Obviously, as the world population increases and uses more power and vehicles, the amount of CO2 in our atmosphere is going to increase and in all probability (though not absolutely proven yet) cause global warming. In the past such an increase in CO2 would have provoked a surge in the growth of oxygen-producing trees and plants to correct the imbalance (Lovelock’s Gaia-effect) and this may still happen, but with man taking over more and more of the planet’s forested areas for urban-development, food crops and pasture-land there’s getting less and less room for the largest oxygen-producing plants i.e. trees. One way to counteract this is to reclaim for the plant kingdom some of the great expanses of desert on our globe and the way to do this is to somehow introduce more moisture into these regions. My first ’Green Solution’ would have this effect, though there would be many problems for the politicians to sort out. The second is a way of augmenting a proposed type of renewable energy i.e. off-shore wind-power, with a more consistent one i.e. tidal power, thus making them both more efficient and lessening the need for CO2-producing power stations.

1) Creating Plant Growth in Desert Areas below Sea Level.

Some desert areas in the world that are below sea level e.g. the Qattara Depression, the Caspian Sea and the Dead Sea could be irrigated with sea-water if canals were dug between them and the nearest major sea. This would have the double advantage of encouraging plant growth in these arid regions and slowing the predicted rise in global sea-levels. Against this, some of the local population would have to be re-located and their drinking water could be contaminated with salt. However, if these problems could be overcome, for instance, by building new dwellings around a desalination plant, the increase in moisture in the area could create a micro-climate with more rainfall and increased plant growth over an ever-widening area. Also, there are saltwater crops that could be grown straight away for bio-fuel production and this would bolster the local economy until further agricultural benefits could evolve in the region.

2) Adapting Proposed Off-shore Wind Farms for Tidal Power

a) Creating Mini-barrages.

Where off-shore wind farms are proposed in areas of strong tidal currents e.g. the Bristol Channel, why not arrange the towers in lines across the currents and dam up the gaps between them to create mini-barrages. Built into these would be banks of hydro-electric turbines which could be generating electricity on a regular basis (unlike the wind-dependant air turbines above them)! The other advantages with this scheme is that the infra-structure for sending the power to the mainland is already in place and the wind-turbine towers themselves form an ideal robust, scaffold for anchoring the dams.
Instead of arranging the wind turbines in lines across the current, another possibility would be to arrange them in a circular formation, again damming the gaps between them, to create a sea-lagoon which would fill and empty with every tide. This might be more efficient than the barrages across-the-current formation. It would also create an area of sea-bed completely protected from human contamination, although there would have to be some sort of sluicing mechanism to allow the passage of fish and sea mammals, and it would be an ideal environment for underwater divers to operate in. They could tie up their boats to the outer rim of the lagoon and use that as a base from which to explore its inner sea-bed - a safer option than diving in the open sea (presumably there would be some sort of grill/covering over the inputs to the water turbines to prevent swimmers or large fish being sucked into them).
Some constructions like this in the Bristol Channel would be more practical and economic than a Severn Barrage.

b) Floating-barrages (a cheaper alternative to mini-barrages).

If the suggestion above is deemed too expensive (or impractical for the available budget), a cheaper alternative would be to suspend banks of water turbines under floating barrages and tether them to the wind towers so that they are always aligned to the tidal-current i.e. by having them in line with the tethering cable, so that the tidal current would always position them correctly. A cross-section of tidal-current roughly equivalent to the cross-section of air used by the wind turbine would produce more power for sure. Although the average flow-velocity of the tide is probably lower than the air driving the wind turbines, it carries more momentum, being denser, and is producing power on a more regularly basis, only stopping during slack water! Wave-power generators could probably also be incorporated into this system so that production would be virtually uninterrupted!