In order to understand climate change, it is first necessary to understand the reasons it is occurring. The process that causes heat to be trapped within the atmosphere, which subsequently leads to climate change in various forms, is commonly known as the greenhouse effect.
- Greenhouse Effect
There are a number of scientific observations supporting the fact that there are increased amounts of greenhouse gases in the atmosphere. Carbon dioxide (CO2) and methane (CH4) are the two most prevalent and well-known greenhouse gases.
There are a number of scientific observations supporting the existence of the greenhouse effect. The first and most obvious is the fact that there are ever-increasing amounts of GHGs in the atmosphere
- Increasing Atmospheric Levels of Greenhouse Gases (GHGs)
Direct measurements of atmospheric CO2 have been taken over decades, but scientists have also found ways to measure CO2 levels over much longer time periods. For example, measurements of the levels of atmospheric CO2 over the past hundreds of thousands of years have been taken from ice core samples from Greenland and the Antarctic.
- Measurements from Ice Core Samples
As atmospheric levels of GHGs have increased, average temperatures at the earth's surface have increased as well.
- Temperature Anomalies
There are a number of other scientific observations that point to rapidly-increasing global surface temperatures. In its Fourth Assessment Report, the IPCC lists several of these observations. One of the most easily observable is a rise in global sea levels.
- Global Sea Levels
- Other Scientific Observations