Examination of New CERES Data for Evidence of Tropical Iris Feedback

Chambers, L. H.; Lin, Bing; Young, David F.

doi:10.1175/1520-0442(2002)015<3719:eoncdf>2.0.co;2

Cited by 39 publications

(21 citation statements)

References 15 publications

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“…This hypothesis is based on the “iris mechanism” [ Lindzen et al , 2001] suggesting a decrease of tropical cirrus clouds with increasing temperature, effectively a negative feedback in the present‐day Earth system. This hypothetical mechanism has been extensively challenged in the literature since no evidence for such an effect could be found in several satellite data sets [ Chambers et al , 2002; Fu et al , 2002; Hartmann and Michelsen , 2002; Lin et al , 2002].…”

Section: Clouds In the Archean Atmospherementioning

confidence: 99%

The faint young Sun problem

Feulner

2012

Reviews of Geophysics

295

212

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[1] For more than four decades, scientists have been trying to find an answer to one of the most fundamental questions in paleoclimatology, the "faint young Sun problem." For the early Earth, models of stellar evolution predict a solar energy input to the climate system that is about 25% lower than today. This would result in a completely frozen world over the first 2 billion years in the history of our planet if all other parameters controlling Earth's climate had been the same. Yet there is ample evidence for the presence of liquid surface water and even life in the Archean (3.8 to 2.5 billion years before present), so some effect (or effects) must have been compensating for the faint young Sun. A wide range of possible solutions have been suggested and explored during the last four decades, with most studies focusing on higher concentrations of atmospheric greenhouse gases like carbon dioxide, methane, or ammonia. All of these solutions present considerable difficulties, however, so the faint young Sun problem cannot be regarded as solved. Here I review research on the subject, including the latest suggestions for solutions of the faint young Sun problem and recent geochemical constraints on the composition of Earth's early atmosphere. Furthermore, I will outline the most promising directions for future research. In particular I would argue that both improved geochemical constraints on the state of the Archean climate system and numerical experiments with state-of-the-art climate models are required to finally assess what kept the oceans on the Archean Earth from freezing over completely.

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Section: Clouds In the Archean Atmospherementioning

confidence: 99%

The faint young Sun problem

Feulner

2012

Reviews of Geophysics

295

212

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“…To justify such extensive clouds, they invoke the "iris" hypothesis (Lindzen et al, 2001) which postulates that cirrus coverage should increase if surface temperatures decrease (this hypothesis has received much criticism, e.g. Hartmann and Michelsen, 2002;Chambers et al, 2002). Rosing et al (2010) focus on decreasing the reflectivity of low level clouds so that the Earth absorbs more solar radiation.…”

Section: We Feel That the Assumption Of Constant Albedo Is As Goodmentioning

confidence: 99%

“…The second premise, of strong cloud feedback, is based on a statistical relationship for Earth's tropics (Lindzen et al, 2001) the authenticity of which has been questioned (e.g. Hartmann and Michelsen, 2002;Chambers et al, 2002). Application to very cold temperatures requires an extreme and unverifiable extrapolation.…”

Section: Cloud Heightmentioning

confidence: 99%

Clouds and the Faint Young Sun Paradox

Goldblatt

Zahnle

2011

Clim. Past

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Abstract. We investigate the role which clouds could play in resolving the Faint Young Sun Paradox (FYSP). Lower solar luminosity in the past means that less energy was absorbed on Earth (a forcing of −50 W m −2 during the late Archean), but geological evidence points to the Earth having been at least as warm as it is today, with only very occasional glaciations. We perform radiative calculations on a single global mean atmospheric column. We select a nominal set of three layered, randomly overlapping clouds, which are both consistent with observed cloud climatologies and reproduced the observed global mean energy budget of Earth. By varying the fraction, thickness, height and particle size of these clouds we conduct a wide exploration of how changed clouds could affect climate, thus constraining how clouds could contribute to resolving the FYSP. Low clouds reflect sunlight but have little greenhouse effect. Removing them entirely gives a forcing of +25 W m −2 whilst more modest reduction in their efficacy gives a forcing of +10 to +15 W m −2 . For high clouds, the greenhouse effect dominates. It is possible to generate +50 W m −2 forcing from enhancing these, but this requires making them 3.5 times thicker and 14 K colder than the standard high cloud in our nominal set and expanding their coverage to 100% of the sky. Such changes are not credible. More plausible changes would generate no more than +15 W m −2 forcing. Thus neither fewer low clouds nor more high clouds can provide enough forcing to resolve the FYSP. Decreased surface albedo can contribute no more than +5 W m −2 forcing. Some models which have been applied to the FYSP do not include clouds at all. These overestimate the forcing due to increased CO 2 by 20 to 25% when pCO 2 is 0.01 to 0.1 bar.

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“…Figure 19 shows DCS radiative forcings from environmental conditions, along with those from clear skies. The environmental condition is obtained from areas surrounding DCS clusters with the technique used by Lin et al (2002) and Chambers et al (2002). These environments are a mix of both clear and cloudy skies but include no high clouds.…”

Section: Radiative Effects Of Dcs Clustersmentioning

confidence: 99%

The Effect of Environmental Conditions on Tropical Deep Convective Systems Observed from the TRMM Satellite

et al. 2006

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This study uses measurements of radiation and cloud properties taken between January and August 1998 by three Tropical Rainfall Measuring Mission (TRMM) instruments, the Clouds and the Earth's Radiant Energy System (CERES) scanner, the TRMM Microwave Imager (TMI), and the Visible and InfraRed Scanner (VIRS), to evaluate the variations of tropical deep convective systems (DCS) with sea surface temperature (SST) and precipitation.This study finds that DCS precipitation efficiency increases with SST at a rate of ~2%/K.Despite increasing rainfall efficiency, the cloud areal coverage rises with SST at a rate of about 7%/K in the warm tropical seas. There, the boundary layer moisture supply for deep convection and the moisture transported to the upper troposphere for cirrus-anvil cloud formation increase by ~6.3%/K and ~4.0%/K, respectively. The changes in cloud formation efficiency, along with the increased transport of moisture available for cloud formation, likely contribute to the large rate of increasing DCS areal coverage. Although no direct observations are available, the increase of cloud formation efficiency with rising SST is deduced indirectly from measurements of changes in the ratio of DCS ice water path and boundary layer water vapor amount with SST.Besides the cloud areal coverage, DCS cluster effective sizes also increase with precipitation.Furthermore, other cloud properties, such as cloud total water and ice water paths, increase with SST. These changes in DCS properties will produce a negative radiative feedback for the earth's climate system due to strong reflection of shortwave radiation by the DCS. These results significantly differ from some previous hypothesized dehydration scenarios for warmer climates, and have great potential in testing current cloud-system resolving models and convective parameterizations of general circulation models.

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Examination of New CERES Data for Evidence of Tropical Iris Feedback

Cited by 39 publications

References 15 publications

The faint young Sun problem

The faint young Sun problem

Clouds and the Faint Young Sun Paradox

The Effect of Environmental Conditions on Tropical Deep Convective Systems Observed from the TRMM Satellite

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