Geoengineering Earth's Climate: Resetting the Thermostat
to remain covered in ice and snow year-round has changed Warmer temperatures in Earth’s atmosphere are melting the top of the glacier sending rivulets of ice water into the ocean Warming waters of the North Atlantic Ocean are melting the glacier from the bottom as well The melting glacier on the Evigheds Fjord is part of a much larger formation called an ice sheet Earth has two major ice sheets one on Greenland and one on Antarctica Measuring more than 660,000 square miles 1 7 million square kilometers Greenland’s ice sheet is approximately the size of Texas On average the ice sheet is 1 mile 1 6 km deep Its greatest depth is 3 miles 4 8 km If it were to melt entirely the total amount of water it contains would raise the oceans by about 23 feet 7 meters The rising waters would flood the coasts of every country on the planet and submerge many inhabited islands While the probability of the entire Greenland ice sheet melting is slim climatologists scientists who study Earth’s climate note that Greenland is shedding more ice during summer than it regains from snowfall in winter The US National Aeronautics and Space Administration NASA reports that Greenland’s ice sheet is losing about 31 billion tons 28 billion metric tons of ice annually Some of the melting ice evaporates turns into water vapor or stays on the land but most of it goes directly into the ocean And studies show that the melting on Greenland is increasing every year NASA uses satellites to measure the depth of Earth’s oceans The agency has noticed a definite rise in ocean levels over the last century with an average yearly rise of about 0 13 inches 3 3 millimeters While that may seem small it adds up to a 4 to 8-inch 10 to 20-centimeter rise over the past one hundred years If that water were lying in the street it could flow over curbs and into houses If you were standing next to the ocean the rising water would cover your legs to mid-calf Imagine that much water flooding the entire world And if the ice sheets continue to melt the water levels will only get higher NASA climate scientist Jay Zwally says that the melting of 8 G e o e nGi n e e r i nG e a r t h s c l i m a t e
NORTH AMERICAN COASTLINES BEFORE AND AFTER PROJECTED MELTING OF EARTH’S ICE NORTH AMERICA P A C I F I C O C E A N Existing coastlines Landmass after melting A T L A N T I C O C E A N SOUTH AMERICA Sea levels have already begun to rise due to global warming if all the polar ice on earth were to melt large areas of coastline would end up underwater this map shows what north America would look like in that case Florida would be submerged along with vast stretches of coast along the Atlantic ocean and the gulf of mexico Greenland’s ice sheet is like a canary in a coal mine Before coal mines used modern air-quality detectors miners sometimes took live canaries with them into mineshafts If the birds stopped singing miners knew that deadly carbon monoxide which is frequently found inside coal mines had risen to dangerous levels and killed the birds Miners then knew it was time to hightail it out of the shaft Climatologists think of Greenland as a canary or an early warning system for the rest of the planet Since the Greenland and Antarctic ice sheets account for almost 99 percent of all freshwater ice on the planet An Abrupt ChAnge in ClimAte 9
ICELAND RISING The country of Iceland is rising out of the North Atlantic Ocean No this scene is not something from a science fiction movie The land is rising due to climate change Iceland’s rocky terrain is home to many glaciers The warming waters of the Atlantic Ocean and increasing air temperatures are beginning to melt some of the glaciers As the glaciers melt the land below them rises a little a phenomenon known as uplift Imagine a heavy person lying on a mattress pressing it down When the person gets up the mattress bounces up a bit That’s what’s happening to the land below Iceland’s glaciers Geologists say that in some places the uplift rate is 1 2 inches 30 mm per year the melting of either sheet would spell trouble As Greenland warms and sheds its ice so do other parts of the Arctic including Alaska Many climatologists think that the melted ice streaming into the Arctic Ocean and other northern waters is a signal that the canary has stopped singing They say that climate change has reached a dire tipping point Why is this occurring The answer is related to Earth’s atmosphere A DELICATE BALANCE Earth’s atmosphere is composed of 78 percent nitrogen and 21 percent oxygen The remaining 1 percent consists of argon and small amounts of greenhouse gases methane nitrous oxide carbon dioxide water vapor water in gas form and ozone Greenhouse gases in the atmosphere act like a blanket holding in heat and shielding Earth from certain kinds of radiation from the sun When solar energy reaches Earth’s atmosphere about 29 percent of it immediately bounces off clouds and gases and travels back into space The atmosphere absorbs 10 GeoenGineerinGearth’sclimate
another 23 percent while 48 percent of solar energy makes it to Earth’s surface The land and the oceans absorb this energy and heat up The first law of thermodynamics which applies to everything in the universe says that energy can neither be created nor destroyed That means that the amount of energy that goes into a system must equal the amount of energy that the system releases So on Earth at the same time the oceans and land are absorbing energy from the sun they are also releasing energy in the form of infrared rays heat When this heat rises and hits greenhouse gases in the atmosphere the gases trap the heat and send it back toward Earth This exchange of energy from the sun down to Earth’s surface back up to the greenhouse gases and back down to the ground naturally keeps Earth at an average temperature of about 59 F 15 C This is a suitable temperature for life THE GREENHOUSE EFFECT Some radiated heat escapes into space Greenhouse gases in the atmosphere Greenhouse gases trap some radiated heat and send it back to Earth e er h p s o m at sunsunsunsunsunsunsunsunsunsunsunsunsunsunsunsunsunsunsunsun incoming solar energy Some solar energy ref lects off clouds Some solar energy is absorbed by Earth’s surface and is radiated as heat the greenhouse effect is an exchange of energy that keeps earth at a suitable temperature for living things in this exchange greenhouse gases in the atmosphere trap some of the sun’s heat near earth however increasing amounts of greenhouse gases are trapping excessive heat leading to global climate change An Abrupt ChAnge in ClimAte 11
