Even if we could technologically produce “hydrocarbons from air using nothing but electricity”, doing so with a reliance on conventional nuclear fission power is not going to solve that problem in the near term. The problem is the rate at which we can both construct and certify new nuclear fission plants and produce enriched fuel. Both of these rates have declined dramatically in the last thirty years, and establishing the knowledge base and infrastructure to increase them is neither trivial nor will it replace other sources of energy in the near term. It should also be noted that the current means of extracting uranium are enormously destructive, as are the intermediate wastes of processing and enrichment, dwarfing the problems of dealing with spent fuel.
However, nuclear fission is inarguably a necessary component of future near- to mid-term energy needs, and despite the political adversity to it and the genuine technical issues in dealing with the caustic and persistent processing waste products, it really is the only current source of energy which can replace demand for coal generated energy in the foreseeable future, but we need to be much smarter about how we use these resources. The current once-through uranium cycle is highly inefficient, leaving products that are both hazardous to store and dispose of, and yet still contain a vast amount of usable energy; less than 1% of the available fissile energy is extracted in conventional pressurized water and boiling water reactors. A two pronged approach to developing fast neutron reactors using existing stocks of weapon-grade and enriched material, as well as thorium-based reactors, both of which can extract far more energy per fuel unit as well as reduce the actinide end products, resulting in fuel wastes which are only hazardous for a few hundred years. (The issues with pollution and wastes due to extraction and processing of the key fissile material still remains, but can potentially be reduced and managed better than in past systems.)
However, you make a very good point about the synthesis of hydrocarbons; for transportation and intermittent use, liquid or readily compressible hydrocarbon fuels are ideal, and of course, we already have an infrastructure and transportation technology built around their use. While we may not be able to synthesize them them from the carbon and water vapor in air, the synthesis of low CO[SUB]2[/SUB] hydrocarbon fuels such as methanol and dimethyl ether from natural gas reserves is a straightforward way of optimizing the use of existing fossil fuels and minimizing the increase atmospheric CO[SUB]2[/SUB]. And while mass sequestration of CO[SUB]2[/SUB] directly from the atmosphere is not feasible with any extant or near-term technology, extracting carbon dioxide from the oceans (where it is essentially at equilibrium with the atmosphere) is readily conceivable and would be an excellent way of storing energy from offshore wind and wave power generation versus trying to run power lines to offshore stations.
There are also substantial benefits to be had in improved efficiencies, especially in transportation, residential and commercial construction, and more efficient use of manufacturing and agriculture such that we don’t expend large amounts of energy moving goods halfway around the world. However, these are likely to be offset by the desire for improved standard of living by populations of developing nations, and cannot be relied upon to realize net reductions in energy demand.
As for the current warming trend, models show that it is likely to increase over the near term even if we minimize CO[SUB]2[/SUB] production, and current methods of carbon sequestration at the source are expensive or marginally practical. We will continue to see effects of climate change which are unprecedented in historical experience (though still within changes in the geological record). Life on Earth isn’t going to end, and while there may be significant impacts on human society and economics, it is unlikely that we’ll all die off in mass famine or that Kevin Costner will grow gills and fly around on a jet ski except in poorly received would-be blockbuster films. It is important to take active steps to reduce carbon emissions and deal with the consequences of warming, but it is not the end of the world.