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A K-Brief (aka. Knowledge Brief) is a series of visual models, each with an explanation that ties them together into a cohesive story that as briefly as possible explains what experts need to know to be able to contribute their knowledge to improve the K-Brief.


Will Achieving Net Zero CO2 Emissions Stop Global Warming at <1.5°C as Expected?

LAST EDITED:  2024-05-21 13:43

ABSTRACT:  The answer to the question above is widely assumed to be "yes", so we're focusing on achieving Net Zero CO2 Emissions; but if CO2 Emissions are not the sole (or at least overwhelmingly dominant) cause of global warming, then the answer will be "no"; if so, we need to learn that now! We are not at all disputing (or supporting) the correlations between CO2 Emissions and global warming, we just accept the IPCC correlations as given; rather, we point out that correlations do not imply causation, and assuming they do can lead to very faulty predictions. As an example of where that assumption is almost surely wrong, this K-Brief will focus on some particular causal paths related to the decline of the ocean's plankton populations that began over 130 years ago, long before the CO2 Emissions-induced global warming, and thus far more likely cause of global warming than effect of global warming.  Thus, to stop global warming, our priorities may need to include restoring our ocean's plankton populations. (As well as further causal analysis, moving beyond just correlations.) And in any case, if we don't stop the decline of the ocean's plankton populations, the ocean food chain will collapse (whether we achieve net-zero CO2 emissions or not), and those mass extinctions will be irreversible and devastating to human welfare.

Background: The Urgent Need for Clarity

We all know that correlation does not imply causation.  And there are numerous examples where assuming it does has resulted in very bad decisions. So, whenever causation is being concluded based on correlation, it is critically important to consider alternate causal models that could be consistent with that correlated data, and then find ways to test or otherwise determine which of the causal models is correct, before settling on a set of decisions based on any one of the causal models, OR to find a set of decisions that work fine regardless of which causal model is correct (such that we know "success is assured" in any case).

We have that situation with the IPCC reports through 2023.  Let us explain…

The IPCC reports show very strong correlations between industrialization activity, carbon dioxide and other greenhouse gas (GHG) emissions from that activity, carbon dioxide and other GHG concentrations in the atmosphere, and global warming. [source: IPCC AR6 SYR Fig 2.1abc]

And on the causal side, we know industrialization has come with the burning of fossil fuels and other activities that absolutely cause some level of increased carbon dioxide in the atmosphere.  And we know carbon dioxide is a greenhouse gas, and thus that increased concentrations of it in the atmosphere will cause some level of global warming.  And finally, we know global warming can cause to some degree the various negative effects that we have correlations on.


So, great, we indeed have both correlations and this causal model to go with it.

LEAD:  Brian Kennedy and the TCC Team

Given that, the IPCC reports predict very strong correlations between different future carbon dioxide emissions scenarios, global warming, and some of the expected effects of global warming.  [source: IPCC AR6 SYR Box 2 Fig 1]

Problem Description

However, we do not yet have a precise enough mathematical model of the cause & effect that we can precisely compute the correlation data. Therefore, we cannot assert that those are the ONLY causes or even the dominant causes of those correlations. So, the following expanded causal model is also possibly true, given those same correlation numbers.


In fact, this model is almost surely more likely than the simpler one above, as we know of numerous other human activities that have ramped up in the same time period (with likely similar correlations) that will also causally contribute to global warming and will also contribute to the impacts of global warming.  For example, other forms of pollution, toxins, microplastics, and so on.

Will Achieving Net Zero CO2 Emissions Stop Global Warming at <1.5°C as Expected? We are currently assuming the answer is "yes" and thus focusing on achieving Net Zero; but if CO2 Emissions are not the sole (or at least overwhelmingly dominant) cause of global warming, then the answer will be "no". We can wait until 2050 to see if achieving Net Zero does indeed result in the expected halt of global warming. But if it does not, then we will have lost 25+ years in the fight against global warming. We need to answer that question now, such that if the answer is likely "no", then we can appropriately expand our focus to cover enough drivers of global warming that "success is assured" -- we cannot afford to be wrong -- we may not get a second chance. [source of figure: IPCC AR6 SYR Fig 3.6]

Why does this matter? Because without knowing the level of contribution of each of the multiple causes, it could be the case that we achieve Net Zero CO2 Emissions, but find that we have only slightly reduced the trajectory of global warming and/or the other negative impacts.  Achieving all our Net Zero goals by 2050, but still being > 2°C warmer would be disastrous:  we don’t want to realize in 2050 that we have lost 25+ years in the battle against global warming by failing to explore the other potential causes of global warming!  That could be catastrophic for us.

The remainder of this knowledge brief will not try to enumerate all other possible causal models.  That effort should be undertaken, but is beyond the scope of this K-Brief.  Rather, the remainder of this K-Brief will focus on just three very-likely additional causal chains to the above causal model and will present a justification that they certainly exist in high enough quantities that they are at least as important as the IPCC causal chain. And then it will expand on that to show other direct impacts that are far more urgent than global warming and will have far more dire effects than global warming during this century, and thus need more urgent focus than they have been getting to-date.

And for those who wish we addressed a lot more alternatives in this K-Brief, please consider that the alternatives examined by this K-Brief can be used as examples to help justify that larger effort to enumerate all possible causal models that could explain the correlative data, which (as mentioned above) should be undertaken.

An Even Bigger Cause of Climate Change May Exist

In the last 70 years, the populations of plankton in our oceans have been cut by half or more by a combination of over-fishing of our oceans and the dumping of human pollution, particularly microplastics, into our oceans, along with temperature increases. Looking at historical chlorophyll measurements, one estimate is that we have been losing 1% of the median global plankton biomass each year since 1899.  [DG Boyce, MR Lewis, B Worm, Global phytoplankton decline over the past century, Nature v 466, July 2010]  More recently, analysis of long-term time series data from Narragansett Bay, RI, has revealed that phytoplankton biomass declined 49% from 1963 to 2019. [PS Thibodeau, G Puggioni, J Strock, TA Rynearson, Long-Term declines in chlorophyll a and variable phenology revealed by a 60-year estuarine plankton time series, PNAS v121 (21), May 2024]


With that half-sized plankton biomass that we have today, the IPCC estimates that the oceans are consuming comparable CO2 as the forests. With that plankton biomass restored to 1950's levels, the oceans would be consuming double that. And note that in the cases of lower emissions, that additional 35% would be more than enough to consume the rest of those human emissions! Restored to 1899 levels, it would be dramatically more.  [source of figure: IPCC AR6 WGI SPM Fig SPM.7]

Oceans cover 71% of the surface of the planet; and forest lands only cover a fraction of the rest. Thus, the potential CO2 consumption by phytoplankton could dwarf the consumption by all our forests combined. Further, unlike the forests where the dying trees tend to release their carbon back into the environment, the dying plankton and fish tend to fall to the ocean floor where the carbon remains trapped for thousands of years.

Thus, if we had IPCC-quality historical numbers on the orange causal chain below (like we do for the blue causal chain), it could very well be that the orange causal change is at least as big, if not much greater, a contributor to the global warming to-date.  And thus achieving Net Zero CO2 Emissions, but doing nothing about the causes of declining plankton, may still result in substantial additional global warming.

(Note: we dig into the many causes of the declining plankton populations (the two cloud shapes below) in a separate K-Brief. See that for deeper understanding of what's driving the plankton declines.)

Unfortunately, the IPCC has not  yet studied that orange causal path, so we do not have numbers that have the same level of reliability as the blue path. However, by building on the IPCC chart above showing the Total Cumulative Emissions Taken Up By Land and Ocean with the following IPCC chart showing the Global Surface Temperature Increase due to those Total Cumulative Emissions, we can estimate the size of the impact that the declining plankton would have on that global warming level.  [source: IPCC AR6 WGI SPM Fig SPM.10]

Given we have been losing 1% of the median global plankton biomass each year since 1899, then we can compute how much more carbon uptake by the ocean should have happened during that period, and thus how much more CO2 entered the atmosphere to-date and will enter the atmosphere by 2050.

Given there may be debate on how much plankton biomass has been lost, and debate on how much additional carbon sequestering it would have done, and on the relative timing of that, we have charted Global Surface Temperature Increase versus the Reduced CO2 Sink Due to Plankton Decline from 0% to 2% per year. You can then choose the ranges of that which you think likely, and focus on that portion of the chart.

So, 0% (left edge of the chart) matches the IPCC expectations for the temperature increase for each SSP scenario; the middle of the chart (1%/a) is what would be expected if the best estimates of plankton population decline and its carbon consumption are accurate, and only started in 1899 (when the measurements started). If you assume they started in 1850, consistent with the IPCC base, then you'd want to look somewhat further right in the chart (or if you believe the plankton impacts are higher for other reasons). Note that the global warming gets significantly higher than the IPCC predictions with any non-trivial levels of that orange causal path added into the modeling.

As further justification of the knowledge gap that exists here, consider the following chart from the Global Carbon Project 2020. Note that there is a substantial carbon sink that is unaccounted for and is an area of active research. Now consider that the ocean phytoplankton has been steadily declining by 1% every year since the 1800's, so it would be logical that the ocean sink has been steadily declining; but note that the ocean sink is shown steadily (but slowly) increasing during that period. It could very well be that the ocean sink was indeed much larger than shown, and in fact there should be another source similar to "Land-use change" shown: "Ocean change" representing the decline of the ocean food chain due to human-caused shifts in nutrients, over-fishing, and toxic dumping into the oceans. [source: Friedlingstein, et al, Global Carbon Budget 2020]


The IPCC should not wait for its next 7 year cycle to study and properly characterize the role of the declining ocean plankton on carbon sequestering and therefore on global warming.  A focused and accelerated study needs to be done, establishing similar scientific consensus on the level of that role, and what beyond achieving Net Zero CO2 Emissions (as currently defined, without restoring the plankton populations) will be necessary to keep global warming below 1.5°C.

Or better yet, we need to move beyond such correlative studies to causal experimentation to determine how much plankton causes how much carbon sequestering, and how much carbon sequestering reduces how much global warming. Without having causal numbers (rather than merely correlative numbers), there is tremendous risk that we will not be making optimal (or even wise) decisions about what needs to be done to fully address global warming and the other negative impacts.

For good reason, the IPCC has warned us that some of the negative effects of global warming can, in turn, cause more global warming, which could potentially lead to positive feedback loops forming, and that could result in run-away global warming. That is a big part of the incentive to keep global warming under 1.5°C, since the IPCC believes we have not yet reached run-away levels of such positive feedback loops.

For example, we know that global warming will increase ocean surface temperatures, and increased ocean surface temperatures will result in more evaporation, which will result in more water vapor (which is 75% of our greenhouse gases), and thus more global warming. Such positive feedback loops certainly have an amplifying effect on the direct causes of global warming (the "forcing" causes).  However, such a positive feedback loop, if large enough in effect, could result in run-away warming!

A Bigger Positive Feedback Loop May Have Emerged

Note however that the orange causal path added in the previous section will reinforce this positive feedback loop!  The reduced plankton populations have a profound effect on the Surface Microlayer (SML) of the ocean that reduces the amount of evaporation off of the surfaces of the oceans (which account for 86% of the evaporation feeding that 75% of greenhouse gases).

And indeed, with the continued decline of plankton, we do see, starting in the late 1970's, increased evaporation off the oceans and concurrently accelerating rates of global warming, beyond what was expected given the continued rates of human emissions. How much of that is due to which of the causes is not known with any certainty.  [source of the chart: L Yu, Global Variations in Oceanic Evaporation (1958–2005): The Role of the Changing Wind Speed, J. Climate, v20 pp 5376-5390, Nov 2007]

The most recent IPCC report notes that the high risk impacts seem to be occurring at lower global warming levels than previously anticipated.  [source: IPCC AR6 SYR Fig 3.3a]

It could be that this pink causal path is already becoming a larger causal path than the orange and blue paths, at which point achieving Net Zero CO2 Emissions may result in no apparent reductions in global warming at all -- the positive feedback loop, reinforced by the declining plankton, could take over as the dominant cause of global warming!


Unfortunately, the IPCC has not yet studied that pink causal path, so again we do not have numbers that have the same level of reliability as the blue path. However, we do have the growing effects since the late 1970's as evidence that those numbers are large, at least comparable in impact to the blue path.


So, to make visual the ranges of the potential effects, we expanded our prior chart to show lines for different levels of increased evaporation from 0 to 5% per 1%/a decline in plankton, which corresponds to the increased levels shown in the evaporation chart above. There is much uncertainty in our computations there, but you can choose what % levels that you think reasonable to look at, and focus on those.


In any case, this shows global warming could be significantly higher than 1.5°C despite achieving Net Zero CO2 Emissions by 2050 (purple lines) if we do nothing about either the orange or pink causal paths.


Again, the IPCC should not wait for its next 7 year cycle to study and properly characterize the role of the declining ocean plankton on the SML and its role in reducing evaporation and therefore on global warming.  A focused and accelerated study needs to be done, establishing similar scientific consensus on the level of that role, and what beyond achieving Net Zero CO2 Emissions will be necessary to keep global warming below 1.5°C (or even lower if that positive feedback loop has already been established -- another knowledge gap that needs to be firmly closed as soon as possible such that we can establish that "success is assured").

Further, given 86% of the evaporation is from the oceans (which cover 71% of our planet surface), which feeds 75% of our greenhouse gases, boosting our plankton populations in the current High-Nutrient Low-Chlorophyll (HNLC) regions of the oceans to both increase carbon sequestering and to reduce evaporation could potentially reverse some or all of the global warming to-date.  The IPCC should encourage extension of our climate models to incorporate those effects, and use that to study the viability of that potential solution to global warming.

Side Note: Water Vapor as a Forcing GHG?

The IPCC reports often seem to ignore water vapor in their data on greenhouse gases (GHGs), which can seem surprising given water vapor is the dominant GHG in our atmosphere. The reason for this is that increased human emissions of water vapor tend to be inconsequential given more water vapor in the air will tend to reduce the evaporation off the oceans, which dwarfs any amount of water vapor produced by humans. Most climate models show relative humidity to remain quite stable. Thus, the oceans tend to naturally balance out any changes in water vapor directly emitted by human activity.  Thus, water vapor tends to be ignored as just a feedback effect amplifying the issue with the other GHGs which are considered the "forcing" GHGs.


However, that is ignoring that human activities (other than GHG emissions) may be changing our oceans and thereby changing the evaporation off of our oceans. If other human activities (e.g., toxins or microplastics dumped into the oceans) change that water vapor balancing effect of our oceans, then water vapor does indeed become a "forcing GHG" and no longer can be ignored as just an amplifying effect of the other GHGs. And as the dominant GHG, small percentage changes in the evaporation off the oceans and thus water vapor in the atmosphere can potentially dwarf the other GHG changes. Ignoring that can lead to very poor predictions and thus very poor decision-making.

Yet Another Cause of Global Warming: Reduced Cloud Cover?

Note that the impact of cloud cover on global warming is inherently complex. The additional water vapor in those clouds is a strong GHG, absorbing long-wave radiation; but, cloud cover is also reflective of incoming short-wave radiation, reducing the radiation reaching the earth. Most models show cloud cover as having a net negative warming (a net cooling) effect. So, reduced cloud cover could be another source of global warming.


Surprisingly, although reduced phytoplankton increases evaporation off the surface of the oceans, it at the same time reduces cloud formation. So, a double warming effect. How does it do that?


The reduced plankton populations have a profound effect on the Secondary Marine Aerosols (SMA) produced by the ocean, which have been shown to be the dominant driver of cloud formation over the oceans. Causal laboratory experiments have shown that cloud formation is enhanced over phytoplankton blooms. The details of the biological impact of the phytoplankton on the biology present in the SMA and cloud formation is still being worked out, but the significance of the effect is clear.  [source: KJ Mayer, X Wang, et al, Secondary marine aerosol plays a dominant role over primary sea spray aerosol in cloud formation, ACS Cent. Sci. 2020, 6, 2259-2266]


Other studies have shown that the phytoplankton impacts on the surface microlayer and the SMA result in increased cloud condensation nuclei (CCN), which in turn significantly reduce the effective radius of the cloud droplets and increase (e.g., double) the cloud droplet number concentration (CDNC), which in turn increase the cloud albedo (reflectivity) and the cloud lifetime as the larger number of small droplets take longer to fall as rain and reflect/refract more light while there. [source: K Sellegri, A Nicosia, et al, Surface ocean microbiota determine cloud precursors, Sci Rep 11(1):281, 2021 Jan 11] [source: K Mansour, M Rinaldi, J Preißler, et al, Phytoplankton Impact on Marine Cloud Microphysical Properties Over the Northeast Atlantic Ocean, J Geophys Res Atmos 127(10):e2021JD036355, 2022 May 27]

Thus, phytoplankton increases the cloud fraction and increases the albedo of the existing and additional cloud cover -- a compounding effect that is currently not accounted for in the climate models.

It has been estimated that a "mere 4% increase in the area of the globe covered by low level stratus clouds would be sufficient to offset the 2-3 °C predicted rise in global temperature". [source: DA Randall, JA Coakley, CW Fairall Jr, RA Kropfli, DH Lenschow, Outlook for research on subtropical marine stratiform clouds, Bull Am Meteorol Soc 65, 1290–1301, 1984]  Alternatively, it has been estimated that a 6% increase in albedo (reflectivity) of the existing marine low clouds would result in similar offset in global temperature. [source: J Latham, P Rasch, C-C Chen, L Kettles, A Gadian, A Gettelman, H Morrison, K Bower, T Choularton, Global temperature stabilization via controlled albedo enhancement of low-level maritime clouds, Phil Trans R Soc A 366, 3969–3987, 2008]

In other words, given the reductions in plankton populations by more than 50% could have easily resulted in either (or both) of those changes to the marine low clouds which currently on average cover 1/3 of the oceans (1/4 of the earth), it is possible that this green causal path has been the source of almost all the global warming experienced to-date. If that is so, then achieving Net Zero CO2 Emissions alone will have almost no impact on global warming.

Human Emissions Reductions might also be Reducing Cloud Cover and Increasing Global Warming

As another example of poorly understood cause & effect leading to poor policy decisions, and as another example of the important role of cloud cover in global warming, consider the recent analyses by James Hansen et al [JE Hansen et al, Global warming in the pipeline, May 2023]. They note that "Earth’s albedo (reflectivity) measured by CERES (Clouds and Earth’s Radiant Energy System) satellite-borne instruments over the 22-years March 2000 to March 2022 reveal a decrease of albedo and thus an increase of absorbed solar energy coinciding with the 2015 change of IMO emission regulations" (which reduced the allowed sulfur in ship emissions to just 0.1%). As a result, they believe that global warming has increased from 0.18°C per decade in the period 1970-2010 to 0.27°C per decade post-2010 (when the ship emissions regulations first went into effect).

Given that dramatic acceleration in global warming due to changes in cloud cover, consider how much of the prior global warming may be due to the century-long declines in plankton, given the effects of plankton on Secondary Marine Aerosols, cloud formation, and cloud albedo.

Hansen et al also note the significant knowledge gaps that exist in the unmeasured levels of aerosols and the poorly understood cause & effect relationships with cloud formation, Earth albedo (reflectivity), and global warming.

First, the magnitude of the impact of cloud formation due to reduced phytoplankton needs to be understood in order to estimate the uncertainty that such may be introducing into our modeling of global warming.  Better understanding that uncertainty will allow proper prioritization of closing the knowledge gaps related to the impacts of cloud cover on global warming. If the uncertainty is small enough, then we can continue to ignore this knowledge gap. If the uncertainty is not small, but the level of impacts of the additional water vapor is large enough, then a focus on restoring the phytoplankton populations will be a priority regardless of the cloud formation impacts, allowing the knowledge gaps to still be ignored. But, if knowing the causal impact of cloud formation on global warming may drive the decision-making, then we may need to get focused on closing those cloud formation knowledge gaps.

Beyond all that, leveraging artificially induced phytoplankton blooms, particularly over the HNLC parts of today's oceans, to increase cloud formation and cloud cover to reduce global warming going forward should be evaluated. That may be a solution for bridging the time delays that are unfortunately likely in achieving Net Zero CO2 Emissions, or for reversing some of the global warming already incurred due to past emissions.

There are existing laboratory efforts working out the true causal impacts of phytoplankton blooms on cloud formation that should be followed and ideally funded to accelerate that learning. And more such controlled experimentation should be conducted to determine the true cause & effect relationships rather than relying on correlative studies.

Side Note: What about the "Near-Linear Relationship" Between CO2 Emissions and Global Warming?

An Even Bigger Problem than Climate Change May Exist

While the reduced plankton populations may be a major cause of global warming, that decline will eventually lead to another problem that may be an even bigger threat to humanity, and far sooner than global warming:  the collapse of the ocean food chain (web)!


Phytoplankton is a huge biomass (comparable to all humanity) that serves as the foundation of the ocean food chain. Zooplankton (also comparable in biomass to all of humanity) feed on the phytoplankton, and most shellfish and fish feed on the plankton (directly or indirectly). So, as the plankton populations decline, so do the fish populations. [source of figure: M Landos, M Lloyd-Smith, J Immig, Aquatic pollutants in oceans and fisheries, International Pollutants Elimination Network (IPEN), April 2021]

The IPCC reports point out the following strong linear correlation between cumulative CO2 emissions and global warming. And based on that, they propose "carbon budgets" that will dictate what level of global warming we will end up with.

This is a classic example of confusing correlation with causation. Q: How could this strong linear correlation not imply that ending the increases in cumulative GHGs will definitively stop global warming?  A: If those emissions are not the sole cause and the other causes just happen to also be linear during that same period of time, then you will have strong linear correlation, but ending the one will NOT cause the other to end. It is not necessarily a strong causal relationship -- correlation does not imply causation.

Consider that during the period from 1899 to present that the pollution of our oceans has been causing the plankton populations to decline at approximately 1% per year.  That is a fairly linear decline in those populations. And so, would be no surprise that it would correlate with linear effects in the orange, pink, and green causal paths, and thus have a linear effect on global warming.

Further, it is not surprising that the pollution of our oceans tracks fairly consistently with the CO2 Emissions, since both are driven by human industrialization and population growth. Thus, any correlation with the one will also be correlation with the other. But that tells you nothing about which has the stronger causal impact. And thus tells you nothing about what effect you'll have if you stop one but not the other.

Given that, achieving Net Zero CO2 Emissions alone, without stopping the decline of the plankton populations, may have limited effect on the rise in global warming. It will change the slope, perhaps; but how much that slope changes due to Net Zero CO2 Emissions alone will depend upon how large the plankton causal paths are relative to the blue direct emissions causal path.  [source of chart: IPCC AR6 WGI SPM Fig SPM.10]

Worse, there are important feedback loops in that food chain.  In particular, the zooplankton dive to avoid predators during the day, and rise to consume the phytoplankton at night. That moves water comparable to the tidal movements due to the moon, and brings the nutrients back to the surface that the phytoplankton need to grow. Thus, human pollution that kills the zooplankton has been shown to result in reduction of the phytoplankton.


When you add in the tremendous level of over-fishing that we do (given the oceans feed a significant portion of the human population) without full understanding of the impacts that fishing may have on the sustainability of that ocean food chain, we have a recipe for disaster.  For example, there is substantial evidence that the modern krill fishing is having dramatic impact on the whole ocean food chain.


Deeper study of the collapse of the ocean food chain may be considered outside the charter of the IPCC, since it is not specifically "Climate Change".  But we have urgent need to establish global scientific consensus on the timeline for the collapse of our ocean food chain.

Existing data and trends certainly put that collapse before 2100, and thus in the same time frames as dangerous levels of global warming. It is possibly that collapse will happen in the next two decades, and so may be even more urgent that global warming. But either way, the loss of the ocean food chain (mass extinctions) will be undoubtedly irreversible, and will directly result in effects at least as large as those feared from global warming (not to mention also contributing to global warming).

Thus, we recommend the IPCC use the significant causal impact of ocean food chain collapse on global warming and other climate change to justify fully including the modeling of the ocean food chain collapse into their analysis efforts.  We do not have time to try to form an IPCC-equivalent focused on the ocean food chain -- and to then make sure its analyses are tied into the Climate Change analyses.

An Even Bigger Problem from CO2 May Soon Exist

One of the negative effects of global warming and increased CO2 concentrations highlighted by the IPCC is the acidification of the oceans. The increased atmospheric CO2 concentration is resulting in higher CO2 concentration in the oceans.  That, in turn, results in declining pH level of the ocean (acidification), which has already dropped from 8.17 in 1940 to 8.03 today. (See the flagged shapes in the Causal Map below.)


Deeper studies of these additional positive feedback loops driven by ocean acidification need to be performed such that we can quantify the causal effects. Without that, it is impossible to assert that global warming will be stopped or even slowed by achieving Net Zero CO2 Emissions alone. In fact, all indications based on the data we do have is that the orange, pink, and green paths already dominate the blue path, and as global warming continues, the positive feedback loops will only increase those orange, pink, and green paths.

All of these knowledge gaps need to be closed as soon as possible such that a concrete plan can be laid out where "success is assured" for halting (or preferably reversing) global warming.

To close these knowledge gaps, continued correlative data analysis of historical numbers is not useful. Rather, we need to perform controlled experiments to determine the relative effects of the different causal paths with adequate precision to drive decision-making. In particular, we need to perform controlled experiments on how much CO2 is sequestered by how much plankton, how much evaporation is reduced by how much plankton, and how much cloud formation is increased by how much plankton. Correlative studies can only point to possible causal effects (or reject causal effects); to understand the causation, you need controlled isolated experimentation that can minimize confounding variables, and determine reasonably precise mathematical cause-and-effect relationships.

As the pH drops below certain levels, it can cause declines or even extinctions of ocean species!  For example, silicate-based diatoms, arguably the most important species of plankton to the ocean food chain (and to carbon sequestering), are very sensitive to pH.  [source: S Trimborn, S Thoms, T Brenneis, JP Heiden, S Beszteri, K Bischof, Two Southern Ocean diatoms are more sensitive to ocean acidification and changes in irradiance than the prymnesiophyte Phaeocystis antarctica, Physiol Plant, 2017, 160(2), 155-70]

The ocean pH predictions by the IPCC of the three higher-emission scenarios have ocean pH dropping to 7.95 in 2045, 2050, and 2055.  [source: IPCC AR6 WGI SPM Fig SPM.8c]

To date, our oceans have been super-saturated in calcite and aragonite, meaning that ocean species with shells made of such won't dissolve. Unfortunately, it is predicted that higher latitude areas of our oceans will become undersaturated as soon as 2030, and much of our oceans may be undersaturated as soon as 2060. In limited testing in sea water with the predicted levels of undersaturation, a species of zooplankton showed significant dissolution of its shell in just 48 hours.  Other testing has shown that various species have more difficulty forming shells at the predicted levels of undersaturation. [source: VJ Fabry, BA Seibel, R Feely, JC Orr, Impacts of ocean acidification on marine fauna and ecosystem processes. ICES J Mar Sci 65, 414–432 (2008)]  More research needs to be done to determine how consistently that is true of calcifying ocean species.  [source of charts: BI McNeil, RJ Matear, Southern ocean acidification: A tipping point at 450-ppm atmospheric CO2, PNAS 105 (48) 18860-18864 (Dec 2008).]

Note that these pH and undersaturation predictions by the IPCC and related scientists are assuming direct human emissions are the dominant source of CO2 increases (just the blue path); but if the reduction of plankton populations (orange path) is also a large contributor, then these IPCC predictions are likely quite optimistic. Given that, hitting pH 7.95 and wider spread undersaturation in 2045 or soon after remains likely, even if we achieve Net Zero CO2 Emissions.


Worse, note that ocean acidification is not merely an effect of global warming if you take into account the orange, pink, and green causal paths that we added in previous sections. Rather, it becomes part of those three causal chains that will further accelerate global warming, including the potentially catastrophic positive feedback loop due to evaporation.


Even worse, acidification establishes an additional positive feedback loop through the orange and green paths, in addition to the pink!

Unlike CO2 Mitigation, It is NOT Enough to Mitigate or Even Stop the Ocean Pollution

CO2 and CH4 are natural parts of our atmosphere, and thus existing elements of our environment will tend to keep them in balance if we humans don't overwhelm those natural systems with our unnatural emissions.

In contrast, microplastics and most of the other toxins that we have been dumping into our oceans are not natural parts of our oceans, will not decay on their own, and there's very little in our ocean that will naturally consume or convert those. Rather, they are just endlessly building up and need to either be cleaned up or otherwise combatted.

Thus, there is a very good chance that we have far more urgent need to be seeking Net Zero Microplastics and Toxins Emissions than Net Zero CO2 Emissions.  (Note: we are not arguing against Net Zero CO2 Emissions -- those efforts should continue -- rather, we are arguing for deep and rapid consideration that we may have more urgent issues that need greater focus.)

To date, the IPCC (and the organizations that support it) have been frustrated by the underwhelming responses to its recommendations. We will argue that the IPCC faces a fundamental marketing problem that is the cause of those underwhelming responses. And we will make a case that re-focusing on these new causal paths can fix that marketing problem.


Note that the IPCC's paths that keep global warming below 1.5°C require immediate action starting in 2020. That has not happened, despite the currently implemented policies being predicted to result in global warming in excess of 3°C.  [source: IPCC AR6 SYR Fig 2.5a]


First, let's look at the stated problem:  our world getting 1.5°C warmer is not scary to most people. In fact, neither is 2°C, or even 3°C. Why not? Because we get that much warmer from morning to afternoon almost every day. The average daily temperatures get that much warmer from winter to spring and then again from spring to summer. Average temperatures for the year vary by more than that year-to-year. And yes, it comes with some negative effects, but also some positive ones. And in any case, we deal with those changing temperatures just fine -- over and over again.


Yes, the IPCC has made a strong case for why people should care by laying out the many negative effects of those temperature changes as climate change (rather than mere weather changes). But they are fighting a steep uphill battle with the focus on that temperature change, given the natural human reaction is that such temperature changes are well-within what we handle all the time.  "We'll deal with it just like we always do" is the natural expectation.  Self-imposing the horrible negative effects of rapidly terminating fossil fuel usage is then hard to justify simply to avoid a few degrees of temperature change that we handle all the time.

The IPCC should turn the focal point from "keep global warming under 1.5°C" to instead "prevent the collapse of the ocean food chain (web) and associated mass extinctions". That is a focus that humans will naturally appreciate the importance of without any need for explanation. Nobody will question whether life on earth will be negatively affected by the loss of the ocean food chain. Widespread human famine is one clear result. Irreversibility of extinctions is another clear result.

Further, there's a lot of people who cherish time at the beach. An ocean cleared of the current ocean food chain will possibly become lifeless, but more likely will become filled with alternate creatures that we did not evolve to eat. In all likelihood, the replacement sea life will be toxic to humans.

As evidence of that, consider the 13Mt mass of sargassum that is twice the width of the continental US that is becoming a toxic problem for the beaches of the Atlantic Ocean as it decomposes, releasing hydrogen sulfide and the associated stench.


Further, the IPCC can lay out the broader impacts on many industries:  tourist areas, cruise lines, shipping industry, boat makers, jet ski makers, surfing, fishing, scuba diving, and so on. People with affinity for any of those particular industries will be extra-motivated to do whatever it takes to prevent those from being destroyed by the collapse of the ocean food chain.

On the Bright Side, an Additional Solution?

Unfortunately, the IPCC has not yet studied the orange, pink, or green causal paths (as causal paths rather than merely effects of global warming), so we do not yet have IPCC-level reliability in the causal impacts of acidification on continued global warming.


We would like to expand our prior chart to show best case and worst case effects of acidification, however there are far too many knowledge gaps to do that in a useful way. In particular, given undersaturation states will likely lead to mass extinctions, there is significant chance that one or more of those positive feedback loops become large enough to cause run-away global warming (which would make the chart irrelevant), not to mention that collapse of the ocean food chain would make global warming the least of our concerns.

While the additional causal paths may render Net Zero CO2 Emissions inadequate to solve global warming, the new causal paths may provide opportunity for additional solutions!


Consider that vast regions of our oceans are currently relatively lifeless, though nutrient-rich (termed High-Nutrient Low-Chlorophyll or HNLC). It is possible for us to fertilize or "seed" those HNLC areas of the ocean and fill them with phytoplankton and zooplankton populations, dramatically increasing carbon sequestering, and notably reducing evaporation and/or increasing cloud formation.


It has been demonstrated that massive phytoplankton blooms can occur in just a few days time. Those sometimes occur naturally due to winds from the deserts fertilizing the oceans with the iron needed. So, we can do similar without stepping into unknown or unnatural territory. Better yet, we can do such experimentally and see the results very quickly and "turn off" those experiments similarly quickly if needed for some reason. There seems to be a huge opportunity here to quickly stop or even reduce global warming.

Given the IPCC has the 11 global climate models of the CMIP6 available to it, which each contain a marine biogeochemical model of the ocean's impact on climate, it would seem we should be able to to quickly evaluate this potential solution. Unfortunately that is not true because those models are correlative rather than causal models.

For example, lacking true causal knowledge of the zooplankton grazing rates on phytoplankton growth, especially as that phytoplankton growth stimulates zooplankton population growth, and further as that zooplankton growth brings nutrients up stimulating more phytoplankton growth, those 11 different models contain dramatically different mathematical models that have simply been tuned to correlate as strongly as possible with recent-past and current global measurements. Due to those very different mathematical models, the resulting tuning parameters used in those different models are dramatically different... by several orders of magnitude. (See the figure below for a visual representation of that variability across those models.)

As a result, such correlative models tend to be near-useless in predicting what will happen if the ocean changes dramatically from the conditions that those models were tuned to correlatively. The further you stray from the past numbers that those correlative models were tuned to, the less accurate they become.  So, evaluating a plan to fertilize or "seed" those HNLC areas of the ocean and fill them with phytoplankton and zooplankton populations (conditions that have not been common in the known recent past, though are likely just restoring those populations closer to pre-industrialization numbers) cannot reasonably be modeled at all using those correlative models.


As evidence of this, Rohr et al varied the tuning parameters of one such marine biogeochemical model by a mere 5% of the variance seen across those 11 CMIP6 climate models to see how big the impact might be.  That resulted in increasing secondary and export production by 5 and 2 PgC/yr!  (See that paper for details on that... link below.)


In other words, well within the variability of the different climate models used by the IPCC, it is entirely possible that we can wholly sequester all human carbon emissions (past and present) by fertilizing the oceans, and at the same time revive and stabilize the ocean food chain. And that can be done quickly at a fraction of the cost necessary to convert all our uses of fossil fuels (which we currently don't even know how to do). Learning the degree to which that solution is viable should be one of humanity's top priorities at this point.

[T Rohr, AJ Richardson, A Lenton, et al, Zooplankton grazing is the largest source of uncertainty for marine carbon cycling in CMIP6 models, Commun Earth Environ 4, 212 (2023).  The figure below is Figure 5 from that paper.]

Not Knowing Causation (Relying on Correlation) Prevents Reliable Predictions

The IPCC/UN desperately need to turn their focus to developing causal models that will allow us to more accurately predict the results of our actions. The correlative models are fine for helping decide what causal models to build; but should not be relied upon to make decisions on the planned solutions that humanity is depending upon being right.

In other words, the correlative models should be used to identify the most critical knowledge gaps that need to be closed to establish that "success is assured", regardless of the uncertainty, if a particular solution is put into action.


In particular, given the apparent potential of the ocean being both the dominant cause of global warming to date and the most achievable solution to global warming going forward, the IPCC/UN should be funding controlled experiments to determine the true cause & effect relationships of fertilization on phytoplankton growth, the circular relationships with zooplankton growth, the resulting carbon sequestering, and the overall impact on global warming considering evaporation and cloud formation effects. We need to move past correlative studies to testing the actual causal relationships.

If the IPCC closes the many knowledge gaps enumerated in this K-Brief, then they will have also built/collected much of the knowledge needed to determine what level of global warming can be impacted by this potential solution, such that we could determine how much of such fertilization or "seeding" would be needed to establish that "success is assured" for stopping or even reversing global warming.

Designing and optimizing a particular cost-effective solution for this fertilization will still need much additional analysis and engineering, but determining whether such a solution can feasibly stop global warming should be established first.  The impact of larger plankton populations on global warming can be modeled without engineering how those plankton populations can most efficiently be grown. Optimizing the fertilization solutions can come after establishing that "success is assured" for such a solution, within the uncertainties that remain after closing those knowledge gaps.

The IPCC has a Marketing Problem (this can help)

Alternative Remedies

This K-Brief is not a static document. It is intended to make visible what we believe we know such that people with expertise in these scientific areas can identify where they can contribute their knowledge and how it should be incorporated into the K-Brief.


The best way to establish scientific consensus is to construct visual models of the causally-sound scientific evidence to facilitate efficient discussion among those with different expertise, such that those experts can see where their knowledge properly connects with the rest.  (The role of this K-Brief is to collect those visual models into a cohesive story for engaging experts in such discussion.)

So, if you have expertise in any area of this K-Brief, and are willing to point out anything that should be corrected or improved in it, please contact us at SaveOurPlanet@TargetedConvergence.Com -- we will continue to evolve this K-Brief accordingly. Similarly, if you believe we should be looking at different charts with different knobs, let us know and we will evolve our models. Our goal is to help facilitate the identification and closing of the knowledge gaps, and thereby accelerate us in the search for more optimal solutions for which we can establish that "success is assured" that our planet will remain safe for humanity.

By following the various Recommendations in order to close the knowledge gaps in the Causal Analysis above, potential remedies to the problem will tend to become apparent. And the Causal Maps will then allow you to explore the different cost-benefit trade-offs in selecting the more desirable of those alternative remedies.

At this time, we have not yet closed those knowledge gaps; and thus, the dominant root causes remain unclear. So, this block remains a placeholder for that future analysis.

However, given the urgency, we do propose a potential partial remedy in this separate Remedy K-Brief. We chose to separate that Remedy out because: (a) it can potentially remedy more than just this Problem; and (b) we don’t want to short-circuit the ongoing analysis of the root causes of this problem, which should remain the focus of this Problem K-Brief.



Call for Expertise and Consensus Building

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