Climate Science: the Basics
- Carbon dioxide traps heat in the atmosphere, causing temperatures to rise.
- Human industries have doubled atmospheric CO2 relative to the past 400,000 years.
- The global average temperature has increased 1 degree Celcius (1.8 Fahrenheit) above pre-industrial levels
- This CO2 causes global warming and climate destabilization.
The Greenhouse Effect. The purpose of a greenhouse is to trap the sun’s heat so that plants inside can stay warm. If you have ever gotten into a car on a sunny day, you are familiar with this effect. The atmospheric greenhouse effect keeps our planet warm enough for life, with greenhouse gases such as carbon dioxide (CO2) playing a similar role to the glass in a greenhouse.
The complete process is described in the image below.
We highly recommend this article from the New York Times, answering some common questions.
Human Impacts. The plot below shows the following things:
- Atmospheric temperature and sea level track CO2 concentrations
- All three variables rise and fall together over about 1000,000 years
- For the past 400,000 years, atmospheric CO2 been less than 300 ppm
- In the past 50 years, atmospheric CO2 has increased to 400 ppm
- Temperatures and sea level are as high as they have ever been
- Implication: it is reasonable to expect rapid warming and sea level rise
Climate Science: Advanced
Infrared Radiation Anything warm emits infrared radiation. Hold the palm of your hand very close to your temple (between your ear and your eye), but your hand should not actually touch your head. Your hand should feel the heat radiating off of your head. That heat is actually infrared radiation; in this infrared image, the hot spot at the man’s temple looks white.
The Electromagnetic Spectrum. Infrared radiation (heat) and visible light are both types of electromagnetic radiation. The sun radiates a tremendous amount of energy, mostly in the form of visible light. That energy causes the earth to warm up, and the earth, in turn, radiates heat. The image below compares the shortwave, visible radiation from the sun (large rainbow peak) with the longwave, infrared radiation from the earth (much smaller peak).
Carbon Dioxide Molecule Human industries and energy production depend on the burning of fossil fuels, which puts carbon dioxide into our atmosphere. The infrared radiation emitted by Earth interacts with atmospheric greenhouse gases, causing the molecules to vibrate. The vibrating molecules then send infrared radiation in all directions. Some of that radiation escapes the atmosphere, but some is returned to earth. This infrared radiation from vibrating gas molecules causes the earth to get warmer.
CO2 is not the only greenhouse gas. Water is a significant greenhouse gas, but the amount of water in the atmosphere is determined by the earth’s temperature and not directly affected by human activities. Our livestock and landfills produce methane, which is a potent greenhouse gas, and we use some very potent greenhouse gases in refrigeration. Handling these other gases correctly is an important task for specialists, but most of us can focus on reducing our CO2 footprint.
So, from the top:
- Energy from the sun comes to earth as lots of visible light
- That energy warms the earth
- The earth then radiates energy in the form of infrared
- The burning of fossil fuels pumps CO2 into the atomosphere,
- The infrared radiation causes CO2 molecules in the atmosphere to vibrate
- The vibrating molecules send some heat back down to earth and some into space
- The heat that returns to earth keeps our planet warm enough for life
- Pumping lots of CO2 into the atmosphere quickly causes rapid climate change