Promoted by Brendan -- very creative and surprisingly practical proposal

I'm not big on hand-wringing, so if global warming is going to cause changes such as a rising global sea level, I think we ought to be doing something other than stainding defiantly on our eroding beaches and crying out at the rising tides, "Take me!!!". Instead, I think we ought to be preparing to do something about it in an orderly and systematic way.

So, let's consider the problem of rising sea levels and figure out if there's something we can be doing about that inevitability while efforts to reduce greenhouse gas emissions are ongoing.

First, some relevant facts:

Ocean surface = 5,000,000 square miles

Square mile = 5280 x 5280 square feet

So, each rise in sea level of 1 foot = 5,000,000 x 5280 x 5280 x 1 = 139,392,000,000,000 cubic feet of salt water. Let's just round that up and call it 140 trillion cubic feet of water per 1 foot of sea level rise.

Now, currently, sea level is rising a few mm per year. Just to simplify things, let's stipulate that sea level is rising by 3mm per year , which is slightly above the average of 2.8mm rise that has occurred since 1992. There are 304.8 mm in a foot. So, seas are rising by approximately .01 feet each year.

So, to keep sea level constant, we need to figure out somewhere to put 140 trillion x .01 = 1.4 trillion cubic feet of water each year.

One option would be to dig a hole. Basically, this would require digging a hole 1000 feet deep and 50 square miles in area each year for the water to flood into. Such a hole would have a capacity of 50 x 5280 x 5280 x 1000 = 1.4 trillion cubic feet.

To be sure, this would represent by far the largest excavation project in history. The largest excavation to date is the Bingham Canyon Mine , an open pit copper mine in Utah-- a hole about 3 square miles in area and nearly 4000 feet deep at its deepest point-- not big enough to hold even one year worth of sea rise. Also, the Bingham Canyon mine is the result of over 100 years of excavation.

Even though the site for our proposed salt water reservoir could be chosen in a geologically favorable area for easy digging, and we don't have to do anything special with the excavated material except put it in a big pile somewhere, this still sounds like a lot of digging.

Another option would be to put the water in existing holes-- natural depressions in the earth's crust such as the Salton Sea Basin in the southern California Desert. The bottom of the Salton Sea basin is already filled with salt water, but the current surface of the Salton Sea is 220 feet below sea level. If the basin were flooded to sea level, the Salton Sea would expand drastically to near the shoreline of the ancient Lake Cahuilla , a freshwater lake about 110 miles long and 30 miles wide which covered this region until just over 500 years ago.

How much water would Lake Cahuilla hold? Well, we will assume an average depth of 110 feet-- halfway between sea level and the -220 foot elevation of the current Salton Sea, and we will assume the lake will have an area of 110 miles x 30 mile = 3300 square miles. This lake would then hold:

3300 x 5280 x 5280 x 110 = 10 trillion cubic feet of water... about 7 years worth of global warming sea level rise.

Of course, there's a cost to this as well that extends beyond digging the salt water canal from the Gulf of California to the basin, as the present-day towns of Indio, Brawley, and El Centro would be flooded as would numerous smaller towns and thousands of acres of irrigated farmland. On the other hand, the new expanded sea, with a nominally constant shoreline at sea level may present new opportunities as well, including a solution to the water shortages of the desert Southwest as solar-based desalinization becomes feasible, algae-based bioenergy farms, and new beachfront real estate on a stable shoreline southeast of Palm Springs.

Having been to El Centro on a humid, 115 degree August day, I can honestly say that I see some promise in this proposal. It sounds like a better approach than simply allowing unfettered coastal erosion or paying hundreds of billions building levees and creating more "bathtub" cities like New Orleans.

For this solution to make a dent in the problem of sea level rise, the world would obviously need to fill other basins as well, such as the Afar Depression near the Horn of Africa. Fortunately, many of these below-sea-level basins are inhospitable desert wastelands. Another possibility would be to pump sea water up to dry basins above sea level, creating inland seas not unlike the Great Salt Lake-- however, pumping rates sufficient to counteract rates of sea level rise may not be feasible.