Climate Change and Greenhouse Gases

Low energy infrared radiation is emitted from the Earth.
Certain atmospheric gases absorb this heat energy and re-emit it, trapping heat in the atmosphere.
This process warms the atmosphere.
Solar energy comes in as long waves and is released as short waves (heat energy, or infrared radiation).

The ozone layer is critical for absorbing UV radiation.
It protects us from the majority of harmful UV rays, though some still get through (hence the need for sunscreen).

Prior to the 1700s, the Earth's energy was balanced: incoming energy equaled outgoing energy.
This maintained a regulated global temperature (equilibrium).
The addition of greenhouse gases to the atmosphere has disrupted this balance.
More energy is now coming in than going out, leading to global warming and climate change.

Diagrams help visualize the steps of the greenhouse effect.
Solar energy arrives as longwave radiation (yellow arrows).
The Earth releases shortwave radiation (red arrows) after absorbing the solar energy.
This outgoing shortwave radiation is increasingly trapped by greenhouse gases.

Greenhouse gases are the primary problem in global warming.
Albedo, surface texture, volcanoes, and forest fires are not the main initial causes, although they can contribute through feedback loops.

Water Vapor:
- Most abundant greenhouse gas.
- Not considered a major factor due to its variability (exists in liquid, solid, and gas forms) and movement.
Carbon Dioxide ($\text{CO}_2$):
- Number one greenhouse gas.
- The primary reason for the current energy imbalance.
Methane ($\text{CH}_4$)
Nitrous Oxide ($\text{N}_2\text{O}$)
Ozone ($\text{O}_3$)
- These three occur naturally.

Livestock farming significantly increases methane emissions.
High concentrations of livestock in specific areas, combined with specific feed, contribute to increased gas production.

Solely man-made gases (e.g., chlorofluorocarbons, hydrofluoride compounds).
- Used in plastics.
- Possess an astounding ability to hold energy.
The government restricted the use of these gases in products like Styrofoam containers to prevent rapid warming.

Driven by the movement of energy from the sun in and out of the atmosphere.
Driven by the movement of heat within the atmosphere and oceans.
The sun's energy reaches the atmosphere.
- Some is absorbed.
- Some is reflected (mainly by clouds).
Most of the remaining energy heats the Earth's surface.
The Earth's surface loses heat through:
- Rising air currents.
- Radiation.
- Evaporation of water.
Some heat passes through the atmosphere back to space.
Some is absorbed by greenhouse gases (carbon dioxide, water vapor, methane, ozone).
Nitrogen and oxygen don't absorb the heat.
The atmosphere re-emits the absorbed heat.
- Some escapes to space.
- Some heats the Earth's surface again.
Eventually, all heat escapes into space.
The greenhouse gases raise the earth so we can survive.

The sun's energy is unevenly distributed across the globe (more heat at the Equator than at the poles).
The climate system moves heat from the Equator to the poles through atmospheric and oceanic processes.

Thunderclouds develop near the Equator, causing warm air to rise and drift towards the poles at high altitudes.
Cooler air flows in the opposite direction at the Earth's surface, setting up cells.
Air rises from the surface (low pressure, precipitation) or falls towards it (high pressure, clear weather).

Changes in sea temperature and saltiness create ocean currents.
The Gulf Stream moves warm water from the Gulf of Mexico to Northwest Europe, moderating the climate.
Cold, dense, salty water sinks and travels towards the Equator deep in the ocean.

Natural Sources of $\text{CO}_2$:
- Volcanic eruptions.
- Forest fires.
Human Sources of $\text{CO}_2$:
- Power plants running on coal.
- Industry.
- Cars.
Since the 1700s, humans have increasingly burned fossil fuels, leading to a significant increase in atmospheric $\text{CO}_2$.

Carbon Dioxide ($\text{CO}_2$):
- Lifespan: Hundreds to thousands of years.
- Global Warming Potential: 1 (baseline).
Methane ($\text{CH}_4$):
- Lifespan: Approximately a decade.
- Global Warming Potential: 80 (more potent than $\text{CO}_2$, but shorter lifespan).
Nitrous Oxide ($\text{N}_2\text{O}$):
- Lifespan: About 110 years.
- Global Warming Potential: 273 (much more heat energy absorption than $\text{CO}_2$).
Fluorinated Gases:
- Lifespan: Less than a century.
- Global Warming Potential: Tens of thousands (most terrifying due to immense energy absorption).

Nitrogen and oxygen are the most abundant atmospheric gases but are not greenhouse gases.
Water vapor is abundant but unreliable for trapping energy.
Natural greenhouse gases:
- Carbon dioxide and methane (more prevalent).
- Nitrous oxide and ozone (trace gases).
Man-made gases (halocarbons, chloride compounds) are the least prevalent.
- There is a push to ban these due to their high heat-trapping potential.

Data from ice cores shows fluctuations in carbon dioxide levels over the past 10,000 years.
Current $\text{CO}_2$ levels are unprecedented compared to the fluctuations, especially since the 1700s.

The United States is a major contributor.
- Size, population, and industrialization are factors.