Climate Science: The Greenhouse Effect, Carbon Budgets, and Physical Evidence

This curriculum explains the physical laws that govern our atmosphere and the methods scientists use to track global changes. You will learn how specific gases trap heat and how we calculate the remaining amount of carbon humans can emit before reaching specific temperature limits. By the end, you will be able to evaluate climate data from satellites, ice cores, and computer models to form your own view on current environmental trends.

How gases trap heat

The learner will be able to explain how greenhouse gases absorb and re-emit infrared radiation.

Key takeaways

  • Greenhouse gases trap heat because their asymmetrical shape allows them to vibrate and absorb infrared radiation.
  • Most energy absorbed by these gases is shared with the rest of the atmosphere through molecular collisions before it is re-emitted.
  • The greenhouse effect depends on the fact that the atmosphere gets colder at higher altitudes.
  • Adding more greenhouse gases increases radiative forcing, which means the Earth keeps more energy than it releases into space.

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Reading the ancient climate

The learner will be able to describe how scientists use ice cores to find past carbon levels.

Key takeaways

  • Ice cores contain tiny bubbles of ancient air that were trapped when snow was squeezed into solid ice.
  • Scientists extract this air by crushing or melting the ice inside a vacuum to prevent modern air from contaminating the sample.
  • The air in an ice core is always younger than the ice surrounding it because gas can move through the snow for a long time before the bubbles close.
  • Antarctic ice cores provide more reliable carbon dioxide data than Greenland cores because Antarctica is too cold for meltwater to interfere with the gas.

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Tracking the planet today

The learner will be able to identify the main tools used to monitor global temperature changes.

Key takeaways

  • Weather stations measure air temperature at a standard height of five feet to ensure consistency across different locations.
  • Satellites use radiometers to measure the heat energy coming off the Earth's surface, which helps fill data gaps in remote areas.
  • Scientists use satellite night-light data and mathematical algorithms to identify and correct for the extra heat generated by cities.
  • Global temperature trends are created by combining data from thousands of ground stations and satellite sensors into a single record.

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The movement of carbon

The learner will be able to map how carbon moves between the air, land, and sea.

Key takeaways

  • Plants and phytoplankton pull carbon from the air to grow, while respiration and decay return it.
  • The ocean acts as a massive sponge that absorbs carbon dioxide, especially in cold water.
  • Rain and rocks move carbon slowly from the land to the sea over millions of years.
  • Human activities like burning fossil fuels are adding carbon to the air faster than natural sinks can remove it.

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The math of carbon budgets

The learner will be able to define a carbon budget and explain why the numbers change.

Key takeaways

  • A carbon budget is the total amount of carbon dioxide humans can emit to stay below a specific global temperature limit.
  • The remaining carbon budget shrinks every year because the world continues to emit about 40 billion tons of carbon dioxide annually.
  • Budget estimates change when scientists update their data on historical warming or change their assumptions about non-carbon gases like methane.
  • Carbon budgets are based on probabilities, meaning a larger budget offers a lower chance of successfully staying below a temperature target.

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Predicting future climates

The learner will be able to explain how computer models simulate the Earth climate system.

Key takeaways

  • Climate models divide the Earth into a 3D grid and use mathematical equations to simulate physical processes in each box.
  • Scientists use parameterization to estimate small-scale events like cloud formation that are too small for the model grid to see directly.
  • Climate sensitivity measures how much the Earth warms when CO2 doubles, with different metrics for short-term and long-term changes.
  • Models are more accurate at predicting global temperature than they are at predicting regional wind patterns and specific storm tracks.

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The state of the climate in 2026

The learner will be able to summarize the most recent global temperature and emission trends.

Key takeaways

  • Global warming is happening twice as fast as it did a few decades ago.
  • A strong El Niño is pushing 2026 and 2027 toward record-breaking heat.
  • Carbon dioxide levels in the atmosphere are the highest they have been in two million years.
  • Renewable energy is growing quickly but has not yet stopped the rise in fossil fuel use.

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