Meaning of climate change and Earth climate variability

Summary

Climate change refers to long-term changes in Earth’s temperature, precipitation, and other atmospheric conditions. When people discuss climate change today, they usually mean human-caused global warming, which is driven mainly by increased greenhouse gases such as carbon dioxide and methane from activities like burning fossil fuels, deforestation, and industrial processes. These changes can lead to impacts including more extreme weather, rising sea levels, and disruptions to ecosystems and agriculture. Earth’s climate has also varied naturally over very long periods—tens or hundreds of millions of years—alternating between hotter and colder times, including ice ages. Ice ages are long colder periods when more ice builds up at the North and South Poles, and sometimes Earth has even been largely covered in ice. Past climate shifts can be caused by factors such as changes in Earth’s orbit, changes in the Sun’s brightness, and variations in Earth’s tilt, as well as influences from living things (for example, events related to oxygen changes in Earth’s history). The current scientific view is that recent solar variations play only a very small role compared with warming from human-produced greenhouse gases.

Key Points

• 1

  Human-caused climate change today is mainly global warming caused by increased greenhouse gases from human activities.

• 2

  Earth’s climate has naturally varied over millions of years, including cycles of hotter and colder periods such as ice ages.

• 3

  Ice ages can be influenced by factors like orbital changes, solar brightness, Earth’s tilt, and biological/atmospheric changes, while recent solar changes are much weaker than greenhouse-gas forcing.