Melting ice and rising ocean levels

GUESTWORK | Roy Wehrle

The big Paris climate conference is now just three months away. The latest research on climate change is just in from the dean of climate scientists, James Hansen. He and his team of 16 climate scientists, using the research findings of hundreds of top scientists, along with the work of the United Nations climate science group, conclude that melting polar ice is an immediate threat and drastic reduction of CO2 emissions is the prime remedy. They describe a climate drama consisting of six major actors: ice ages, ice sheets, ice shelves, ocean heat currents, feedback loops, and CO2 warming. Let’s see what they say.

Ice ages end when small changes in the earth’s position in respect to the sun continuing over thousands of years create extra heat which causes the great ice sheets of Greenland, the Arctic and Antarctica to start melting. This happened 120,000 years ago and again 17,500 years ago.

Feedback cycles can increase the ongoing warming. Melting Arctic sea ice is an example of an existing feedback loop that has already magnified warming in the Arctic. Dark sea water replaces sea ice that formerly reflected the sun’s rays. Dark water absorbs the sun’s rays warming the water and melting more sea ice, which warms the water even more, etc. Today, this cycle is far advanced in the Arctic. The big worry is that fast Arctic warming will ignite a second self-accelerating cycle: warming air melts the permafrost and turns on a giant earth-warming stove that we can’t turn off. This monster potential feedback loop could melt billions of tons of long frozen carbon which when released would warm the Arctic even more, melting more permafrost, etc.

Our continued loading of the atmosphere with CO2 causes increased melting of the ice sheets, dumping billions of tons of fresh, cold water into the polar seas. After a time this water deluge turns off the great ocean currents that transfer equatorial heat north and bring Arctic cold water south to the equator. Stopping this immense heat exchange causes the equatorial waters to become much warmer. The increased heat differential between polar and equatorial regions causes super storms and high winds. But in the Southern Hemisphere the hotter equatorial waters circulate subsurface to Antarctica where they warm and melt the underside of the ice shelves, causing some in time to disintegrate.

The Antarctica ice shelves are extensive protrusions of ice floating on the sea extending far out from the Antarctica shore. Though thousands of years old, warm water lapping on their underside and warm air wafting their topside make them vulnerable to disintegration. These ice shelves act as ice dams, blocking the movement of immense quantities of ice and glaciers that would like to slide off the Antarctica continent into the sea, raising the sea level. When such an ice shelf plug is removed, the Antarctica glaciers speed into the sea sometimes eight times faster than their previous lethargic pace. Three major ice shelves have now disintegrated, so we know the process of collapse is commencing. The Hansen Study emphasizes that such accelerating melting portends that the ocean will rise significantly, but how fast is hard to predict.

About 120,000 years ago when that Ice Age started to thaw, the global temperature was just 1 degree C. warmer than our planet today. Yet, through processes like those described, the ocean level rose nine meters in just a few centuries. So the Hansen scientists conclude that ocean levels will rise at least 3 meters, say 10 feet, over the next 50 to 200 years. Approximately 100 million people live within the area a one-meter rise will cover.

We are accustomed to climate stability interspersed with erratic weather. But ice core measurements of the great ice sheets show that geologic history is rife with sudden and erratic changes in climate -- in CO2, temperature and sea levels. The ice record shows rapid temperature changes from 9 to 15 degrees Fahrenheit across the globe have appeared 23 times in the last 100,000 years. The changes lasted for centuries. The fastest and biggest change of all happened in only two to three years. Across Greenland the temperature change was 25 to 35 degrees F. So we can’t count on just gradual and predictable climate change.

Based on this picture and on the realization that even a small risk of such irreversible change to our planet cannot be accepted, Paris is our opportunity to act. The Hansen study ends by stating that the major control knob determining climate warming and ice melting is the density of CO2 in our atmosphere. To prevent ocean flooding and much else we must turn down the earth heat stove by feeding less fossilfuel-creating CO2 into the atmosphere as quickly as possible. Paris is our opportunity to act. It’s coming in three months.

Roy Wehrle is a longtime environmentalist in Springfield and emeritus professor at UIS. Contact him at [email protected].