What causes Earth’s climate to change?
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Summary
Over the 4.5 billion years of Earth’s existence the climate has changed many times. The causes are known as climate forcings, that is, they apply a force, pushing the climate to be warmer or cooler. For example, a volcanic eruption that sends huge quantities of sulphur dioxide (SO₂) into the atmosphere ‘forces’ global temperatures to drop because SO₂ blocks sunlight. That can change the climate for a few years, even a century or two.
When several forcings push the climate in one direction they can create feedback effects and impacts that reinforcing one another, altering the climate for hundreds of thousands to many millions of years.
Today Earth’s naturally eccentric orbit is once again slowly taking us a little further from the sun. As it has in the past, receiving a little less sunlight naturally ‘forces’ the planet into a period of cooling (see also How to start an Ice Age). However man-made forcings, greenhouse gases are rapidly overwhelming the planet’s natural cooling cycle by changing the chemistry of the atmosphere and the ocean. These gases come from industrial-scale agriculture and burning fossil fuels for energy. As a consequence, Earth is now heating faster than at any time since an asteroid took out the dinosaurs:
The pace is tens of times faster than those seen in previously stable climates of the geologic past. No evolution of CO₂ levels this rapid has been observed in the 800,000 years of ice core data, nor in the last 66 million years of geological data, and the current level of 430ppm has not been seen for 5 to 8 million years. Even the Paleocene Eocene Thermal Maximum (PETM), 56 million years ago, only saw CO₂ levels and temperatures rise at one tenth of today’s rate. – Collin & Harris; Climate Uncovered 02 Sept. 2026
Denying this is like standing on a railway track with eyes closed and fingers in ears, declaring that the speeding locomotive is a ‘hoax, a con job‘ or ‘akin to a cult‘. Fundamental laws of physics and chemistry prove that greenhouse gases trap heat in the atmosphere, separating science from ideological belief. The page on Climate forcings and Earth’s energy budget explains this in straightforward terms.
Because some causes, effects, and impacts reinforce one another due to feedback effects they appear in several sections of the Climate Wiki.
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