* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download PPT
Michael E. Mann wikipedia , lookup
Soon and Baliunas controversy wikipedia , lookup
Low-carbon economy wikipedia , lookup
2009 United Nations Climate Change Conference wikipedia , lookup
German Climate Action Plan 2050 wikipedia , lookup
Climate change adaptation wikipedia , lookup
Climate change denial wikipedia , lookup
Effects of global warming on human health wikipedia , lookup
Climate engineering wikipedia , lookup
Climate change and agriculture wikipedia , lookup
Climate change in Tuvalu wikipedia , lookup
Climate governance wikipedia , lookup
Citizens' Climate Lobby wikipedia , lookup
Climatic Research Unit documents wikipedia , lookup
Fred Singer wikipedia , lookup
Global warming controversy wikipedia , lookup
Economics of global warming wikipedia , lookup
Mitigation of global warming in Australia wikipedia , lookup
Climate change in the Arctic wikipedia , lookup
Media coverage of global warming wikipedia , lookup
Climate change in Canada wikipedia , lookup
United Nations Climate Change conference wikipedia , lookup
United Nations Framework Convention on Climate Change wikipedia , lookup
Global warming hiatus wikipedia , lookup
Carbon Pollution Reduction Scheme wikipedia , lookup
Future sea level wikipedia , lookup
Effects of global warming wikipedia , lookup
Effects of global warming on humans wikipedia , lookup
Instrumental temperature record wikipedia , lookup
Scientific opinion on climate change wikipedia , lookup
Climate change and poverty wikipedia , lookup
Politics of global warming wikipedia , lookup
Climate sensitivity wikipedia , lookup
Global warming wikipedia , lookup
Climate change in the United States wikipedia , lookup
Solar radiation management wikipedia , lookup
Surveys of scientists' views on climate change wikipedia , lookup
General circulation model wikipedia , lookup
Climate change, industry and society wikipedia , lookup
Attribution of recent climate change wikipedia , lookup
Public opinion on global warming wikipedia , lookup
Modern Climate Change Debunking Common Misconceptions Climate predictability Climate forcing Climate models Emission “scenarios” & climate of the 21st century Responding to “Climate Skeptics” Media Myths about Climate Be skeptical … be very skeptical ! • Concern about global warming is based on recent temperature trends – – “9 of the 10 hottest years on record …” If somebody could find some other cause for recent warming, we could quit worrying • Global warming is a theory based on complicated computer models • CO2 is “air pollution” … cutting emissions will lead to falling CO2 and therefore cooling • If we stop burning coal, we’ll freeze in the dark! Global Warming is Based on Common Sense not computer models … not recent temperatures … not complicated! Planetary Energy Balance Energy In = Energy Out S (1 ) R 4 R T 2 2 4 T 18o C But the observed Ts is about 15° C Dancing Molecules and Heat Rays! • • Nearly all of the air is made of oxygen (O2) and nitrogen (N2) in which two atoms of the same element share electrons Infrared (heat) energy radiated up from the surface can be absorbed by these molecules, but not very well O O N N Diatomic molecules can vibrate back and forth like balls on a spring, but the ends are identical Dancing Molecules and Heat Rays! • Carbon dioxide (CO2) and water vapor (H2O) are different! • They have many more ways to vibrate and rotate, so they are very good at absorbing and emitting infrared (heat) radiation O C O O H H Molecules that have many ways to wiggle are called “Greenhouse” molecules Absorption spectrum of CO2 was measured by John Tyndall in 1863 Common Sense 4 Watts • Doubling CO2 would add 4 watts to every square meter of the surface of the Earth, 24/7 • Doing that would make the surface warmer John Tyndall, January 1863 • This was known before light bulbs were invented! Common Misconception #1 “Expectations of future warming are based on extrapolation of recent warming trends” WRONG! They are based on the idea that when we add energy to the surface, it will warm up 19th Century Climate Physics (Svante Arrhenius, 1897) aS0 S0 (1 ) r 2 TS 4 (4 r 2 ) esTs4 S0 S0 (1 ) 4 TS 4 Differentiate, apply chain rule Ts Earth 0 4 TS 4 4 (4 TS 4 ) TS TS 4 Arrhenius worked out a simple formula for the change in surface temperature given a change in effective atmospheric emissivity due to CO2 19th Century Climate Physics(cont’d) TS TS 4 Plug in measured values TS 4 240 W m-2 (from satellite data) ( )( TS 4 ) 4 W m-2 (for 2 x CO2 from radiative transfer) 4 240 Ts = 288 K 288K 4 TS 1.2K 4 240 For CO2 alone (no feedback), expect about 2 °F warming for 2 x CO2 Climate Feedback Processes • Positive Feedbacks (amplify changes) D hi cloud D LW D lo cloud De DTS D albedo Dvapor – Water vapor – Ice-albedo – High clouds • Negative feedbacks (damp changes) – Longwave cooling – Low clouds Learning from the Past Past climate changes reveal climate sensitivity Tiny Bubbles … Priceless ice age ice age ice age ice age CO2 and the Ice Ages • Over the past 420,000 years atmospheric CO2 has varied between 180 and 280 ppm, beating in time with the last four glacial cycles CO2 300 370 ppm in 2000 275 250 ice ice ice ice 225 200 Vostok (400k yr) Ice Core data (Petit et al, 1999) 175 -400000 -300000 -200000 Year -100000 0 Estimating Total Climate Sensitivity • At the Last Glacial Maximum (~ 18k years ago) surface temp ~ 6 °C colder • CO2 was ~ 180 ppm (weaker greenhouse, 4.1 W m-2 more LW) • Brighter surface due to snow and ice, estimate 3.4 W m-2 more reflected solar TS TS (now) TS (then) F F(now) F(then) 6K K 0.8 2 (4.1 3.4)Wm Wm 2 Or, for doubling of CO2: expect 4 x 0.8 = 3.2 °C of Review: 19th Century Physics (updated using paleo-data) • Forcing: changes in properties of atmosphere as measured by spectroscopy (4 W m-2 per doubling of CO2) • Feedback: both positive and negative, total response to forcing estimated from Ice Age climate data (about 0.8 °C per W m-2) • Response: about 3.2 °C warming for 2 x CO2 No climate models required … just based on observations (modern calculations agree … coincidence?) CO2 and the Modern Age • Over the past 420,000 years atmospheric CO2 has varied between 180 and 280 parts per million, beating in time with the last four glacial cycles • Since the Industrial Revolution, CO2 has risen very rapidly CO2 380 370 ppm in 2000 388 ppm in 2009 330 280 230 ice ice ice ice Vostok (400k yr) Ice Core data (Petit et al, 1999) 180 -400000 -300000 -200000 year -100000 from measurements 0 CO2 and the Future • Over the past 420,000 years atmospheric CO2 has varied between 180 and 280 parts per million, beating in time with the last four glacial cycles 1000 CO2 900 ppm in 2100 800 • Since the Industrial Revolution, CO2 has risen very rapidly • If China & India develop using 19th Century technology, CO2 will reach 900 ppm in this century 600 400 200 388 ppm in 2009 ice ice ice ice Vostok (400k yr) Ice Core data (Petit et al, 1999) 0 -400000 -300000 -200000 -100000 0 year You ain’t seen nothing yet! Climate vs. Weather “Weather tells you what to wear today … climate tells you what clothes to buy!” • Climate is an “envelope of possibilities” within which the weather bounces around • Weather depends very sensitively on the evolution of the system from one moment to the next (“initial conditions”) • Climate is determined by the properties of the Earth system itself (the “boundary conditions”) Climate Predictability • Predicting the response of the climate to a change in the radiative forcing is not analogous to weather prediction • If the change in forcing is large and predictable, the response can also be predictable • I can’t predict the weather in Fort Collins on December 18, 2009 (nobody can!) • I can predict with 100% confidence that the average temperature in Fort Collins for December, 2009 will be warmer than the average for July! Climate Forcing • Changes in climate often reflect changes in forcing, as amplified or damped by climate feedbacks – – – – – – Diurnal cycle Seasonal cycle Ice ages Response to volcanic aerosol Solar variability Greenhouse forcing • If forcing is sufficiently strong, and the forcing itself is predictable, then the response of the climate can be predictable too! Greehouse Radiative Forcing • Note different scales • Modern changes comparable to postglacial, but much faster! Aerosol Our Variable Star • Changes of ~ 0.2% (= 2.7 W m-2) reflect 11-year sunspot cycle BOOM! • Volcanos release huge amounts of SO2 gas and heat • SO2 oxidizes to SO4 aerosol and penetrates to stratosphere • SO4 aerosol interacts with solar radiation Mt. Pinatubo, 1991 Stratospheric Aerosol Forcing Reconstructed Radiative Forcings Observations • Much stronger trend on land than ocean • North > South • Surface > Troposphere • Acceleration of trend 140 Years of Data Paleotemperature Water Vapor Trends Trends in annual mean surface water vapour pressure, 1975 to 1995, expressed as a percentage of the 1975 to 1995 mean. Areas without dots have no data. Blue shaded areas have nominally significant increasing trends and brown shaded areas have significant decreasing trends, both at the 5% significance level. Biases in these data have been little studied so the level of significance may be overstated. From New et al. (2000). Accelerating Hydrologic Cycle Cryospheric Change Local melting can change both the thickness of ice sheets and the extent of sea ice Both sea ice and ice sheets are dynamic (they move in response to a PGF, friction, etc) Accumulating ice in cold areas due to enhanced precipitation and melting in warmer areas leads to stronger pressure gradients and accelerating ice movement toward coasts Melting sea ice has no effect on sealevel, but melting land ice does (~7 m for Greenland) Historical Sealevel Changes Climate Model Structure “Flux Coupler” Climate Model Grids Typical climate model x ~ 200 km Typical NWP model x ~ 40 km Normalized pressure coordinate =p/p0 (terrain following, “stretched”) 20th-Century Temperatures • Black lines show obs, yellow lines show each model, red line shows model mean Tsfc • With all forcings, models capture much of historical record • Bottom panels: models do not include greenhouse emissions Emission Scenarios • A1: Globalized, with very rapid economic growth, low population growth, rapid introduction of more efficient technologies. • A2: very heterogeneous world, with selfreliance and preservation of local identities. Fertility patterns across regions converge very slowly, resulting in high population growth. Economic development is regionally oriented and per capita economic growth & technology more fragmented, slower than other storylines. • B1: convergent world with the same low population growth as in A1, but with rapid changes in economic structures toward a service and information economy, reductions in material intensity, introduction of clean and resource-efficient technologies. The emphasis is on global solutions to economic, social, and environmental sustainability, including improved equity, without additional climate initiatives. • B2: local solutions to economic, social, and environmental sustainability. Moderate population growth, intermediate levels of economic development, and less rapid and more diverse technological change than in B1 and A1. Each “storyline” used to generate 10 different scenarios of population, technological & economic development Emission Scenarios 30 ) -1 25 20 15 Actual emissions: CDIAC 450ppm stabilisation 650ppm stabilisation A1FI A1B A1T A2 B1 B2 10 2 (GtC y Emissions CO 5 Recent emissions 0 1850 1900 1950 2000 2050 2100 Sensitivity to Emission Scenarios Emissions CO2 Temperature • Uncertainty about human decisions is a major driver of uncertainty in climate change • Model ensemble simulated warming ranges ~ 2.5º K in 2100 Warming in 2090’s Low Emissions • Land vs ocean! • North vs South • Global mean warming of 2º to 5º C • North American warming of 3º to 6º C Moderate Emissions = 5º to 11º F • Arctic warming of 8º to 14º F Rainfall? Water supply? High Emissions Agriculture? Ski industry? Mass immigration? Sealevels and Emission Scenarios Common Misconception #2 “When we reduce or stop the burning of fossil fuel, the CO2 will go away and things will go back to normal” CO2 from fossil fuel will react with oceans, but only as fast as they “mix” Eventually, fossil CO2 will react with rocks About 1/3 of today’s emissions will stay in the air permanently! Archer et al, Ann. Rev. Earth Plan. Sci. (2009) So What? More Paleoclimate Data More Paleoclimate Data More Paleoclimate Data Historical Perspective Climate change, CO2, and energy will likely be dominant themes in human history for centuries, much as religious wars, feudalism, colonialism, and industrialization in the previous millenium Climate Skeptics • Observed warming in the past is caused by something else – Natural cycles (e.g., recovery from Little Ice Age) – Changes in the sun – Volcanos – Etc • Climate system is too complicated to be predicted, and climate models are too simplistic to represent real physics • “Conspiracy theories” Responding to Skeptics • Observed warming not caused by humans: – There hasn’t been much warming yet, because CO2 hasn’t increased very much (about 30%) – Does that mean that there won’t be warming when CO2 increases by 300%? • Models are insufficiently complicated: – Predictions of warming don’t require complicated models, just simple physics – Predicting that climate will not change if we double or triple CO2 requires some kind of huge offsetting forcing (“follow the energy”) – Complicated models don’t show any such thing – Observations favor the simple solution