Plowing Under a Carbon-fixing Crop

The common criticism of ocean fertilization by upwelling nutrients from the depths is that it also brings up CO2 from the depths. If one does not explore the issue more fully, it makes one think that upwelling nutrients is counterproductive.

Things look different if one uses push-pump pumps rather than simply upwelling of nutrients. Some of you may recall this argument from my GLOBAL FEVER book from the Univ of Chicago Press, but the following is an excerpt from my more recent THE GREAT CO2 CLEANUP, chapter six:

To avoid competing with the world’s food production and supplies of fresh water, most sequestered carbon must come from new biomass grown in new places. Here I explore how paired ocean pumps might uplift nutrients and then sink the new organic carbon back into the ocean depths.

Instead of sinking only the debris that is heavy enough to settle out, as in iron fertilization, we would be using bulk flow to sink the entire organic carbon soup of the wind-mixed layer (organisms plus the hundred-fold larger amounts of dissolved organic carbon) before its carbon reverts to CO2 and equilibrates with the atmosphere.
        The CO2 later produced in the depths by the sunken carbon soup will reach the surface 400-6,000 years later. Smearing it out over that period greatly reduces the damaging peaks in ocean acidification and global fever.
...If we fertilize via pumping up and sink nearby via bulk flow (a push-pull pump), we are essentially burying a carbon-fixing crop, much as farmers plow under a nitrogen-fixing cover crop of legumes to fertilize the soil. Instead of sinking only the debris that is heavy enough, we would be sinking the entire organic carbon soup of the wind-mixed layer. 

        Algaculture minimizes respiration CO2 from higher up the food chain and so allows a preliminary estimate of the size of our undertaking. Suppose that a midrange 50 g (as dry weight) of algae can be grown each day under a square meter of sunlit surface, and that half is carbon. Thus it takes about 10-4 m2 to grow 1 gC each year. To produce our 30 GtC/yr drawdown would require 30 x 10¹¹ m² (0.8% of the ocean surface, about the size of the Caribbean).

        But because we pump the surface waters down, not dried algae, we would also be sinking the entire organic carbon soup of the wind-mixed surface layer: the carbon in living cells plus the hundred-fold larger amounts in the surface DOC. Thus the plankton plantations might require only 30 x 10⁹ m² (closer to the size of Lake Michigan). 

        The space requirement will be more because downpumps will not capture all of the new plankton; it might be less because the relevant algaculture focuses on oil-containing algal species and on harvesting a biofuel crop, not on plowing under the local species as quickly as possible. The ocean pipe spacing, and the volume pumped down, will depend on the outflow needed to optimize the organic carbon production. [The chemostat calculation FYI.] Only field trials are likely to provide a better estimate for the needed size of sink-on-the-spot plankton plantations, pump numbers, and project costs. Though ocean fertilization is usually proposed for low productivity regions where iron is the limiting nutrient, another strategy is to boost the shoulder seasons in regions of seasonally high ocean productivity. For example, ocean primary productivity northeast of Iceland drops to half by June as the nutrients upwelled by winter winds are depleted. Continuing production then depends on recycling nutrients within the wind-mixed layer. However, to the southwest of Iceland, productivity stays high all summer.

       Because not all of the new plankton will be successfully captured and sunk, fertilization will stimulate the marine food chain locally. Most major fisheries have declined in recent decades and, even where sustainable harvesting is practiced, it still results in fish biomass 73% below natural levels. At least for fish of harvestable size, there is niche space going unused.

       Locating the new plankton plantations over the outer continental shelves is more likely to supply a complete niche for many fish species, whereas deep-water plantations will lack variety. (The main commercial catch in deep water is tuna.) Also, down-pumping near the shelf edge would deposit the organic carbon in the bottom’s offshore “undertow” stream, carrying it over the cliff onto the Continental Slope into deeper ocean.

        Note that pumps would be tethered to the bottom so that the ocean currents are always creating a plume downstream: a plume of fertilizer near the surface and a second plume of carbon soup in the depths. (Pumping up from a different depth than pumping down will prevent the interaction that characterizes the oceanographers’ box models.) While the water might come back around in a thousand years, the plumes for the clean-up will only be about twenty years long and well diluted by that time.

The Emergency Cleanup of Excess CO2 via a Second Manhattan Project

Briefly: Pull up sunken nutrients to create CO₂-capturing plankton blooms, then push new organic carbon into the ocean depths before it reverts to CO₂. This push-pull pump avoids many of the problems of up-only pumps for fertilizing the ocean surface.

Suppose our CO₂-based overheating became an emergency via abruptly rearranging the winds—say, a supersized El Nino that doesn’t quit? More emissions reduction would be too little, too late—nor would it fix ocean acidification.

   An emergency drawdown of atmospheric CO₂ would address all three issues—but it would need to be big, quick, and sure-fire.

   How big? Aim at removing all 350+ GtC emitted since 1750.

   How quickly? We must back out of the danger zone before being weakened by resource wars and economic collapse. During a 20 yr project period, another 250 GtC are likely be emitted from business-as-usual, so make that goal 600 GtC. That's 30 GtC/yr. Once the drawdown is complete, half of the sequestration capacity might still be needed to continuously counter out-of-control emissions from developing countries; the rest goes on standby for future emergencies.

   Sure to work the first time? With no second chance, our initiative needs to be sure-fire, since we must avoid the human population crash that a global economic collapse would trigger.

   Most candidates suitable for long-run improvements will be too small, too slow, or too uncertain for an emergency. Even fertilizing the ocean surface enough to settle out 30 GtC/yr of the usual debris into the depths would require an unachievable 3x increase in ocean productivity worldwide.

The proposed push-pull pump plantations need less than 1% of the ocean surface. Pump up nutrients from the depths to enhance plankton production (what winter winds do)—but with an essential addition.

Simultaneously, emulate the natural downwellings of eddies and whirlpools. Pump down the carbon-enriched surface waters within a week, before the new organic carbon reverts to CO₂. This also sinks the 240x larger amounts of organic carbon from feces and decomposition, which are dissolved in surface waters. This sinks far more organic carbon than is needed to offset any upwelled CO2.

A plankton plantation that uses windmill power. 

Wave-powered pumps should be more economical.

   Just as farmers grow a nitrogen-fixing crop of legumes and then plow it under, we would be growing a carbon-fixing crop of plankton and then pumping it under.

   This simplified sketch shows the ballpark in which we are forced to play. Charge the experts gathered for the Second Manhattan Project with deploying this or something equally big, quick, and sure-fire within four years using wartime priorities. If nothing major intervenes in the following ten years, the climate threat might be cut in half.

This latest version of the CO2 cleanup was a finalist in MIT's 2013 geoengineering climate contest.

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William H. Calvin is a professor emeritus at the University of Washington’s medical school in Seattle and the author of Global Fever: How to Treat Climate Change  (University of Chicago Press, 2008). 

September 2014    WCalvin@UW.edu      faculty.washington.edu/wcalvin

The Important Warming Isn't Global

Yes, the world is overheating. Yes, that tends to cause climate change in ways that go beyond hotter afternoons--say, the widening of the tropics, the desertification of the Mediterranean, and more extreme weather.

One would think (irony alert) that the best way to summarize the climate threat is to average the near-surface temperature 1) over day and night, 2) over all four seasons, and 3) over both ocean surface and land surface.

There is fifty years of tradition in producing the annual number this very way. This globally averaged annual surface temperature, once we subtract what it was back in the good old days, is known as "global warming."

"Global" warming is global only in the sense of including both ocean surface and land surface, not in the sense of incorporating everything. It leaves out the air blanket above your head and the ocean depths, both major places where the excess heat has been stashed. Global is just what you see on a globe—and thus a somewhat misleading use of the term.

Since there is twice as much ocean surface as there is land, the land warming only counts half as much as the ocean surface warming when calculating "global" warming. Most of us live on land and so this global average number underestimates what we experience.

We now have a half-century of experience summarizing the growing climate problem via this unnatural number. Logical as it seemed fifty years ago when introduced to track the planet's heat budget (and it is still very useful for that), it has turned out to only roughly track climate changes.

Furthermore, this unfortunate choice of terminology has generated endless confusion among nonscientists, eagerly exploited by promoters of "unfettered business as usual" who seek to delay climate action by prolonging our confusion.

Then there is that word "warming," another somewhat misleading term. It has sounded cozy to some people. "Warming" just doesn't imply an excess in the way that "overheating" does.

Some have wondered, not unreasonably, how an unusually cold winter could be consistent with a general warming. Or how there could be a pause in "global warming" while the CO2 concentration keeps rising. The climate scientists have perfectly good answers to these concerns, but they tend not to be heard—in about the same way as corrections to yesterday's news articles tend not to be read.

It has become increasingly apparent over the last fifteen years that we can have a lot of climate change, and a lot of CO2 increase, without much trend in that "global warming" number. We had a similar period from 1950 (when Popular Mechanics had a nice article on global warming) until 1977. It didn't seem to be globally warming at all, despite a lot of additional CO2 accumulation from the soaring post-war emissions.

The climate system has a lot of sectors; sometimes, cooling influences can temporarily counter the extra heating of greenhouse gases. More clouds or greater ocean downwelling could do it.

Just as a map is not the terrain, an index is often not where the action is. An analogy: the Dow-Jones Industrial Average, "The DJI," tends to underestimate what is happening in tech stocks. "The market" may go nowhere while some market sectors are thriving. 

Is something like that happening to our index of what alters climate? However useful the global average overheating may be for working out the heat budget and finding hidden sinks, is there a better index for drivers of climate change than just averaging over oceans and continents?

It is certainly worth looking for one. The two major topics at all three climate science conferences that I attended in a ten-day period in September were the Arctic Amplification and, separately, the so-called "hiatus" in global warming of the last ten years. During the third meeting, one possibility occurred to me: Don't add. Subtract.

Subtracting Arctic temperature from continental land temperature would have helped understand Arctic Amplification, prolonged heat waves, and those frigid "Arctic outbreaks."

Subtracting ocean temperature from land temperature would have been a better idea than adding them. That's important because the extra heating warms the land twice as fast as it does the ocean surface. That has consequences.

So let's talk about movers of climate change rather than the usual statistical abstractions. As is well known from monsoons, hot land heats the air just above the surface, causing it to rise, which sucks in cooler moist air from offshore.

It's just like the draw of the fireplace. This "sea breeze" peaks in the late afternoon and helps sailors get home in time for supper. Suppose climate change is strengthening the sea breeze?

So rather than adding together two parts ocean to one part land, subtract ocean from land. Compare that to what it was in the good old days. Call it enhanced coastal contrast if you like.

Think of it as a rough index of what should strengthen the moist onshore winds. That's already an improvement over that weighted sum of land and ocean temperatures which, to nonscientists, mostly suggests warmer afternoons and the need for more air conditioning.

[It's not as if atmospheric scientists don't already create climate indices based on regional differences. A pre-overheating classic is the North Atlantic Oscillation ("NAO"), which subtracts the air pressure at Iceland in the north from the higher pressure at the Azores in the south. When the difference is big (NAO+), the storm tracks often take a left turn into Europe. When the pressure difference becomes less pronounced (NAO-), the Atlantic storm tracks deliver the rain to the Mediterranean rather than Europe. Once shifted, it tends to stay that way for a decade or more, enabling predictions about winter storm tracks.]

Subtraction's focus on stronger onshore winds also helps us think in terms of rainfall, or its lack. But a stronger wind need not follow the customary path and may well deliver its moisture somewhere else. Result? Some places will get unexpected rain, others will lack enough.

Flood here, drought there, and who knows when? This generality tells us quite a lot about what’s ahead. Even minor rearrangements in wind can produce trouble. Change the month when the rains arrive and fields that supported two crops each year may only support one, cutting food yield in half. Note that no change in the annual rainfall is required for trouble—nor does it take extreme weather, as when prolonged heat waves bake all of the water out of the topsoil and the plants collapse.

Were a new pattern of moisture delivery to stick around for decades, we might slowly adapt. But no. That’s because the watery laggard in the global warming race just keeps falling further behind the continents with the years, thanks to all of that evaporative cooling of the ocean surface, its greater heat capacity, and the way surface waters are flushed into the depths in a few places. And so the continent's winds keep changing around unpredictably. That's a recipe for even more climate chaos.


As long as “Hot-Spot Temperature” keeps increasing its lead over “Sea Surface Temperature” in this horse race to Hell, the strengthening temperature contrast across coastlines can strengthen the moisture-laden winds coming off the ocean and thus change where the rain falls (or doesn't).

Welcome to climate instability, where all bets are off when recent history doesn't help you decide what to plant where.

William H. Calvin is a professor emeritus at the University of Washington’s medical school in Seattle and the author of Global Fever: How to Treat Climate Change (University of Chicago Press, 2008). The latest version of the CO2 cleanup was a finalist in MIT's 2013 geoengineering climate contest.

 October 2014 WCalvin@UW.edu faculty.washington.edu/wcalvin