1 / 17

Clouds: The Wild Card

This study explores the intricate role of clouds in the Earth's climate system, highlighting their dual effects of cooling and warming. By analyzing radiative forcing from low and high-level clouds, we reveal how clouds absorb and re-emit longwave radiation, ultimately influencing global temperatures. The research emphasizes the need to understand cloud feedback mechanisms and their implications for climate change. By using climate models and satellite data, we aim to clarify uncertainties surrounding clouds' net effects on climate and temperature dynamics.

gavan
Télécharger la présentation

Clouds: The Wild Card

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Clouds:The Wild Card Bruno Tremblay McGill University bruno.tremblay@mcgill.ca

  2. Effect of CloudsNight Time

  3. Facts about Clouds Clear-sky day are warm Cloudy-sky day day are cold Clear-sky night are cold Clear-sky day are warm

  4. Greenhouse effect of Clouds Clouds absorb LW radiation from the surface and then re-emits upwards at their own temperature Since clouds are colder than the surface – temperature decreases with heights – the earth-atmosphere system emits less radiation to space

  5. Thick Clouds Reflect SW Emits at low temp Neutral effect Low level clouds Reflects SW emits at high temp Cools the earth High Level Clouds Transparent to SW Emits at low temp Warms the earth

  6. Radiative Forcing of Clouds Low Cloud Forcing High Cloud Forcing

  7. Different clouds

  8. Global Annual Mean Cooling Effect of Clouds = 48 W/m2 Warming Effect of Clouds = 31 W/m2 Net Effect of Clouds = 17 W/m2 (Cooling) Clouds – in today’s climate – act to cool the climate

  9. Comparison with CO2 Anthropogenic increase in CO2: 280  490ppm (40% increase) Reduction in thermal outgoing radiation: 1.6 W/m2 Equvalent to placing a 60W light buld every 6m by 6m surface area over the entire earth surface.

  10. Conparison with CO2 • CO2 increase in the atmosphere is equivalent to: • 1.6/48 * 100 = 3% change in reflection of solar radiation by clouds • 1.6/31 * 100 = 5% change in the reduction of thermal radiation by clouds • 1.6/17 * 100 = 9% change in net effect of clouds on radiation • Are clouds sensitive to changes in earth temperature?

  11. Cloud feedbacks on Climate Stronger GH Effect Exacerbate Weaker Warming Stronger mitigate Cloud reflection Weaker

  12. Positive feedback More high level of clouds Fewer low level clouds Increase in height of cloud top Decrease in cloud thickness

  13. Positive feedback Fewer high level of clouds More low level clouds Decrease in height of cloud top Increase in cloud thickness

  14. What are the cloud net effect on climate? We don’t know – But we can try! Use Climate Model Use data from the last 50 years

  15. GCM - Uncertainties

  16. Satellite Data • Two problems: • Changes in clouds may not be linked with temperature changes • Satellite were made for weather not climate monitoring • Satellite data show decrease of high level clouds over ocean and land in accord with land obs • Satellite data show a decrease in low level clouds over ocean and land in disagreement with land obs

More Related