Stratocumulus Cloud Deck Collapse and other Tipping Elements in the Climate System that Can Smush Us // May 12, 2020
Stratocumulous cloud decks cover lots of ocean and block sunlight providing some cooling offset to GHG warming. Typically these clouds are 1 km above ocean surfaces and are about 370 meters thick, and are sustained by long wave radiation cooling at their tops.
As CO2 concentration increases, convective circulation resupplying moisture to the clouds from ocean evaporation can be disrupted, leading to less long wave cooling cutting off the source of surface moisture, leading to disintegration of the clouds and abrupt, acute surface warming of up to 8 C.
Mechanisms, Evidence, and Impacts of Climate Tipping Elements: Earth System Dynamics // May 12, 2020
A new review paper called “ESD Reviews: mechanisms, evidence, and impacts of climate tipping elements” was published online a few weeks ago and assessed the latest science on risks and impacts of various tipping elements. In the last video, here, and in the next video I chat about the risks of these tipping elements. The discussion includes the usual suspects:
- Ice melt,
- AMOC shutdown (other posts, on AMOC, here)
- Methane release from hydrated and permafrost,
- Amazon forest collapse, etc., but significantly included a new one called
- Stratospheric cloud deck evaporation.
Ref: ‘ESD Reviews: Mechanisms, Evidence, and Impacts of Climate Tipping Elements‘, Seaver Wang and Zeke Hausfather. The Breakthrough Institute, Oakland, USA, Received: 26 Mar, Accepted for review: 20 Apr, Discussion started: 21 Apr 2020.
Abstract: ‘Increasing attention is focusing upon climate tipping elements – large-scale earth systems anticipated to respond through positive feedbacks to anthropogenic climate change by shifting towards new long-term states. In some but not all cases, such changes could produce additional greenhouse gas emissions or radiative forcing that could compound global warming. Developing greater understanding of tipping elements is important for predicting future climate risks. Here we review mechanisms, predictions, impacts, and knowledge gaps associated with ten notable climate tipping elements.‘
Tipping Elements in the Earth’s Climate System // May 11, 2020
In 2007 Lenton et. al drew on results from experts at an international conference to identify “Tipping elements in the Earth’s climate system”. They assessed the likelihood of thresholds being reached to trigger tipping, timescales of tipping and transition times, and consequences to the climate system and humanity.
Canada Geese and their chicks have hijacked my bike…
And, of course, the famed Shackleton
A new review paper published in the journal Earth System Dynamics assessed the latest scientific analysis on risks and impacts of the various tipping elements. Here, and in the next few videos I chat about the risks of these tipping elements.
Ref: ‘Tipping elements in the Earth’s climate system.
Lenton Kriegler Hall Lucht, Rahmstorf, Schellnhuber, Proc Natl Acad Sci U S A. 2008 Feb 12;105(6):1786-93.
Abstract: ‘The term “tipping point” commonly refers to a critical threshold at which a tiny perturbation can qualitatively alter the state or development of a system. Here we introduce the term “tipping element” to describe large-scale components of the Earth system that may pass a tipping point.
‘We critically evaluate potential policy-relevant tipping elements in the climate system under anthropogenic forcing, drawing on the pertinent literature and a recent international workshop to compile a short list, and we assess where their tipping points lie. An expert elicitation is used to help rank their sensitivity to global warming and the uncertainty about the underlying physical mechanisms. Then we explain how, in principle, early warning systems could be established to detect the proximity of some tipping points‘.
How Aerosol Driven Water Droplet Concentrations Control Low Level Cloud Coverage Affecting Climate // May 8, 2020
In a nutshell, with more aerosols (particles and non-water liquids) in the atmosphere, there are more cloud condensation nuclei so many more and smaller water droplets in clouds. Thus clouds are much more reflective of incoming sunlight, causing some cooling to partially offset GHG warming.
Smaller water droplets in clouds means that they rain less, become thicker, hold more water, cover a larger fraction of the sky and persist for a lot longer causing even more cooling offset. With global industrial shutdowns from our coronavirus responses, we have less aerosols in the skies, thus less of this cooling offset occurring.
Science of Aerosol-Cloud Interactions Vital to Reduce Uncertainty in Climate Models and Projections // May 7, 2020
In this video and the next I explain the basic science of
- Direct aerosol effects (scattering; blocking sunlight) and
- Indirect effects (smaller cloud droplets increasing reflectivity in the Twomey Effect, suppressing drizzle,
- Increasing cloud heights and cloud lifetimes in the Albrecht Effect, and Heating Effects dissipating clouds).
Scientists can determine the number of droplets Nd and the vertical updraft velocity (Wb) at the base of Marine Stratospheric Clouds from satellite measurements, allowing determination of the number of Cloud Condensation Nuclei (CCN) which is key to understanding aerosol and cloud climate interactions.
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