It seems unlikely to me that emissions will continue to increase, exponentially or even linearly. We are at a point now where renewable energy is actually cheaper than fossil for electricity, and electric land vehicles are well on their way to being cheaper and more practical than fossil-based vehicles. At that point, market forces take over.

Do you have any data to support this worldview? I wish you were right, but I am not so sure. People have been predicting the turning point to be just around the corner for decades. Meanwhile

https://cleantechnica.com/2019/03/22/banks-funneled-1-9-tril...

I suspect your link is not handling data in a nonpartisan manner. I can provide more meat for my arguments, but do your own googling.

Data point 1: Coal-fired power plants are closing at a rapid pace across the US, and no one is building new ones. Nuclear plants are also closing well before their end-of-life plans, largely because they are losing major industrial customers to cheaper sources.

Data point 2: The key cheaper sources are natural gas (due to fracking, which has caused supply to increase and prices to plummet), wind, and solar. The cost of utility-scale solar has dropped over 80% in the past decade(!), and plants are being built based on unit prices of under $60/Mwh, compared to around $100/Mwh for coal and nuclear. Onshore wind is under $50/Mwh and has a solid experience base of data for wind variations etc. Fracked gas is around $40/Mwh, but may be passed soon by both wind and solar. Storage tech (batteries etc) for stabilizing the grid with wind and solar in play are also becoming much cheaper, due to manufacturing improvements and economies of scale.

Data point 3: Electric cars are becoming common, if still a minority, and their prices are also dropping toward being in line with fossil-powered cars. There's every reason to believe this trend will continue, not just because they're getting more affordable, but because they're just plain better cars in many ways.

I know these data points. And they look great. Yet, I look at the co2 ppm chart and somehow it just keeps going up. With no sign of slowing down.

That's because it takes time. It will take decades to convert a lot of key systems, even if renewable energy is cheaper.

The infrastructure that burns fossil fuel is highly distributed. Millions (billions?) of cars on the road. Worse, millions (billions) of cold-climate buildings heated by gas or coal.

In the meantime, it's not growing exponentially. It had actually leveled off. There was a spike in the past couple of years, but it doesn't seem reasonable that it's a sustained pattern.

Spending less than 2B usd purchasing and distributing iron sulfate in the oceans, we could cause a snowball earth. If we spend 1.2 or so, and harvest all the excess salmon to blunt the cascade of the algae blooms, we could keep temps whatever we want.

The bigger problem is that it's an absurd amount of trees.

Why absurd? We've removed 3 trillion trees since the beginning of agriculture and replanting 1 trillion is absurd? Or do you think its infeasible?

Estimated cost is a few hundred billion dollars. A lot cheaper than most methods of carbon sequestration. It also has the benefit that it could restore ecosystems if done well. People who focus just on carbon emissions miss that the are more systemic problems with destroying ecosystems i.e. in the long term biosphere collapse.

The larger problem is that it takes 50 years (or longer) for most of the carbon sequestration to happen.

https://www.biocarbonengineering.com/

Let's also not forget how many seasonal jobs in rural areas this will create.