IPCC carbon budget: Missing feedbacks ignored. | Brussels Blog

IPCC carbon budget: Missing feedbacks ignored.

posted by on 7th Dec 2013

Missing and underestimated feedbacks in the CMIP5 climate models used for the IPCC carbon budget (25th November 2013)

This is a note for the Parliamentary Office of Science and Technology listing papers on missing or underestimated feedbacks in the CMIP5 climate models used to calculate the carbon budget in the recent IPCC report (AR5).

Papers on missing/underestimated feedbacks.

December 2011

High risk of permafrost thaw: Climate change: High risk of permafrost thaw

September 2012

Permafrost feedback: Significant contribution to climate warming from the permafrost carbon feedback

March 2013

Reduced global dimming: Faustian Bargain & The Missing Climate Data

May 2013

Climate impact of Jellyfish: Stung! On Jellyfish Blooms and the Future of the Ocean. Lisa-ann Gershwin

July 2013

Climate sensitivity underestimated:Review Article,Climate sensitivity in the Anthropocene
Guardian report: Climate change to have double impact – study

August 2013:

Extreme weather events: Extreme meteorological events and global warming: a vicious cycle?

August 2013

Reduced sulphur fluxes: Global warming amplified by reduced sulphur fluxes as a result of ocean acidification

August 2013

Ocean acidification reduces carbon sink: Arctic ocean acidification: pelagic ecosystem and biogeochemical responses during a mesocosm study

September 2013

Reduced plant growth: Drought Drives Decade-Long Decline in Plant Growth

September 2013

Carbon Models Underestimate Role of Animals: Animating the Carbon Cycle

September 2013

Climate models underestimate the variability of Amazon dry-season length: Increased dry-season length over southern Amazonia in recent decades and its implication for future climate projection

September 2013

Water vapor feedback underestimated in models: Stratospheric water vapor feedback

October 2013

Wildfires projected to worsen with climate change: Ensemble projections of wildfire activity and carbonaceous aerosol concentrations over the western United States in the mid-21st century
Also here

November 2013

Methane from small thaw ponds: Small Thaw Ponds: An Unaccounted Source of Methane in the Canadian High Arctic

November 2013

Seabed methane release: Ebullition and storm-induced methane release from the East Siberian Arctic Shelf


Postscript 26th November 2013

Nearly all of the items in the list above reference papers that have been peer reviewed. I think there are occasions when the usually valuable demands of peer review exclude the less knowable and the very recent so there are occasions when points, which are important cannot easily be found in the peer reviewed literature.

Last hours

One feed back mentioned above that I would like to draw attention to concerns dissociating methane hydrates. I had previously raised concerns to get an official response to the Last Hours video. This video concerning the longer term should be considered by POST as well.

Neven’s Sea Ice Blog

A good place to find up to the hour information can often be found on Neven’s Sea Ice Blog. Yesterday a new topic was started And the wind cries methane. POST should look at this and read the comments. The piece by Neven ends “Remember, you can track methane yourself on MethaneTracker.org.” “Looking yourself” is somewhat faster than peer review although not as reliable.

Postscript 28th January 2014

POST note 454, Risks from Climate Feedbacks

A note from the Parliamentary Office of Science and Technology, Risks from Climate Feedbacks (POST-PN-454,January 2014) says

“Compared to existing model estimates, it is likely that climate feedbacks will result in additional carbon in the atmosphere and additional warming. This is because the majority of poorly represented climate feedbacks are likely to be amplifying feedbacks. This additional atmospheric carbon from climate feedbacks could make it more difficult to avoid a greater than 2°C rise in global temperatures without additional reductions in greenhouse gas emissions. The strength of many amplifying feedbacks is likely to increase with warming, which could increase the risk of the climate changing state.

Some commentators suggest the uncertainties in our knowledge of carbon cycle and physical feedbacks may mean the Earth will warm faster than models currently estimate.”

Postscript 27th January 2016

Papers showing climate models are under powered

Posts by contributor ALSR on Neven’s Arctic Sea Ice Forum point to recent papers supporting the view that the climate models in the last IPCC report (AR5).  These may not be easy to follow for the non-technical but they indicate something very serious.

Conservative Scientists & its Consequences. Message 69023

The linked reference could not make it more clear that paleo-evidence from inter-glacial periods indicates that ECS is meaningfully higher than 3C and that climate models are commonly under predicting the magnitude of coming climate change.

Dana L. Royer (2016), “Climate Sensitivity in the Geologic Past”, Annual Review of Earth and Planetary Sciences, Vol. 44


Abstract: “The response of temperature to CO2 change (climate sensitivity) in the geologic past may help inform future climate predictions. Proxies for CO2 and temperature generally imply high climate sensitivities: ≥3 K per CO2 doubling during ice-free times (“fast-feedback” sensitivity) and ≥6 K during times with land ice (Earth-system sensitivity). Climate models commonly under predict the magnitude of climate change and have fast-feedback sensitivities close to 3 K. A better characterization of feedbacks in warm worlds boosts climate sensitivity to values more in line with proxies and produce climate simulations that better fit geologic evidence. As CO2 builds in our atmosphere, we should expect both slow (e.g., land ice) and fast (e.g., vegetation, clouds) feedbacks to elevate the long-term temperature response over that predicted from the canonical fast-feedback value of 3 K. Because temperatures will not decline for centuries to millennia, climate sensitivities that integrate slower processes do have relevance for current climate policy.”

Edit: These finding concur with those of Köhler et al (2015) cited in Reply #1253; which indicates that inter-glacial values for specific ECS was about 45% higher than during glacial periods.  See also Reply #1254.

Conservative Scientists & its Consequences. Message 67721

I provide the following selected quotes from the Kohler et al (2015) paper; which emphasize that the AR5 projections do not include many potentially important feedback mechanisms (note that just because AR5 assumes that slow feedbacks will only effect the distant future does not mean that this is true at our current high rates of forcing):

Extracts: “…. important feedbacks of the climate system are not incorporated into all models. For example, when coupling a climate model interactively to a model of stratospheric chemistry, including ozone, the calculated transient warming on a 100-year timescale differs by 20% from results without such an interactive coupling (Nowack et al., 2015).

A major restriction of any geological-data-based estimate of climate sensitivity is that there was no period in Earth’s history during which the atmospheric CO2 concentration and global temperature changed as rapidly as today. Therefore, in all these data-based approaches (including our study here), ECS defined as global equilibrium temperature rise in response to a doubling of atmospheric CO2 can only be roughly estimated.

Slow feedbacks are of interest in a more distant future (Zeebe, 2013) but are not yet considered in climate simulations using fully coupled climate models underlying the fifth assessment report of the IPCC (Stocker et al., 2013).”


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