13 Climate Change and Earth Mommy, what were glaciers like?

13 Goals The Earth’s unique atmosphere? How does what we know about natural climate change relate to what humans can do?

13 The Terrestrial Planets World Atmos. Compsn. Surface Pressure Ave Surface Temp. Winds, Weather Clouds, Hazes Mercury He, Na, O barDay: 800F Night: -280F none Venus 96% CO2 3.5% N2 90 bars880FSlow winds, acid rain Sulfuric acid clouds Earth 77% N2 21% O2 H2O 1 bar60FWinds, hurricanes, rain, snow H2O clouds, pollution Moon He, Na, Ar barDay:260F Night: -280F none Mars 95% CO2 2.7% N bar-60FWinds, dust storm H2O and CO2 clouds, dust

13 Why is Earth so Different? 1.Why do we have oceans of water? Why do we have so little carbon dioxide? Why do we have so much O 2 and N 2 ? Why do we have a UV-absorbing stratosphere?

13 Concept Test The Earth retained so much outgassed water relative to Venus and Mars because: a.The Earth is closer to the Sun than Mars and so was kept warmer, whereas Venus was too hot. b.The Earth is farther from the Sun than Venus and so didn’t lose water due to thermal escape, but Mars was too cold and it all froze. c.Both Venus and Mars lost their water due to evaporation and then UV-dissociation (while much of Mars’ water also froze). d.The Earth simply outgassed much more water than the other two. e.None of the above.

13 I like Rain 1.Temperature just right. 2.Water vapor could rain. 3.Liquid oceans didn’t completely evaporate. 4.CO 2 could dissolve in oceans. –60x CO 2 dissolved in oceans as atmosphere. –170,000x CO 2 in carbonate rocks as atmosphere.

13 N and O Nitrogen is the third most common product of outgassing. Water in oceans. Carbon dioxide in oceans/rocks. Oxygen is from life. –Galileo spacecraft performed experiment to see if there was life on Earth. Life produces oxygen: O and O 2. Oxygen produces ozone O 3. Ozone absorbs UV-rays, not present on mars or Venus.

13 Goldilocks Planet Delicate balance: Earth is just right. –No oceans without greenhouse gasses. –Without oceans too many greenhouse gasses. –Without oceans no life. –Without life, no ozone. –No ozone, no life. How does Earth maintain this balance?

13 Carbon Cycle Tectonics are crucial!

13 Nature’s Thermostat Carbon Cycle has negative feedback. Increasing temperatures lead to feedback that decreases temperatures, etc. Positive and negative feedbacks have nothing to do with desirability of outcome.

13 Too Cool Less Rain Less CO 2 dissolves from oceans. More CO 2 builds up in atmosphere Increased greenhouse Heats Up.

13 Too Warm More Rain More CO 2 dissolves from oceans. Less CO 2 builds up in atmosphere Decreased greenhouse Cool Down.

13 Ice Ages and Cycles

13 Concept Test Under what circumstances is thermal escape likely to be important? a.Light gases on big planets far from the Sun b.Heavy gases on big planets far from the Sun c.Light gases on small planets near the Sun d.Light gases on small planets far from the Sun e.Equally well on any kind of gas from any kind of planet

13 Cycles

13 Human Input Affecting CO 2 cycle. Moving C from ground to air at increased rate. No increase in rate of C from air to ground.

13 Mars Today

13 Positive Feedback Fossil Fuels – Increase CO 2 to atmosphere. Deforestation – decrease CO 2 from atmosphere Increase CO 2 – Increase greenhouse effect Increase temp – Melting glaciers, ice sheets, polar caps Less ice – lower planetary albedo Lower albedo – Earth absorbs more light More absorption – Increasing surface temperatures.

13 Homework #18 Due Friday 14-Nov: Read Hansen and other web articles. Do: me a single question about global warming of the form “But, I heard that ….”