use pattern - Urbanization - Agriculture and Animal Husbandry - Energy intensive activity - **Radiative forcing:** - The changes that have a cooling effect are called negative forcing. **For example**, an increase in Aerosol concentration causes a higher reflection of sunlight and cooling of the surface. - A variety of physical and chemical changes which can affect the global energy balance and force changes in the earth's climate are called radiative forcing. ## GLOBAL WARMING (2:10 PM) - **Green Houses Gases:** - The major GHGs arranged in increasing order as per the global warming potential***: C02*** - ***Global Warming Potential:*** - *![GWP](https://i.ibb.co/ygc7RvD/GWP.png)* - ***Global Warming Potential** is the measure of how much energy the emission from one tonne of gas is observed over a given period relative to the emission of 1 tonne of CO2.* - ***CO2:*** - ***Sources:** fossil fuel, agriculture, industries (thermal, cement, etc), deforestation, etc* - ***Note:** For the keeling curve kindly refer to the PPTs shown by the faculty.* - ***Methane:*** - ***Sources:**Wetland, ruminant emissions, biomass burning, termite emissions, landfills, geological sources, wild animals, etc.* - ***Nitrous oxides:*** - ***Sources:** Agricultural soil management, wastewater treatment, stationary combustion, chemical production, transportation, and manure management etc.* - ***Note:** Kindly refer to the PPTs shown by the faculty for a better understanding of fluorinated gas.* *## EVIDENCE OF CLIMATE CHANGE (2:58 PM)* - *1. **Global rise in the temperature:** AR6 of IPCC has observed that the average temperature of the earth has increased by 1.09°C since the late 19th century, out of which 1.07°C is due to human factors.* - *2. **Ocean warming:** The top 100 m of oceans have shown warming of more than 0.33°C since 1969.* - *3. The **hottest year on record** is 2023. Every decade has been the warmest compared to its previous.* - *4. **Global sea level rise** of 20 cm on average in the last century.* - *5. **Melting of snow cover:** The Arctic sea Ice has decreased by 40% in summers and 10% in March. It is expected that within 15 years there will not be any ice left in the Arctic region during the summers* - *6. **Retreat of glaciers** in almost every mountain i.e. Himalayas, Alps, Rockies and Andes, etc.* - *7. **Ocean acidification:** Since the beginning of the Industrial Revolution the acidity of the oceanic surface has increased by 30%.* *## IMPACT OF CLIMATE CHANGE (3:15 PM)* - *Increased **melting of glaciers** will impact the flow of river water.* - *More **glacial lakes** are formed which may result in **GLOF**.* - *It reduces the availability of water in the long run, creating **water stress**.* - *Impact water supply to **agriculture*** - *Crops may become more **water-intensive*** - *Increase rate of evaporation and disturbance in the condensation process due to an increase in air temperature.* - *Intensity and frequency of rainfall changes.* - *Increases the **occurrences of drought** due to irregular rainfall.* *## OCEAN WARMING (3:20 PM)* - ***Ocean warming** causes more heating of the sea surface and disturbs various atmospheric phenomena such as the formation of cyclones, and the occurrence of El Nino, La-Lina and Indian Ocean dipole.* - *The warming results in the formation of more stable and stratified upper layers.* - *It leads to less mixing of deeper and colder nutrient-rich water with the surface.* - *The oxygen supply to the lower layer is limited creating oxygen-minimum zones.* - ****At higher temperatures, dissolved oxygen in the water decreases.**** - *The high temperature of the water is harmful to marine species. **For example:** Coral bleaching.* - *Higher temperature increases metabolic activities causing an increase in the oxygen demand.* *## OCEAN ACIDIFICATION (3:30 PM)* - ***Ocean acidification** is increasing the acidity level of ocean water due to the observation of higher levels of CO2 is called ocean acidification.* - *It reduces the availability of carbonate ions in the water and increases the bicarbonate ions.* - ***Note:** For Impact kindly refer to the handout shared by the faculty.* *## OZONE DEPLETION (3:44 PM)* - ***Ozone** is an allotrope of oxygen with three oxygen atoms.* - *It is a pale blue gas with a **pungent odour**.* - *It is mainly present in the stratosphere (90%) and helps in the filtration of UV rays.* - *When UV rays pass through the ozone layer 100% of UV-A, 90% of UV-B and 5% of UV-C rays are absorbed.* - ***UV B** - skin burning, Skin Cancer, etc.* - ***UV A** - maximum tanning* - ***UV C** - skin cancer, DNA damage, etc (most dangerous).* - ***Ozone Oxygen cell:*** - ****O2 (Oxygen) + UV rays = O3 (Ozone)**** - ***O3 + Uv rays= O2*** - ***Ozone-depleting substance (ODS):*** - ***Chlorine:*** - ***Substances:** CFC, Carbon tetrachloride and Methyl Chloroform* - ***Sources:** Refrigerant, propellants of aerosol, fire extinguisher, etc* - ***Bromine:*** - ***Substances:** HBFC, Methyl Bromide* - ***Sources:** Fire extinguishers and pesticides* - ***Nitric Oxide:*** - ***Substances:** Nitrous oxide* - ***Sources:** Industrial and agricultural use* - ***Why they were used?*** - *Most of these compounds were non-corrosive, non-inflammable, low toxic chemically stable, and long lifetime.* *## THE TOPICS FOR THE NEXT CLASS: CONSERVATION*