Even without a runaway feedback via the carbon cycle, warming will be substantial and critical: Markus Reichstein

Climate scientist: “Positive carbon-climate feedback is still very likely” — and even without “a runaway feedback,” warming will be “substantial and critical”

Plus a review of recent research on amplifying feedbacks

Wonk Room and Climate Progress, July 8, 2010

As the United States, like much of the rest of the world, bakes in record, killer heat, climate scientists continue to refine our understanding of the dire future of global warming in the years to come. The United Nations has named the 831 scientists who will author the fifth Intergovernmental Panel on Climate Change report, to be published in 2013 with new model runs and observations of the ongoing destruction of our habitable environment.

They do this work despite the endless assault from the fossil-fueled right wing, weathering death threats and media and politicians who ignore, downplay, distort, or lie about the science.  Brad Johnson has yet another instance of this criminal deception (with an addendum by JR reviewing the recent literature on feedbacks).

The First Post, a website of Great Britain’s The Week run by Tim Edwards, has claimed that new climate research from the Max Planck Institute for Biogeochemistry “is set to rock the boat again.” Edwards’ headline, promoted by climate disinformer  Marc Morano, blares:

‘Runaway climate change’ ‘unrealistic’, say scientists

“Climate change skeptics might say the new study is yet another nail in the coffin of the IPCC report,” Edwards writes.

His headline and fevered speculation was based on a quote from the Max Planck researchers’ press release, which quoted Max Planck scientist Markus Reichstein saying, “Particularly alarmist scenarios for the feedback between global warming and ecosystem respiration (CO2 production) thus prove to be unrealistic.”
Via Twitter, Tim Edwards defended his piece as a “balanced story about an interesting development in climate change science.” However, by giving credence to conspiracy theorists who believe that mainstream science is a fraud, Edwards utterly misrepresented the research, which was published in a pair of papers in Science.

The researchers’ work in reality reduces uncertainties about how ecosystems respond to changes in temperature, precipitation, and solar input with respect to the carbon cycle, and will be very useful for improving the resolution of global climate models. Far from being “yet another nail in the coffin of the IPCC report,” this research is yet another building block in the vast edifice of climate science that underlies the IPCC work.

In an email interview with the Wonk Room, Dr. Reichstein excoriated the First Post story as a “very bad report,” saying that his research does not show that runaway climate change is “unrealistic.” In fact, Reichstein told the Wonk Room that “positive carbon-climate feedback is still very likely.”

This is indeed a very bad report about our research, strongly misinterpreted and with a unnecessarily sensational tone. In particular the statements in relation to the IPCC report are exactly opposite to what I said (and what is correctly reported in other newspapers). The 4th IPCC report is not challenged at all by our study, because it does not contain “alarmist” scenarios at all. On the contrary, the simulations therein still do not contain the carbon cycle feedback.

Our point is that now for the next IPCC report models are including this feedback and they are doing this in very different way, for example also with different temperature sensitivities. This will lead to a relatively large range of model predictions, a range which can hopefully be reduced by using our data for model improvement.

Reichstein’s research makes the speculative scenario of a feedback loop between warmer temperatures and faster CO2 production from plants less likely. However, as he explained to the Wonk Room, there are many other feedback loops that could give rise to runaway warming:

There are enough other feedbacks which are not touched in our studies. These include permafrost melting and subsequent CO2 and CH4 release to the atmosphere. The positive carbon-climate feedback is still very likely.

The IPCC Fourth Assessment Report’s predictions of climate catastrophe exclude these runaway feedback scenarios. “Even without a runaway feedback via the carbon cycle,” Reichstein said, agreeing with the IPCC assessment, “the warming will be substantial and critical.”
– Brad Johnson

Cross posted from Wonk Room.

The rest of this post is by Joseph Romm.

Here’s some of the recent research and observation on  the dangerous positive carbon-cycle feedbacks that threaten to amplify the impacts of human-caused GHGs.

• Science: “Clouds Appear to Be Big, Bad Player in Global Warming” — an amplifying feedback (sorry Lindzen and fellow deniers)
• Science: Vast East Siberian Arctic Shelf methane stores destabilizing and venting, NSF issues world a wake-up call: “Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.”
• Science: Global warming is killing U.S. trees, a dangerous carbon-cycle feedback
• Study: Water-vapor feedback is “strong and positive,” so we face “warming of several degrees Celsius”

Indeed, the best evidence is that the climate is now starting to be driven by amplifying feedbacks, most notably:

• The defrosting of the permafrost [see figure below]
• The drying of the Northern peatlands (bogs, moors, and mires).
• The destruction of the tropical wetlands
• Decelerating growth in tropical forest trees — thanks to accelerating carbon dioxide
• Scientists: “There are multiple, consistent lines of evidence from ground-based studies published in the peer-reviewed literature that Amazon forests are, indeed, very susceptible to drought stress.”
• Wildfires and Climate-Driven forest destruction by pests
• The desertification-global warming feedback

Using the first “fully interactive climate system model” applied to study permafrost, the researchers found that if we tried to stabilize CO2 concentrations in the air at 550 ppm, permafrost would plummet from over 4 million square miles today to 1.5 million. If concentrations hit 690 ppm, permafrost would shrink to just 800,000 square miles:



The term “runaway feedback” is ill-defined in any case.  I think the more plausible scenario is simply that if we cross a key threshold for any extended period of time, certainly 450 ppm and possibly 400 (or lower), the amplifying feedbacks will accelerate and gravely complicate any effort to constrain emissions.

Even models that don’t fully account for (or even ignore entirely) the amplifying feedbacks we know are the most likely — like the tundra –  show catastrophic outcomes if we don’t get off our current path of unrestricted greenhouse gas emissions:

• M.I.T. doubles its 2095 warming projection to 10 °F — with 866 ppm and Arctic warming of 20 °F
• Hadley Center: “Catastrophic” 5-7 °C warming by 2100 on current emissions path

• Our hellish future: Definitive NOAA-led report on U.S. climate impacts warns of scorching 9 to 11°F warming over most of inland U.S. by 2090 with Kansas above 90 °F some 120 days a year — and that isn’t the worst case, it’s business as usual!”
• Ocean dead zones to expand, “remain for thousands of years”
• U.S. media largely ignores latest warning from climate scientists: “Recent observations confirm … the worst-case IPCC scenario trajectories (or even worse) are being realised” — 1000 ppm

Few detailed studies have been done of the scenario with high emissions and high positive feedbacks.  One recent analysis makes clear it ain’t pretty:

• UK Met Office: Catastrophic climate change, 13-18 °F over most of U.S. and 27 °F in the Arctic, could happen in 50 years, but “we do have time to stop it if we cut greenhouse gas emissions soon.”

This is the “plausible worst case scenario” for 2060 from the UK Met Office that occurs in 10% of model runs of high emissions with the carbon cycle feedbacks [temperature in degrees Celsius, multiple by 1.8 for Fahrenheit]:



The time to act is most certainly now.

Link:  http://climateprogress.org/2010/07/08/climate-feedback-loops/#more-29323