So, have any communities been displaced to date by sea rises attributable to human-caused climate change?

I have heard of only one island, pop. 10,000, in the Indian Ocean that has been evacuated, and I'm told that Tuvalu, an 11-island nation-state in Micronesia with a maximum height of about 9 meters, has discussed possible asylum with Australia and New Zealand.  

The problem for small island states and countries with large lowland areas like Bangladesh is not one of plain old rise in sea levels, but of the magnitude of storm events due to major climatic disruption. These events are predicted to increase not necessarily in number but in severity, and this change has already begun.  Low areas will be flooded and increasingly washed away. This also leads to saltwater incursion into rock that had previously been holding freshwater, reducing the amount of arable land even more.  

We can expect to see mass migration ... in the many millions ... as people leave homelands where they can no longer live.  

These millions will be in addition to those from areas where changes in patterns of precipitation are a big factor in the spread of desertification.

Truly, friends, we need to see things on a global level and take compassion more seriously tomorrow than we do today.

Your bluebird of happiness,
Mary

I'm confused. In high school biology I learned that water is one of the few liquids that actually expands when frozen. A frozen pond shows the warmer water moving to the bottom of the pond, therefore more dense so that fish can still survive the winter. If global cooling occurred, what would happen to sea levels? Would the expanded ice masses then help to rise levels? Or is glacial ice different in its mass than pond or lake ice? High school was 37 years ago, maybe I'm misremembering.

Know of any good dike-producing companies? Vancouver is going to have to invest in a few - check out the map that the B.C. Sierra Club produced on Google Earth. The San Francisco Bay Area has a lot of housing built on land reclaimed from the bay, including the island of Alameda, elevation 8. We're also going to have to get on the phone to Seawalls R Us (Amsterdam).

For bailsout - All matter, including H2O, can exist in three forms - a gas, a liquid, a solid.  The planet Earth, because it is located in the "Goldilocks" zone (not too hot, not too cold, but just right), supports the co-existence of all three states of being for water, the only substance in which the solid form is less dense than the liquid form.  Which is why your icecube floats in your glass of rye and ginger instead of sinking to the bottom.  This is also why ice-sheets form on top of lakes, ponds, and the oceans, when it's cold enough.  

When ice melts it increases the volume of the water into which it is dissolving.  When Water freezes, the ice forming on land from snow reduces the volume of the oceans, which extends the shorelines and beaches outward (which is where the landbridge from Asia to Alaska comes from, but slowly is submerged as the last ice age melts away and lets the ocean volume increase).

But ice itself which forms at Zero Degrees Centigrade (32 degrees F) can drop many degrees in cold intensity, which is why Arctic and Antarctic ice persist for so many centuries.

If global cooling occurred, there would be a lot of ice forming into glaciers, on land, thus storing water out of the oceans and lowering sea-levels. Global Warming allows more water, stored away in glaciers to reach sea-level and increase the amount of liquid water, causing coastal flooding.

I hope this short explanation contains enough information to supplement your high school biology.

For bailsout - H2O has many peculiar properties. At 4°C H2O expands on heating or cooling. As H2O cools, it contracts - until it starts to freeze - then, because it forms rather large crystals it's volume suddenly expands This is why precipitation that falls as snow can be  many inches thick, the same amount of H2O falling as water wouldn't occupy the same volume of space. If ice is cooled further after it has completely frozen, it will contract again.

Like all materials H2O also expands when heated (thermal expansion). With H2O this occurs between 4°C and 100°C. A simple school experiment is to take a Pyrex flask of water at room temperature and heat it gently, measuring the rise in water level as it heats. Another is to fill a screw-top (to prevent evaporation) glass container with warm water and mark its surface level on the side. Then place in a fridge for a few hours then see if there's been a change. Invariably the level will now be a little lower. (Perhaps by only a mm or so if a small container, so exact measuring is important.)

NB: All household hot water heaters require thermal expansion tanks to provide a safe place for expanded heated water to go. (Most water meters are installed with devices that prevent backflow, this creates a closed system.) For example, water heated from 32ºC to a thermostat setting of 60ºC in a 40 gallon hot-water heater will expand by almost half a [US] gallon (1.8 litres). This is because when water is heated, its density decreases and its volume expands. Since water is not compressible, the extra volume created by expansion must go somewhere. Pipes in a home may burst unless there is somewhere for the expanded water to go. There are temperature/volume tables to help engineers work out how much a volume of water will expand by at any given temperature.

With seawater salinity differences within the oceans will affect the local water density and thus the expansion rates of local sea levels, but have little effect on the overall global average sea level change.

Mary, above, was absolutely right in pointing out that areas most at risk are those affected by storms. Even a small rise in sea levels can affect the size of a storm surge. A storm surge is primarily caused by the extremely high winds that accompany a hurricane. This wind pushes the water towards land, building it up into huge waves. At the same time, the low pressure caused by a hurricane also causes the water level to rise up in the lowest-pressure spots and to sink in areas of higher pressure, exacerbating the wave build-up caused by the winds. So even a small increase in the volume of seawater can lead to bigger storm surges than before reaching further inland than previously. As well as the devastation this causes, longer term effects include salt contamination of the ground which affects crop productivity. Given how many subsistence farmers live in delta and low lying areas of India, SE Asia and China this could have major impacts.

Even small rises in sea levels also will cause greater penetration of salt into coastal water tables. I understand that some previously healthy Palm trees in Florida are now being killed off because salt has contaminated more of the water table. A small rise in sea levels can have a bigger impact than you'd first think.