geol lecture 1 - 4

How do we study weather

Through real-time observations and measurements of atmospheric conditions (temperature, pressure, humidity, wind, precipitation) using instruments like thermometers, barometers, radar, weather balloons, and satellites.

How do we study climate

By analyzing long-term statistical patterns, trends, and averages of weather variables over extended periods (typically 30 years or more), using instrumental records, historical data, and climate models.

How do we study past climate?

Using climate proxies—preserved natural archives such as tree rings, ice cores, sediment layers, coral reefs, and pollen grains that record past environmental conditions.

What are the spheres of the climate system?

Atmosphere (gases surrounding the Earth) Hydrosphere (liquid water on Earth) Cryosphere (frozen water/ice) Biosphere (living organisms) Lithosphere / Geosphere (solid Earth, crust, rocks, and soil)

What is climate inertia?

The delay or lag in the climate system's response to changes in forcing (such as greenhouse gas emissions), largely caused by the immense heat capacity of the oceans.

What are climate tipping points?

Critical thresholds where a small change triggers a larger, often abrupt and irreversible, shift or collapse in a component of the climate system (e.g., the melting of the Greenland ice sheet or Amazon rainforest dieback).

Why study climate change?

To understand how human activities impact Earth's life-support systems, predict future environmental risks, protect ecosystems, and inform policy for adaptation and mitigation.

What is the role of the atmosphere in the Earth's climate system?

It acts as a blanket that regulates surface temperature via the greenhouse effect, transports heat and moisture globally, protects life from harmful solar radiation, and supplies essential gases (carbon dioxide, oxygen, nitrogen).

What is the electromagnetic spectrum and why does it matter in terms of Earth's climate system?

It is the range of all types of electromagnetic radiation, categorized by wavelength and frequency (from gamma rays to radio waves). It matters because the Sun emits mostly shortwave (visible/ultraviolet) radiation, while the Earth emits longwave (infrared) thermal radiation, driving the planetary energy balance.

How does energy enter and leave our planet?

Shortwave solar radiation from the Sun. / Reflected solar radiation and outgoing longwave infrared radiation emitted by the Earth and its atmosphere back into space.

How and why does temperature vary in the Earth's atmospheric layers?

Temperature varies due to how different layers absorb specific wavelengths of solar and terrestrial radiation. For example, the stratosphere warms with altitude because ozone absorbs UV radiation, whereas the troposphere cools with altitude because it is heated from below by the Earth's surface.

Why does humidity matter to climate?

Water vapor is the most potent natural greenhouse gas, amplifying warming through feedback loops. Humidity also influences cloud formation, precipitation patterns, and latent heat transfer.

Why do the different gases in our atmosphere matter to Earth's climate system?

Trace gases like carbon dioxide (CO_2), methane (CH_4), and water vapor absorb outgoing infrared radiation, trapping heat. Nitrogen and oxygen make up the bulk of the atmosphere but are largely transparent to infrared radiation.

What causes the loss of ozone in the stratosphere?

Chemical reactions involving human-made chlorine and bromine compounds (such as chlorofluorocarbons or CFCs) that break down ozone molecules (O_3) faster than they are naturally formed.

Where/when does the ozone hole form? Why?

It forms over Antarctica during the Southern Hemisphere spring (September to November). Cold winter temperatures create polar stratospheric clouds that trap chlorine, which is then activated by returning sunlight to destroy ozone.

Is the situation improving or not?

Yes, it is improving. Thanks to the global ban on ozone-depleting substances under the Montreal Protocol, the stratospheric ozone layer is slowly healing and showing signs of recovery.

What is the link between climate change and ozone?

While distinct issues, they interact: ozone-depleting substances are also powerful greenhouse gases, and stratospheric cooling (caused by greenhouse gas accumulation trapping heat in the lower atmosphere) alters polar vortex dynamics and ozone recovery rates.

Why does it matter that there are heating and pressure differences on Earth?

Differential heating creates pressure gradients, which drive global wind patterns, ocean currents, and the atmospheric circulation needed to redistribute heat from the equator to the poles.

What do Hadley Cells do for Earth's climate system?

They are tropical atmospheric circulation cells that transport warm air upward at the equator, move it poleward, and cause it to sink at around 30° latitude, creating major global deserts and driving trade winds

Why do most deserts exist where they do?

They generally lie near 30° north and south latitudes underneath the descending, dry air branches of the Hadley cells, and in the "rain shadows" of major mountain ranges.

What do midlatitude westerlies and polar easterlies do for Earth's climate system?

They are major surface wind belts that circulate air between the midlatitudes and the poles, helping to transport heat and moisture across the globe.

Why is the jet stream important to Earth's climate system?

It is a fast-flowing band of upper-level air that steers weather systems, separates cold polar air from warm tropical air, and can influence extreme weather persistence when it meanders.

What is the role of the ocean in the Earth's climate system?

It acts as the planet's primary thermal and carbon sink, absorbing over 90% of excess heat generated by global warming and roughly a quarter of anthropogenic carbon emissions, while driving global weather and climate patterns.

Why does latent heat matter for Earth's climate system?

It represents the energy absorbed or released during phase changes of water (like evaporation and condensation). It transports enormous amounts of heat energy from the Earth's surface into the atmosphere, fueling storms and regulating regional climates.

How does the heat capacity of water change as it changes temperature?

Water has a uniquely high specific heat capacity, meaning it can absorb or release vast amounts of heat with only minimal changes in its own temperature, making the oceans great climate stabilizers.

What is the link between ocean salinity and Earth's climate system?

affects seawater density. Variations in salinity (driven by evaporation, precipitation, sea-ice formation, and freshwater runoff) combine with temperature to drive global ocean thermohaline circulation.

Why does the 3D structure of the ocean matter? What changes with depth?

The ocean is stratified into layers (surface mixed layer, pycnocline/thermocline, and deep ocean). With increasing depth, temperature drops rapidly, pressure increases, light decreases, and density generally increases. This structure regulates how heat and carbon are sequestered in the deep ocean.

Why are ocean currents important for Earth's climate system?

They redistribute heat from the equatorial regions toward the poles, balancing the planet's energy budget and shaping regional climates.

Why is the Gulf Stream important for Earth's climate system?

It is a powerful surface current that carries warm tropical water up the East Coast of North America and across the Atlantic toward Europe, keeping Western and Northern Europe significantly milder than other regions at similar latitudes.

Why are upwellings and downwellings important in terms of Earth's climate system?

brings cold, nutrient-rich deep water to the surface, supporting productive marine ecosystems and fisheries. / transports surface waters, dissolved oxygen, and carbon down into the deep ocean, ventilating the deep sea.

What causes the thermohaline circulation to move?

Differences in water density, which are controlled by temperature (thermo) and salinity (haline). Cold, salty water becomes dense, sinks in polar regions, and drives the global conveyor belt of ocean currents

How are the ocean and atmosphere linked? Why does this matter for Earth's climate system?

They are coupled through continuous exchanges of heat, moisture, momentum (wind stress), and gases (like CO_2). This coupling drives climate variability phenomena like El Niño-Southern Oscillation (ENSO) and dictates global weather patterns.

How does heat move around the planet and why is this important?

Through atmospheric circulation (winds) and oceanic circulation (currents). This transport prevents the equator from overheating and the poles from freezing completely, making the entire planet habitable.

What impact does ENSO have on interannual climate variability in the Pacific Northwest and other parts of the world?

El Niño typically brings warmer and drier winters to the Pacific Northwest (reducing snowpack), while causing heavy rainfall in the southern US and droughts elsewhere.

La Niña typically brings cooler and wetter winters with heavier mountain snowpack to the Pacific Northwest.

How have atmospheric concentrations of CO2 and CH4 changed in the recent past? Why does this matter for Earth's climate system?

Both have risen dramatically since the Industrial Revolution due to fossil fuel combustion, agriculture, and land-use changes. This matters because they enhance the greenhouse effect, trapping more outgoing heat and accelerating global warming.

Why do CO2 concentrations vary seasonally?

Primarily because of the Northern Hemisphere's landmass vegetation. During spring and summer, plants absorb CO2 through photosynthesis (lowering levels); during autumn and winter, plant growth slows or decays, releasing CO2 back into the atmosphere (raising levels).

What is CO2 growth rate and why does it vary year to year?

It is the annual increase in atmospheric CO2 concentration. It varies year to year largely due to climate oscillations like El Niño (which can reduce terrestrial carbon uptake via droughts and wildfires) and variations in human emissions.

Why are the emissions of CH4 so uneven spatially across our planet?

Because methane sources are concentrated in specific geographic regions, such as major agricultural zones (rice paddies and livestock), wetlands, thawing permafrost regions, and fossil fuel extraction fields.

Where is most of the carbon on our planet stored?

In geological reservoirs (rocks, limestone, and fossil fuels), with the deep ocean serving as the largest active surface reservoir.

What is the carbon cycle and why does it matter in terms of Earth's climate system?

It is the continuous movement of carbon atoms among the Earth's spheres. It matters because carbon gases (CO2 and CH4) regulate the planet's greenhouse effect and surface temperature.

What are the largest reservoirs?

Lithosphere/sedimentary rocks (by far the largest), followed by the deep ocean, soil, fossil fuels, vegetation, and the atmosphere.

What is the long-term carbon cycle and why does it matter?

It operates over millions of years, involving volcanic outgassing, chemical weathering of rocks, and the burial of organic matter into sedimentary rock. It sets the baseline thermostat for the Earth's climate over geological time scales.

How are humans influencing the long-term carbon cycle?

By burning fossil fuels, which rapidly releases carbon stored away for millions of years into the active short-term cycle.

What is the short-term carbon cycle and why does it matter to Earth's climate system?

It operates over days to decades, involving photosynthesis, respiration, decomposition, and air-sea gas exchange. It controls seasonal fluctuations and the annual carbon balance.

How are humans influencing the short-term carbon cycle?

Through deforestation, land-use changes, and agricultural practices that disrupt natural carbon storage in plants and soils.

How is the release of methane impacting Earth's climate system? Why is this so concerning in terms of climate change?

Methane is a potent greenhouse gas with a global warming potential far higher than CO2 on a decadal time scale. Its release (e.g., from melting permafrost or leaks) accelerates short-term warming rapidly.

What are the relationships between CO2, pressure, and temperature in ocean water? Why does this matter?

Cold water can dissolve more gas (CO2) than warm water. As oceans warm up, their capacity to absorb CO2 decreases, potentially leaving more CO2 in the atmosphere and creating a feedback loop

Where is most carbon stored in the ocean?

In the deep ocean interior, mostly as dissolved inorganic carbon (bicarbonate and carbonate ions).

What are the ocean carbon pumps and how do they influence Earth's carbon cycle?

Solubility Pump: Physical transport of carbon from the surface to the deep ocean via cold, sinking water masses. Biological Pump: Phytoplankton fixing carbon via photosynthesis, which then sinks as organic matter into the deep ocean. Carbonate Pump: Marine organisms forming calcium carbonate shells, which sink and form sedimentary rock.

How are the oceans becoming more acidic and why does it matter?

As oceans absorb excess anthropogenic CO2, chemical reactions lower the pH of seawater (ocean acidification). This makes it difficult for calcifying organisms (like corals, clams, and certain plankton) to build and maintain their shells and skeletons, disrupting marine food webs.

What happens to energy that moves through the atmosphere and is absorbed by the Earth or its atmosphere?

It is converted into thermal energy (heat), driving weather systems, ocean currents, and evaporation, and is eventually re-radiated outward as longwave infrared radiation.

How does the greenhouse effect work and what does it mean in terms of anthropogenic climate change?

Greenhouse gases let incoming shortwave solar radiation pass through, but absorb and re-emit outgoing longwave infrared radiation, warming the lower atmosphere. Anthropogenic climate change means humans are artificially intensifying this natural effect by adding extra greenhouse gases.

What are the natural and anthropogenic influences on Earth's energy budget?

Solar output variations, volcanic aerosols, and orbital changes (Milankovitch cycles).

Greenhouse gas emissions, aerosols/pollution, and land-use changes that alter surface albedo.

What happens to surplus energy on Earth?

It is stored within the climate system, with the vast majority (~90%) going into warming the oceans, and the rest melting ice, warming the land, and heating the atmosphere.

What is radiative forcing?

A measure of the net change in the Earth's energy balance (incoming minus outgoing radiation) measured at the top of the atmosphere, usually expressed in watts per square meter (W/m^2).

Which radiative forcings are positive/negative? Why?

(warm the planet): Greenhouse gases (CO2, CH4), black carbon soot. They trap outgoing heat.

(cool the planet): Sulfate aerosols, volcanic ash, high-albedo surfaces. They reflect incoming sunlight or encourage reflective cloud formation.

What is atmospheric residence time and why does it matter?

The average length of time a gas or particle remains in the atmosphere. It matters because gases with long residence times (like CO_2, which lasts centuries) cause long-lasting, cumulative climate warming.