If he traveled in 10- to 15-year hops he could go quite far, I would think. He may have to change locations occasionally; an empty field outside of town isn’t as likely to build up as a vacant lot in an urban area. Nor is it as likely to be as densely traveled in the air as someplace in town.
Marty returns fairly close to a moving train.
“Fairly close” is not the same thing as “co-located”.
But…pendant whine…the algae bloom would prevent the global warming that would cause him to go back in time and dump the iron in the first place…
On a more realistic note, it wouldn’t accomplish anything. Yes, there’d be more algae. The algae would absorb some C02. Then, the algae would die and release that C02 and we’d be right back where we started. It takes special, rare events to actually sequester carbon permanently - forests of trees over peat bogs where the dead trees get buried under the ground and don’t fully rot, that kind of thing. And millions of years.
Who said he was going back in time to do it? He goes forward slightly to perform the experiment, then hops further forward to gauge the effects, then back before the experiment to leave a series of notes on refinements to the process. He gets to repeat the experiment until it works, while actually doing it only once. (As long as he keeps moving ahead of the changewave or, alternatively, arranges to be undergoing displacement while the changewave passes, he can retain his memory of events.)
I’m not sure where the current research stands on it, but some experimental studies of iron fertilization have shown that as much as 50% of the algae mass sinks, becoming buried in sediment. A brief review suggests that diatoms are particularly prone to doing so. There are lots of unanswered questions about the approach, of course–real effectiveness, deoxygenation, food web impacts, and more–but it’s just the sort of crazy thing Doc might attempt.
That seems really unlikely. If 50% of algae sank and was permanently buried, you would expect that the earth’s C02 levels would be almost zero and the planet would be starved for carbon.
More likely, of that 50%, nearly all of it rots down in the sediment and the C02 gas bubbles back to the surface of the ocean, returning the C02 to the atmosphere.
“My” theory is much, much, much more likely to be true because if it were not, we wouldn’t be here to have this discussion as there would not be enough plant life on the planet to support large creatures like ourselves.
You’re assuming that all algae growth follows the same patterns as an induced bloom, which may not be valid. First–blooms, natural or induced, are different from normal growth. Second, if the bloom contains a disproportionate number of diatoms–and the induced blooms may be diatom-heavy–and the target area is low in krill, much more of the induced bloom may sink than would normally be expected. Third, diatoms, because of their structure, may be more prone to trapping their carbon as they sink into the sediment.
This, however, is not the place to debate geoengineering techniques. This is a place for silly time-travel shenanigans, like filling the sky with flying trains. Or rather, a flying train.
Now I’m envisioning a BttF/Terminator mashup, where the already convoluted timelines get hopelessly tangled. I tell you, if the Time Lords were still around they wouldn’t tolerate this sort of thing.