Iris hypothesis

from Wikipedia, the free encyclopedia
Convection over warm subsoil allows moisture to reach great heights, where it leads to the formation of cirrus clouds.

The iris hypothesis was introduced by Richard Lindzen in 2001. It is assumed that a higher sea surface temperature in tropical latitudes would lead to a reduced formation of cirrus clouds and thus also to an increased infrared radiation. According to Lindzen, the effect represents a negative feedback in the context of global warming . The warming effect of greenhouse gases would be greatly weakened by the iris effect; the climate sensitivity is therefore considerably lower than is commonly assumed.

The name of the hypothesis was chosen based on the iris of the eye, which reacts to changing brightness with a variable opening of the pupil . Similarly, according to the iris hypothesis, an increase in surface temperatures close to the equator is supposed to create an "opening", i. H. Decrease in cirrus cloud cover in these latitudes. Roy Spencer , a climate denier who denies the scientific consensus on man-made global warming, and Lindzen himself, on the other hand, published two studies in the 2000s that appeared to support the hypothesis.

In the meantime (as of 2018) the hypothesis has been rejected by climate research both on the basis of observations and for conceptual reasons (as of 2018). Climatologists who tested the thesis found no evidence that it was true. Measurement data from the Clouds and Earth's Radiant Energy System also contradict the hypothesis, so that NASA literally writes: "Evidence Against the Iris Hypothesis". Other researchers found an effect, but it was positive (warming) feedback and not negative, as Lindzen had postulated.

Individual evidence

  1. ↑ Lindzen, RS, M.-D. Chou, and AY Hou: Does the Earth have an adaptive infrared iris? . In: Bull. Amer. Met. Soc. . 82, 2001, pp. 417-432. doi : 10.1175 / 1520-0477 (2001) 082 <0417: DTEHAA> 2.3.CO; 2 .
  2. ↑ Spencer, RW, Braswell, WD, Christy, JR, Hnilo, J .: Cloud and radiation budget changes associated with tropical intraseasonal oscillations . In: Geophys. Res. Lett. . 34, 2007, p. L15707. doi : 10.1029 / 2007GL029698 .
  3. ^ Lindzen, RS, and Y.-S. Choi: On the determination of climate feedbacks from ERBE data . In: Geophys. Res. Lett. . 36, 2009, p. L16705. doi : 10.1029 / 2009GL039628 .
  4. ↑ Michael E. Mann , Tom Toles: The madhouse effect. How climate change denial threatens our planet, destroys our politics and drives us insane . Erlangen 2018, p. 67f.
  5. ↑ Hartman, DL, and ML Michelsen: No evidence for iris . In: Bull. Amer. Met. Soc. . 83, 2002, pp. 249-254. doi : 10.1175 / 1520-0477 (2002) 083 <0249: NEFI> 2.3.CO; 2 .
  6. ↑ NASA Earthobservatory Online
  7. ↑ NASA Test of the Iris-Hypthesis ( Memento of the original from June 9, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 2.0 MB) @1@ 2Template: Webachiv / IABot / science.larc.nasa.gov
  8. ↑ Fu, Q., Baker, M., and Hartman, DL: Tropical cirrus and water vapor: an effective Earth infrared iris feedback? . In: Atmos. Chem. Phys. . 2, No. 1, 2002, pp. 31-37. doi : 10.5194 / acp-2-31-2002 .
  9. ↑ Lin, B., B. Wielicki, L. Chambers, Y. Hu, and K.-M. Xu: The Iris Hypothesis: A Negative or Positive Cloud Feedback? . In: J. Clim. . 15, No. 1, 2002, pp. 3-7. doi : 10.1175 / 1520-0442 (2002) 015 <0003: TIHANO> 2.0.CO; 2 .

Web links