2010 Diary week 31
Global warming, climate change and weather extremes
Book Review
These are some snippets from Part IV of the review of The Weather Makers: How Man is Changing the Climate and What it Means for Life on Earth by Tim Flannery: “The Kyoto protocol may be the most bitterly contested international treaty ever to be realized, which when one considers its modest goals appears strange indeed. Two big reasons for this are economics and politics.” “In the developed world, energy use is growing at the rate of 2% per annum or less, and with such low rates of growth the only way for one sector (such as wind, gas, or coal) to grow is to take from another sector’s share. A furious struggle is ensuing between the potential winners and losers.” “Australia has the highest per capita greenhouse emissions of any industrialized country – 25% higher than the United States – and Australia’s growth in emissions over the last decade has been faster than that of other OECD countries. 90% of Australia’s electricity is generated by burning coal.” “Given Kyoto’s manifest problems, it may seem best to tax carbon emissions at the smokestack, yet this simple and effective solution finds no favor in Australia or the United States.” “For those who urge abandonment or who criticize Kyoto, there are two questions: What do you propose to replace Kyoto with, and how do you propose to secure international agreement for your alternative?” “One of the key decisions in our war on climate change is whether to focus our efforts on transport or the electricity grid. Decarbonizing the grid wins hands down. For with that achieved, we can use renewable power thus generated to decarbonize transport.”
THE WEATHER MAKERS
HOW MAN IS CHANGING THE CLIMATE AND WHAT IT MEANS FOR LIFE ON EARTH
TIM FLANNERY
ATLANTIC MONTHLY PRESS 2005
PART IV
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.
· The first evidence of such a shift emerged in Africa’s Sahel region during the 1960s. Four decades have now passed since the 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 used computer models to simulate rainfall regimes in the region between 1930 and 2003.
· A single climatic variable was responsible for much of the rainfall decline: rising sea-surface temperatures in the Indian Ocean, which resulted from an accumulation of greenhouse gases.
· 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.
· So big is the Sahelian climate shift that it could influence the climate of the entire planet.
· 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%.
· The deficit was felt at once on farms where variation of a few inches makes the difference between a good crop and failure. Winter rainfall has declined by more than 15%, while summer rainfall has increased.
· 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 most crucial impact from the decline in winter rainfall tended to fall 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 1966. Between 1997 and 2004 it had fallen more than a third from three decades earlier.
· Sydney’s water supply is one of the largest domestic water supplies in the world, able to store four times as much per capita as New York’s water supplies and nine times as much as London’s. Yet even this capacious storage has proved insufficient with a decline of 45% between 1990 and 2003.
· Much of the American west is in its fifth year of drought. Such dry conditions have not been seen in the region for around 700 years.
· 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. Changes under way are so vast that even a new program of dam building would be insufficient to counter them. The biggest problem is for cities of the U.S. west, which are tethered to ever dwindling water supplies.
Chapter 14: An Energetic Onion Skin
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; and there are signs that after 8,000 years, these remnants are beginning to melt away. 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 highest parts of both Greenland and the Antarctic ice domes are the only places on earth where significant negative temperature trends are occurring. This is comforting since a recent study concluded that should the Greenland ice cap ever melt, it would be impossible to regenerate it, even if our planet’s atmospheric CO2 was returned to preindustrial levels.
· 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 are important as this 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.
· As recently as 2001, rising seas looked to be one of the least pressing problems as over the preceding 150 years the oceans had risen by only 4 to 8 inches, or about a half inch per year. But over the last decade of the 20th century the rate of sea level rise doubled.
· Much of the sea level rise over the past century has come from expansion of the oceans. This thermal expansion is expected to raise sea levels by 20 to 80 inches over the next 500 years. From recent studies it has become evident that 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. While the Weddell Sea’s deep waters had warmed by 0.58°F since 1972, it was 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 were nearing a point that could allow them to float free of their “anchors” on the ocean bed and collapse like Larsen B.
· There is one bright spot in all this. The increased precipitation at the Poles is expected to bring more snow to the high Antarctic ice cap, which may compensate for some of the ice being lost at the continent’s margins.
· So swift have been the changes in ice plain science, and so great is the inertia of the ocean juggernaut, that 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 16: Model Worlds
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.
· How does this commitment relate to concerns that Earth may cross some threshold of climate change, beyond which lies extreme danger? What is the threshold of dangerous climate change?
· Life is flexible and if given sufficient time it can adapt to the most extreme conditions. It is the rate, not the direction or overall scale of change that is important. Which raises another question – dangerous to whom?
· Never in the history of humanity has there been a cost-benefit analysis that demands greater scrutiny.
Chapter 18: Leveling the Mountains
Chapter 19: How Can They Keep on Moving?
Chapter 20: Boiling the Abyss
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” that scientists are aware of for Earth’s climate: 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
· The importance of the Gulf Stream to the Atlantic rim countries is enormous. 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.
· The impacts would be compounded by the projected lack of cooperation between nations in the face of the disaster; 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; it is complex, spreading out into a series of gyres and subcurrents as its waters move northward.
· The volume of water is simply stupendous, being 100 times as great as that of the Amazon.
· At 46°F, its northern section is far warmer than the freezing waters that surround it. 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
· Scientists have discovered that the plants of the Amazon effectively create their own rainfall, for so vast is the volume of water transpired by them that it 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 all of these changes 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 – perhaps twice as much in energy terms as all other fossil fuels combined. 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.
· We have seen the consequences of one such release in the North Sea 55 million years ago, but paleontologists now suspect that the unleashing of the clathrates may have been responsible for a far more profound change – 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.
· Such was the total impact of the increasing temperature thereby generated that it triggered the release of huge volumes of methane from the tundra and clathrates on the sea floor.