Editing Geologic temperature record (section)

=== Other temperature changes in Earth's past ===
About {{Ma|800|1800}}, there was a period of climate stasis, also known as the [[Boring Billion]]. During this period there was hardly any tectonic activity, no glaciations and the atmosphere composition remained stable. It is bordered by two different oxygenation and glacial events.

Temperature reconstructions based on oxygen and silicon isotopes from rock samples have predicted much hotter Precambrian sea temperatures.<ref>{{cite journal|last1=Knauth|first1=L. Paul|title=Temperature and salinity history of the Precambrian ocean: implications for the course of microbial evolution|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|date=2005|volume=219|issue=1–2|pages=53–69|doi=10.1016/j.palaeo.2004.10.014|bibcode=2005PPP...219...53K}}</ref><ref>{{cite journal|last1=Shields|first1=Graham A.|last2=Kasting|first2=James F.|title=A palaeotemperature curve for the Precambrian oceans based on silicon isotopes in cherts|journal=Nature|date=2006|volume=443|issue=7114|pages=969–972|doi=10.1038/nature05239|pmid=17066030|bibcode=2006Natur.443..969R|s2cid=4417157}}</ref> These predictions suggest ocean temperatures of 55–85&nbsp;°C during the period of {{Ma|2000|3500}}, followed by cooling to more mild temperatures of between 10-40&nbsp;°C by {{Ma|1000}}. [[Ancestral sequence reconstruction|Reconstructed proteins]] from Precambrian organisms have also provided evidence that the ancient world was much warmer than today.<ref>{{cite journal|last1=Gaucher|first1=EA|last2=Govindarajan|first2=S|last3=Ganesh|first3=OK|title=Palaeotemperature trend for Precambrian life inferred from resurrected proteins|journal=Nature|date=2008|volume=451|issue=7179|pages=704–707|doi=10.1038/nature06510|pmid=18256669|bibcode=2008Natur.451..704G|s2cid=4311053}}</ref><ref>{{cite journal|last1=Risso|first1=VA|last2=Gavira|first2=JA|last3=Mejia-Carmona|first3=DF|title=Hyperstability and substrate promiscuity in laboratory resurrections of Precambrian b-lactamases|journal=J Am Chem Soc|date=2013|volume=135|issue=8|pages=2899–2902|doi=10.1021/ja311630a|pmid=23394108|hdl=11336/22624 |hdl-access=free}}</ref>

However, other evidence suggests that the period of {{Ma|2000|3000}} was generally colder and more glaciated than the last 500 million years.{{Citation needed|date=February 2017}} This is thought to be the result of [[sun|solar]] radiation approximately 20% lower than today. [[Solar luminosity]] was 30% dimmer when the Earth formed 4.5 billion years ago,<ref>{{Cite web | url=http://faculty.wcas.northwestern.edu/~infocom/The%20Website/evolution.html |title = The Sun's Evolution}}</ref> and it is expected to increase in luminosity approximately 10% per billion years in the future.<ref>{{cite web|url=http://www.universetoday.com/18847/life-of-the-sun/|title=What is the Life Cycle Of The Sun? - Universe Today|date=22 December 2015|website=universetoday.com|access-date=7 April 2018}}</ref>

On very long time scales, the evolution of the sun is also an important factor in determining Earth's climate. According to standard solar theories, the sun will gradually have increased in brightness as a natural part of its evolution after having started with an intensity approximately 70% of its modern value. The initially low solar radiation, if combined with modern values of greenhouse gases, would not have been sufficient to allow for liquid oceans on the surface of the Earth. However, evidence of liquid water at the surface has been demonstrated as far back as {{Ma|4400}}. This is known as the [[faint young sun paradox]] and is usually explained by invoking much larger greenhouse gas concentrations in Earth's early history, though such proposals are poorly constrained by existing experimental evidence.