We don't need a time machine to learn from the past (but let us know if you find one)! Air bubbles trapped in ice for millennia and ancient pollen grains can tell us a lot about climate shifts hundreds of thousands of years ago!

We're conducting a survey of our viewers! If you have time, please give us feedback: https://www.surveymonkey.com/r/SciShowSurvey2017

Hosted by: Olivia Gordon
----------
Support SciShow by becoming a patron on Patreon: https://www.patreon.com/scishow
----------
Dooblydoo thanks go to the following Patreon supporters: KSam Lutfi, Kevin Knupp, Nicholas Smith, Inerri, D.A. Noe, alexander wadsworth,
سلطان الخليفي, Piya Shedden, KatieMarie Magnone, Scott Satovsky Jr, Bella Nash, Charles Southerland, Bader AlGhamdi, James Harshaw, Patrick Merrithew, Patrick D. Ashmore, Candy, Tim Curwick, charles george, Saul, Mark Terrio-Cameron, Viraansh Bhanushali, Kevin Bealer, Philippe von Bergen, Chris Peters, Fatima Iqbal, Justin Lentz
----------
Looking for SciShow elsewhere on the internet?
Facebook: http://www.facebook.com/scishow
Twitter: http://www.twitter.com/scishow
Tumblr: http://scishow.tumblr.com
Instagram: http://instagram.com/thescishow
----------

Sources:

https://www.amnh.org/exhibitions/climate-change/changing-atmosphere/what-s-an-ice-core/
https://www.amnh.org/exhibitions/climate-change/changing-atmosphere/the-ups-and-downs-of-co2
https://www.researchgate.net/publication/284275913_Pronounced_variations_in_Fagus_grandifolia_abundances_in_the_Great_Lakes_region_during_the_Holocene
https://sites.nd.edu/paleonproject/synthesizing-fire-history-records-to-understand-fire-regime-variability-across-alaska/
https://sites.nd.edu/paleonproject/oak-trees-and-climate-in-the-midwest/
https://www.newscientist.com/article/dn16892-natural-mechanism-for-medieval-warming-discovered/
https://phys.org/news/2017-07-carbon-dioxide-world-water-wise.html

Images:

https://en.wikipedia.org/wiki/File:Palais_de_la_Decouverte_Tyrannosaurus_rex_p1050042.jpg
https://en.wikipedia.org/wiki/File:Sediment_in_the_Gulf_of_Mexico_(2)_edit.jpg
https://en.wikipedia.org/wiki/File:Picea_glauca_taiga.jpg
https://commons.wikimedia.org/wiki/File:Beech_growth_rings.jpg
https://en.wikipedia.org/wiki/File:Opening_and_Closing_of_Stoma.svg
https://en.wikipedia.org/wiki/File:GISP2_1855m_ice_core_layers.png
https://commons.wikimedia.org/wiki/File:Core_samples.jpg
https://en.wikipedia.org/wiki/File:Null_point_theory_image1.png