Global Climate Change Notes

Medieval Climate Anomaly (MCA)

  • The Medieval Warm Period (MWP) lasted from approximately 950-1250 C.E.

  • Some regions experienced warmth exceeding the current post-industrial era.

  • Historical events possibly influenced by this period:

    • Vikings could cross ice-free seas, leading to colonization of southern Greenland and Newfoundland.

    • Europe and Asia saw high crop yields and economic prosperity.

Little Ice Age (LIA)

  • The Little Ice Age was a cooling period from the 16th to 19th centuries.

  • Viking colonies in Greenland failed and were abandoned.

  • North American Indian tribes formed alliances due to food shortages.

  • The River Thames frequently froze over, resulting in frost fairs.

  • The Great Belt froze, allowing Sweden to invade Denmark.

Natural Causes of Climate Change

  • Milankovitch Cycles: The Earth periodically undergoes three changes affecting global solar radiation:

    • The shape of its orbit around the sun (approximately every 100,000 years).

    • Tilt of the Earth’s axis (approximately every 41,000 years).

    • Wobbling of the Earth’s axis (approximately every 23,000 years).

  • Volcanic Eruptions:

    • Release sulfur dioxide and particulates, scattering solar radiation and causing cooling.

    • Example: The 1816 eruption of Mount Tambora in Indonesia led to summer snow in North America, causing crop losses and food shortages.

  • Sunspots:

    • Darker areas on the sun's surface are created by intense magnetic fields.

    • More sunspots mean slightly more radiation; fewer sunspots mean slightly less radiation.

    • Sunspot numbers fluctuate on an 11-year cycle.

  • Great Ocean Conveyor Belt:

    • Underwater current is driven by mixing warm and cold salt water.

    • The influx of cold freshwater from melting ice could disrupt the flow.

    • Releases heat, keeping Western Europe warmer than its latitude would suggest.

  • El Niño-Southern Oscillation (ENSO):

    • Periodic warming and cooling of surface ocean temperatures in the Pacific Ocean.

    • Affects evaporation rates, influencing temperatures and precipitation worldwide.

Evidence of Climate Change

  • Atmospheric carbon dioxide levels measured daily in Hawaii since 1958.

  • Hawaii was chosen to avoid influences from large forests or cities.

Atmospheric Basics

  • Atmosphere: Thin blanket of gases surrounding the Earth.

  • Density: Number of gas molecules per unit of air volume; decreases with higher altitude.

  • Atmospheric Pressure: Force per unit area of an air column; decreases with higher altitude.

Signs of a Changing Climate

  • Glaciers are melting at an accelerating rate in summer due to atmospheric warming.

  • Greenland's ice loss has contributed to about one-sixth of global sea-level rise over the past 20 years.

Key Vocabulary

  • Greenhouse Gas: Gas that absorbs infrared radiation.

  • Positive Feedback: Change triggers a response that intensifies the initial change.

  • Infrared Radiation: Radiation wavelength is longer than visible light but shorter than radio waves.

  • Greenhouse Effect: Increase of heat in a system where energy enters, is absorbed, and released later.

  • Global Change: Alterations in the chemical, biological, and physical properties of the planet.

  • Global Climate Change: Changes in average weather over years or decades.

  • Global Warming: Warming of oceans, land masses, and atmosphere.

The Greenhouse Effect

  • The greenhouse effect is a natural and essential process.

  • Heat-holding gases absorb heat.

  • Historical changes in carbon dioxide correlate with global temperature changes.

  • Greenhouse Effect: Absorption of infrared radiation by atmospheric gases and reradiation back toward Earth

Anthropogenic Causes of Greenhouse Gases

  • Human activities contribute to greenhouse gas production:

    • Burning fossil fuels

    • Agricultural practices

    • Deforestation

    • Landfills

    • Industrial production

Increases in Atmospheric Greenhouse Gases (Pre-Industrial to Present)

  • Carbon dioxide: Preindustrial - 288 ppm, 2010 - 391 ppm

  • Methane: Preindustrial - 848 ppb, 2010 - 1800 ppb

  • Nitrous oxide: Preindustrial - 285 ppb, 2010 - 323 ppb

  • Chlorofluorocarbon-12: Preindustrial - 0 ppt, 2010 - 530 ppt

  • Chlorofluorocarbon-11: Preindustrial - 0 ppt, 2010 - 245 ppt

*ppm = parts per million.
*ppb = parts per billion.
*ppt = parts per trillion.

Intergovernmental Panel on Climate Change (IPCC)

  • The international panel of scientists and government officials, established in 1988.

  • Presents reports synthesizing scientific information on climate change.

Major CO2 Emitters

  • Largest Emitters (Millions of metric tons of CO_2):

    • China

    • United States

    • India

    • Russia

    • Japan

    • Germany

  • Largest Emitters (Per capita metric tons of CO_2)

    • United States

    • Australia

    • Saudi Arabia

    • Canada

    • Taiwan

    • South Korea

Significance of Carbon Dioxide

  • Abundant greenhouse gas, a major contributor to global warming.

  • Human activities have increased atmospheric concentrations from 280 ppm to 383 ppm.

  • Highest levels in more than 650,000 years.

Impacts of Increased Greenhouse Gases

  • Severe Droughts:

    • Extra heat depletes soil moisture.

    • Prolongs and intensifies droughts.

    • Higher temperatures intensify the water cycle.

    • Additional water vapor warms the atmosphere.

    • Increased wildfires.

    • Reduced plant growth.

  • Melting Ice Caps and Glaciers

  • Polar bears are starving

  • Storms are increasing

  • Sea ice is thinning

  • Rising Sea Levels:

    • Thermal expansion.

    • Melting land ice.

  • Rising Sea Levels:

    • IPCC projects sea-level rise of 18-59 cm by 2100.

    • Thermal expansion and melting land ice contribute.

    • Melting has positive feedback: decreased ice decreases albedo, leading to further warming.

  • Wildfires

Ocean Acidification

  • Coral reefs can be bleached due to increased water temperature, affecting coral symbiotes and making them susceptible to diseases.

  • Surface waters have increased acidity by 30% since 1800 and could reach dangerous levels before 2050.

  • CO2 combines with water to become carbonic acid (H2CO_3), threatening corals, snails, other shelled organisms, and phytoplankton.

General Impacts of Increased Greenhouse Gases

  • Melting of polar ice caps, Greenland, and Antarctica.

  • Melting of many glaciers around the world.

  • Melting of permafrost.

  • Rising sea levels due to melting ice and thermal expansion.

  • Heat waves and cold spells.

  • Changes in precipitation patterns.

  • Increase in storm intensity.

  • Shift in ocean currents.

Effects on Organisms

  • Organisms are adapted to their environments and are affected by changes.

  • Global warming modifies temperature-dependent phenomena, such as the timing of migration and breeding.

  • Causes spatial shifts in the range of organisms.

  • Animals and plants will move towards the poles or upward in elevation.

  • 20-30% of all species will be threatened with extinction.

  • Plants act as carbon sinks; fewer plants increase CO_2 in the atmosphere.

Rising Number of Endangered Species

  • The most endangered species are

    • Mammals

    • Reptiles

    • Birds

    • Insects

    • Molluscs

    • Fish

    • Amphibians

Impacts on Humans

  • Human society is beginning to feel the impacts of climate change.

    • Agriculture: growing seasons are shortened, crops are more susceptible to droughts and failure, and crop production will decrease, worsening hunger.

    • Forestry: increased insect and disease outbreaks, increased chance of forest fires.

    • Health: heat waves and stress can cause death, respiratory ailments, expansion of tropical diseases, increased chance of drowning if storms become intense, and hunger-related ailments.

What Can You Do?

  • Diet choices: Processed foods require more energy than fresh fruits and vegetables, and beef requires more energy than chicken.

  • Political involvement.

  • Two-thirds of the average American’s carbon footprint is embedded in carbon.

Legislation

  • The Kyoto Protocol

    • 1997 treaty to slow climate change

    • Not signed by the United States

  • 2014: the United States and China agreed to cap carbon emissions within 15–20 years (Nothing Binding)

  • 2015 Paris Agreement

    • Countries pledged to meet certain goals

    • No provision of money to assist poorer countries in reaching goals

    • US pulled out of the agreement in 2017, Rejoined in 2021, and Left again in January of this year.

Solutions: Mitigation and Adaptation

  • Mitigation: Pursue actions that reduce greenhouse gas emissions.

    • Examples: Renewable energy sources, farm practices to protect soil integrity, and preventing deforestation.

  • Adaptation: Accept climate change and minimize its impacts.

  • Both are necessary.

Carbon Offsets

  • Voluntary payment to another entity to reduce greenhouse emissions that one cannot or will not reduce themselves.

  • Becoming popular among utilities, businesses, universities, governments, and individuals trying to achieve carbon neutrality.

  • Carbon offsets often fall short due to a lack of oversight.