How High Could the Tide Go?

Click here to read the full article from Justin Gillis in the New York Times

"In previous research, scientists have determined that when the earth warms by only a couple of degrees Fahrenheit, enough polar ice melts, over time, to raise the global sea level by about 25 to 30 feet. But in the coming century, the earth is expected to warm more than that, perhaps four or five degrees, because of human emissions of greenhouse gases.

Experts say the emissions that may make a huge increase of sea level inevitable are expected to occur in just the next few decades. They fear that because the world’s coasts are so densely settled, the rising oceans will lead to a humanitarian crisis lasting many hundreds of years.

Scientists say it has been difficult to get people to understand or focus on the importance, for future generations, of today’s decisions about greenhouse gases. Their evidence that the gases represent a problem is based not just on computerized forecasts of the future, as is commonly believed, but on what they describe as a growing body of evidence about what occurred in the past.

To add to that body of knowledge, Dr. Raymo is studying geologic history going back several million years. The earth has warmed up many times, for purely natural reasons, and those episodes often featured huge shifts of climate, partial collapse of the polar ice sheets and substantial increases in sea level.

“I wish I could take people that question the significance of sea level rise out in the field with me,” Dr. Raymo said. “Because you just walk them up 30 or 40 feet in elevation above today’s sea level and show them a fossil beach, with shells the size of a fist eroding out, and they can look at it with their own eyes and say, ‘Wow, you didn’t just make that up.’"