GEO217 Climate Change & Sustainability Lecture PDF

GEO217 – Climate Change and Sustainability Mohamed Mahmoud, PhD Email: [email protected] & Tarek Abdel Shafy, PhD Email: [email protected] gu.edu.eg  Understanding the Climate System Weather - Day-to-day (short-term) changes in meteorolo...

GEO217 – Climate Change and Sustainability Mohamed Mahmoud, PhD Email: [email protected] & Tarek Abdel Shafy, PhD Email: [email protected] gu.edu.eg  Understanding the Climate System Weather - Day-to-day (short-term) changes in meteorological parameters (e.g., rainfall, temperatures, pressure, etc.) at a given time in a specific location. - Often perceived in terms of extreme events: heat waves, downpours, and cold spells. Climate is the average weather over a long time period (30 – 50 years) in a region. 1 Climate variability is the way aspects of climate (such as temperature and precipitation) differ from an average. Climate variability occurs due to natural and sometimes periodic changes in the circulation of the air and ocean, volcanic eruptions, and other factors. Climate system is a complex, interactive system consisting of the atmosphere, land surface, snow and ice, oceans and other bodies of water, and living things. 2 3 4 How Can Climate be changed? The climate system evolves in time under the influence of its own internal dynamics and due to changes in external factors that are called forcings. External forcings include: Natural Variations (such as Changes in the earth’s orbit and Changes in solar intensity) Volcanic eruptions (such as altering aerosols in the atmosphere (blocking sunlight) and altering carbon dioxide concentrations) Human activities (e.g., burning of fossil fuels). 5  Greenhouse gases? - Since the Industrial Revolution started over Purpose: Glass house to 200 years ago, human activities have added keep plants warm during winter. very large quantities of GHG into Earth’s atmosphere. How works? Sun’s rays hit the glass - These GHGs act like a greenhouse (or a Some rays blanket or car windshield) to trap the sun’s immediately reflected energy and heat, rather than letting it reflect Some pass through back into space. glass and reach plants. Inside gets hot. - When the concentration of GHG is too high, Heat cannot escape due to glass. too much heat is trapped, and the Earth’s Glass very important!!! temperature rises outside the range of natural variability. 6  Greenhouse gases? The atmosphere around the Earth is like glass!!! How works? - Solar radiation hits the atmosphere - 30% reflected and 70% reaches the earth - Earth warms and gives off heat. - Certain gases in the atmosphere prevent most heat from escaping (e.g. CO2, methane, and nitrous oxide), which are known as greenhouse gases!!! There are many GHGs, each with a different ability to trap heat (known as “global warming potential”) and a different half-life in the atmosphere. - GHGs are sometimes called “climate active pollutants” because most have additional effects, most notably on human health. 7  Examples of greenhouse gases? o Water vapor is the most abundant greenhouse gas in the atmosphere. The surface warming caused by human production of other greenhouse gases, however, leads to an increase in atmospheric water vapor because warmer temperatures make it easier for water to evaporate and stay in the air in vapor form. This creates a positive “feedback loop” in which warming leads to more warming. o CO2 has a GWP of 1 regardless of the period used, since it is the gas being used as the reference. CO2 remains in the climate system for a very long time (potent GHG), which can last thousands of years. o Methane (CH4) is estimated to have a GWP of 27 - 30 over 100 years. CH4 emitted today lasts about a decade on average, which is much less time than CO2. But CH4 also absorbs much more energy than CO2. The net effect of the shorter lifetime and higher energy absorption is reflected in the GWP. The CH4 GWP also accounts for some indirect effects, such as the fact that CH4 is a precursor to ozone, and ozone is itself a GHG. o Nitrous Oxide (N2O) has a GWP 273 times that of CO2 for a 100-year timescale. N2O emitted today remains in the atmosphere for more than 100 years, on average. o Chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6) are sometimes called high-GWP gases because, for a given amount of mass, they trap substantially more heat than CO2. (The GWPs for these gases can be in the thousands or tens of thousands.) 8 - Carbon dioxide (CO2) is the GHG responsible for the greatest amount of warming to date. - CO2 accounted for 82% of all human-caused GHG emissions. - The majority of CO2 is released from the complete combustion of fossil fuels - coal, oil, and gas — used for electricity production, transportation, and industrial processes. Together, these three activities account for more than 80% of the CO2 released into the atmosphere. 9 10  What are the impacts of climate change? 1. Warming temperature of the earth’s surface and the oceans: The earth has warmed at a rate of 0.13 °C per decade since 1957, almost twice as fast as its rate of warming during the previous century. 2. Changes in the global water cycle (‘hydrologic’ cycle): Over the past century there have been distinct geographical changes in total annual precipitation, with some areas experiencing severe and long-term drought and others experiencing increased annual precipitation. The frequency and intensity of storms increase as the atmosphere warms and is able to hold more water vapor. 3. Declining glaciers and snowpack: Across the globe, nearly all glaciers are decreasing in area, volume, and mass. One billion people living in river watersheds fed by glaciers and snowmelt are thus impacted. 4. Sea level rise: Warmer water expands, so as oceans warm the increased volume of water is causing sea level rise. Melting glaciers and snowpacks also contribute to rising seas. 5. Ocean acidification: Oceans absorb about 25% of emitted CO2 from the atmosphere, leading to acidification of seawater. 11 12  A flood in Kerala, A forest fire in Dry land in the India (2018) Northern California African Sahel (2018) 13  Is climate change real? The vast majority of actively publishing climate scientists (i.e., 97 %) agree that: Humans are causing global warming and climate change. We have to act urgently to reduce its impact and progression. 14 Thank You gu.edu.eg 15