Pentagon report 2020
Courtesy ECES Org
Pentagon report warns of nuclear war, mega-droughts, famine, mass migrations and widespread rioting around the world by 2020 as abrupt climate change due to global warming causes massive disruption of the world’s food and water supplies.
According to the U.K. Guardian, a Pentagon report warns that major European cities could be sunk beneath rising seas, Britain plunged into a “Siberian” climate by 2020, and nuclear war, mega-droughts, famine and widespread rioting will erupt across the world as global warming increasingly disrupts the global climate and food and water supplies around the world.
Unlike most climate change studies which examine global warming over more than a century, the Pentagon study is based on an “abrupt climate change” that scientists say has happened in the past and could happen again soon, according to Knight Ridder. The planning document predicts that abrupt climate change could bring the planet to the edge of anarchy as countries develop nuclear weapons to defend and secure dwindling food, water and energy supplies. The threat to global stability vastly eclipses that of terrorism, say the experts privy to its contents.
“Disruption and conflict will be endemic features of life,” concludes the Pentagon analysis. “Once again, warfare would define human life.”
Key findings of the report include:
Future wars will be fought over the issue of survival rather than religion, ideology or national honor.
By 2007 violent storms will smash coastal barriers rendering large parts of the Netherlands inhabitable. Cities like The Hague are abandoned. In California, levees in the Sacramento river delta are breached, disrupting the aqueduct system transporting water from north to south.
Between 2010 and 2020 Europe is hardest hit by climatic change with an average annual temperature drop of 6°F. Climate in Britain becomes colder and drier as weather patterns begin to resemble Siberia.
Deaths from war and famine run into the millions until the planet’s population is reduced by such an extent the Earth can cope.
Riots and internal conflict tear apart India, South Africa and Indonesia.
Access to water becomes a major battleground. The Nile, Danube and Amazon are all mentioned as being high risk.
A “significant drop” in the planet’s ability to sustain its present population will become apparent over the next 20 years.
Rich areas like the U.S. and Europe will become “virtual fortresses” to prevent millions of migrants from entering after being forced from land drowned by sea-level rise or no longer able to grow crops. Waves of boat people pose significant problems.
Nuclear arms proliferation is inevitable. Japan, South Korea, and Germany develop nuclear-weapons capabilities, as do Iran, Egypt and North Korea. Israel, China, India and Pakistan also are poised to use the bomb.
By 2010 the U.S. and Europe will experience a third more days with peak temperatures above 90F. Climate becomes an “economic nuisance” as storms, droughts and hot spells create havoc for farmers.
Europe will face huge internal struggles as it copes with massive numbers of migrants washing up on its shores. Immigrants from Scandinavia will seek warmer climes to the south. Southern Europe is beleaguered by refugees from hard-hit countries in Africa.
Mega-droughts affect the world’s major breadbaskets, including America’s Midwest, where strong winds bring soil loss.
China’s huge population and food demand make it particularly vulnerable to the impacts of global warming.
Bangladesh will become nearly uninhabitable because of rising sea levels which contaminate inland water supplies.
Military showdowns could be fast and furious: In 2015, conflict in Europe over supplies of food and water leads to strained relations. In 2022, France and Germany battle over the Rhine River’s water. In 2025, as energy costs increase in nations struggling to cope with warmer and colder weather, the United States and China square off over access to Saudi Arabian oil.
The Pentagon report’s findings will prove embarrassing to the Bush administration, which has repeatedly denied that climate change even exists. Experts said the report will also make unsettling reading for a president who has insisted national defence is a priority.
The report was commissioned by influential Pentagon defence adviser Andrew Marshall, who has held considerable sway on U.S. military thinking over the past three decades. He was the man behind a sweeping recent review aimed at transforming the U.S. military under Defense Secretary Donald Rumsfeld. Marshall, 82, is a Pentagon legend who heads a secretive think-tank dedicated to weighing risks to national security called the Office of Net Assessment. Dubbed “Yoda” by Pentagon insiders who respect his vast experience, he is also credited with being behind the Department of Defense’s push on ballistic-missile defence.
An imminent scenario of catastrophic climate change is “plausible and would challenge United States national security in ways that should be considered immediately,” say the authors, Peter Schwartz, a CIA consultant and former head of planning at Royal Dutch/Shell Group, and Doug Randall of the California-based Global Business Network.
Climate change “should be elevated beyond a scientific debate to a U.S. national security concern,” Schwartz and Randall conclude after warning that as early as next year widespread flooding by a rise in sea levels will create major upheaval for millions.
Already, according to Randall and Schwartz, the planet is carrying a higher population than it can sustain. By 2020 “catastrophic” shortages of water and energy supply will become increasingly harder to overcome, plunging the planet into war. They warn that 8,200 years ago climatic conditions brought widespread crop failure, famine, disease and mass migration of populations that could soon be repeated.
Randall said the potential ramifications of rapid climate change would create global chaos. “This is depressing stuff,” he said. “It is a national security threat that is unique because there is no enemy to point your guns at and we have no control over the threat.”
Randall added that it is already possibly too late to prevent a disaster happening. “We don’t know exactly where we are in the process. It could start tomorrow and we would not know for another five years,” he said. “The consequences for some nations of the climate change are unbelievable. It seems obvious that cutting the use of fossil fuels would be worthwhile.”
Last week the Bush administration came under heavy fire from a large body of respected scientists who say it cherry-picks science to suit its policy agenda and suppresses studies that it doesn’t like. Jeremy Symons, a former whistleblower at the Environmental Protection Agency (EPA) who left the EPA in protest at political interference, said suppression of the report for four months is a further example of the White House trying to bury the threat of climate change: “It is yet another example of why this government should stop burying its head in the sand on this issue.”
Symons said the Bush administration’s close links to high-powered energy and oil companies is vital in understanding why climate change is received sceptically in the Oval Office. “This administration is ignoring the evidence in order to placate a handful of large energy and oil companies,” he said.
Senior British climatologists believe their verdicts could prove the catalyst in forcing Bush to accept climate change as a real and happening phenomenon. A group of eminent U.K. scientists recently visited the White House to voice their fears over global warming, part of an intensifying drive to get the US to treat the issue seriously. Reportedly, U.S. officials were extremely sensitive about the issue when faced with the British scientists’ complaints that the U.S. public stance appears increasingly out of touch. One source even claims that the White House has written to complain about some of the comments attributed to Professor Sir David King, Tony Blair’s chief scientific adviser, after he branded the President’s position on the issue as indefensible.
Among those scientists present at the White House talks were Professor John Schellnhuber, former chief environmental adviser to the German government and head of the U.K.’s leading group of climate scientists at the Tyndall Centre for Climate Change Research. He said that the Pentagon’s internal fears should prove the “tipping point” in persuading Bush to accept that global warming-driven climate change is real.
Sir John Houghton, former chief executive of the Meteorological Office – and the first senior figure to liken the threat of climate change to that of terrorism – said: “If the Pentagon is sending out that sort of message, then this is an important document indeed.”
Robert Watson, chief scientist for the World Bank and former chair of the Intergovernmental Panel on Climate Change, added that the Pentagon’s dire warnings could no longer be ignored. “Can Bush ignore the Pentagon? It’s going be hard to blow off this sort of document. It’s hugely embarrassing. After all, Bush’s single highest priority is national defense. The Pentagon is no wacko, liberal group, generally speaking it is conservative. If climate change is a threat to national security and the economy, then he has to act. There are two groups the Bush Administration tend to listen to, the oil lobby and the Pentagon,” said Watson.
So dramatic are the report’s scenarios, Watson said, that they may prove vital in the U.S. elections. Democratic frontrunner John Kerry is known to accept climate change as a real problem. Scientists disillusioned with Bush’s stance are reportedly threatening to make sure Kerry uses the Pentagon report in his campaign.
Apparently there is a significant and very interesting split developing among the ruling elite over what to do about the potentially disastrous impacts of global warming, as evidenced by following article on the Pentagon report – Climate Collapse: The Pentagon’s Weather Nightmare – from Fortune magazine:
Global warming may be bad news for future generations, but let’s face it, most of us spend as little time worrying about it as we did about al Qaeda before 9/11. Like the terrorists, though, the seemingly remote climate risk may hit home sooner and harder than we ever imagined. In fact, the prospect has become so real that the Pentagon’s strategic planners are grappling with it.
The threat that has riveted their attention is this: Global warming, rather than causing gradual, centuries-spanning change, may be pushing the climate to a tipping point. Growing evidence suggests the ocean-atmosphere system that controls the world’s climate can lurch from one state to another in less than a decade – like a canoe that’s gradually tilted until suddenly it flips over. Scientists don’t know how close the system is to a critical threshold. But abrupt climate change may well occur in the not-too-distant future. If it does, the need to rapidly adapt may overwhelm many societies – thereby upsetting the geopolitical balance of power.
Though triggered by warming, such change would probably cause cooling in the Northern Hemisphere, leading to longer, harsher winters in much of the U.S. and Europe. Worse, it would cause massive droughts, turning farmland to dust bowls and forests to ashes. Picture last fall’s California wildfires as a regular thing. Or imagine similar disasters destabilizing nuclear powers such as Pakistan or Russia – it’s easy to see why the Pentagon has become interested in abrupt climate change.
Climate researchers began getting seriously concerned about it a decade ago, after studying temperature indicators embedded in ancient layers of Arctic ice. The data show that a number of dramatic shifts in average temperature took place in the past with shocking speed – in some cases, just a few years.
The case for angst was buttressed by a theory regarded as the most likely explanation for the abrupt changes. The eastern U.S. and northern Europe, it seems, are warmed by a huge Atlantic Ocean current that flows north from the tropics – that’s why Britain, at Labrador’s latitude, is relatively temperate. Pumping out warm, moist air, this “great conveyor” current gets cooler and denser as it moves north. That causes the current to sink in the North Atlantic, where it heads south again in the ocean depths. The sinking process draws more water from the south, keeping the roughly circular current on the go.
But when the climate warms, according to the theory, fresh water from melting Arctic glaciers flows into the North Atlantic, lowering the current’s salinity – and its density and tendency to sink. A warmer climate also increases rainfall and runoff into the current, further lowering its saltiness. As a result, the conveyor loses its main motive force and can rapidly collapse, turning off the huge heat pump and altering the climate over much of the Northern Hemisphere.
Scientists aren’t sure what caused the warming that triggered such collapses in the remote past. (Clearly it wasn’t humans and their factories.) But the data from Arctic ice and other sources suggest the atmospheric changes that preceded earlier collapses were dismayingly similar to today’s global warming. As the Ice Age began drawing to a close about 13,000 years ago, for example, temperatures in Greenland rose to levels near those of recent decades. Then they abruptly plunged as the conveyor apparently shut down, ushering in the “Younger Dryas” period, a 1,300-year reversion to ice-age conditions. (A dryas is an Arctic flower that flourished in Europe at the time.)
Though Mother Nature caused past abrupt climate changes, the one that may be shaping up today probably has more to do with us. In 2001 an international panel of climate experts concluded that there is increasingly strong evidence that most of the global warming observed over the past 50 years is attributable to human activities – mainly the burning of fossil fuels such as oil and coal, which release heat-trapping carbon dioxide. Indicators of the warming include shrinking Arctic ice, melting alpine glaciers, and markedly earlier springs at northerly latitudes. A few years ago such changes seemed signs of possible trouble for our kids or grandkids. Today they seem portents of a cataclysm that may not conveniently wait until we’re history.
Accordingly, the spotlight in climate research is shifting from gradual to rapid change. In 2002 the National Academy of Sciences issued a report concluding that human activities could trigger abrupt change. Last year the World Economic Forum in Davos, Switzerland, included a session at which Robert Gagosian, director of the Woods Hole Oceanographic Institution in Massachusetts, urged policymakers to consider the implications of possible abrupt climate change within two decades.
Such jeremiads are beginning to reverberate more widely. Billionaire Gary Comer, founder of Lands’ End, has adopted abrupt climate change as a philanthropic cause. Hollywood has also discovered the issue – next summer 20th Century Fox is expected to release The Day After Tomorrow, a big-budget disaster movie starring Dennis Quaid as a scientist trying to save the world from an ice age precipitated by global warming.
Fox’s flick will doubtless be apocalyptically edifying. But what would abrupt climate change really be like? Scientists generally refuse to say much about that, citing a data deficit. But recently, renowned Department of Defense planner Andrew Marshall sponsored a groundbreaking effort to come to grips with the question. A Pentagon legend, Marshall, 82, is known as the Defense Department’s “Yoda” – a balding, bespectacled sage whose pronouncements on looming risks have long had an outsized influence on defense policy. Since 1973 he has headed a secretive think tank whose role is to envision future threats to national security. The Department of Defense’s push on ballistic-missile defense is known as his brainchild. Three years ago Defense Secretary Donald Rumsfeld picked him to lead a sweeping review on military “transformation,” the shift toward nimble forces and smart weapons.
When scientists’ work on abrupt climate change popped onto his radar screen, Marshall tapped another eminent visionary, Peter Schwartz, to write a report on the national-security implications of the threat. Schwartz formerly headed planning at Royal Dutch/Shell Group and has since consulted with organizations ranging from the CIA to DreamWorks – he helped create futuristic scenarios for Steven Spielberg’s film Minority Report. Schwartz and co-author Doug Randall at the Monitor Group’s Global Business Network, a scenario-planning think tank in Emeryville, Calif., contacted top climate experts and pushed them to talk about what-ifs that they usually shy away from – at least in public.
The result is an unclassified report, completed late last year, that the Pentagon has agreed to share with Fortune. It doesn’t pretend to be a forecast. Rather, it sketches a dramatic but plausible scenario to help planners think about coping strategies. Here is an abridged version:
A total shutdown of the ocean conveyor might lead to a big chill like the Younger Dryas, when icebergs appeared as far south as the coast of Portugal. Or the conveyor might only temporarily slow down, potentially causing an era like the “Little Ice Age,” a time of hard winters, violent storms, and droughts between 1300 and 1850. That period’s weather extremes caused horrific famines, but it was mild compared with the Younger Dryas.
For planning purposes, it makes sense to focus on a midrange case of abrupt change. A century of cold, dry, windy weather across the Northern Hemisphere that suddenly came on 8,200 years ago fits the bill – its severity fell between that of the Younger Dryas and the Little Ice Age. The event is thought to have been triggered by a conveyor collapse after a time of rising temperatures not unlike today’s global warming. Suppose it recurred, beginning in 2010. Here are some of the things that might happen by 2020:
At first the changes are easily mistaken for normal weather variation – allowing skeptics to dismiss them as a “blip” of little importance and leaving policymakers and the public paralyzed with uncertainty. But by 2020 there is little doubt that something drastic is happening. The average temperature has fallen by up to five degrees Fahrenheit in some regions of North America and Asia and up to six degrees in parts of Europe. (By comparison, the average temperature over the North Atlantic during the last ice age was ten to 15 degrees lower than it is today.) Massive droughts have begun in key agricultural regions. The average annual rainfall has dropped by nearly 30% in northern Europe, and its climate has become more like Siberia’s.
Violent storms are increasingly common as the conveyor becomes wobbly on its way to collapse. A particularly severe storm causes the ocean to break through levees in the Netherlands, making coastal cities such as the Hague unlivable. In California the delta island levees in the Sacramento River area are breached, disrupting the aqueduct system transporting water from north to south.
Megadroughts afflict the U.S., especially in the southern states, along with winds that are 15% stronger on average than they are now, causing widespread dust storms and soil loss. The U.S. is better positioned to cope than most nations, however, thanks to its diverse growing climates, wealth, technology, and abundant resources. That has a downside, though: It magnifies the haves-vs.-have-nots gap and fosters bellicose finger-pointing at America.
Turning inward, the U.S. effectively seeks to build a fortress around itself to preserve resources. Borders are strengthened to hold back starving immigrants from Mexico, South America, and the Caribbean islands – waves of boat people pose especially grim problems. Tension between the U.S. and Mexico rises as the U.S. reneges on a 1944 treaty that guarantees water flow from the Colorado River into Mexico. America is forced to meet its rising energy demand with options that are costly both economically and politically, including nuclear power and onerous Middle Eastern contracts. Yet it survives without catastrophic losses.
Europe, hardest hit by its temperature drop, struggles to deal with immigrants from Scandinavia seeking warmer climes to the south. Southern Europe is beleaguered by refugees from hard-hit countries in Africa and elsewhere. But Western Europe’s wealth helps buffer it from catastrophe.
Australia’s size and resources help it cope, as does its location – the conveyor shutdown mainly affects the Northern Hemisphere. Japan has fewer resources but is able to draw on its social cohesion to cope – its government is able to induce population-wide behavior changes to conserve resources.
China’s huge population and food demand make it particularly vulnerable. It is hit by increasingly unpredictable monsoon rains, which cause devastating floods in drought-denuded areas. Other parts of Asia and East Africa are similarly stressed. Much of Bangladesh becomes nearly uninhabitable because of a rising sea level, which contaminates inland water supplies. Countries whose diversity already produces conflict, such as India and Indonesia, are hard-pressed to maintain internal order while coping with the unfolding changes.
As the decade progresses, pressures to act become irresistible – history shows that whenever humans have faced a choice between starving or raiding, they raid. Imagine Eastern European countries, struggling to feed their populations, invading Russia – which is weakened by a population that is already in decline – for access to its minerals and energy supplies. Or picture Japan eyeing nearby Russian oil and gas reserves to power desalination plants and energy-intensive farming. Envision nuclear-armed Pakistan, India, and China skirmishing at their borders over refugees, access to shared rivers, and arable land. Or Spain and Portugal fighting over fishing rights – fisheries are disrupted around the world as water temperatures change, causing fish to migrate to new habitats.
Growing tensions engender novel alliances. Canada joins fortress America in a North American bloc. (Alternatively, Canada may seek to keep its abundant hydropower for itself, straining its ties with the energy-hungry U.S.) North and South Korea align to create a technically savvy, nuclear-armed entity. Europe forms a truly unified bloc to curb its immigration problems and protect against aggressors. Russia, threatened by impoverished neighbors in dire straits, may join the European bloc.
Nuclear arms proliferation is inevitable. Oil supplies are stretched thin as climate cooling drives up demand. Many countries seek to shore up their energy supplies with nuclear energy, accelerating nuclear proliferation. Japan, South Korea, and Germany develop nuclear-weapons capabilities, as do Iran, Egypt, and North Korea. Israel, China, India, and Pakistan also are poised to use the bomb.
The changes relentlessly hammer the world’s “carrying capacity” – the natural resources, social organizations, and economic networks that support the population. Technological progress and market forces, which have long helped boost Earth’s carrying capacity, can do little to offset the crisis – it is too widespread and unfolds too fast.
As the planet’s carrying capacity shrinks, an ancient pattern reemerges: the eruption of desperate, all-out wars over food, water, and energy supplies. As Harvard archeologist Steven LeBlanc has noted, wars over resources were the norm until about three centuries ago. When such conflicts broke out, 25% of a population’s adult males usually died. As abrupt climate change hits home, warfare may again come to define human life.
Over the past decade, data have accumulated suggesting that the plausibility of abrupt climate change is higher than most of the scientific community, and perhaps all of the political community, are prepared to accept. In light of such findings, we should be asking when abrupt change will happen, what the impacts will be, and how we can prepare – not whether it will really happen. In fact, the climate record suggests that abrupt change is inevitable at some point, regardless of human activity. Among other things, we should:
Speed research on the forces that can trigger abrupt climate change, how it unfolds, and how we’ll know it’s occurring.
Sponsor studies on the scenarios that might play out, including ecological, social, economic, and political fallout on key food-producing regions.
Identify “no regrets” strategies to ensure reliable access to food and water and to ensure our national security.
Form teams to prepare responses to possible massive migration, and food and water shortages.
Explore ways to offset abrupt cooling – today it appears easier to warm than to cool the climate via human activities, so there may be “geo-engineering” options available to prevent a catastrophic temperature drop.
In sum, the risk of abrupt climate change remains uncertain, and it is quite possibly small. But given its dire consequences, it should be elevated beyond a scientific debate. Action now matters, because we may be able to reduce its likelihood of happening, and we can certainly be better prepared if it does. It is time to recognize it as a national security concern.
The Pentagon’s reaction to this sobering report isn’t known – in keeping with his reputation for reticence, Andy Marshall declined to be interviewed. But the fact that he’s concerned may signal a sea change in the debate about global warming. At least some federal thought leaders may be starting to perceive climate change less as a political annoyance and more as an issue demanding action.
If so, the case for acting now to address climate change, long a hard sell in Washington, may be gaining influential support, if only behind the scenes. Policymakers may even be emboldened to take steps such as tightening fuel-economy standards for new passenger vehicles, a measure that would simultaneously lower emissions of greenhouse gases, reduce America’s perilous reliance on OPEC oil, cut its trade deficit, and put money in consumers’ pockets. Oh, yes – and give the Pentagon’s fretful Yoda a little less to worry about.
Finally, two side articles (here and (here) to the above Fortune article helps to further explain the increasing urgency about the global warming “debate”:
If abrupt climate change is on the way, the driving force will probably be a great ocean current that one scientist calls the “Achilles’ heel of our climate system.” The current, known as the great conveyor, sweeps north through the Atlantic, carrying warmth from the tropics to the eastern U.S. and northern Europe before looping south. If the current shuts down – which apparently can occur rapidly during times of global warming – the huge heat pump goes off, potentially causing drastic weather changes in just a few years.
Freezing. Deprived of the flow of warmth from the tropics, northern Europe could become more like Labrador – or Siberia.
Dust Bowl. Meanwhile, in North America, drought coupled with higher winds could ravage the Midwest’s farmlands.
Wildfires. Past conveyor shutdowns are linked to massive fires in North America, which left telltale ash in ancient Arctic ice.
Scientists used to think that major climate changes, like the onset of an ice age, took thousands of years to unfold. Now they know such dramatic transitions can occur in less than a decade. The probable trigger of abrupt climate changes, at least in the Northern Hemisphere, is the shutdown of a huge ocean current in the Atlantic Ocean. The current is driven by dense, salty water that flows north from the tropics and sinks in the North Atlantic. If fresh water is pumped into the northerly part of the current – which can occur as global warming melts Arctic ice – its salinity drops, making it less dense. This diminishing density can prevent the water from sinking in the North Atlantic, stopping the current’s flow. Much of Europe and the U.S. could become colder and drier if that happened.
Many details of this big picture remain hazy, including whether recent global warming threatens to shut down the Atlantic current. But over the past few years, scientists have detected disquieting trends:
In tandem with rising average temperatures across the globe, 3% to 4% of the Arctic ice cap has melted per decade since about 1970.
Recently the Arctic’s largest ice shelf broke up near Canada’s Ellesmere Island, releasing an ice-dammed freshwater lake into the ocean. (Scientists believe that the similar melting of an Arctic ice dam 8,200 years ago triggered an episode of abrupt climate change.)
The North Atlantic’s salinity has declined continuously for the past 40 years – the most dramatic oceanic change ever measured.
The flow of cold, dense water through a North Atlantic channel near Norway – part of the great ocean current that warms northern Europe – has dropped by at least 20% since 1950, suggesting that the current is weakening.
Scientists still don’t know whether a climate disaster is on the way. But taken together, these changes appear strikingly similar to ones that preceded abrupt climate shifts in the past. Many researchers now believe the salient question about such change is not “Could it happen?” but “When?”
Much research confirms that something on the order of this amount of heat applied continuously for many years has contributed significantly to the rise in the global average surface air temperature of 0.7-0.8°C (1.2-1.4°F) observed since 1900. Study of climate history has shown that small forces, maintained long enough, can cause climate change. Unless huge reductions are made in fossil fuel use, the atmospheric carbon dioxide concentration, now at 370 ppm, is expected to reach 560-1,000 ppm by the end of this century. This will raise heating due to greenhouse gases to at least 3 W per m2 and average global temperatures a further 1.4-5.8°C (2.5-10.4°F).
Clearly, Earth is warming. Surface air temperature records, radiosonde (a small instrument package suspended below a balloon) data, and satellite observations all indicate that the planet has heated up over the past century. The 11 warmest years since the beginning of instrumental records have occurred since 1990. The warming observed in the Northern Hemisphere since 1900 has been greater than any other during the past millennium. At the same time, ocean temperatures have risen significantly since the mid-1950s.
Even without temperature records, there is strong evidence the planet is heating up. Mountain glaciers all over the world are retreating. Snow cover is decreasing. Snow is falling later in the season and melting earlier than it did a few decades ago.
Concomitant with the warming have been increases in cloud cover and precipitation at mid to high latitudes in the Northern Hemisphere, and decreases in precipitation in the subtropics. Droughts are more severe in Asia and Africa and in some parts of the U.S. and Europe. Since 1900, sea levels have risen 10 to 20 cm, from thermal expansion and melting glaciers. El Niño events – the periodic warming of the tropical Pacific that affects weather patterns around the world – have apparently become more intense and more frequent.
At the same time, there have been opposing and neutral trends. For example, most of Antarctica, not including the West Antarctic Peninsula, has grown cooler in the past few decades. So far, there is no evidence that hurricanes have increased in intensity or frequency. And data trends for tornadoes are ambiguous.
These developments were announced in 2001 by the United Nations Intergovernmental Panel on Climate Change (IPCC) in its third assessment report. The assessment represents the work and review of thousands of leading climate scientists and other specialists from more than 40 countries.
The most striking evidence of climate change has appeared in the Arctic over the past three decades. Perennial or year-round sea ice in the North Polar region has decreased 3% per decade, and the area of the Greenland ice sheet surface that melts during summer has increased dramatically. The extent of tundra, which until recently covered about 24% of land in the Northern Hemisphere, has also declined steeply – 15% since the 1970s. As permafrost melts, some of the grayish mosses that typically blanket the tundra are replaced by greener and darker shrubs and trees, says James E. Overland of the National Oceanic & Atmospheric Administration’s (NOAA) Pacific Marine Environmental Laboratory in Seattle.
During the past two decades, temperatures have risen faster in the Arctic than anywhere else on the planet. Josefino Comiso, research scientist at NASA Goddard Space Flight Center, found that temperatures over Arctic summer sea ice increased 1.22°C per decade beginning in 1980. The Arctic as a whole warmed has eight times faster over the past two decades than over the past 100 years, he says.
The changes under way in the Arctic are likely to have profound, mostly negative consequences for the weather and economy in the continental U.S. and Europe, says Jonathan Overpeck, director of the Institute for the Study of Planet Earth at the University of Arizona. It cannot be proven that Arctic changes are not solely the consequence of natural variability, but they are totally consistent with the predictions climate scientists made about 20 years ago. “At that time, we said the Arctic would be one of the first places to show noticeable changes from greenhouse gases,” he explains.
Because trends in the Arctic are so dramatic and so unsettling in their rapidity, the National Science Foundation is leading a multiagency initiative to understand their full scope. It has established a program called Study of Environmental Arctic Change (SEARCH). In this program, scientists are investigating exactly how the observed changes relate to the Arctic’s natural variability and if they indicate the start of a major climate shift in the North.
To be sure, there are uncertainties in the science of climate change. But the uncertainties are not about whether Earth has already warmed or whether greenhouse gases are responsible for a large part of this warming, says John P. Holdren, physicist and professor in the Kennedy School of Government at Harvard University. What they do concern “is the precise magnitude of the changes to be expected by 2030, or 2050, or 2100 if civilization does not change course,” he explains. “The character, geographic distribution, and timing of damages to human well-being” from greenhouse warming are other uncertainties, he says.
Natural and human influences – called “forcings” in the climate-science community – alter the flow of radiant energy in the atmosphere, cooling and warming Earth by perturbing its energy balance. Positive forcings warm the planet while negative ones cool it.
One of these forcings is greenhouse gases, which alter the planet’s energy balance by absorbing infrared radiation that would otherwise escape to space. The major greenhouse gases include carbon dioxide, methane, nitrous oxide, tropospheric ozone, chlorofluorocarbons (CFCs), and water vapor. With the exception of water vapor, the concentrations of all the greenhouse gases are controlled more or less directly by human activities. (Water vapor levels depend on Earth’s temperature and the availability of liquid water, and thus are indirectly affected by humans.)
Other forcings include reflective aerosols (mostly sulfate particles from burning of fossil fuel), black carbon particles (soot), land-cover changes, variations in solar output, and cloud-cover changes resulting from global temperature variations and aerosols.
According to the IPCC third assessment report, the atmospheric concentrations of nearly all greenhouse gases have climbed more or less continuously since preindustrial times. The carbon dioxide concentration increased from 280 ppm in preindustrial times to 368 ppm in 2000, and there are no indications that its rate of increase is slowing greatly or stopping. IPCC projects that the carbon dioxide level will rise to 580 ppm by mid-century and about 840 ppm by 2100, if present trends continue.
The methane level rose from about 700 ppb in preindustrial times to about 1,750 ppb in 2000. The abundance of nitrous oxide grew from 270 ppb to 314 ppb. The average level of tropospheric ozone increased from 25 dobson units to 34 dobson units (one dobson unit equals 2.7×1016 ozone molecules per cm3 of air). In contrast, the atmospheric abundances of most CFCs have been decreasing recently due to production cutbacks agreed to in the Montreal Protocol on Substances That Deplete the Ozone Layer.
Although none of the greenhouse gases was measured continuously in the atmosphere before 1958, earlier levels have been determined by analyzing tiny air bubbles trapped in ice cores drilled from ice sheets and glaciers, especially those in Greenland and Antarctica. Every year, a new layer of snow accumulates on glaciers, and as the layers are compressed by overlying snow and ice, air bubbles are trapped. Ice cores thus yield stratigraphic information about atmospheric chemicals and particulates for each year of the glacier’s existence.
Fine particles known as aerosols have complex effects on global temperatures that are not well understood or measured. Some aerosols, such as sulfates, are highly reflective and cool Earth, Hansen says. Also, reflective aerosols have indirect effects on clouds, making them brighter and therefore more likely to reflect sunlight, thus causing cooling as well.
But soot from incomplete burning of coal and diesel fuel acts primarily to heat the planet by warming the atmosphere. However, in regions where airborne soot is dense, it cools by reducing the amount of sunlight reaching the surface. Unlike carbon dioxide, which has an atmospheric lifetime of about 100 years and therefore builds up in the atmosphere over long periods, aerosols are generally washed out by precipitation in two weeks or less.
When forests are replaced by cropland, the landscape becomes lighter and thus more reflective, so this has a cooling effect, Hansen says. On timescales of 1,000 years, the sun’s irradiance has been fairly steady, varying up and down by a few tenths of a watt per square meter around a constant mean. Over the past century, it increased by a few tenths of a watt per square meter. The net sum of positive and negative forcings – those from greenhouse gases, aerosols, landscape changes, and sun and cloud variations – is 1.6 +- 1 W per m2, Hansen estimates.
Although the uncertainties are great, there is evidence this net forcing is approximately correct, Hansen says. When this figure is used as an input in climate models, the average global temperatures predicted by the models closely match observed temperatures over the past several decades.
The net positive forcing has driven average Northern Hemisphere temperatures to levels not seen for almost 2,000 years, says Michael E. Mann, professor of environmental sciences at the University of Virginia. Mann used what are called proxy temperature data for eight distinct regions of the globe to construct a graph of Northern Hemisphere temperatures spanning nearly two millennia. The proxy indicators consist of tree-ring measurements and pollen records in sediments, as well as ice-core data. In warm years, trees tend to grow faster, so wider tree rings usually indicate higher temperatures.
The isotopic composition of the oxygen from the water in each ice layer also indicates what the global temperature was during the year when the layer was deposited. In warm years, the ratio of 18O to 16O is higher because the heavier isotope is more common in precipitation when temperatures are higher. Some roughly 2,800-meter-long ice cores drilled from Greenland and Antarctica provide climate history for the past 110,000 years.
Mann’s graph shows that the late-20th-century warmth in the Northern Hemisphere is unprecedented for almost two millennia. The historical period from 800 to 1400 was moderately warmer than the periods preceding and following it, he concludes, “but this was dwarfed by the late-20th-century warming.” For the Southern Hemisphere, however, there are not enough proxy data to make definitive statements about temperatures, he says.
Several myths create confusion about past global temperatures, says Mann. According to a C&E News side article, climate change skeptics use these misconceptions to try to show that there were periods during the past millennium when global temperatures were higher than they have been in recent times.
One myth is that Greenland was much warmer during the so-called medieval warm period than it is today, and that the warmth enabled the Norse to settle there. The truth is that a few hundred Norse settled in the fjord region of southwest Greenland beginning in 986 because it was the warmest part of the island, as it is today, Mann says.
The settlements collapsed totally by 1500, not primarily because of climate change, but because of social factors, Mann argues. Shipping routes changed, and the inhabitants had no way to get supplies or sell their products. The regional cooling in Greenland that set in between 1000 and 1400 was of the order of 1 °C or less–“not the kind of cooling that’s going to cause massive upheaval,” he explains.
Another myth is that grapes could be grown in England during medieval times but have not been cultivated there recently. “However, there are roughly 10 times as many vineyards in England today than at the height of the so-called medieval warm period,” Mann explains. England has never been a major wine-producing region, not in medieval times and not today, he notes. However, “it has been suitable for grape growing for most of the past 1,000 years,” he says.
The impacts of higher global temperatures include more precipitation, a larger part of the precipitation coming in extreme events, earlier snow melt, and more drought. As global temperatures rise, more water evaporates, so inevitably greater amounts of rain and snow fall over the planet as a whole. Global warming has already affected hydrological systems in many parts of the world. According to Munich Re, a large reinsurance company that provides insurance to insurance firms, total global monetary losses from weather and flood catastrophes in the 1990s were more than three times what they were in the 1980s.
Analyses conducted in the past decade show that precipitation increased 5-10% over land areas of the Northern Hemisphere during the 20th century. At the same time, droughts have become more frequent and intense in parts of Asia and Africa and in some areas of the U.S. and Europe.
Recently, Pavel Groisman, a researcher at NOAA’s National Climatic Data Center, analyzed weather data spanning more than a century for the U.S., excluding Hawaii and Alaska. He reports in an upcoming article in the Journal of Hydrometeorology that since 1895 rainfall increased 7% over the lower 48 states. In most regions, precipitation rose, but it declined in the Southwest. He also finds that heavy rains increased much faster than the total amount of rainfall. Since 1895, the amount of rainfall coming in extreme events rose 14%, but most of the increase occurred during the past three decades.
Droughts have been more intense and frequent in the Southwest, in California in the spring – and surprisingly – in the Northeast, even though the total amount of annual precipitation there has risen, Groisman reports. In the West, spring now comes two to three weeks earlier than it did 50 years ago, he notes.
Outside the U.S., precise trend data for precipitation and drought over the past century are not available for most regions.
According to the IPCC third assessment report, El Niño events became “more frequent, persistent, and intense during the past 20 to 30 years,” compared with earlier in the century. Some well-established effects of El Niño are enhanced rainfall over Peru, Ecuador, the southern U.S., and the central Pacific Ocean, and drought in Indonesia, Australia, southern Africa, and northeastern Brazil. When El Niños are very intense, floods and droughts in those regions can be catastrophic.
Beginning in the 1980s, some researchers began using computer models to reproduce the physics of the ocean and atmosphere as they evolve during El Niño events. These models are fully coupled mathematical simulations of the physics, chemistry, and biology of the atmosphere, land surface, cryosphere (the frozen part of Earth’s surface), and oceans. They have been used to reproduce many of the oceanic and atmospheric effects of El Niños in the tropical Pacific and to predict the onset of such events months in advance.
In 1992, scientists at the National Center for Atmospheric Research (NCAR) used computer models to simulate the evolution of an El Niño when the atmospheric concentration of carbon dioxide is about 560 ppm, a level expected long before the end of this century. The results indicate that El Niños may become more intense as carbon dioxide concentrations rise.
From the observational record, “we can say that El Niños have been more intense and more frequent in the past 30 years,” says Kevin E. Trenberth, head of the climate analysis group at NCAR. There is evidence they are behaving in unusual ways, he says.
Also, Trenberth notes, there is evidence that the incidence of tornadoes has been increasing over the past few decades. “But it is very hard to tell if this represents a real increase or just that there are more people in more places to find them. You just can’t get reliable tornado records to compare with,” he explains.
One unambiguous feature of the warming Earth is that alpine (mountain) glaciers are melting all over the world. Lonnie G. Thompson, professor of geological sciences at Ohio State University, has been studying glaciers in Peru, Bolivia, Antarctica, Greenland, China, Africa, Kyrgyzstan, and Russia for the past 25 years. On 45 expeditions, he and his team have drilled ice cores from glaciers in all these areas and taken them back to Ohio State’s Byrd Polar Research Center for analysis. The analyses provide many clues to Earth’s past climate.
From his expeditions and the work of other glaciologists, Thompson concludes that every tropical glacier on the planet is retreating and that the retreat of lower elevation tropical glaciers is accelerating.
For any individual glacier, “you could argue that the rapid melting is caused by something other than climate change,” Thompson says. For example, in the case of Tanzania’s Kilimanjaro, which is an ancient volcano, “some have suggested that extra heat is coming from the bedrock beneath, even though measurements show the bedrock is below freezing,” he says. But the fact that tropical glacier retreat is so universal “argues for something bigger as a driver,” he explains. “For me, it is the weight of the evidence that really makes a compelling case for large-scale human impact from greenhouse gases,” he says.
By studying maps and aerial photos that show the extent of the Kilimanjaro glacier at different times during the 20th century, Thompson estimates it will be gone by 2015-20.
In the Andes of Peru, the Quelccaya Glacier is not just retreating, but “what we see there is a very strong exponential acceleration in the rate of retreat,” Thompson says. On the edge of the glacier, he recently found a perfectly preserved non-woody plant that looked as if it had been put in a freezer yesterday. Carbon-14 analyses at four separate labs dated the plant at about 5,200 years old. “This shows you the ice field has not been smaller than it is today for 5,200 years,” Thompson says.
“What you very clearly see from the individual and combined records from glacier cores is that what has happened in the past few decades is unusual, certainly in the context of the past 2,000 years,” Thompson says. “What the melting glaciers and the isotopes are telling us is Earth is getting warmer.”
Thompson sees the loss of tropical ice as not just a vivid sign of a warming planet, but as a large loss of a way to study past climates. “You are losing the history of Earth as it is recorded in the ice,” he says.
The disappearance of glaciers can also cause severe economic disruption. For example, Kilimanjaro is the number one foreign currency generator for Tanzania. “There is a big debate about how many tourists will still come to this mountain if there is no ice on it,” Thompson says. Also, “in Peru during the dry season, many hydroelectric plants depend on meltwater from the glaciers,” he says. When the glaciers are gone, they will have to shut down in the dry season.
The changes in the Arctic over the past few decades are so striking and rapid that it would be hard to exaggerate them. Since 1970, temperatures in the Arctic have been increasing about twice as fast as the global average.
In 2002, “we saw sea ice thinning dramatically and retreating to the smallest area it has ever been in summer,” says the University of Arizona’s Overpeck. The reduction began about 30 years ago. In September 2002, the area covered by sea ice in the Arctic reached an all-time minimum – 14% below the long-term average – and in 2003, the area was almost as small.
The extent of sea ice is measured by satellite with passive microwave imagery that detects radiation emitted from Earth’s surface. Perennial sea ice has been decreasing 3% per decade since satellite records started in 1979, while summer sea ice has decreased 9% per decade. In summer, Arctic sea ice used to cover an area about the size of the U.S., so a 14% loss represents an area about the size of Colorado and New Hampshire combined.
“In the past, if you had a record-low ice extent in one summer, quite typically it would be followed by a more normal year the next summer,” says Mark C. Serreze of the National Snow & Ice Data Center at the University of Colorado. The graphs of sea ice extent from year to year used to resemble a sawtooth around a constant mean, he says. This has not been happening recently. A minimum in one year is followed by another low that almost matches it.
At the same time that the extent of Arctic sea ice has shrunk, the ice has also thinned rapidly. Careful measurements taken by U.S. Navy submarines in some areas show the ice is much thinner than in the past. But submarines have not been used to measure ice thickness in all parts of the Arctic, Overland says.
Another dramatic change can be seen in the tundra. There has been a 15% loss of tundra in the Arctic since the 1970s. As tundra warms up, shrubs and trees replace some of the lichen and mosses growing there. Matthew Sturm, geophysicist at the U.S. Army Cold Regions Laboratory, in Alaska, has been comparing photographs of tundra taken about 50 years apart on Alaska’s North Slope. Photographs shot from helicopters at precisely the same location in 1948 and 2002, for example, show that some of the tundra has been invaded by shrubs.
Laboratory experiments demonstrate that as tundra warms, some of the mosses and lichens are replaced by shrubs. So this photographic evidence is a clear sign the tundra is warming, Sturm says.
Satellite photos also reveal that the tree line has moved north in the Arctic as tundra heats up and air temperatures increase.
Many investigators have detected changes in temperatures in permafrost, the permanently frozen layer below the surface. For example, researchers at the U.S. Geological Survey have been measuring permafrost temperatures from deep holes drilled in northern Alaska since the late 1940s. Through the mid-1980s, permafrost in the region generally warmed 2-4°C. There were brief periods of cooling in the early 1980s and from 1990-93, but the permafrost has since warmed. The overall trend from 1940 until today is toward warmer temperatures. Similar trends have been reported in Russia.
In most parts of northern Alaska, permafrost has not warmed up enough to melt, but in some Alaskan towns farther south, it has melted. In those places, buildings, roads, electric utility poles, and other structures built on permafrost have fallen over or collapsed as the ground sinks beneath them.
The summer melting of the Greenland ice sheet since 1979 is one of the most graphic alterations taking place in the Arctic. Konrad Steffen, professor in the geography department at the University of Colorado, uses passive microwave satellite data to detect the total area of surface melt on the ice sheet. From 1979 to 2003, the melted area as measured in September increased 16%. In 2002, the year of maximum melt, the melted area covered 264,400 sq miles. In 2003, it was almost as large.
One surprising aspect was that the melting extended up to an elevation of 2,000 meters (6,560 feet) on the northern and northeastern parts of the ice sheet, Steffen says. The conditions on the ice sheet are confirmed with 20 automatic weather stations that transmit data hourly via satellite. Using the Internet, anyone can access this weather information here.
Another change is that the Greenland ice sheet is shrinking along the margins, the areas of the ice sheet near the coastline. NASA used an aircraft fitted with a highly sensitive laser altimeter that can measure elevation with an accuracy of 1 cm to detect elevation changes in Greenland. It conducted two missions over Greenland five years apart along the same path. Data from these flights show that the central portion of the ice sheet, which is about 3 km thick, is basically stable, with little or no change in elevation.
But in some places along the margins of the ice sheet, the elevation of the surface is falling by more than 1 meter per year. This means that the margins, which are about 1 km thick, are losing more than 1 meter of thickness per year in some areas. Seventy percent of the ice sheet that has an elevation less than 2,000 meters is thinning significantly, Steffen says.
The loss of thickness cannot be explained by melting alone, Steffen says. There is not enough energy to melt that much ice. However, because there is so much meltwater on the surface of the ice sheet, it penetrates the ice and lubricates the interface between the ice and the bedrock, allowing the ice sheet to flow faster. The increased flow results in higher than normal iceberg production. Between winter and summer, the flow speed of some Greenland glaciers increases 10-15%, Steffen says, and when winter comes, the flow slows again. Flow speeds fluctuate with available meltwater.
The Jacobshavn Glacier, a major outlet of the ice sheet in western Greenland, flows 10 km per year into the ocean, Steffen says. “You can hear it flowing when you are sleeping [in camp] on the glacier,” he says.
The melting in Greenland and increased flow of Greenland glaciers into the sea could cause a dramatic sea-level rise, even in the next 100 years, Overpeck says. “It could be more than a meter by 2100,” he explains, “and over the next few centuries, up to 5-6 meters if much of Greenland melts.”
Partly as a consequence of surface melting and accelerated ice flow from the Greenland ice sheet, “the North Atlantic Ocean is freshening dramatically around Greenland,” Overpeck says. But the primary reason for this freshening is probably increased rainfall in the vicinity of the Arctic Basin, which means that the rivers flowing into Arctic waters have greatly increased flow.
Increased freshwater coming into the Arctic could result in climate change for regions outside the Arctic. Currently, the Gulf Stream, which resembles a large river of warm water on the ocean surface, flows north and warms Northern Europe. As it cools, the atmosphere gains heat, and the water becomes more dense. Then, the river descends to great depths in the Greenland, Iceland, and Norwegian Seas, and returns south.
This deep-water production is not just a function of temperature. It is also a function of salinity. The theory is that “if you could freshen the upper ocean enough, you could potentially shut down this deep-water production,” called the thermohaline circulation, Serreze says.
There are several ways that could happen: with increased river discharge to the Arctic Ocean or with more meltwater and icebergs coming from the Greenland ice sheet, Serreze says.
A recent paper in Geophysical Research Letters indicates that by 2080, so much meltwater and icebergs could come off the Greenland ice sheet that they would strongly slow the thermohaline circulation. If this happens, there would be a marked temporary cooling in eastern Greenland and the North Atlantic, which would make parts of northwestern Europe colder. However, if Earth as a whole continued to warm from rising levels of carbon dioxide, this regional cooling would eventually be overwhelmed.
The aim of the 1992 UN Framework Convention on Climate Change is to stabilize atmospheric concentrations of greenhouse gases to prevent dangerous anthropogenic interference with climate. In a presentation to the U.S. Council on Environmental Quality in June 2003, Hansen argued that “we are much closer to dangerous anthropogenic interference than is generally realized.”
The IPCC third assessment report assumes that the great ice sheets in Greenland and Antarctica will remain stable over this century. Consequently, it estimates that sea level will rise only 20-50cm, on average, by 2100 as Earth warms several degrees Celsius.
Building up a great ice sheet takes a long time, Hansen pointed out. It is limited by the amount of snow that falls each year. In contrast, ice sheet breakup “is driven by highly nonlinear processes and feedbacks,” he explained. One feedback is that as ice melts in Greenland, for example, the Arctic region grows darker and is thus able to absorb, rather than reflect, more sunlight. Meltwater absorbs more sunlight than ice.
About 14,000 years ago, as the planet was coming out of the last ice age, Hansen said, 14,000 km3 of ice melted each year for 400 years, which caused sea levels to rise 1 meter every 20 years during those centuries.
Given how quickly sea levels rose following the last ice age, when temperatures in Antarctica were only 1°C higher than those in the mid-20th century, it may be incorrect to assume, as the IPCC report does, that sea levels will rise only moderately by 2100, Hansen said. For this reason, he said, allowing the average global temperature to rise more than 1°C may constitute dangerous interference with climate.