GEOL 108Lg 1st Edition Lecture 20Outline of Last Lecture-Climate forcings and paleoclimate-Man made, global climate changeOutline of Current Lecture-Anthropogenic attribution-Carbon Cycle-Climate SystemCurrent LectureClimate Forcings and ResponseClimate forcing: the amount of energy we receive from the sun, and the amount of energy weradiate back into space. Variances in climate forcing are determined by physical influences onthe atmosphere such as orbital and axial changes as well as the amount of greenhouse gas inour atmosphere.Climate forcings are the initial drivers of a climate shift. Solar irradiance is one example of a forcing. If the sun generates more light, the Earth will warm.Things that infuence the total positive or negative forcing of the earth climate system include:1. Surface reflectivity (albedo)2. Greenhouse gases3. Atmospheric aerosols (volcanic sulfates, industrial output)Understanding climate forcing is actually easy. Force is generally understood as strength or energy, the cause of motion or change, or active power. This could be a person pushing a shopping cart or an engine that powers a car. For example, gravitational force is how the moonsgravity causes the tides to change. Radiative forcing caused by greenhouse gases in our atmosphere keeps the earth from being a frozen ball in space, because the sun provides energy,and the greenhouse gases in our atmosphere trap the heat on earth... a positive forcing.“To understand the climate forcing, you just add all the components of forcing that are positive and negative and you end up with a view of the total forcing in the climate system of earth.”In our case, the sun provides our heat energy; the Milankovitch forcing is the general regulator of climate forcing over 100k year time scales. That combined with terrestrial components, such as greenhouse gases, aerosols, and changes in land use comprise the major factors that determine climate forcing.Energy absorption (how much energy we get from the sun) and energy radiation (how much we radiate back out into space) part of the climate system.Major Terrestrial Biomes (ecosystems)●Geographic distribution of biomes are dependent on temperature, precipitation, altitude and latitude●Weather patterns dictate the type of plants that will dominate an ecosystemP h en o l o g ical (p l a n ts ch ang i n g w ith s e a s o n ) c h a ng es●Life-cycles of plants and animals have been afected by global change●Temperatures afecting plants growing season, flowering time and timing of pollination by insects haveall been altered●Studies already showing●Mediterranean deciduous plants now leaf 16 days earlier and fall 13 days later than 50 years ago●Plants in temperate zones fowering time occurring earlier in the season●Growing season increased in Eurasia 18 days and 12 days in North America over past two decadesSo w h at are pre d ict i o n s?Arid deserts in Southwestern U.S. will shrink as precipitation increases-Savanna/shrub/woodland systems will replace grasslands in the Great Plains-Eastern U.S. forests will expand northerly . Weather conditions will become more severe-Southeastern U.S. increasing droughts will bring more fres . triggering a rapid change from broad leaf forests to SavannasP red i c t ed Ch ang e in B i o m e sLoss of existing habitat that could occur under doubling of CO2 concentration. Shades of red indicate percentage of vegetation models that predicted a change in biome typeCarbon CycleThe element Carbon can exist as- GAS = CO2- SOLUTE = DISSOLVED CO2 + HCO3- + CO32-- SOLID = CaCO3 + CH2O (=Organic Carbon)Cyclically…C Enters Ocean => gas, solute carried by riversC Leaves Ocean => gas, organic C (dead plants), CaCO3 (particles that sink)The Planetary C cycle is dominated by the recycling between CaCO3, HCO3 and CO2The Planetary C cycle---can only run on a planet that has plate tectonic ‘recycling’Earths Car b o n c y cleI.CO2 gets into atmosphere from volcanic eruptionsII.CO2 in rain water weathers continental rocks and carries HCO3 to oceanIII.HCO3 in the ocean forms, CaCO3, which falls to sea foor and gets carried down into subduction zonesThe Earths/Global/Geologic C Cycle-Emission of CO2 from magma-- CO2 increases -Weathering of rocks on Land-Rivers carry HCO3 to ocean -HCO3 forms CaCO3 in ocean-CaCO3 falls to sea floor -Subduction carries ocean floor into earth’s interior where CaCO3converted to CO2 -Emission of CO2 from magmaThis is a Self-Regulating system (Negative feedback) in that: As CO2 i n crea s e s , temp increasesAs temp increases, rate of weathering increasesAs weathering increases, Levels of CO2 d ec r easeWeathering reaction important, more efcient at higher temperatures-Planetary C cycle regulates climate over long time scales (e.g. Millions of years)We are changing climate at a very rapid speed, which counteracts the planetary c cycle’s normal regulation (which happens over periods of millions of years). This is problematic. Global Warming/Climate ChangeIce age ShorlinesCurrent ShorelinesThey are expected to decrease by even more.Over the last 100 years, the global sea level has risen by 10 to 25 cm. Due to both melting ice and thermal expansion.We can get a feeling by looking at more simplified systemsStability: a curve shows the ball sitting on a landscape with two valleys. This is an energy function as a function of space - a potential. There’s different “states” local equilibrium - metastable state (“tipping point”), where a push could make it go either way, global equilibriumClimate is a nonlinear system•- Non-linear systems can be- Metastable- Phase state depends critically on parameters- Chaotic: Sensitive dependence on initial conditions (Butterfy Efect), Unpredictable over long times (weather forecast)Rate of greenhouse gas emission per personTotal Co2 emissionsRecently, China has overtaken US in greenhouse emission, having the US as a close second. Twoof theworld’s superpowers (US and China) account for 40% of global Carbon emissions. Prediction for