Effects of Global Warming: Sea Level Changes

Effects of Global Warming: Sea Level

We have seen that an average drop of just 5 degrees Celsius over thousands of years can cause an ice age; so what will happen if the Earth's average temperature increases a few degrees in just a few hundred years? There is no clear answer. Even short-term weather predictions are never perfectly accurate because weather is a complex phenomenon. When it comes to long-term climate predictions, all we can manage are educated guesses based on our knowledge of climate patterns through history.

Glaciers and ice shelves around the world are melting [Source: Guardian Unlimited]. The loss of large areas of ice on the surface could accelerate global warming because less of the sun's energy would be reflected away from Earth to begin with (refer back to our discussion of the greenhouse effect). An immediate result of melting glaciers would be a rise in sea levels. Initially, the rise in sea level would only be an inch or two. Even a modest rise in sea levels could cause flooding problems for low-lying coastal areas. However, if the West Antarctic Ice Sheet were to melt and collapse into the sea, it would push sea levels up 10 meters (more than 32 feet), and many coastal areas would completely disappear beneath the ocean [Source: NASA].

Research predictions indicate a rising sea level.
Photo courtesy Earth Observatory, NOAA

The IPCC estimates that sea levels rose 17 centimeters (or about 6.7 inches) in the 20th century. Scientists project rising sea levels to continue through the 21st century, with levels increasing between 7 and 22 inches by 2100. The IPCC did not consider changes in ice flow in these projections due to a lack of scientific data. Sea levels will likely be greater than the range of projections, but we can't be sure by how much until more data can be gathered about the effect of global warming on ice flows.

With a rise in the overall temperature of the ocean, ocean-borne storms such as tropical storms and hurricanes, which get their fierce and destructive energy from the warm waters they pass over, could increase in force.

If the rising temperature affects glaciers and ice shelves, could the polar ice caps be in danger of melting and causing the oceans to rise? We'll look at this danger in the next section.

Water Vapor, The Other Greenhouse Gas

Water vapor is the most abundant greenhouse gas, but it is more often than not a result of climate changes rather than man-made emissions. Water or moisture on the Earth's surface absorbs heat from the sun and the surroundings. When enough heat has been absorbed, some of the liquid's molecules may have enough energy to escape from the liquid and begin to rise into the atmosphere as a vapor. As the vapor rises higher and higher, the temperature of the surrounding air becomes lower and lower. Eventually, the vapor loses enough heat to the surrounding air to allow it to turn back into a liquid. Earth's gravitational pull then causes the liquid to "fall" back down, completing the cycle. This cycle is also called a "positive feedback loop."

Water vapor is more difficult to measure than the other greenhouse gases and scientists are uncertain as to the exact part that it plays in global warming. Scientists believe there is a correlation between the increase of carbon dioxide in our atmosphere and the increase of water vapor. The NOAA Web site has this to say:

As water vapor increases in the atmosphere, more of it will eventually also condense into clouds, which are more able to reflect incoming solar radiation (thus allowing less energy to reach the Earth's surface and heat it up).