<blockquote>So the idea is to ship electricity back and forth from the southern to the northern hemisphere?</blockquote>Perhaps I should have said “<i>storage, <strike>or </strike><b>and</b> long-distance transmission from solar investments in more sunny climes.</i>” But for immediate needs, I suspect investments in large-scale utility PV in central Spain might not only meet the imposed requirements, but provide welcome injections of commercial activity. You'd probably know more about that than I.
The <a href="http://www.timeanddate.com/worldclock/distanceresult.html?p1=141&p2=16" rel="nofollow">distance</a> is perhaps around 3 times that from <a href="https://www.google.com/maps/dir/Hoover+Dam/Los+Angeles,+CA/@35.0387815,-118.8210119,7z/data=!3m1!4b1!4m14!4m13!1m5!1m1!1s0x80c92b497f82a14b:0x89d59d0bd29de37!2m2!1d-114.7377325!2d36.0160655!1m5!1m1!1s0x80c2c75ddc27da13:0xe22fdf6f254608f4!2m2!1d-118.2436849!2d34.0522342!3e0" rel="nofollow">Hoover Dam to Los Angeles,</a> so I'd guess it would be a challenge, but doable with modern transmission technology.
Note first of all, though, that the thrust of my argument is that there isn't really any hurry, because technology is solving the problem. What the people behind this decision are really after is to <b>break</b> technological capitalism by imposing too great a rush on it.
Longer term, solar investments could probably be cost-effective floating on the Atlantic, west of Spain or North Africa. (IMO the cost of sea-borne floating PV will become lower than land-based within a decade, obviously if you don't agree you don't.)
In the short term, both Norway and Sweden have huge potential for pumped hydro storage, especially if the ocean is used for the lower reservoir. Longer term, as the technology matures, deep-sea pumped hydro will probably become cost-effective, as manufactured lower reservoirs 500-700 meters under the surface could probably be <b>mass-produced</b> more cheaply than building dams, with learning curve and economies of scale.
Battery storage of some sort might become cheap enough to compete, but I doubt it.
Even longer term, the power→gas/liquid fuel conversion option would allow today's investments in gas- (and oil-) fired power generation to run off carbon-neutral fuel. Granted current projections of efficiency are around 30% for the round trip, which would probably never be pushed above 50%, but as the cost of PV continues its exponential decline, it will probably be cost-effective.
Point is, with investments now in R&D pointing to the right technology, a large-scale transition away from fossil carbon could almost certainly be achieved by, say, 2050. Along with mature, high-volume, technology for capturing ambient CO2 which could, <b>if necessary</b> then be deployed for capture and sequestration to remove the excess currently being dumped into the environment. All <b>without</b> impacting the current roll-out of cheap energy to the less-developed world.
Thus, there's no need for the huge expensive "urgency" except for those with a primarily anti-capitalist agenda.