The iris hypothesis was a hypothesis proposed by Richard Lindzen and colleagues in 2001 that suggested increased sea surface temperature in the tropics would result in reduced cirrus clouds and thus more infrared radiation leakage from Earth's atmosphere. His study of observed changes in cloud coverage and modeled effects on infrared radiation released to space as a result seemed to support the hypothesis.[1] This suggested infrared radiation leakage was hypothesized to be a negative feedback in which an initial warming would result in an overall cooling of the surface.
The idea of the iris effect of cirrus clouds in trapping outgoing radiation was reasonable, but it ignored the larger compensating effect on the blocking of incoming sun's rays, and effects of changes in altitude of clouds.[2]: 92 [3] Moreover, a number of errors were found in the papers.[4][5] For this reason, the iris effect no longer plays a role in the current scientific consensus on climate change.
Scientists subsequently tested the hypothesis. Some concluded that there was no evidence supporting the hypothesis.[3] Others found evidence suggesting that increased sea surface temperature (SST) in the tropics did indeed reduce cirrus clouds but found that the effect was nonetheless a positive climate feedback rather than the negative feedback that Lindzen had hypothesized.[6][7]
A later 2007 study conducted by Roy Spencer et al. using updated satellite data potentially supported the iris hypothesis.[8] In 2011, Lindzen published another paper on this topic.[9] This work has been described as "gravely flawed and its results wrong on multiple fronts. Their choice of observational periods distorted the results and underscored the defective nature of their analysis."[2]: 92 [5]
In his memoirs in 2023, Kevin E. Trenberth rebutted the Iris hypothesis in strong words:[2]: 92
"On the science front, Lindzen made great waves with a widely touted paper on possibilities that might nullify global warming (Lindzen et al. 2001) hyping an iris effect that would allow more longwave radiation escape to space as more widespread subsidence occurred as a consequence of stronger convection with increased heating. The idea of the iris effect was reasonable in of itself, but it focused only on the role of the areal extent of tropical cirrus on the outgoing infrared radiation, with no accounting for the huge and largely compensating effects on incoming solar radiation, or changes in altitude. In terms of SST (sea surface temperature) response, the solar effects are greater!"
In other words, Trenberth said that the concept itself was not necessarily wrong but very much incomplete. Furthermore, he pointed out that Lindzen's papers on this topic had substantial errors in them.[5]
In 2015, a paper was published which again suggested the possibility of an "Iris Effect".[10] It also proposed what it called a "plausible physical mechanism for an iris effect." In 2017, a paper was published which found that "tropical anvil cirrus clouds exert a negative climate feedback in strong association with precipitation efficiency".[11]
^Lindzen, Richard S.; Chou, Ming-Dah; Hou, Arthur Y. (2001). "Does the Earth have an adaptive infrared iris?" (PDF). Bull. Amer. Meteor. Soc. 82 (3): 417–432. Bibcode:2001BAMS...82..417L. doi:10.1175/1520-0477(2001)082<0417:DTEHAA>2.3.CO;2. hdl:2060/20000081750.
^ abcTrenberth, K. E. (2023). A personal tale of the development of Climate Science. The life and times of Kevin Trenberth. ISBN978-0-473-68694-9.
^ abHartmann, Dennis L.; Michelsen, Marc L. (2002). "No evidence for iris". Bull. Amer. Meteor. Soc. 83 (2): 249–254. Bibcode:2002BAMS...83..249H. doi:10.1175/1520-0477(2002)083<0249:NEFI>2.3.CO;2.
^Trenberth, Kevin E.; Fasullo, John T.; O'Dell, Chris; Wong, Takmeng (2010). "Relationships between tropical sea surface temperature and top‐of‐atmosphere radiation". Geophysical Research Letters. 37 (3). Bibcode:2010GeoRL..37.3702T. doi:10.1029/2009GL042314. ISSN 0094-8276. S2CID 6402800.
^ abcTrenberth, Kevin E.; Fasullo, John T.; Abraham, John P. (2011). "Issues in Establishing Climate Sensitivity in Recent Studies". Remote Sensing. 3 (9): 2051–2056. Bibcode:2011RemS....3.2051T. doi:10.3390/rs3092051. ISSN 2072-4292.
^Fu, Q.; Baker, M.; Hartmann, D. L. (2002). "Tropical cirrus and water vapor: an effective Earth infrared iris feedback?" (PDF). Atmos. Chem. Phys. 2 (1): 31–37. Bibcode:2002ACP.....2...31F. doi:10.5194/acp-2-31-2002.
^Lin, Bing; Wielicki, Bruce A.; Chambers, Lin H.; Hu, Yongxiang; Xu, Kuan-Man (2002). "The Iris Hypothesis: A Negative or Positive Cloud Feedback?". J. Clim. 15 (1): 3–7. Bibcode:2002JCli...15....3L. doi:10.1175/1520-0442(2002)015<0003:TIHANO>2.0.CO;2.
^Spencer, Roy W.; Braswell, William D.; Christy, John R.; Hnilo, Justin (2007). "Cloud and radiation budget changes associated with tropical intraseasonal oscillations". Geophys. Res. Lett. 34 (15): L15707. Bibcode:2007GeoRL..3415707S. doi:10.1029/2007GL029698.
^Lindzen R.S.; Y.-S. Choi (2011). (PDF). Asia-Pacific J. Atmos. Sci. 47 (4): 377–390. Bibcode:2011APJAS..47..377L. CiteSeerX10.1.1.167.11. doi:10.1007/s13143-011-0023-x. S2CID 9278311. Archived from the original (PDF) on 2019-01-04. Retrieved 2014-01-11.
^Mauritsen T.; Stevens B. (2015). "Missing iris effect as a possible cause of muted hydrological change and high climate sensitivity in models". Nature Geoscience. 8 (5): 346–351. Bibcode:2015NatGe...8..346M. doi:10.1038/ngeo2414.
^Choi, Yong-Sang; Kim, WonMoo; Yeh, Sang-Wook; Masunaga, Hirohiko; Kwon, Min-Jae; Jo, Hyun-Su; Huang, Lei (2017). "Revisiting the iris effect of tropical cirrus clouds with TRMM and A-Train satellite data". Journal of Geophysical Research: Atmospheres. 122 (11): 2016JD025827. Bibcode:2017JGRD..122.5917C. doi:10.1002/2016JD025827. ISSN 2169-8996. S2CID 134384103.
External linksedit
NASA summary of Global Warming and Iris Hypothesis (June 2002)
April 11, 2024
iris, hypothesis, iris, hypothesis, hypothesis, proposed, richard, lindzen, colleagues, 2001, that, suggested, increased, surface, temperature, tropics, would, result, reduced, cirrus, clouds, thus, more, infrared, radiation, leakage, from, earth, atmosphere, . The iris hypothesis was a hypothesis proposed by Richard Lindzen and colleagues in 2001 that suggested increased sea surface temperature in the tropics would result in reduced cirrus clouds and thus more infrared radiation leakage from Earth s atmosphere His study of observed changes in cloud coverage and modeled effects on infrared radiation released to space as a result seemed to support the hypothesis 1 This suggested infrared radiation leakage was hypothesized to be a negative feedback in which an initial warming would result in an overall cooling of the surface The idea of the iris effect of cirrus clouds in trapping outgoing radiation was reasonable but it ignored the larger compensating effect on the blocking of incoming sun s rays and effects of changes in altitude of clouds 2 92 3 Moreover a number of errors were found in the papers 4 5 For this reason the iris effect no longer plays a role in the current scientific consensus on climate change Contents 1 Scientific discussion 2 See also 3 References 4 External linksScientific discussion editScientists subsequently tested the hypothesis Some concluded that there was no evidence supporting the hypothesis 3 Others found evidence suggesting that increased sea surface temperature SST in the tropics did indeed reduce cirrus clouds but found that the effect was nonetheless a positive climate feedback rather than the negative feedback that Lindzen had hypothesized 6 7 A later 2007 study conducted by Roy Spencer et al using updated satellite data potentially supported the iris hypothesis 8 In 2011 Lindzen published another paper on this topic 9 This work has been described as gravely flawed and its results wrong on multiple fronts Their choice of observational periods distorted the results and underscored the defective nature of their analysis 2 92 5 In his memoirs in 2023 Kevin E Trenberth rebutted the Iris hypothesis in strong words 2 92 On the science front Lindzen made great waves with a widely touted paper on possibilities that might nullify global warming Lindzen et al 2001 hyping an iris effect that would allow more longwave radiation escape to space as more widespread subsidence occurred as a consequence of stronger convection with increased heating The idea of the iris effect was reasonable in of itself but it focused only on the role of the areal extent of tropical cirrus on the outgoing infrared radiation with no accounting for the huge and largely compensating effects on incoming solar radiation or changes in altitude In terms of SST sea surface temperature response the solar effects are greater In other words Trenberth said that the concept itself was not necessarily wrong but very much incomplete Furthermore he pointed out that Lindzen s papers on this topic had substantial errors in them 5 In 2015 a paper was published which again suggested the possibility of an Iris Effect 10 It also proposed what it called a plausible physical mechanism for an iris effect In 2017 a paper was published which found that tropical anvil cirrus clouds exert a negative climate feedback in strong association with precipitation efficiency 11 See also editClimate change Fixed anvil temperature hypothesis Global dimmingReferences edit Lindzen Richard S Chou Ming Dah Hou Arthur Y 2001 Does the Earth have an adaptive infrared iris PDF Bull Amer Meteor Soc 82 3 417 432 Bibcode 2001BAMS 82 417L doi 10 1175 1520 0477 2001 082 lt 0417 DTEHAA gt 2 3 CO 2 hdl 2060 20000081750 a b c Trenberth K E 2023 A personal tale of the development of Climate Science The life and times of Kevin Trenberth ISBN 978 0 473 68694 9 a b Hartmann Dennis L Michelsen Marc L 2002 No evidence for iris Bull Amer Meteor Soc 83 2 249 254 Bibcode 2002BAMS 83 249H doi 10 1175 1520 0477 2002 083 lt 0249 NEFI gt 2 3 CO 2 Trenberth Kevin E Fasullo John T O Dell Chris Wong Takmeng 2010 Relationships between tropical sea surface temperature and top of atmosphere radiation Geophysical Research Letters 37 3 Bibcode 2010GeoRL 37 3702T doi 10 1029 2009GL042314 ISSN 0094 8276 S2CID 6402800 a b c Trenberth Kevin E Fasullo John T Abraham John P 2011 Issues in Establishing Climate Sensitivity in Recent Studies Remote Sensing 3 9 2051 2056 Bibcode 2011RemS 3 2051T doi 10 3390 rs3092051 ISSN 2072 4292 Fu Q Baker M Hartmann D L 2002 Tropical cirrus and water vapor an effective Earth infrared iris feedback PDF Atmos Chem Phys 2 1 31 37 Bibcode 2002ACP 2 31F doi 10 5194 acp 2 31 2002 Lin Bing Wielicki Bruce A Chambers Lin H Hu Yongxiang Xu Kuan Man 2002 The Iris Hypothesis A Negative or Positive Cloud Feedback J Clim 15 1 3 7 Bibcode 2002JCli 15 3L doi 10 1175 1520 0442 2002 015 lt 0003 TIHANO gt 2 0 CO 2 Spencer Roy W Braswell William D Christy John R Hnilo Justin 2007 Cloud and radiation budget changes associated with tropical intraseasonal oscillations Geophys Res Lett 34 15 L15707 Bibcode 2007GeoRL 3415707S doi 10 1029 2007GL029698 Lindzen R S Y S Choi 2011 On the observational determination of climate sensitivity and its implications PDF Asia Pacific J Atmos Sci 47 4 377 390 Bibcode 2011APJAS 47 377L CiteSeerX 10 1 1 167 11 doi 10 1007 s13143 011 0023 x S2CID 9278311 Archived from the original PDF on 2019 01 04 Retrieved 2014 01 11 Mauritsen T Stevens B 2015 Missing iris effect as a possible cause of muted hydrological change and high climate sensitivity in models Nature Geoscience 8 5 346 351 Bibcode 2015NatGe 8 346M doi 10 1038 ngeo2414 Choi Yong Sang Kim WonMoo Yeh Sang Wook Masunaga Hirohiko Kwon Min Jae Jo Hyun Su Huang Lei 2017 Revisiting the iris effect of tropical cirrus clouds with TRMM and A Train satellite data Journal of Geophysical Research Atmospheres 122 11 2016JD025827 Bibcode 2017JGRD 122 5917C doi 10 1002 2016JD025827 ISSN 2169 8996 S2CID 134384103 External links editNASA summary of Global Warming and Iris Hypothesis June 2002 Retrieved from https en wikipedia org w index php title Iris hypothesis amp oldid 1208893427, wikipedia, wiki, book, books, library,
