What is Climate sensitivity?
The [[global warming|Earth is getting warmer]] because people are putting [[greenhouse gases]] into the [[atmosphere]]. This is called the [[greenhouse effect]] because a [[greenhouse]] stops some of the sun's heat from escaping, and these gases stop some heat escaping from Earth. The greenhouse gas which makes the most warming is [[carbon dioxide]] (short name CO<sub>2</sub>), and burning [[coal]] is the biggest thing which puts it in the atmosphere. '''Climate sensitivity''' means how much the Earth will warm when a certain amount of CO<sub>2</sub> is released into the atmosphere.<ref>{{Cite web|url=https://www.metoffice.gov.uk/research/climate/understanding-climate/climate-sensitivity-explained|title=What is 'climate sensitivity'?|website=Met Office|language=en|access-date=2020-02-14}}</ref> Usually it means how much warmer the Earth would be if the atmosphere had twice as much CO<sub>2</sub> as the year 1750, before [[Industrial Revolution|people started burning lots of coal]]. Scientists think that when CO<sub>2</sub> in the atmosphere doubles an extra 4 [[Joule|joules]] of heat gets trapped every second on every square metre on Earth,<ref>{{Cite web|url=https://www.youtube.com/watch?v=kAawuOJTmZI|title=Energy basics|website=[[YouTube]]}}</ref> and that after a long time the Earth will be about 3&nbsp;°C hotter. ==How sensitive is the climate?== [[Climatology|Climate scientists]] don't know the climate sensitivity very well but they think it is probably between 1.5&nbsp;°C and 4.5&nbsp;°C. So if the atmosphere had twice as much CO<sub>2</sub> as it had in 1750 then Earth would likely be between 1.5&nbsp;°C and 4.5&nbsp;°C warmer, after thousands of years.<ref>{{Cite web|url=https://www.environment.gov.au/system/files/resources/d3a8654f-e1f1-4d3f-85a1-4c2d5f354047/files/factsheetclimatesensitivitycsiro-bureau.pdf|title=Climate sensitivity: fact sheet|publisher=Australian government. Department of the Environment.|access-date=2020-02-18|archive-date=2020-02-12|archive-url=https://web.archive.org/web/20200212