>They seem so defeatist instead of trying to fix the actual issue.

Because fixing it would be the greatest engineering project mankind has ever attempted.

Y Combinator even admits that it is a daunting task via their http://carbon.ycombinator.com/

If we look at the desert flooding idea http://carbon.ycombinator.com/desert-flooding/

>Moving vast quantities of water - 9 trillion m3 per year - is the main energy requirement of the project. Desalination, at this scale and its current rate of energy efficiency, would itself require 10.8 tw of additional solar capacity, compared to 6.4 tw of total global power capacity in 2016. While this energy requirement dwarfs the energy of constructing and maintaining the system of reservoirs, the millions of drones necessary to do this will add significant additional energy requirements.

Comparison for the water - an Olympic size pool is 2,500 m3. That's 3.6 billion Olympic size pools, annually, for that proposed solution to the problem and would require more energy than we current produce just to pump the water and handle the necessary desalination.

And like I told Sam last summer when disagreeing about this as even a remotely plausible idea - this solution is almost certainly going to cause drastic global weather pattern changes and it is worth noting the Sahara actually fertilizes the rain forests of South America so this project could have potentially devastating consequences on its own.

This is arguably the simplest solution that we currently have on paper and likely the 'easiest' to do. However simply producing the materials needed would add a staggering amount of CO2, the concrete you'd need to pour for the thousands of power plants to power it would, you'd have to do something with all of the brine from the desalination process and dumping it back into the ocean would absolutely destroy any local habitats, you're going to change weather patterns and likely start dumping a lot more rain somewhere, you're going to stop fertilizing the rain forests of South America, and you're going to have to do something with the insane amount of algae you are growing to actually sequester the carbon (plus you'll have to be introducing enough minerals into the water to allow the algae to grow, something that would require massive strip mining).

Unless a fleet of alien trade ships show up in orbit soon and go "hey we have these machines, they'll process the carbon out of the air and make solid carbon cubes, don't worry they have power cells that will last centuries. But, in exchange, we'd like extrasolar rights to your greatest sitcoms and 3/4 of the carbon cubes" then, we probably aren't going to fix the problem.

To even retard the problem, we need to immediately stop using all fossil fuels. Instead China is still getting 70%~ of its power from coal, is still building hundreds of coal power plants, is putting millions of new drivers on the roads each year and is building an insane number of new roads and bridges that are using insane amounts of concrete and asphalt. Not to mention all of the other countries. It's just not realistic to cease all greenhouse gas emissions short of perhaps a CME forcing us to by frying most of the world's electronics.

It is a gloomy situation and it is going to likely require tens of revolutionary inventions in the very near future if we want to get back to even how it was 10 years ago.