The Iris Hypothesis: A Negative or Positive Cloud Feedback?

Lin, Bing; Wielicki, Bruce A.; Chambers, L. H.; Hu, Yongxiang; Xu, Kuan‐Man

doi:10.1175/1520-0442(2002)015<0003:tihano>2.0.co;2

Cited by 105 publications

(70 citation statements)

References 7 publications

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“…Lin et al [127] used measurements from the Clouds and Earth's Radiant Energy System (CERES) sensor and got significantly different results from those reported by Lindzen et al [126]. It was found that clouds in the tropics do change in response to warmer sea surface temperatures, but that the cloud changes serve to slightly enhance warming at the surface.…”

Section: "Adaptiv Iris"mentioning

confidence: 97%

“…It was found that clouds in the tropics do change in response to warmer sea surface temperatures, but that the cloud changes serve to slightly enhance warming at the surface. Specifically, whereas the Lindzen et al experiment predicts that cirrus clouds change in extent to reduce warming at the surface by anywhere from 0.45°C to 1.1°C [126], the Lin et al experiment predicts that changes in the tropical clouds will help warm the surface by anywhere from 0.05°C to 0.1°C [127].…”

Section: "Adaptiv Iris"mentioning

confidence: 99%

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The role of clouds in the climate system

Quante¹

2004

J. Phys. IV France

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Abstract. Clouds are important for global climate since they have a strong impact on solar and terrestrial radiation as well as on the formation of precipitation. The different types of clouds in the atmosphere are linked to the climate system by a multitude of dynamical and thermodynamical processes including numerous feedback mechanisms. In present-day climate, on average, clouds cool our planet, the net cloud radiative forcing at the top of the atmosphere is about -20 Wm -2 . One of the most interesting questions concerning clouds is: how will they respond to a change in climate? A slight change in cloud amount or a shift in the vertical distribution of clouds might have a considerable impact on the energy budget of the Earth. The Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) states clearly that cloud processes and related feedbacks are among the physical processes leading to large uncertainties in the prediction of future climate. The main reason for this is that many microphysical and dynamical processes controlling the life cycle and radiative properties of clouds are not adequately implemented in global climate models. The interaction of aerosols and clouds and the resulting radiative forcing (indirect and semidirect aerosol effect) is one of the major fields of active cloud research at present. This chapter introduces various aspects of the cloud-climate relation and summarizes the discussions of topics currently under scientific debate.

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Section: "Adaptiv Iris"mentioning

confidence: 97%

Section: "Adaptiv Iris"mentioning

confidence: 99%

The role of clouds in the climate system

Quante¹

2004

J. Phys. IV France

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“…The net radiative effect on shortwave and thermal radiation is still not fully resolved (Lindzen et al, 2001;Lin et al,2002;Fu et al, 2002), but the effect of cirrus on the radiation balance depends strongly on the coverage of thin relative to thick cirrus cloud (Chou et al, 2002) and generally has a net warming effect.…”

Section: Introductionmentioning

confidence: 99%

The effect of observed vertical structure, habits, and size distributions on the solar radiative properties and cloud evolution of cirrus clouds

Yang

Dobbie

Herbert

et al. 2011

Quart J Royal Meteoro Soc

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Cirrus observations taken during EMERALD1 clearly showed vertical structure in ice crystal habit and size distribution. In this study, we use these observations along with radiative and cloud modelling to assess the importance of this observed vertical structure in size and habit on radiative properties and cloud evolution. We show that neglecting the vertical structure results in changes to the solar upwelling and downwelling fluxes of 10 and 8 W m Often, general circulation models have highly parametrized treatments of cloud properties. We illustrate that crude assumptions about ice crystal effective sizes used in models (from the literature) can result in fluxes being in error by 100 W m −2 or more compared to using the observations. The above results are contrasted with effects of ice crystal roughness (altering the asymmetry). We show that moderate estimates of roughness lead to changes in the upward and downward fluxes of about 10-15 W m −2 . This shows that vertical structure, habits and knowledge of size distribution are key factors and on a par with such effects as ice particle roughness, which is considered to have a highly uncertain but important cirrus radiative effect. Copyright c 2011 Royal Meteorological SocietyKey Words: cirrus; ice crystals; habits, radiative properties; EMERALD; vertical structure; ice optics

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“…This circumstance has caused an intense scientific debate on the actual climate impact of possible and observed cloudiness changes (e.g. Kristjánsson and Kristiansen, 2000;Lindzen et al, 2001;Lin et al, 2002;Hartmann and Michelsen, 2002). Consequently, it is of great importance that new and accurate methods capable of observing clouds over the entire globe with a high spatial resolution are developed.…”

Section: Introductionmentioning

confidence: 99%

A 10 year cloud climatology over Scandinavia derived from NOAA Advanced Very High Resolution Radiometer imagery

Karlsson

2003

Intl Journal of Climatology

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Results from a satellite-based method to compile regional cloud climatologies covering the Scandinavian region are presented. Systematic processing of multispectral image data from the NOAA Advanced Very High Resolution Radiometer (AVHRR) instrument has been utilized to provide monthly cloud climatologies covering the period 1991-2000. Considerable local-scale variation of cloud amounts was found in the region. The inland Baltic Sea and adjacent land areas exhibited a large-amplitude annual cycle in cloudiness (high cloud amounts in winter, low cloud amounts in summer) whereas a weak-amplitude reversed annual cycle (high cloud amounts with a weak maximum in summer) was found for the Scandinavian mountain range. As a contrast, conditions over the Norwegian Sea showed high and almost unchanged cloud amounts during the course of the year. Some interesting exceptions to these patterns were also seen locally. The quality of the satellite-derived cloud climatology was examined through comparisons with climatologies derived from surface cloud observations, from the International Satellite Cloud Climatology Project (ISCCP) and from the European Centre for Medium-range Weather Forecasts ERA-40 data set. In general, cloud amount deviations from surface observations were smaller than 10% except for some individual winter months, when the separability between clouds and snow-covered cold land surfaces is often poor. The ISCCP data set showed a weaker annual cycle in cloudiness, generally caused by higher summer-time cloud amounts in the region. Very good agreement was found with the ERA-40 data set, especially for the summer season. However, ERA-40 showed higher cloud amounts than SCANDIA and ISCCP during the winter season. The derived cloud climatology is affected by errors due to temporal AVHRR sensor degradation, but they appear to be small for this particular study. The data set is proposed as a valuable data set for validation of cloud description in numerical weather prediction and regional climate simulation models.

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The Iris Hypothesis: A Negative or Positive Cloud Feedback?

Cited by 105 publications

References 7 publications

The role of clouds in the climate system

The role of clouds in the climate system

The effect of observed vertical structure, habits, and size distributions on the solar radiative properties and cloud evolution of cirrus clouds

A 10 year cloud climatology over Scandinavia derived from NOAA Advanced Very High Resolution Radiometer imagery

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