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Atmosphere, the Water Cycle and Climate Change OCN 623 – Chemical Oceanography Outline 1. The water cycle 2. Climate and climate-change • Atmosphere radiation balance • CO2 and other greenhouse gases • Aerosol effects • Cloud effects 3. Climate change implications • Sea-level rise • Sea ice loss • Storm intensification 4. Climate change mitigation The Water Cycle “The annual circulation of H2O is the largest movement of a chemical substance at the surface of the Earth” The distribution of water at the Earth's surface: % of total Oceans 97.25 Ice caps and glaciers 2.05 Groundwater 0.68 Lakes 0.01 Soils 0.005 Atmosphere (as vapor) 0.001 Rivers 0.0001 Biosphere 0.00004 70% of the sun’s energy is absorbed at the Earth’s surface, where it drives the hydrologic cycle Solar Energy Budget Three-cell Model of Atmospheric Circulation (1) Polar cells (2) Midlatitude cells (3) Hadley cells Idealized vs. actual zonal (E-W) pressure belts Non-uniform surface = uneven heating Unstable windflow = eddies Sun doesn’t remain over the equator year-round = 23.5N-23.5S Movement of H2O through the atmosphere determines the distribution of rainfall Global average precip ≈ 943mm/yr Net evaporation from the surface ocean • affects surface water salinity in the ocean • increases surface water density • controls thermohaline circulation of ocean Surface water salinity in the Atlantic Ocean The maxima in evaporation-precipitation results in the highest surface water salinities in the mid-latitudes around 30 N and 30S What does “Climate” mean? Webster: “Climate: the average condition of the weather at a place over a period of years as exhibited by temperature, wind velocity, and precipitation” So “climate” refers not to the weather today or this week or this year, but rather to the range of weather (including hot and cold years, wet and dry years) that is typical of each region. 10 Is Climate Change / Global Warming Happening or Not? Global mean surface temperature has increased >0.5˚C in this time. Is this natural variability or anthropogenic climate change?? How does climate change work? The Earth’s temperature is set by a Radiation Balance: If more heat arrives from the sun than can escape as infrared (IR) rays, the Earth gets warmer. The average Albedo (reflectivity) of Earth is 0.3 The majority of outgoing IR comes from gases 13 From the Terra satellite, you can actually see the regions where IR radiation escapes (left) and solar radiation is absorbed (right) Greenhouse gases trap IR, causing a warming effect. Source: TERRA Mission; CERES Instrument; NASA Mauna Loa Monthly Carbon Dioxide Record Keeling Record 1958 - 2008 ppmv CO2 is the most important greenhouse gas (one that prevents the escape of IR that would normally cool the Earth) 1900 – 293 ppmv 1940 – 307 ppmv Challenges of a Changing Earth — July 2 upload.wikimedia.org 001 Ocean CO2 Increase Tracks Atmosphere “Ocean Acidification” Preindustrial (1700s) pH Global Carbon Cycle Reservoirs in GtC and fluxes in GtC/yr Most carbon has been stored in the ocean*. It plays a huge role in controlling greenhouse gases and climate *although most of the CO2 man has released is still in the atmosphere CO2 Emissions and Uptake Since 1800 (Gt C) CO2 Emissions 140 Deforestation Land use change Coal Oil 265 ? 115 Oceans 110 Natural Fossil gas emissions Cement making Where the CO2 goes ? Dissolution into the ocean Reforestation Terrestrial 180 Atmosphere Our fuel burning is converting fossilized carbon (coal, oil, and natural gas) into CO2, and 45% of it stays in the air We can look at ice cores to see that CO2 was pretty constant for the last thousand years. The rapid increase began about the time of the industrial revolution Global Temperatures Are Linked to Atmospheric CO2 Vostok Ice Core CO2 Concentration and Temperature Variation Record 325 4 300 2 275 0 250 -2 225 -4 200 -6 175 -8 150 -10 Floor at ~190 ppm 400,000 300,000 200,000 100,000 Years Before Present Source: Barnola, et.al.; Petit et.al. (PAGES / IGBP) Challenges of a Changing Earth — July 2001 0 Temperature CO2 concentration (ppmv) Ceiling at ~290 ppm CO2 Concentration CO inConcentration Ice Cores and Atmospheric CO2 in Ice Core Samples and for Next 100 Years Projected Projection for Next 100Projections Years (2100)(2100) Projected 2 700 The Earth is now in a NO-ANALOG zone! 600 VostokEarth Record has never before dealt with these conditions. The inhabited 550 IPCC IS92a Scenario Law Dome Record Mauna Loa Record Therefore, paleo records cannot be 100% reliable tests of climate models. 500 450 400 Current (2001) Current (2001) 350 300 250 200 150 400,000 300,000 200,000 100,000 0 Years Before Present Source: C. D. Keeling and T. P. Whorf; Etheridge et.al.; Barnola et.al.; (PAGES / IGBP); IPCC Challenges of a Changing Earth — July 2001 21 CO2 Concentration (ppmv) 650 Model predictions from IPCC: Models Observations Paleo Record Source: IPCC Third Assessment Report, WG1 “Global temperature will rise from 1.45.8˚C over this century unless greenhouse gas emissions are greatly reduced.” 22 Aerosol Radiative Forcing of Climate Climate Models didn’t do a very good job of reproducing temperature trends in the last 150 years when they did not include aerosol impacts. Radiative Forcing Direct Indirect Models do much better when they include aerosols, even using crudely understood aerosol effects Models with Aerosol Effects Not every place is warming, though - the blue spots are areas that have been cooling. How could that be? Each of these areas is polluted with aerosols. Aerosol Forcings Cause the Largest Uncertainty in the Earth’s Radiation Budget Level of Scientific Understanding 27 Source: IPCC ThirdB.Huebert Assessment Report Dust can have a huge impact on climate, both by scattering light to space and by absorbing light Where this Saharan dust cloud is, there is more light reflected back to space than over the dark ocean: Smoke and Dust Both Affect Climate Image courtesy of NASA and Orbimage . The whitest things (most reflective of sunlight) in this SeaWiFS image are clouds Changing the extent or density of clouds is called the radiative indirect effect on climate Image courtesy of NASA and Orbimage MODIS Image NW Pacific 29 April 2002 Indirect effect of aerosols: What are these wiggly lines among the clouds? Ship tracks in the Atlantic. These are strong evidence of the Indirect Effect of aerosols on clouds: More aerosol nuclei make clouds whiter (more reflective of sunlight) 31 SOLAS Summer School 2009 SOLAS Summer School 2009 Likely Impacts of Climate Change Why should we worry about global warming? Would an extra degree or two of warming hurt anything? What changes might we see? Would an Extra Degree or Two of Warming Hurt Anything? YES!! It’s NOT just about warming: “Climate Change” includes: Sea-level rise Droughts & flooding Severe storms increasing Spread of diseases to new areas A warmer climate would melt glaciers, expand the ocean, and submerge many Polynesian islands! Temp Forecast Temperature Rise +1 to 3°C ⇓ Sea Level Rise +10 to 90 cm (5 to 37”) Sea Level Forecast Recent Analyses Increase the Sea Level Rise Forecast Intergovernmental Panel on Climate Change 4th Assessment Report (FAR) Feb 2007 The last time the polar regions were significantly warmer than present for an extended period (about 125,000 years ago), reductions in polar ice volume led to 4 to 6 metres of sea level rise.” Arctic Sea-Ice Extent is Shrinking Rapidly Change from 1980 to 2009 Arctic sea ice has lost half its thickness 1958-76 1993-97 www.grida.no/climate/vital/30.htm Positive Feedback: Warming Causes More Warming! 1 Light colored ice reflects back the Sun’s energy efficiently. 2 Exposed land is darker and absorbs more energy; warming. 3 As the ice melts, more land is exposed. This absorbs more heat, melting more ice, and causing further warming. 4 The altitude of the melting ice is reduced so it becomes harder for new ice to form (esp for Greenland). Melt water flows to the base of the Greenland ice sheet. Ice is melting MUCH faster than glaciologists had forecast Positive Feedback can cause Runaway Warming, by darkening originally-light surfaces. The climate system is full of feedbacks Hurricanes are Becoming More Intense Webster et al., Science, 309, 1844-1846, 2005 The number of Category 4 and 5 hurricanes worldwide has nearly doubled over the past 35 years, even though the total number of hurricanes has dropped since the 1990s. The shift occurred as global sea surface temperatures have increased over the same period. This is compelling evidence that global climate change is making tropical storms more powerful and more damaging. Climate change is expected to increase the range of diseases like malaria There are arguments against Climate Change … which have been debunked by the (reputable) scientific community www.skepticalscience.com … and dozens more are addressed at this URL You can always find someone who is willing to be bought and corporations with the money to do so Some of the unexpected cold winter weather is due to a (natural) Arctic Oscillation in weather patterns. Such oscillations can obscure longer-term trends. What are the Dominant Forcings? Jim Hansen -- NASA Goddard Institute for Space Studies Observed temperature change simulations for different forcings Soot (black carbon) + O3 +CH4 yields ~ same warming as CO2 Inferences 1. Non-CO2 Forcings are Substantial Comparable to CO2 forcing today 2. Strategic Mitigation Role If coal is phased out, non-CO2 even more important 3. Aerosols Complicate the Story If all pollution is reduced, how much will aerosol cooling effect be altered? How Can Climate be Stabilized? Must Restore Planet’s Energy Balance Modeled Imbalance: +0.75 ± 0.25 W/m2 Ocean Data Suggest: +0.5 ± 0.25 W/m2 Requirement Might be Met Via: Reducing CO2 to 350 ppm or less - and Reducing non-CO2 forcing ~ 0.25 W/m2 Are Needed Actions Feasible? Coal must be phased out & Unconventional Fossil Fuels avoided Requires Carbon Tax & Dividend ‘Cap & Trade’ a Proven Failure Do not lump non-CO2 forcings w/ CO2 Methane + Ozone most important (reduction feasible as fossil fuel use declines) Emphasize black carbon reductions among aerosols The nature of our future environment depends strongly on which “scenario” forecasters use. The scenarios differ only in the extent of society’s effort to conserve and reduce fossil-fuel use. YOUR behavior will determine how badly Earth is damaged. Oil and power companies are not to blame for climate change. We all are!! CO2 Concentration in Ice Cores and CO2 Concentration in Ice Core and Atmospheric CO2 Projection for Samples Next 100 Years Projections for Next 100 Years 700 Projected Projected (2100) (2100) 650 600 Vostok Record IPCC IS92a Scenario Law Dome Record Mauna Loa Record 500 We’re Living in A No-Analog Zone 450 400 Current (2001) Current (2001) 350 300 250 200 150 400,000 300,000 200,000 100,000 0 Years Before Present (BP 1950) Source: C. D. Keeling and T. P. Whorf; Etheridge et.al.; Barnola et.al.; (PAGES / IGBP); IPCC Challenges of a Changing Earth — July 2001 50 CO2 Concentration (ppmv) 550