GEO217 Climate Change and Sustainability

Climate Change and Sustainability

• GEO217 course on climate change and sustainability
• Course instructors: Mohamed Mahmoud, PhD, and Tarek Abdel Shafy, PhD
• Contact information provided for instructors

Understanding the Climate System

• Weather: Day-to-day changes in meteorological parameters (e.g., rainfall, temperature, pressure) at a specific location. Often described by extreme events like heat waves, downpours, and cold spells.
• Climate: The average weather over a long time period (30-50 years) in a region.

Climate Variability

• Climate variability: The way aspects of climate (like temperature and precipitation) differ from an average. Driven by natural factors like changes in the circulation of air and ocean currents, volcanic eruptions, and other factors.

Climate System

• Climate system: A complex interactive system encompassing the atmosphere, land surface, snow, ice, oceans, other water bodies, and living things.

What is Climate Change?

• Climate change: A change in climate directly or indirectly attributed to human activity altering the global atmosphere's composition, in addition to natural climate variability over comparable time periods.
• Long-term changes in climate, happening over decades, centuries, or longer.
• Caused by increasing greenhouse gases produced by burning fossil fuels (e.g., coal, oil, and natural gas).

What Causes Climate Change?

• Climate change: Driven by imbalances in Earth's energy balance—how much energy from the sun enters the Earth's system versus how much is released back into space.
• This imbalance can be likened to people gaining weight due to an excess of calories in comparison to calories burned.

How Can Climate Be Changed?

• External forcings: Factors that alter the climate system, such as natural variations (e.g., changes in Earth's orbit, solar intensity), volcanic eruptions (altering aerosols blocking sunlight, and altering carbon dioxide concentrations), and human activities (e.g. burning fossil fuels).
• These external forces drive changes in climate over time.

Greenhouse Gases

• Greenhouse gases (GHGs): Gases that trap the sun's energy, thus preventing it from escaping back into space and impacting the Earth's temperature.

• Added to the atmosphere in significant quantities due to human activities since the Industrial Revolution.

• Acting like a blanket or windshield to trap heat, leading to rising temperatures outside the range of natural variation.

• Key greenhouse gases: Water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), Chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), hydrochlorofluorocarbons (HCFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6)

Carbon Dioxide (CO2)

• Carbon Dioxide (CO2): The most significant human-caused GHG.
• Major source of CO2 emissions: the combustion of fossil fuels (coal, oil, and natural gas) for electricity production, transportation, and industrial processes.
• CO2 emission from these three activities accounts for more than 80% of the CO2 released into the atmosphere.
• Dominates the warming effect among human-caused GHG emissions to date: 82%

Examples of Greenhouse Gases

• Water vapor: The most abundant greenhouse gas, its concentration increases with warming.
• Carbon dioxide (CO2): Has a global warming potential (GWP) of 1. Remains in the atmosphere for a long time (thousands of years).
• Methane (CH4): Estimated GWP of 27–30 over 100 years. Short atmospheric lifetime (approximately a decade) but higher energy absorption than CO2 leading to a higher GWP.
• Nitrous Oxide (N2O): High GWP of 273 times that of CO2 over 100 years and long atmospheric lifetime (more than 100 years)
• Other strong GHGs: Chlorofluorocarbons, hydrofluorocarbons, hydrochlorofluorocarbons, perfluorocarbons, and sulfur hexafluoride (high global warming potential and often thousands or tens of thousands times higher than CO2).

Impacts of Climate Change

• Warming temperatures: Earth's surface and oceans have warmed at a rate of .13°C per decade since 1957—twice as fast as the previous century.
• Changes in the global water cycle: Significant geographic changes in total annual precipitation (some areas experiencing severe drought or increased rainfall).
• Declining glaciers and snowpack: Nearly all glaciers are shrinking in area, volume, and mass.
• Sea level rise: Warmer water expands, and melting glaciers contribute to rising seas.
• Ocean acidification: Oceans absorb significant CO2, leading to acidification.

Global Average Surface Temperature

• 2021 was the sixth-warmest year on record.
• Averaged across land and ocean, the 2021 surface temperature was 0.84°C warmer than the twentieth-century average (13.9°C) and 1.04°C warmer than the pre-industrial period (1880–1900).

Is Climate Change Real?

• The vast majority of actively publishing climate scientists (approximately 97%) agree that humans are causing global warming and climate change and urgent action is needed to mitigate its impacts.