If you could snap your fingers and invent something that would cure a pressing global problem, what would it be?

A cheap way to extract salt from seawater so we can drink it? Several countries are already coping with the impact of rising populations and shrinking lakes and wells. For example, in Amman, Jordan, the pipes go dry on some days because there is no water. Droughts in China, Australia and Ukraine have led to crop failures, rising food prices and dwindling grain stocks.

In the middle of the 20th century, the world had about 4,000 cubic meters of fresh water per person per year, according to DHI Water Group. Now we're close, globally, to 1,000 cubic meters per person per year – and 1,000 cubic meters per person per year is defined as water scarcity.

Because 97 percent of the world's accessible water is in the ocean, inexpensive green technology like desalination – the process of turning seawater into fresh – would open up vast new sources.

What is the ultimate green invention? Synthetic food? Perfect solar harvesting?But from another perspective, industrial desalination – which typically involves building big plants that will convert millions of liters of ocean water into something that can be sent to your home – is really a problem of finding cheap energy. Two-thirds of the cost of converting seawater into fresh water is soaked up by the power budget. (In these plants, water gets pressurized and passed through a membrane.) Thus, if you came up with a machine that produced electricity cheaply and cleanly, you'd solve both the water problem and the energy problem.

But what concept or technology holds even a glimmer of hope for inexpensive, ubiquitous power? Nuclear fusion? At Lawrence Berkeley Laboratories, researchers have created a system with 192 high-powered lasers aimed at a chamber about the size of a breath mint. If all works out, tremendous amounts of energy will get released when the lasers fuse the hydrogen atoms to make helium. The problem? No one knows if it will work. While initial testing is promising, a full demonstration may not be ready for more than a decade.

[partner id="greentechmedia" align="right"]Other technologies for producing power – like wave power – might be more realistic, but they don’t offer the same promise.

Another green idea: meatless meat. Beef production accounts for 1.3 percent of calories consumed by the global human population, but cattle occupy 60 percent of the agricultural land. It takes 31.5 kilowatt hours and 2,500 gallons of water to produce a pound of meat. Grain for human consumption takes less than a kilowatt-hour and 25 gallons, according to various estimates. But even if a "meatless" meat substitute were developed, would people eat it?

What would you like to see?