Earth Midterm 1

Climate proxies

•Tree Rings: Width and density can indicate past climate conditions; wider rings typically correlate with warmer, wetter years.

•Stomatal Density: Changes in leaf stomatal density can indicate atmospheric CO2 levels; higher CO2 typically leads to fewer stomata.

•Ice Cores: Layers in ice cores capture historical climate data, including greenhouse gas concentrations and temperature fluctuations over hundreds of thousands of years.

Oxygen isotopes

•Oxygen isotopes (O-16 and O-18) are used to reconstruct past temperatures. The ratio of O-18 to O-16 in ice cores indicates temperature changes; warmer periods lead to lower O-18 ratios in precipitation.

Instrumental Records

•Instrumental data, such as temperature and precipitation measurements, have been collected since the late 19th century. This data shows clear trends in global warming and extreme weather events.

Last glacial maximum

•Occurred approximately 20,000 years ago; characterized by extensive ice sheets covering much of North America and Europe. Conditions included lower sea levels and cooler global temperatures.

Orbital Cycles

•Milankovitch cycles (eccentricity, axial tilt, precession) influence Earth's climate over tens of thousands of years, affecting seasonal solar radiation and contributing to glacial-interglacial cycles.

Paleocene-Eocene Thermal Maximum (PETM)

• An abrupt climate warming event around 55 million years ago, caused by massive carbon release (likely from volcanic activity and methane hydrate destabilization), leading to higher temperatures and acidification of oceans.

Global Mean Temperature

• Recent data indicates a significant rise in global mean temperature, with an increase of about 1.2°C since the late 19th century. Human activities, particularly fossil fuel combustion, are the primary drivers.

Warming at different latitudes

• High latitudes are warming faster than the global average due to feedback mechanisms like albedo changes (melting ice reduces reflectivity).

impact of volcanism

• Volcanic eruptions can lead to short-term cooling by releasing ash and sulfur dioxide, which reflect sunlight. Long-term impacts vary based on eruption frequency and magnitude.

El Nino-Southern Oscillation (ENSO)

• ENSO affects global weather patterns, with El Niño leading to warmer ocean temperatures and La Niña causing cooler temperatures. This impacts precipitation patterns, tropical storms, and agriculture.

Sea surface temperature (SSTs) vs. Air temperatures

• SSTs are crucial for climate modeling as they influence atmospheric temperatures. Changes in SSTs can affect weather patterns and the intensity of storms.

Future Precipitation changes

• Climate models project that precipitation will become more variable, with some regions experiencing increased rainfall and others facing droughts, impacting water resources and agriculture.

U.S. Drought-Prone Areas

• Regions like the Southwest U.S. are particularly susceptible to drought, exacerbated by climate change, leading to water shortages and agricultural impacts.

Glacial melting and sea level

• Melting glaciers contribute to sea-level rise; for every 1 meter of global sea level rise, millions of people may be displaced, affecting coastal ecosystems and infrastructure.

Hurricane activity

• Rising sea surface temperatures contribute to more intense hurricanes. Areas like the Gulf Coast and Eastern Seaboard are particularly vulnerable.

Polar Vortex

• A large area of low pressure and cold air surrounding the poles; disruptions can lead to extreme winter weather in mid-latitude regions.

Basic climate concepts

• Heat vs. Temperature: Heat is energy transfer, while temperature measures the average kinetic energy of particles.

• Black Body: An idealized object that absorbs all incoming radiation.

• Stefan-Boltzmann Law: Relates the temperature of a body to its emitted energy; hotter bodies emit more radiation.

• Emissivity: Measure of a material’s ability to emit thermal radiation.

Albedo

• The reflectivity of a surface. High albedo (e.g., ice) reflects more sunlight, while low albedo (e.g., forests) absorbs more heat. Changes in albedo due to melting ice contribute to warming.

Solar constant and insolation

• The solar constant is the amount of solar energy received at the top of Earth's atmosphere. Insolation varies based on latitude, season, and time of day, affecting climate.

Sunspots

• Dark spots on the Sun’s surface that correlate with solar activity cycles. Higher sunspot activity can lead to increased solar output, influencing climate.

Heat capacity

• The amount of heat required to change a substance's temperature. Water has a high heat capacity, moderating Earth's climate.

greenhouse effect

• The process by which certain gases trap heat in the atmosphere, preventing it from escaping into space. Key greenhouse gases include CO2, CH4, and N2O.

feedback mechanisms

• Positive Feedback: Amplifies initial changes (e.g., melting ice reduces albedo, leading to more warming).

• Negative Feedback: Counteracts changes (e.g., increased cloud cover can cool the Earth).

General circulation models (GCMs)

• Complex computer models that simulate Earth's climate system to project future climate scenarios based on various emission pathways.

Emission scenarios

• Different projections (e.g., RCPs) based on potential greenhouse gas emissions, ranging from high emissions (RCP8.5) to low emissions (RCP2.6), influencing future climate impacts.

• A1B – optimistic

• A2 – business-as-usual

• B1 – more ecologically friendly world

• A1B – a rapid, strong, and global commitment to the reduction of carbon emissions

Stream Flow changes

• Changes in precipitation and snowmelt patterns affect river flow, impacting water supply, ecosystems, and agriculture.

High latitude warming

• The Arctic is warming at a rate approximately twice the global average, affecting ice coverage, ecosystems, and global weather patterns.

2 C threshold

• The target set in international agreements (e.g., Paris Agreement) to limit global warming to below 2°C above pre-industrial levels to mitigate severe climate impacts.

Paris climate agreement & clean power plan

• International treaty aiming to limit global warming and reduce greenhouse gas emissions. The Clean Power Plan aims to reduce emissions from power plants in the U.S.

Ocean chemistry

• Increasing CO2 levels lead to ocean acidification, impacting marine life, especially organisms with calcium carbonate shells.

nutrients and primary productivity

• Upwelling brings nutrient-rich waters to the surface, supporting high levels of primary productivity, crucial for marine ecosystems.

Temperature range of seawater

• Seawater temperature varies by depth and location; temperature stratification affects marine life and ocean circulation.

Ocean circulation

A large-scale movement of water within the world's oceans, driven by factors such as wind, temperature, salinity, and the Earth's rotation. It plays a crucial role in regulating climate, distributing heat, and supporting marine ecosystems. Key components include surface currents, deep ocean currents, and thermohaline circulation.

Current pCO2 and historical measurements

• Current atmospheric CO2 levels are around 420 ppm, with significant increases due to human activities since the Industrial Revolution, impacting climate.

Deforestation and climate change

• Deforestation contributes to CO2 emissions, disrupts ecosystems, and reduces the capacity of forests to act as carbon sinks.

Photosynthesis

• The process by which plants convert CO2 and sunlight into glucose and oxygen; plays a critical role in the carbon cycle and mitigating climate change.

Permafrost thawing

• Thawing permafrost releases stored carbon (in the form of methane and CO2), further exacerbating climate change.

Energy sources and CO2 emissions

• Different energy sources (fossil fuels vs. renewables) vary in their carbon emissions. Transitioning to renewable energy is crucial for reducing emissions.