1Lecture 332. Global warming deniers or so-called “skeptics”1. Impacts of rising sea-level720 km3 of Larsen B iceshelfdisintegrated Jan-Mar 2002= 29 trillion bags of party ice!http://nsidc.org/iceshelves/larsenb2002/Ice shelves continuedLARSEN B ICE SHELF DISINTEGRATION, ANTARCTICAAir temperatures on the Larsen peninsula rose 2.5°Cin the 20th century. Shelf thinned by up to 18 m from 1992-2001Dec 2003: Glaciers flowing down to Larsen B have sped up from 2000 to2003 by 250% according to satellite image data.This shows what would happen if the much larger Ross Ice Shelf were todisintegrate, i.e. not a gradual thinning but a non-linear step response (c.f.Hansen (2004) Sci. Amer. , concerned that IPCC has underestimated sea-level rise).WARD HUNT ICE SHELF, Ellesmere Is., Canada (NW of Greenland)Sept 2003: A 3000-year old ice shelf fractured in two releasingthe Northern Hemisphere’s largest lake of ice-dammed freshwaterinto the sea. (About twice volume of Lake Washington).Sea-level rise:Past and Futureabout 0.15 m in 20th centuryIPCC total range = 0.09-0.88 mrise in 21st centuryIPCC assumes maincontribution fromthermal expansion;glacier/icesheet partis considered small2Sea-level impactsStorm surge flooding (IPCC)50 cm rise: increase of victims from 46m to 92m people /year1 m rise: increase to 118m people/yearFlooding/submergence issues (IPCC)50 cm rise: inundate 8500-19000 km2 of USA dry landeliminate 50% of coastal westlands in USA1 m rise: 17.5% of Bangladesh disappears (where most live)1% of Egypt (Nile area, where most agriculture)many small island states flooded/submergeddisplacement of 10s of millions of people“[West Artarctic ice sheet] dynamics are still inadequatelyunderstood to make firm projections” (IPCC, 2001, p.642)IPCC gave it a 5% chance of making a substantial contribution by 2100IPCC (2001) summaryMain points• The annual mean temperature of the Earth is increasing• Most of the warming of the last 50 years can be attributed to humans• GHGs (cause of warming) are projected to rise substantially• aerosols (partial offset of warming) are not projected to rise substantially• Mean annual surface temperature projection for 2100: +1.4 to +5.8 K • Sea-level projection by year 2100: +0.1 to +0.9 m• Projection in context: "The projected rate of warming is much larger than the observed changes during the 20th century and is very likely to be without precedent during at least the last 10,000 years based on paleoclimate data." Global warming skepticsScientific skepticism = a healthy questioning ofcurrent paradigms based on uncertainty,new evidence, and/or the discovery of flaws inold science. This is how science advances.So-called “skeptics” of global warming usually counter the paradigmof global warming with misinformation. Often they repeat old,discredited ideas, or falsehoods, or half-truths.This is neither skepticism nor healthy.Why spend classroom time on false arguments of skeptics? Becausethey are influential in(a) public perception(b) current US government policy -- e.g., skeptic “science” wasinfluential in the defeat of the McCain-Lieberman ClimateStewardship Act of 2003.Leaked strategy document of Luntz Research, political consultantsfor the Bush Administration - What does this say about the attitude towards science?3General arguments of the "skeptics"It isn't warming• satellites do not show warming• surface thermometers are biased by urban heat-island effect• this or that region is not warming It is warming…but the warming is natural• the Earth is still coming out of the Little Ice Age• it was warmer during the Medieval Warm Period• all changes are due to the SunClimate models are hopelessly simplistic and unreliable•past predictions have been wrong; why believe new ones?CO2 does not cause warming• it is a trivial part of the Earth's greenhouse effect, which isalmost entirely due to water vapor• all changes are due to the Sun (again)CO2 and warming are beneficial; they will improve the Earth• CO2 is a plant fertilizer, not a pollutant• a warmer Earth will be more productive biologically and more widelyinhabitable, especially at high latitudesoftenused bythe sameskeptic!1998 PetitionPetition mailed to thousands of U.S. people, mostly with bachelors degrees only,and nearly all not involved in climate research. Enclosed:• "review article" formatted to look like a National Academy of Sciencspublication that was, in fact, never published in any refereed journal."Fake" article included in petitionThe satellite temperature recordGlobal warming denierssay that the satellitedata since 1979 shows no warmingof the troposphere.In fact the data (along withradiosondes (weather balloons))tell us basically the same story asthe surface temperaturerecords. Note the coherentvariations between records.As expected with global warming,the stratosphere has cooled.Qu.) Why is this expectedwith global warming?Fig source:Hadley Centre Report, Dec 2003http://www.met-office.gov.uk/research/hadleycentre/index.html4WMO(WorldMeteorologicalOrganization)radiosondenetwork-sparse overoceans,high latitudesWMO surfacestation network,includingship-based,and buoysSource: NationalAcademy of Sciences(2000) reportSolar-cycle hypothesis in Wall Street Journal, Dec 4, 1997Solar-climate connection: Critical reviewAbstract:Hypotheses about solar-climate connections have been raised in both publicand scientific debates about the possibility of man-made global climatechange. I have analyzed a number of published graphs that have played amajor role in these debates and which have been claimed to support solarhypotheses. My analyses show that the apparent strong correlations displayedon these graphs have been obtained by an incorrect handling of the physicaldata.Solar-cycle length vs GAAST: last 4 centuriesFriis-Christensen (2000): optimalcorrelation to industrial-era data(improper method for testing thecause of industrial-era warming)Objective replotting by Laut (2003):by optimal correlation to pre-industrialdata (known to lack human influence).Test of whether solar variations explainthe industrial-era warming now fails.5Questions that "skeptics" fail to confrontFirst some indisputable facts• CO2 is increasing due to human activity• CO2 absorbs infrared radiation and participates in the Earth's greenhouse effect• anthropogenic CO2 currently imposes a climate forcing of +1.5 W/m2 (more than 10-times any time-averaged variations in