[throw_away1525]

DAC makes no sense from an energy accounting perspective.

Simple argument: DAC requires energy.

In some places, that energy is stranded. Think of the DAC plant in Iceland using geothermal. Fine. In that case, DAC makes a meaningful contribution.

If the energy used for DAC is not stranded and could instead be used to offset fossil fuels, it would be far better to offset the fossil fuel use. This is trivially proven true when you consider the 2nd law of thermodynamics. Better to prevent the entropy increase from adding CO2 to the atmosphere in the first place.

Therefore, attempting to use DAC to mitigate climate change while fossil fuels are still being burned is pointless. If you can build the energy infrastructure you will need to power DAC, you would be far better off just using it to offset and eliminate fossil fuel use.

Once you have eliminated the use of fossil fuels, sure, DAC makes sense. But the idea that DAC will save or even help us without complete decarbonization as a prerequisite is just nonsense in my opinion.

[tzs]

The atmosphere does a pretty good job of mixing, with the CO2 concentration uniform to within +/- 1% around most of the world so if there are enough places with stranded energy just building DAC plants there could help the whole world.

If there aren't enough places with stranded energy maybe we can make more. All that takes is installing more solar in some place than there is infrastructure to transport the electricity out. That excess is stranded.

The amount of energy available for solar is insane. To illustrate how ridiculously abundant solar power if you wanted to build a solar farm whose output during the day matched the power use of the entire world you'd only need about 500 000 km^2 worth of panels.

At night the power falls to near zero, but so what? If all it is doing is running a DAC plant it doesn't need to run overnight.

I'm sure there are hundreds of places around the world with good daytime sunlight, enough room for a DAC plant and a solar farm to power it, and limited grid infrastructure.

[mucle6]

"Only" need about France (~551,000 km^2) worth of panels. I see your point though

[tzs]

Note that is how much is needed to produce an amount of energy equal to the current consumption of the entire world. It is to illustrate how abundant solar energy is.

That would be enough energy with current DAC technology to remove each year about 50% of the year's CO2 emissions. That would effectively knock us back to 1970 levels of net yearly emissions.

There are 5 subtropical deserts in the world with areas greater than 500 000 km^2. There's room in those 5 deserts for about 30 of those 500 000 km^2 solar farms. That's enough energy to in 1 year bring atmospheric CO2 down to around 320 PPM, which is around 1960 levels. 2 years to get back back to 1800 levels. 6 years to get to pre-industrial levels.

Of course it is possible that at that scale energy isn't the bottleneck for DAC. It may depend on other resources that cannot scale that well.

[Maursault]

> Therefore, attempting to use DAC to mitigate climate change while fossil fuels are still being burned is pointless.

Because no one has suggested using DAC to offset fossil fuel use without reducing fossil fuel use, this is a straw man. DAC may very well be a valid strategy when used in conjunction with the reduction of fossil fuels to better reduce the amount of atmospheric carbon in a given time frame.

[Paul-Craft]

Nobody seems to be doing anything to reduce emissions, either. Except for the blip due to COVID, globally, we're still on the same trend we have been forever: https://ourworldindata.org/co2-emissions

[bryanlarsen]

You're looking at absolute numbers. CO2 usage used to be accelerating rapidly. The first step to reducing the absolute number is to change the second derivative, the acceleration. We've done that, the second derivative of that graph is significantly negative. Once the area under the curve of the second derivative is negative enough, the first derivative, the velocity, will go negative. We're about there, the year on year change is now about zero. Once the first derivative is negative the absolute number starts dropping.

So yes, more than nothing has been done to reduce emissions, but you need to look at the right numbers and graphs.

[ZeroGravitas]

Your link says we've stabilized over the last decade.

> We see that while emissions from fossil fuels have increased, emissions from land use change have declined slightly in recent years. Overall, this means total emissions have roughly stabilised over the past decade.

There is some hope that fossil fuel emissions are peaking right around now. See the recent Ember info:

https://ember-climate.org/insights/research/global-electrici...

[Paul-Craft]

Look at the graph of global emissions. US emissions essentially don't matter in the big picture. This is why massive, coordinated, global action is the only thing that will save us.

This is not a fatalistic "oh, let's not even try then" statement. It's just facts. Yes, we should try. No, we won't succeed if it's just the US reducing emissions.

[Maursault]

> Nobody seems to be doing anything to reduce emissions,

No one is working on carbon-free renewable energy? Solar power hasn't doubled in efficiency since development began? No one is building wind farms? ICE vehicle fuel efficiency has not been massively increased? No one is making electric vehicles? Supply chains are not getting more efficient? There are no waste reduction strategies being implemented anywhere? There are no efforts to reduce methane emissions?

[throwaway5947]

That’s all well and good but you still have to account for Jevon’s Paradox, that it might not matter if consumption keeps rising. It seems really, really hard to do that in a socioeconomic system built upon continuous industrial growth and consumption.

[bryanlarsen]

I don't think any of the realistic models have DAC providing a significant percentage of the carbon reduction. For example, 99% of the reduction from green electrification, and 1% from DAC.

DAC is still in the research phase, and is probably a decade a way from widespread use.

Solar power, wind power and electric transportation are already well into the production phase and are happening today.