THE WEATHER MAKERS
HOW MAN IS CHANGING THE CLIMATE AND WHAT IT MEANS FOR LIFE ON EARTH
TIM FLANNERY
ATLANTIC MONTHLY PRESS 2005
PART III
Chapter 13: Liquid Gold: Changes in Rainfall
· From the poles to the equator, our earth spans a range of temperatures from around 104°F below zero to 104°F above. Air at 104°F holds 470 times as much water vapor as air at -104°F.
· For every degree of warming we create, our world will experience an average 1% increase in rainfall. But the critical fact is that this rainfall increase is not evenly distributed in time and space.
· Climate change will tip some regions into perpetual rainfall deficit, some into new Saharas, and make some untenable for human habitation. Droughts are transient but in the areas under discussion there is no prospect that the rain will return.
· During the 1960s Africa’s Sahel region experienced a sudden decline in rainfall and there is no sign that the life-giving monsoon rains will return.
· Climatologists at the National Center for Atmospheric Research in Boulder, Colorado found that a single climatic variable was responsible for much of the rainfall decline: rising sea-surface temperatures in the Indian Ocean.
· The Indian Ocean is the most rapidly warming ocean on earth, and the computer study showed that as it warms, the conditions that generate the Sahelian monsoon weaken. As a result, by the 1960s the Sahelian “drought” had begun.
· Global dimming, due in large part to particles spewed out into the air by coal-fired power plants, automobiles, and factories, is a phenomenon that cuts down the amount of sunlight reaching Earth’s surface. It has caused a cooling of the oceans around Europe, which has further weakened the monsoon.
· Around half of the global dust in the air today originates in arid Africa, and the impact of the drying is so great that the planet’s atmospheric dust loading has increased by a third.
· During the first 146 years of European habitation of the southwest of Australia (1829-1975), the reliable winter rainfall brought prosperity and opportunity. Since then the region has endured a decrease in rainfall averaging 15%.
· Under every square yard of this land lies an average of between 150 and 250 pounds of salt. Water far saltier than sea water began to creep upward, killing everything it touched. Today, impoverished and bankrupt farmers are facing the worst case of dry-land salinity in the world.
· For Perth, the decline in winter rainfall resulted in light showers that soaked into the soil and did not reach the dams, a cut of 50% of the city’s surface water supply between 1975 and 1996. Sydney’s water supply declined 45% between 1990 and 2003.
· Between 1998 and 2002 waters in the eastern Pacific were a few degrees cooler than normal, while those in the central western Pacific were warmer – around 86°F – than average. These conditions shifted the jet stream northward, pushing storms that would usually track at around 35° of latitude to north of 40°.
· It would be a mistake to assume that any region is safe from megadrought. The biggest problem is for cities of the U.S. west, which are tethered to ever dwindling water supplies.
Chapter 15: Playing at Canute
· 5,000 years ago the oceans stood at least 300 feet lower than they do today. The North American continent was a veritable empire of ice, exceeding even the Antarctic in the volume of frozen water it supported.
· As the great American ice caps melted, they alone released enough water to raise global sea levels by 243 feet. The sea rose rapidly until around 8,000 years ago, when it reached its present level and conditions stabilized.
· All that remains of the great Northern Hemisphere ice caps today is the Greenland ice sheet, the sea of ice of the Artic Ocean, and a few continental glaciers. Alaska’s spectacular Columbia Glacier has retreated seven miles over the last 20 years.
· The Greenland ice cap contains enough water to raise sea levels globally by around 23 feet. In the summer of 2002, it, along with the Arctic ice cap, shrank by a record 400,000 square miles – the largest decrease ever recorded. Two years later, in 2004, it was discovered that Greenland’s glacier’s were melting ten times faster than previously thought.
· The greatest extent of ice in the Northern hemisphere is the sea ice covering the polar sea, and since 1979 its extent has contracted 20%. The remaining ice is only 60% as thick as it was four decades earlier.
· This prodigious melting has no direct consequence for rising seas. The Arctic ice cap is sea ice, nine-tenths of which is submerged. Only land ice, as it melts and runs into the sea, adds to sea levels.
· The indirect effects of melting sea ice will significantly change the Earth’s albedo. Ice, particularly at the Poles, reflects back into space up to 90% of the sunlight hitting it. Water reflects a mere 5% to 10% of light back into space. Replacing Arctic ice with a dark ocean is a classic case of a positive feedback loop which will hasten the melting of the remaining continental ice.
· Over the last decade of the 20th century the rate of sea level rise doubled, much coming from expansion of the oceans. This thermal expansion is expected to raise sea levels by 20 to 80 inches over the next 500 years. Melting polar ice will be by far the greatest contributor to a rising sea in the coming decades.
· In February 2002 the Larsen B ice shelf – at 1268 square kilometers it was the size of Luxembourg – broke up over a matter of weeks. Almost immediately the glaciers that fed into the now fragmented ice sheet began to flow more rapidly.
· In 2003 a study summarizing a decade of satellite data revealed the ultimate cause of Larsen’s collapse – the melting of the ice from below. The Weddell Sea had warmed by 0.58°F since 1972 – enough to initiate the melting.
· A NASA study published in 2004, reported that a large section of the Amundsen ice plain had become so thin that they might float free of their “anchors” on the ocean bed and collapse like Larsen B.
· Climate scientists are debating whether humans have already tripped the switch that will create an ice-free earth. If so, we have already committed our planet and ourselves to a rise in the level of the sea of around 220 feet.
PART 3: THE SCIENCE OF PREDICTION
Chapter 17: The Commitment and the Approaching Extreme Danger
· Researchers at the Hadley Centre talk of a “physical commitment to climate change.” This refers to the fact that the full impact of the greenhouse gases already in the atmosphere will not be felt until around 2050.
· Most of the damage was done starting from the 1950s, when our parents and grandparents drove about in their fin-tailed Chevrolets and powered their labor-saving household appliances from inefficient coal-burning power stations.
· The baby-boomer generation is most culpable: Half of the energy generated since the Industrial Revolution has been consumed in the last 20 years.
· Life is flexible and if given sufficient time it can adapt to the most extreme conditions. It is the rate of change that is important.
Chapter 21: The Pack of Jokers
· Earth’s systems sometimes snap, and a new world order is suddenly created, to which the survivors must adapt or perish.
· There are three main tipping points: a slowing or collapse of the Gulf Stream; the demise of the Amazon rain forests; and the release of gas hydrates from the sea floor.
Scenario 1: Collapse of the Gulf Stream
· In 2003 the pentagon commissioned a report outlining the implications for U.S. national security should the Gulf Stream collapse. Their scenario involves a slowing of the Gulf Stream as a result of freshwater from melting ice accumulating in the North Atlantic, triggering a “magic gate” that will abruptly change the world’s climate. There would be persistent drought over critical agricultural regions and a plunge in temperatures of more than 5°F for Europe, just under 5°F for North America, and 3.6°F increases for Australia, South America, and southern Africa.
· Mass starvation would be followed by mass emigration as regions as diverse as Scandinavia, Bangladesh, and the Caribbean become incapable of supporting their populations. New political alliances would be forged as a scramble for resources ensues, and the potential for war would be greatly heightened.
· With water supplies and energy supplies strained, Australia and the United States would focus increasingly on border protection to keep out the migrating hordes from Asia and the Caribbean. The European Union will either be unified with a focus on border protection or driven to collapse and chaos by internal squabbling.
· The Gulf Stream is the fastest ocean current in the world. The volume of water is simply stupendous, being 100 times as great as that of the Amazon. In the North Atlantic where the Gulf Stream releases its heat, it warms Europe’s climate as much as if the continent’s sunlight were increased by a third.
· As the waters of the Gulf Stream yield their heat, they sink, forming a great midocean waterfall. This waterfall is the powerhouse, as well as the Achilles heel, of the ocean currents of the entire planet, for history shows us that it has been interrupted time and again.
· As the earth’s climate shifted from full ice-house mode 20,000 years ago to the mild climate of today, the Gulf Stream was repeatedly destabilized – most spectacularly between 12,700 and 11,700 years ago, when winter temperatures in the Netherlands plunged below -4°F, and summer temperatures averaged just 55°F to 57°F.
· Between 8,200 and 7,800 years ago, there was another collapse, while between 4,200 and 3,900 years ago, it may have slowed again.
· On the two earliest occasions the disruption was caused by vast influxes of freshwater into the north Atlantic: the first by the bursting of an ice-dammed lake; and then with the implosion of the remains of North America’s Laurentide Ice Sheet.
· Freshwater disrupts the Gulf Stream because it dilutes its saltiness, preventing it from sinking and thus disrupting the circulation of the oceans worldwide.
· The likelihood of the Gulf Stream slowing down again depends on whether a sufficient flow of freshwater can still be generated. The frozen north contains enough ice to realize that liquid potential, and to this we must add the increasing rainfall already manifesting itself across the region.
· From 1970, a steady freshening of the surface waters of the northeast Atlantic has been recorded: The salinity graph describes a graceful, downward arc that speaks powerfully of the emerging trend.
· Ice cores from Greenland indicate that, as the Gulf Stream slowed in the past, the island experienced a massive 18°F drop in temperature in as little as a decade.
Scenario 2: Collapse of the Amazon Rain Forest
· The plants of the Amazon effectively create their own rainfall. Water transpired forms clouds that are blown ever westward, where the moisture falls as rain, only to be transpired again and again.
· Plants don’t want to lose their vapor, but inevitably they do lose some whenever they open the breathing holes in their leaves (stomata), to gain CO2 from the atmosphere. As CO2 levels increase, transpiration will be reduced. And with less transpiration there will be less rain.
· Other factors contribute to a decline in rainfall, the cumulative impact of which is to reduce rainfall from the current basin-wide average of 0.2 inch per day to 0.08 inch per day by 2100, while in northeastern Amazonia it will fall to almost zero.
· These conditions, combined with a basin-wide rise in temperature of 10°F will, the model indicates, stress plants to the point that collapse of the Amazonian rain forest will become inevitable.
· The ultimate outcome of this series of positive feedback loops is that by 2100 the earth’s atmosphere will have close to 1,000 parts per million of CO2 rather than the 710 predicted in earlier models.
· Surface temperatures will rise by 18°F rather than the 10°F predicted, rainfall in the basin will drop by 64%, there will be a 78% loss of carbon stored in vegetation and a 72% loss of soil carbon.
· If the model is correct we should see signs of forest collapse around 2040. What is so terrifying about this scenario is that it will greatly hasten climate change, making many of its most pernicious consequences in evitable.
Scenario 3: Methane release from the sea floor
· Clathrates refers to the structure of an ice-methane combination in which ice crystals trap molecules of methane in tiny “cages.” They contain lots of gas under high pressure.
· Massive volumes of clathrates lie buried in the seabed around the world. The material is kept solid only by the pressure of the overlying water and the cold. If pressure on the clathrates was ever relieved, or the temperature of the deep oceans were to increase, colossal amounts of methane could be released.
· One such release in the North Sea 55 million years ago. Paleontologists now suspect that the unleashing of the clathrates may have been responsible for the biggest extinction of all time.
· So vast was the input of greenhouse gas to the atmosphere that it was thought to have led to an initial rise in global average temperatures of about 11°F. This co-occurred with widespread acid rain caused by the sulphur dioxide, which released yet more carbon. The increasing temperature triggered the release of huge volumes of methane from the tundra and clathrates on the sea floor.
Chapter 22: Civilization: Out With a Whimper?
· Our civilization is built on two foundations: our ability to grow enough food to support a large number of people who are engaged in tasks other than growing food; and our ability to live in groups large enough to support great institutions.
· The basic needs of cities are food, water, and power. Water will be the first of the critical resources to be affected, for it is heavy, commands a low price, and thus is unprofitable to transport long distances. Perth and Sydney sit on the knife edge in terms of their water supply, and doubtless more cities will join the list as water shortages increase around the world.
· The peak in cereal reserves, of around 100 days, was reached in 1986, and fell to a low of 55 days in 1995. Although substantial wheat surpluses were recorded in 1999 and 2004, overall the trend in world food security has been a downward one.
· In future, crops will be stressed by higher temperature, more ozone at ground level, and changes in soil moisture, all of which will decrease yields. Thus, rather than an agricultural paradise, a CO2-rich world promises to be one in which crop production is lower than today.
· There is abundant evidence to support Lovelock’s idea that climate change may well, by destroying our cities, bring about the end of our civilization. Humanity, of course, would survive such a collapse, for people will persist in smaller, more robust communities such as villages and farms.
· If humans pursue a business-as-usual course for the first half of this century, I believe the collapse of civilization due to climate change becomes inevitable.