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Risky Feedbacks – Not In Models; Understated Solutions

Feedbacks are best understood by example. Austin’s 2023 ice storm that caused massive tree damage and excessive power outages was caused by a feedback. The ice storm stalled in a classic climate change-caused effect, creating a longer ice accumulation time than in our old climate. This additional accumulation beyond the evolutionary boundaries of our Central Texas forests is what caused all the downed limbs that took out the power. Our infrastructure is not designed for this amount of ice accumulation. Electric utility tree trimming practices were designed based on data from our old climate with less ice accumulation. This new article on feedbacks helps us understand that the climate models, upon which our new climate policies are based, only poorly include feedbacks, where policies that drive infrastructure design criteria do not yet acknowledge the severity or the cumulative impacts of the feedback effects of these extreme weather events we have been enduring.

The cloud machine feedback in a forest is another good example of a feedback. Remove the forest and the forest-caused rain machine goes away too. Another kind of feedback is the ice and snow feedback (albedo feedback) that has longer, larger, and cumulative effects. A little bit of warming melts a little ice and snow earlier in the season creating more warmth because ice and snow reflect most of the sun’s light energy back into space; but plants, rock, soil and open water absorb most of that light energy and change it into heat energy where it can trapped on Earth by the greenhouse effect. This additional trapped warmth then melts a little more snow that in turn causes even more warmth to be trapped in a continual loop until all the ice and snow are gone.

The moisture feedback is the biggest and least known of all feedbacks, so far as our current knowledge understands feedbacks. The following description is from NASA’s Global Climate Change Program (1):

As greenhouse gases like carbon dioxide and methane increase, Earth’s temperature rises in response. This increases evaporation from both water and land areas. Because warmer air holds more moisture, its concentration of water vapor increases. Specifically, this happens because water vapor does not condense and precipitate out of the atmosphere as easily at higher temperatures. The water vapor then absorbs heat radiated from Earth and prevents it from escaping out to space. This further warms the atmosphere, resulting in even more water vapor in the atmosphere. This is what scientists call a “positive feedback loop.” Scientists estimate this effect more than doubles the warming that would happen due to increasing carbon dioxide alone.

The great challenge with feedbacks is that our current state of knowledge does not yet robustly understand how big and fast these feedback responses are, and how they interact with one another creating cascading feedbacks that wildly increase natural greenhouse gas emissions in uncontrollable ways. The following is the subtitle for this new article by a team led by William Ripple at the University of Oregon’s Department of Forest Ecosystems and Society, “Many risky feedback loops amplify the need for climate action” in the journal One Earth (2):

Many feedback loops significantly increase warming due to greenhouse gas emissions. However, not all of these feedbacks are fully accounted for in climate models. Thus, associated mitigation pathways could fail to sufficiently limit temperatures. A targeted expansion of research and an accelerated reduction of emissions are needed to minimize risks.

These feedback emissions happen in addition to the greenhouse gases we add to our atmosphere creating more warming than the greenhouse gases alone. As shown above by the US Global Change Program, the water vapor feedback alone doubles the warming impact of the greenhouse gases we emit. This moisture feedback is also nonlinear; a little warming does not allow a little more moisture in the atmosphere, it allows a lot more. These feedbacks are now happening in a big way, amplifying warming beyond what the climate models suggest.

The great challenge with these feedbacks is that once started, they do not self-restore unless the warming that created them is removed and importantly, there comes a point, labelled “the point of no return” by James Hansen, former 32-year director of the NASA Goddard Institute for Space Studies. This point of no return is very similar to the response of Earth systems collapses to warming in that, once a collapse begins it self-fulfills, or becomes irreversible once beyond the point of no return. (3).

Hansen defines the point of no return and tipping as, “the point of no return, a climate state beyond which the consequence is inevitable, even if climate forcings are reduced. A point of no return can be avoided, even if the tipping level is temporarily exceeded. Ocean and ice sheet inertia permit overshoot, provided the climate forcing is returned below the tipping level before initiating irreversible dynamic change.”

Timothy Lenton at the University of Exeter has published that more than half of known tipping systems are now active (4). In other words, they have initiated collapse where these tipping systems or Earth systems like tropical forests and permafrost, have warmed beyond their evolutionary boundaries where their species and mechanisms are stable. Once a system changes beyond its evolutionary boundaries it collapses so it can re-evolve with species and mechanism tolerant of the changed conditions. This collapse of an Earth system results in that system no longer absorbing greenhouse gases, but emitting them during the re-evolution phase. This re-evolution phase with forests for example can last decades or generations.

This new reporting on feedbacks by Ripple tells us, “Despite major recent progress in incorporating a host of interacting feedbacks, climate models may still be underestimating the acceleration in global temperature change that a large and interrelated set of amplifying feedback loops and tipping points could cause. In a likely short-term scenario, our lack of dramatic emission reductions could result in a future with ongoing and intensifying climate impacts. In the worst case long-term scenario, interactions among feedback loops could result in an irreversible drift away from the current state of Earth’s climate to a state that threatens habitability for humans and other life forms.”

It is this long-term scenario that creates a mandatory action to restore our climate back to within the evolutionary boundaries of our Earth systems instead of allowing it to warm further to 1.5 degrees C above normal from the late 19th century, where we are at 1.2 C warming now and tipping systems with their attendant feedbacks are now active, and at some point that our less than robust tipping and feedback science can state, these collapses will become irreversible, self-fulfilling, and be beyond our control.

Ripple 2023 has identified 20 physical and 21 biophysical feedback loops. The physical feedbacks are like the snow and ice feedback listed above. The permafrost tipping feedback is where warming thaws permafrost a little, releasing warming gases methane and CO2 that warm our atmosphere and create further thaw, releasing even more methane and CO2 and so on. We are still learning about feedback loops where some physical feedbacks create biologic feedback loops and vice versa. Ripple et al., tells us these new feedbacks loops will likely see publishing in the near future.

This list of feedbacks in this article includes: tropical, temperate and boreal forests, peatlands, wetlands, permafrost, snow cover, increased polar rainfall, sea ice, ice sheets, northern greening where trees grow in polar regions where only tundra existed before where trees stick up above snow cover and absorb sunlight creating heat, wildfire, soil drying, desertification, and ocean processes.

Ripple 2023 continues, “there is deep uncertainty associated with unlikely but extreme feedbacks and tipping points. Specific concerns include slowing of ocean circulation and the large scale loss of ice sheets, permafrost, and forests. In the worst case, if positive feedbacks are sufficiently strong, this could result in tragic climate change outside the control of humans.”

The importance of feedbacks and tipping is the risks they pose where, “further small increases in short-term warming are a big risk, considering the suffering that we are already experiencing from climate disasters of ‘unprecedented’ wildfires, intense storms, coastal flooding, permafrost thaw, and extreme weather that have occurred with just 1.1 C to 1.2C global average warming… Given the potential for catastrophic climate change and the lack of complete scientific understanding to date, policymakers should strongly consider the potentially dangerous effects of feedback loops, tipping points, and climate cascades, even if all desired scientific data are not available at this time.”

Critiquing this article, the authors only vaguely addresses a restoration warming target less than our current amount of warming, even though they suggest tipping and feedbacks are now active, and the main coauthor (Lenton) has published that more than half of known tipping systems have activated since 2010 including, Arctic sea ice, Greenland ice sheet, boreal forests, permafrost, the Gulf Stream, the Amazon, coral, the West Antarctic Ice Sheet and parts of the East Antarctic Ice Sheet (4).

Because tipping has already activated, these systems’ collapses will proceed unless we reduce the warming that caused them to activate.  Ripple’s interpretation of this fundamental behavior of systems remains colored by the Intergovernmental Panel on Climate Change 1.5 C scenarios where we have a carbon budget and fundamental atmospheric greenhouse gas level that must be eliminated or reduced to achieve this target that nonetheless, is warmer than the tipping activation threshold.

The thrust of the reporting by Ripple is “an immediate and massive international mobilization must occur to advance climate science with an increase in research priorities and funding to quickly get the impacts and interactions of feedbacks better assessed.”

Ripple 2023 closes with an acknowledgement of great risks posed by tipping feedbacks, “if the worst-case risks posed by feedback loops and tipping points have been underestimated, the future of a hospitable planet Earth may be at stake.”


Cover Image: One Earth journal cover, February 17, 2023. Description: Forest die-off in the Amazon.

(1) Buis, Steamy Relationships: How Atmospheric Water Vapor Amplifies Earth’s Greenhouse Effect, NASA Jet Propulsion Laboratory, February 8, 2022.,caused%20by%20other%20greenhouse%20gases.&text=It%20works%20like%20this%3A%20As,both%20water%20and%20land%20areas.

(2) Ripple et al., Many risky feedback loops amplify the need for climate action, One Earth, February 17, 2023.

(3) Hansen et. al., Target Atmospheric CO2 Where should humanity aim?, Open Atmospheric Science Journal, 2008.

(4) Lenton et al., Climate tipping points-too risky to bet against, Nature, November 27, 2019.
University of Exeter Press –