The Evidence Against The Existence of A Positive Carbon Budget Continues to Mount

The Arctic Sea Ice Forum (ASIF) is an invaluable source of information that I regularly read and contribute to. One of the discussion threads on the forum is entitled “Conservative Scientists & its Consequences” that addresses the divergence between public statements on climate change and the findings of recent scientific research. This divergence facilitates much of the soft-denial maintained in official policy circles, with the concept of a carbon budget being a good example. Even Non-Governmental Organizations, such as Carbon Tracker, keep using carbon budgets that do not take into account more recent research findings. As such, they propagate the myth that a carbon budget exists and that we still have two to three decades to reduce emissions to zero.

In a previous post I have addressed some of the issues that argue for the lack of a carbon budget. Below, I list some more such issues that have come to light as an increasing pace of scientific studies invalidates the assumptions used in the mainstream climate models.

Over-estimation of Carbon Dioxide sinks

CO2 Enhanced Plant Growth

The enhanced plant growth that is assumed in climate models as COlevels increase may be limited by the availability of plant nutrients. An experiment with trees grown in low-phosphorous soil, typical of the tropics and subtropics, showed that such trees could store 10% less carbon than expected. “The finding suggests forests will store around a tenth less carbon than expected, meaning CO2 levels will rise even faster than computer models are projecting. “’It can make a huge difference in the projections,’ says David Ellsworth of Western Sydney University in Australia, whose team carried out the experiment.”[i] A tree ring study of tropical forests seems to point to the same conclusion.[ii]

A meta-analysis of studies on the effect of increased CO2 levels on plants, taking into account the possible skewing of data by reporting biases, concludes that estimates are overstated by between 20% and 40%[iii]. This leads to an overestimation of future crop yields in a warming world, and overestimates the uptake of carbon dioxide by plants (reducing the carbon budget). “The issue of reporting bias is widely acknowledged in medicinal science; it is estimated that studies that demonstrate a positive effect are 94% more likely to be submitted and then published in leading journals. These journals are most likely to be indexed and their studies included in meta-analyses. This skew toward positive studies is driven by publication bias (where journals prefer to publish positive studies), data availability bias (studies with a large effect size are more likely to be written up in comparison to those where the replication is insufficient to demonstrate a significant effect) and reviewer bias (where reviewers favor manuscripts reporting strong treatment effects confirming a prevailing consensus).”


Under climate change, the oceans will both warm and become more acidic (as they take in large amounts of carbon dioxide). “Over the last ten years, one-fourth of human-emissions of carbon dioxide as well as 90 percent of additional warming due to the greenhouse effect have been absorbed by the oceans. Acting like a massive sponge, the oceans pull from the atmosphere heat, carbon dioxide and other gases, such as chlorofluorocarbons, oxygen and nitrogen and store them in their depths for decades to centuries and millennia.”[iv] Over time, their ability to take up heat from the atmosphere will be degraded much more than their ability to take up carbon dioxide, a new NASA study finds. If all of the extra heat slows down the oceans overturning currents, the impact will be exacerbated for both carbon dioxide and heat. The overall effect will be to accelerate climate change, as the atmosphere is forced to hold more of the increased heat and carbon dioxide.

Observations are also showing that oxygen levels in the oceans are falling at a rate 2 to 3 times faster than that assumed in climate models. It “found that oxygen levels started dropping in the 1980s as ocean temperatures began to climb”[v]. If this continues it will increase the areas of deoxygenated dead zones and reduce the ocean’s ability to take up carbon dioxide; both speeding up climate change and killing the population of our oceans. With the oceans also warming up faster than predicted, such a scenario could become a reality earlier than expected[vi]. An earlier study found that once the oceans are severely affected, it is virtually impossible to undo the changes on a human-generation timescale[vii].

Increasing Non-Anthropogenic Emissions

Rivers and Lakes

Could the Amazon River be emitting enough carbon dioxide to offset the uptake of the rain forest? This study seems to point to that conclusion, seeing almost 50% higher emissions from rivers and lakes[viii]. “Forests have always been considered huge carbon stores, helping to absorb greenhouse gas emissions, but new research in Brazil has found that rivers in the Amazon emit far more carbon dioxide (CO2) than previously estimated, suggesting that the Amazon Basin is closer to net carbon neutral. The results increase the most recent global estimates of CO2 emissions from rivers and lakes by almost 50%, with potentially huge implications for global climate policy.”[ix]

Very importantly, “These increasing emission estimates in the Amazon alone, which still don’t consider the tidal reaches of other large rivers, suggest that the terrestrial biosphere does not absorb as much anthropogenic CO2 as previously assumed”, says Dr Ward, with serious implications for global climate policy, “Politicians and policy makers should recognize that the presence of a tree does not imply carbon sequestration, per se, we must track the history of carbon as it moves from land to sea.”

Warmer temperatures may have the effect of reducing the ability of ponds to sequester carbon and greatly increase their emissions of methane, another study concluded. This was the first experiment to look at the effects of long-term warming in aquatic environments “Lakes and ponds cover about 4% of Earth’s surface (excluding areas covered by glaciers and ice sheets) but they are disproportionately large sources of methane and CO2 to the atmosphere … This accelerating effect in ponds, which could have serious impacts on climate change, is not currently accounted for in Intergovernmental Panel on Climate Change models.”[x]


The boreal forests are burning at a rapidly increasing rate, releasing the carbon stored within them into the atmosphere. A good example is that of Siberia, where massive areas of forest fires are occurring each year. “Those forests are burning at a rate unheard of in at least 10,000 years due largely to rising temperatures”[xi]. Alaska has also had an explosive early start to the forest fire season, and “Large fires in Alaska are twice as common as they were 75 years ago …. Alaskan wildfire season is 40 percent longer as well. Similar changes have been observed in Canada as well.”[xii] Such boreal forests store about 30% of the world’s carbon, so accelerating levels of forest fires will be a significant positive feedback.

The mixture of anthropogenic land use changes and climate change may lead to the rate of loss from forest fires in the Amazon greatly increasing, turning significant areas into a carbon source rather than sink. As a recent study states “These results underscore the potential for a fire-driven transformation of Amazon forests if recent regional policies for forest conservation are not paired with global efforts to mitigate climate change”[xiii].

Recent actions by the Brazilian government to open up more areas of the Amazon to development do not auger well for its future as a carbon sink. This will only add to the return of deforestation in recent years after the previous years successful policies to control it, “Following about a decade of stability, the last three years have seen rising deforestation again. Last year saw a 29 per cent rise in Amazon deforestation over the previous year.” Drastic cuts to the Ministry of Environment and science research budgets will also greatly impede any attempts to monitor and control deforestation, “The necessary enforcement [of environmental laws] in Amazonia is being reduced to virtually zero … Even the fire prevention department will have no vehicles or funds to fight fires.” [xiv] The real possibility of the Amazon rainforest turning into a carbon source is shown by a study that found strong evidence that the 2010 drought in the region significantly reduced its carbon uptake for two years[xv].

Soil and Permafrost

The omission of any possibility of increasing GHG emissions from soil and melting permafrost by the UN IPCC is one of the most glaring problems with the IPCC’s forecasts. The evidence for such increased emissions as temperatures rise continues to mount. These increased emissions will include nitrous oxide[xvi], as well as carbon dioxide and methane. For example, the process already seems to have started in Alaska “Data from the National Oceanic and Atmospheric Administration’s Barrow station indicate that October through December emissions of CO2 from surrounding tundra increased by 73% since 1975, supporting the view that rising temperatures have made Arctic ecosystems a net source of CO2”[xvii]. The same earlier-than-expected thawing is being seen in Northwest Canada[xviii].

Another study estimates that the deeper levels of soil will increase CO2 emissions faster than expected in response to higher temperatures, “Soil organic carbon harbors three times as much carbon as Earth’s atmosphere, and its decomposition is a potentially large climate change feedback and major source of uncertainty in climate projections. The response of whole-soil profiles to warming has not been tested in situ. In this deep warming experiment in mineral soil, CO2 production from all soil depths increased significantly with 4°C warming—annual soil respiration increased by 34-37%. All depths responded to warming with similar temperature sensitivities, driven by decomposition of decadal-aged carbon. Whole-soil warming reveals a larger soil respiration response than many in situ experiments, most of which only warm the surface soil, and models.”[xix]

Hopes For The Next UN IPCC Assessment Report (number 6)?

The policy-making community, including NGOs, seems to treat the latest UN IPCC estimates as the “gold standard” until the next assessment report comes out. The problem with this is two-fold. Firstly, the science in the assessments tends to be quite outdated given the many years required to produce an assessment, and it is open to a general bias toward the “politically acceptable”. The ongoing abuse of climate scientists has also certainly increased the inherent conservativeness of the scientific process. Secondly, many years separate one report from another. The last one, AR5, came out in 2014. The next one, AR6, is coming out in 2022. This means that until 2022, the policy-making community will be relying on an extremely conservative view of the state of climate science prior to 2010.

It will be another 5 years until the “gold standard” will be updated to reflect the current state of climate science, which invalidates many of the assumptions used in the previous assessment report. It may very well be true by then that it has become apparent even to the UN IPCC that the carbon budget does not exist and that a climate paradigm shift is required. Or perhaps the writers of the report will find new ways to dodge that message; reducing probabilities from 66% to 50%, even greater reliance on future carbon capture technologies, perhaps even a hint of climate modification? We will have to wait until 2022 to see, and another 5 years worth of anthropogenic GHG emissions.

Given the speed at which new scientific insights, and real-world events, are moving the UN IPCC process is simply not up to the job of providing timely inputs into policy-making. Other avenues must be found that speed up the interactions between the scientific and policy-making communities, and accept that there will always be a level of uncertainty in such processes. The political complexities of managing such changing inputs will be considerable, given society’s general expectations for relative certainty. Given what is at stake though, that challenge must be faced up to. Otherwise, society runs the risk of being left behind by the Earth as it awaits the next status update.


[i] Michael Le Page (2017), Global greening may soak up less carbon dioxide than projected, New Scientists. Accessible at

[ii] Elizabeth Hardball (2014), As Carbon Dioxide Grows, Tropical Trees Do Not, Scientific American. Accessible at

[iii] Matthew Haworth et. al. (2017), Has the Impact of Rising CO2 on Plants been Exaggerated by Meta-Analysis of Free Air CO2Enrichment Studies?, frontiers in Plant Science. Accessible at

[iv] NASA (2017), NASA-MIT Study Evaluates Efficiency of Oceans as Heat Sink, Atmospheric Gases Sponge, NASA. Accessible at

[v] Takamitsu Ito et. al. (2017), Upper ocean O2 trends: 1958–2015, Geophysical Research Letters. Accessible at

[vi] Lijing Cheng et. al. (2017), Improved estimates of ocean heat content from 1960 to 2015, Science Advances. Accessible at

[vii] Sabine Mathesius et. al. (2015), Long-term response of oceans to CO2 removal from the atmosphere, Nature Climate Change. Accessible at

[viii] Henrique O. Sawakuchi et. al. (2017), Carbon Dioxide Emissions along the Lower Amazon River, frontiers in Marine Science. Accessible at

[ix] Frontiers (2017), Study finds Amazon River carbon dioxide emissions nearly balance terrestrial uptake, Accessible at

[x] University of Exeter (2017), Warming ponds could accelerate climate change, Accessible at

[xi] Brian Kahn (2017), These NASA Images Show Siberia Burning Up, Climate Central. Accessible at

[xii] Brian Kahn (2017), These NASA Images Show Siberia Burning Up, Climate Central. Accessible at

[xiii] Le Page Y. et. al. (2017), Synergy between land use and climate change increases future fire risk in Amazon forests, Earth System Dynamics Discussions. Accessible at

[xiv] Richard Schiffman (2017), Amazon rainforest under threat as Brazil tears up protections, New Scientist. Accessible at

[xv] Caroline B. Alden et. al. (2016), Regional atmospheric CO2 inversion reveals seasonal and geographic differences in Amazon net biome exchange, Global Change Biology. Accessible at

[xvi] Carolina Voigt et. al. (2017), Increased nitrous oxide emissions from Arctic peatlands after permafrost thaw, Proceedings of the National Academy of Sciences. Accessible at

[xvii] Roisin Commane et. al. (2017), Carbon dioxide sources from Alaska driven by increasing early winter respiration from Arctic tundra, Proceedings of the National Academy of Sciences. Accessible at

[xviii] Steven V. Kokelj (2017), Climate-driven thaw of permafrost preserved glacial landscapes, northwestern Canada, Geology. Accessible at

[xix] Caitlin E. Hicks Pries et. al. (2017), The whole-soil carbon flux in response to warming, Science. Accessible at


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2 Responses to The Evidence Against The Existence of A Positive Carbon Budget Continues to Mount

  1. Joe says:

    All very plausible, but there are other feedbacks not mentioned, such as the negative feedback of boreal forest expansion and the positive feedback of arctic methane clathrate thawing. The intricacies of the carbon cycle may be too complex to fully model and understand, but the final result is easy to see, increasing atmospheric CO2. Since that indicator is already well into dangerous territory, one could easily claim that the 'budget' has already been busted and the only thing to do is reduce carbon emissions to zero immediately and then go negative.

    Of course such a thing will never happen voluntarily, since it would mean collapsing economies and mass famine. Our only slim hope for a livable climate is an involuntary economic collapse very soon. We still get the mass famine, but at least the Keeling Curve would stop rising. Whether even that would be enough to keep natural positive feedbacks at bay remains to be seen.

    • rboyd says:


      Its hard to keep track of all the positive feedbacks, each week it seems some paper identifies another one. Fundamentally the climate "safe zone" is a very restricted one, and I tend to agree with Hansen that 350 was the safe zone. We are already into the Pliocene scenario given the CO2 levels and temperature, and changing things at a rate 1000's of times faster than natural processes have in the past.

      Even with an economic crash, with emissions perhaps dropping 20%-30%+, CO2 concentrations will keep rising. We will also suddenly get a lot less dimming from sulfate aerosols. At the same time the focus would go toward dealing with the crash rather than with the climate.

      I think that we will most probably end up trying whatever scheme (geo-engineering, sucking carbon out of the air ...) is possible in an attempt to get back to/stay within the safe zone. Whether we will be successful or not does remain to be seen.

      At some point there will be the "paradigm shift" on the level of urgency with respect to climate change, but may very well be too late no matter what we try.


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