In Bill Gates' 2010 TED talk, Bill Gates: Innovating to zero! [YouTube], Gates mentions that he has

asked the top scientists on this several times: Do we really have to get down to near zero? Can't we just cut it in half or a quarter? And the answer is, until we get near to zero, the temperature will continue to rise. And so that's a big challenge. It's very different than saying, "We're a twelve-foot-high truck trying to get under a ten-foot bridge, and we can just sort of squeeze under." This is something that has to get to zero.

[emphasis mine]

This is in relation to the emissions that we are producing and the need for these levels to go right down to near zero. This intrigues me as it's a very substantial claim.

Do the Climate Emissions need to go right down to near zero to stop the temperatures rising?

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    He almost certainly means net emission. – DJClayworth Jan 24 at 16:06
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    @DJClayworth if you look at the full transcript he says: "Now, we put out a lot of carbon dioxide every year — over 26 billion tons... somehow, we have to make changes that will bring that down to zero". So he means the gross anthropological amount, not the net amount. singjupost.com/innovating-to-zero-bill-gates-full-transcript – DavePhD Jan 24 at 16:14
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    @DavePhD he means zero - and as it happens, net zero effectively requires anthropogenic additions to the carbon cycle to go to gross zero anyway, because of the limited scope for increasing sinks. – 410 gone Jan 24 at 20:02
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    @Möoz You'll be far better off asking this on Earth Science - that's where the genuine experts are. Here, you've just received a pseudo-scientific answer. – 410 gone Jan 24 at 20:04
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    @Möoz Well, looks like someone's been playing Thanos already, using a "wild" zoonotic virus as a disguise. – y chung Jan 27 at 19:56

Below is Fig. 3 of Global Carbon Budget 2018 Earth Syst. Sci. Data, vol. 10, pages 2141–2194, 2018.

enter image description here

Here, it is shown that current annual emissions are about 11 Gigatons of carbon (GtC), of which the land and ocean are incorporating about 5 GtC.

So at a minimum, a reduction by a factor of 5/11 is needed to stabilize the concentration of carbon dioxide in the atmosphere. However, this would only be a temporary stabilization because the ocean would eventually approach saturation with carbon dioxide. Similarly, as explained in CO2 is making Earth greener—for now, land plants are currently taking up a high net amount of CO2, but if the CO2 concentration started to stabilize, this amount would decreased to the historical lower amount similar to the early portion of the above graph, where only about 1 GtC is being incorporated annually into the land and ocean.

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  • I'm honestly more excited than I should be to see the emissions graph levelling out at 2012 instead of continuing to shoot upwards. It's a very hopeful plateau. – F1Krazy Jan 24 at 13:38
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    @F1Krazy Does it, though? There are several plateaus like that in the graph which are then followed by even sharper increases. – Philipp Jan 24 at 17:14
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    You've completely misunderstood the carbon cycle. This answer is simply wrong. The detail is in the IPCC documents - go read up on the outputs from AR5 WG1. ipcc.ch/report/ar5/wg1 Please don't just guess at an answer based on a naive reading of a graph. – 410 gone Jan 24 at 20:00
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    @EnergyNumbers perhaps you can write a better answer? As someone who knows almost nothing about environmental science, the "naive reading" of the graph seems correct to me. If it's wrong, we should fix that. – PC Luddite Jan 25 at 4:05
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    @Oddthinking It's not at equilibrium. The timescale to reach equilibrium is on the 100-10,000 year frame agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2004GL020612 , but it depends how deep you consider. But, yes, if the concentration of CO2 in the atmosphere became low enough, the ocean would release CO2. – DavePhD Feb 25 at 0:30

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