2010 Diary week 35
Global warming, climate change and weather extremes
Book Review
Below is the review of Part III of With Speed and Violence: Why Scientists Fear Tipping Points in Climate Change by Fred Pearce. These are some snippets: “Over three days in March 2002, there occurred one of the most dramatic alterations to the map of Antarctica since the end of the last ice age. A shelf of floating ice larger than Luxembourg and some 650 feet thick, which had been attached to the peninsular for thousands of years, shattered like a huge pane of glass, each a huge iceberg that floated away into the South Atlantic.” “Then in three climactic days at the start of March, the entire structure gave way. Some 500 billion tons of ice burst into the ocean.” “The discovery of the accelerating glaciers has, once again, turned conventional thinking about the dynamics of ice on its head. At Pine Island Bay the impacts of coastal melting are swiftly being felt throughout the glacier’s network of tributaries across the ice sheet.” “NASA glaciologist Eric Rignot reported in 2004 that the two glaciers are dumping more than 200 million acre-feet of ice a year into Pine Island Bay. This dwarfs even the very heavy snowfall, which adds about 130 million acre-feet a year.” “The net “mass loss” of ice from the Pine Island Bay catchment has tripled in a decade.” “Studies of the Pine Island glacier show that its ice shelf is thinning fast. As it thins, ever more warm seawater penetrates beneath the glacier. The “grounding line,” the farthest point downstream where the ice makes contact with solid rock, has been retreating by more than a mile a year.” “The glacier is primed for runaway destruction.”
WITH SPEED AND VIOLENCE
WHY SCIENTISTS FEAR TIPPING POINTS IN CLIMATE CHANGE
FRED PEARCE
BEACON PRESS 2007
PART III
Chapter 7: On the Slippery Slope (Continued)
The Shelf: Down south, shattering ice uncorks the Antarctic
• Over three days in March 2002, there occurred one of the most dramatic alterations to the map of Antarctica since the end of the last ice age. A shelf of floating ice larger than Luxembourg and some 650 feet thick, which had been attached to the peninsular for thousands of years, shattered like a huge pane of glass, each a huge iceberg that floated away into the South Atlantic.
• Then in three climactic days at the start of March, the entire structure gave way. Some 500 billion tons of ice burst into the ocean.
• In many ways, says Richard Alley, what happened at Larsen B mirrored the processes under way in Greenland. “Water-filled cracks more than a few tens of yards deep can be opened easily by the pressure of water. Ponding of water at the ice surface increases the water pressure wedging cracks open.”
• Study of the diatoms in the sediment beneath the former shelf suggested that Larsen B had been there for the entire 12,000 years since the end of the last ice age, when a single ice sheet covered the whole region.
• Disappearing ice shelves do not contribute to sea level rise because their ice is already floating. But their disappearance does change what happens inland. Ice shelves buttress the glaciers that feed them.
• The glaciers that once discharged their ice onto the Larsen B shelf are now flowing into the sea eight times faster than they did before the shelf collapsed.
• Similar acceleration has happened after other ice sheet collapses. And that faster discharge of ice from land into ocean is raising sea levels.
• With the Ross Sea being the main outlet for several of the largest glaciers on the West Antarctic ice sheet, which contains enough ice to raise sea levels by six yards, the stakes are rising.
The Mercer Legacy: An Achilles heel at the bottom of the world
• At a time when everyone else saw Antarctic ice as just about the most dependable glacial feature on the planet, Mercer began to argue that much of it may have entirely disintegrated during the last interglacial era, about 125,000 years ago.
• “I contend that a major disaster – a rapid deglaciation of West Antarctica – may be in progress … within about 50 years.”
• The two ice sheets covering Antarctica are vast. The smaller of them, the West Antarctic ice sheet, covers around 1.5 million square miles. It is vulnerable because, like a giant ship that has foundered in shallows, it is perched precariously on an archipelago of largely submerged mountains.
• Ocean currents are swirling beneath its giant ice shelves. The sea temperatures today are close to freezing, but the risk is that as they rise, melting will loosen the ice sheet’s moorings.
• The discovery of the accelerating glaciers has, once again, turned conventional thinking about the dynamics of ice on its head. At Pine Island Bay the impacts of coastal melting are swiftly being felt throughout the glacier’s network of tributaries across the ice sheet.
• NASA glaciologist Eric Rignot reported in 2004 that the two glaciers are dumping more than 200 million acre-feet of ice a year into Pine Island Bay. This dwarfs even the very heavy snowfall, which adds about 130 million acre-feet a year.
• The net “mass loss” of ice from the Pine Island Bay catchment has tripled in a decade.
• Studies of the Pine Island glacier show that its ice shelf is thinning fast. As it thins, ever more warm seawater penetrates beneath the glacier. The “grounding line,” the farthest point downstream where the ice makes contact with solid rock, has been retreating by more than a mile a year.
• The glacier is primed for runaway destruction.
• If the Pine Island and Thwaites glaciers are on a one-way trip to disaster, the implications are global. Together they drain an area containing enough water to raise sea levels worldwide by 1-2 yards.
• In all probability, the Pine Island and Thwaites glaciers are already the biggest causes of sea level rise worldwide.
Chapter 10: Rising Tides: Saying “toodle-oo” to Tuvalu
• The Carteret Islands are to be abandoned. Life is simply too hard for their 2,000 inhabitants, huddled on a clutch of low-lying coral islands in the South Pacific, with a total surface area of just 150 acres, and rising sea levels threatening to wash them away.
• Their fields have been invaded by salt water, and the breadfruit crops have died.
• In 2001, when strong winds and rough seas cut off the atoll and prevented them from going to sea to catch fish, many resorted to eating seaweed.
• The 10,000 citizens of the nine inhabitated South Pacific islands of Tuvalu are also abandoning ship. It seems to be destined to be the first modern nation-state to disappear beneath the waves. One by one the island nations of the South Pacific are drowning.
• The world’s sea levels have been largely stable for the past 5,000 years, since the main phase of melting of ice sheets after the end of the last ice age abated. But around 1900, the rise began to increase and has accelerated in the past 50 years to around 0.08 inches a year.
• About half this increase is probably due to thermal expansion and half due to the resumed melting of the world’s glaciers and ice caps.
• The first signs of a further acceleration emerged in the early 1990s, when satellite data suggested a sudden rise of 0.11 inches a year. Since 1999, it may have risen further, to 0.14 inches.
• The planet has a history of startling sea level rise that cannot be explained by the conventional models used by glaciologists to predict future change.
• Around 20,000 years ago, at what glaciologists call the “glacial maximum,” so much water was tied up in ice on land that sea levels were around 400 feet lower than they are today. Then a thaw began.
• Sea levels initially rose by around 0.4 inches a year – 4 or 5 times faster than today. Then something happened.
• About 14,500 years ago, the tides went haywire. Within 400 years, sea levels rose by 65 feet, an average of a yard every 20 years.
• If such a rise happened today, you could say “toodle-oo” to Tuvalu by 2010; most of Bangladesh would be under water by 2020; millions of people on the Nile Delta would be looking for new homes by 2025; London would need a new Thames Barrier immediately.
• New Orleans? Well, forget New Orleans, and Florida, and most of the rest of the U.S. seaboard, too.
• Lagos, Karachi, Sydney, New York, Tokyo, Bangkok: you name your coastal megacity, and it would be abandoned by mid-century.
• How could such a thing have happened? It required the transfer into the oceans of about 13 billion acre-feet of ice every year throughout the 400 year period.
• Such discharges required the physical collapse of ice sheets on a grand scale. That can have happened only if the ice sheets were lubricated at their base by great rivers of meltwater, and destabilized at the coasts by the shattering of ice shelves.
• We can expect that temperatures will rise by about 3 to 5 degrees within the coming century. That, says Hansen, would make them as high as they were 3 million years ago, before the ice ages started, when sea levels were about 25 yards higher than today, plus or minus 10 yards.
• Jim Hansen already sees evidence of the start of runaway melting in Greenland and Antarctica, and anticipates that “sea levels might rise by a couple of yards this century, and several more the next century.”
• The world’s ice sheets are a ticking time bomb. There is no reason why the events of 14,000 years ago should not be repeated in the 21st century.
• Hansen’s hunch is that an increasing amount of global warming will be harnessed to melting the ice sheets. That could slow the heating of the atmosphere, but at the price of faster-rising sea levels.
• Within a few decades, vast armadas of icebergs could be breaking off the Greenland ice sheet, making shipping lanes impassable and cooling ocean surfaces like the ice in a gin and tonic.
• Sea level rise is “the big global issue.” He believes it will transcend all others in the coming century.
PART III: RIDING THE CARBON CYCLE
CHAPTER 11: In the Jungle: Would we notice if the Amazon went up in smoke?
• The Amazon rainforest is the largest living reservoir of carbon dioxide on the land surface of Earth. Its trees contain some 77 billion tons of carbon, and its soils perhaps as much again.
• The rainforest is also an engine of the world’s climate system, recycling both heat and moisture. More than half the raindrops that fall on the forest canopy never reach the ground; instead they evaporate back into the air to produce more rain downwind.
• The forest needs the rain, but the rain needs the forest.
• Hard as they try, farmers armed with chain saws and firebrands can destroy the rainforest only slowly. Despite many decades of effort, most of this jungle, the size of western Europe, remains in tact. Climate change, on the other hand, could overwhelm it in a few years.
• Just as with the Greenland ice sheet, the idea that the Amazon is stable has taken a knock: some researchers believe it is in reality a very dynamic place, and that the entire ecosystem may be close to a tipping point beyond which it will suffer runaway destruction in an orgy of fire and drought.
• Dan Nepstad is a forest ecologist nominally attached to the Woods Hole Research Center but based for more than two decades in the Amazon, conducting large experiments in it.
• The forest can handle two years of drought without great trouble, but after that the trees start dying, releasing carbon to the air as they rot, and exposing the forest floor to the drying sun.
• Nepstad’s experiments are part of a huge international effort to monitor the health of the Amazon, called the Large-scale Biosphere-Atmosphere Experiment in Amazonia. The current estimate is that fires in the forest are releasing some 200 million tons of carbon a year – far more than is absorbed by the growing forest.
• The Amazon has become a significant source of carbon dioxide, adding to global warming.
• The experiment is discovering a drying trend across the Amazon that leaves it ever more vulnerable to fires.
• The rains failed across the Amazon through 2005, killing trees, triggering fires, and reducing the ability of the forest to recycle moisture in the future – thus increasing the risk of future drought.
• The 2005 drought was caused by extremely warm temperatures in the tropical Atlantic – the same high temperatures that are believed to have caused the record-breaking hurricane season that year.
• The Amazon rainforest will be dead and gone before the end of the century. “The region will be able to support only shrubs or grass at most,” said a study published by the Hadley Centre in 2005.
• The Amazon rainforest does not just create rain for itself. By one calculation, approaching 6 trillion tons of water evaporates from the jungle each year, and about half of that moisture is exported from the Amazon basin.
• The forest is a giant rainmaking machine for most of South America. As much as half of Argentina’s rain may begin as evaporation from the Amazon. If the rainforest expires, the hydrological engine, too, is likely to falter, and the link will be cut.
Chapter 12: Wildfires of Borneo. Climate in the mire from burning swamp
• It was late 1997, and the rainforest was burning. The most intense El Niňo event on record in the Pacific Ocean had stifled the storm clouds that normally bring rain to Borneo and the other islands of Indonesia.
• Landowners took advantage of the dry weather to burn the forest and carve out new plantations for palm oil and other profitable crops. The fires got out of control, and the result was one of the greatest forest fires in human history.
• In 2004, U.S. government researchers published a detailed analysis of gas measurements made around the world. It showed that roughly 2.2. billion tons more carbon than usual entered the atmosphere during 1998 – and two thirds of that excess came form Southeast Asia.
• The Borneo fires must have contributed most of that, and burning peat was almost certainly the major component.
• Every year, farmers continue burning forest in Borneo to clear land for farming. Whenever the weather is dry, those fires spread out through the jungle and down into the peat.
• Satellite images suggest that 12 million acres of the swamp forests were in flames at one point during late 2002.
• Fire in Borneo and the Amazon may be turning the world’s biggest living “sinks” for carbon dioxide into the most dynamic new source of the gas in the 21st century.
Chapter 13: Sink to Source. Why the carbon cycle is set for a U-turn
• In 2003, the carbon sink blew a fuse. During July and August when Europe’s ecosystems would normally have been in full bloom and soaking up carbon dioxide at their fastest, around 550 million tons of carbon escaped from western European forests and fields – roughly equivalent to twice Europe’s emissions from burning fossil fuels during those two months.
• Ning Zeng, of the University of Maryland, found an area of drought stretching from the Mediterranean to Afghanistan. It had lasted from 1998 to 2002, and had eliminated a natural carbon sink across the region that had averaged 770 million tons a year over the previous two decades.
• Through the 1980s and into the early 1990s, the “CO2 fertilization effect” had been working rather well, with increased photosynthesis in the Northern Hemisphere soaking up ever more carbon dioxide. Sometime around 1993 that had tailed off, probably because of droughts and higher temperatures. Since the mid-1990s, the carbon sink had been in sharp decline.
• The findings, said Alon Angert of the University of California at Berkely, dashed widespread expectations of a continuing “greening trend” in which warm summers would speed plant growth and moderate climate change. Instead, “excess heating is driving the dieback of forests, accelerating soil carbon loss and transforming the land from a sink to a source of carbon to the atmosphere.”
• Further north, beyond the tree line, where some of the fastest warming rates in the world are currently being experienced, fear is growing about the carbon stored in the thick layers of permanently frozen soil known as permafrost.
• David Lawrence of the NCAR, reported in 2005 that he expected the top 3 yards of permafrost across most of the Arctic to melt during the 21st century. This will leave a trail of buckled highways, toppled buildings, broken pipelines, and bemused reindeer; it will also unfreeze tens and perhaps hundreds of billions of tons of carbon.
• In those bogs and lakes where there is very little oxygen, most of the carbon will be converted into methane – which, as we will see in the next chapter, is an even more potent greenhouse gas.
• The day the biosphere turns from sink to source will be another tipping point in Earth’s system. Once under way, the process, like collapsing ice sheets, will be unstoppable.
• Nobody is sure when the tipping point might occur; much will depend on how fast we allow temperatures to rise.
• Only one country has completed anything like a national study of the current impact of these changes on its carbon budget. Guy Kirk, of the National Soil Resources Institute, part of Cranfield University, has done the job for Britain.
• His conclusion is that the British biosphere is releasing about 1% of its carbon store into the atmosphere every year – enough to turn the whole country into desert in one century.