This headline appeared in the London Independent in early February of 2005, following a conference at the Hadley Centre in Exeter, England, where 200 of the world’s leading scientists issued the most urgent warning to date: that dangerous climate change is taking place today, and not the day after tomorrow.
Floods, storms, and droughts. Melting polar ice, shrinking glaciers, oceans turning to acid. Scientists from the fields of glaciology, biology, meteorology, oceanography, and ecology reported seeing a dramatic rise over the last 50 years of all the indicators of climate change: increase in average world temperatures, extreme weather events, in the levels of CO2 and other greenhouse gases, and in the level of the oceans.
The award winning environmental writer Geoffrey Lean wrote: “Future historians, looking back from a much hotter and less hospitable world . . . will puzzle over how a whole generation could have sleepwalked into disaster -- destroying the climate that has allowed human civilization to flourish over the past 11,000 years.”
The overwhelming majority of scientists and international climate monitoring bodies now agree that climate change is taking place, that humans are responsible, and that time is running out. In fact, we could reach “the point of no return” in a decade, reported Lean.
Melting glaciers all across the world include: the Broggi in the Peruvian Andes, Glacier Ururashraju in the Cordillera Blanca of Peru, the Pasterze in Austria, Portage Glacier near Anchorage, Alaska, Mount Hood in Oregon, Mount Kilimanjaro in northeastern Tanzania, the Grinnell Glacier in Glacier National Park, and the Rhone Glacier in Switzerland.
The earth is getting warmer. While average warming is just under 1 degree Celsius worldwide, the Polar Regions show warming of 2 to 3 degrees Celsius, due to feedback effects. With the melt of white snow, that previously reflected some of the heat back into the atmosphere (albedo effect), newly exposed darker surfaces absorb heat, and accelerate melting of more ice and snow.
A world average warming of under 1 degree Celsius may seem small. However, historically, the difference between warm periods and an ice age has been only 5 to 6 degrees Celsius. The transformation from the last ice age to the present climate resulted from a slow rise in temperature, which took 5,000 years to fully complete, allowing life on Earth to adapt to the changes. We could bring about a 5- to 6- degree change in only 150 years if we don’t start constraining the use of fossil fuels.
It is not only the fundamental change in the composition of air, water, and soil that we need to consider. The speed at which these changes are forced upon the planet already leads to high extinction rates.
Scientists at the Exeter meeting agreed that warming over 2 degrees Celsius above pre-industrial temperatures would be dangerous -- and we are almost half way there. To burn up the world’s remaining coal reserves, they estimated, would raise the average temperature by 3 to 8 degrees C in less than 150 years.
Quite a few climate “skeptics”, fossil fuel executives, and members of the Bush administration are still denying that there is such a thing as human-caused global warming. Many of them claim that the sun has just grown hotter. However, a warmer sun would have heated the stratosphere as well. In contrast, the stratosphere is cooling -- suggesting a blanket of greenhouse gases that prevents the earth’s heat from radiating back into space.
We know how the greenhouse effect works. Venus, with a thick greenhouse cover is hot; Mars, with a thin greenhouse is cold. Earth’s blanket of greenhouse gases is made up of the byproducts of the industrial age and an outdated Victorian technology. Even though methane is a more powerful greenhouse gas, it is CO2 that makes up over 80% of the greenhouse gas mix. Ice core studies show that CO2 concentrations on this planet had been stable for the last millennium, never rising or falling more than 10 ppm, and fluctuating between 275 and 285 ppm. Now CO2 concentrations are beginning to exceed 370 ppm, and are rising from year to year. Other greenhouse gases show the same dramatic increase -- mainly in the past 40 to 50 years. We are already living under a dome of air that no one has breathed in a million years.
Ocean Warming and Acidification
The average temperature of the surface waters of the oceans, extending to a depth of several hundred meters, has risen by a 1/2 degree Celsius. This has occurred in just the past 40 years. The oceans have also become more acidic, due to the uptake of anthropogenic CO2. The Plymouth Marine Laboratory in England estimates that 48% of fossil-fuel CO2, or 400 billion tons, have been absorbed by the oceans, making them the largest reservoir of carbon, a load greater than that borne by the atmosphere or the earth. CO2, while more inert in the atmosphere, becomes highly reactive in oceans, leading to physical, biological, and geological changes.
Carol Turley, head of science at the Plymouth Marine Laboratory, warns that no such ph changes in oceans have occurred in the past 20 million years, and that the capacity of oceans to take up CO2 is limited.
What might the consequences of such changes in the oceans be? An August 2005 article in the Globe and Mail, on starving sea birds washing up on Pacific coast beaches from California to British Columbia, reports that scientists believe that, at least for this year, the “bottom has fallen out of the coastal food chain.” Off the Oregon coast, the waters near the shore are 5 to 7 degrees warmer than normal. A layer of warm water along the whole Pacific coastline prevents the usual upwelling of cool water rich in phytoplankton, the base of the food web for all marine life.
Zooplankton, such as krill, depend on phytoplankton. The disappearance of zooplankton in turn affects seabirds and fish from sardines to whales. NOAA, the National Oceanic and Atmospheric Administration, found a 20 to 30 per cent drop in juvenile salmon off the coasts of Oregon, Washington, and British Columbia; and monitoring in Central and Northern California shows the lowest number of juvenile rockfish in more than 20 years.
The world has not yet felt the real impact of global warming since the oceans have absorbed so much heat and CO2. The US National Center for Atmospheric Research (NCAR) put out two studies in March 2005. They suggest that due to the thermal inertia of the oceans global temperatures and sea levels will continue to rise for the next 100 years - even if greenhouse gas emissions come under control.
First Signs of a Gulf Stream Collapse
The opening presentations at the Exeter, UK conference gave the most comprehensive assessment of so-called “wild cards”, climate change events that risk feedback loops no longer responsive to human intervention. The run-away events, or ecological landslides include accelerated melting of the enormous ice sheets of Antarctica and Greenland, as well as the decline and possible reversal of the Gulf Stream that conveys heat from the tropics to Europe.
In the Hollywood movie “The Day After Tomorrow,” the Gulf Stream stops flowing in a matter of days, creating an instant ice age on the Atlantic coast and Western Europe. Scientists at Exeter said it would take at least ten years for such an event to unfold and a few hundred years to set up the conditions. But they warned that the Thermohaline Circulation, as they call the Gulf Stream, has stopped flowing before -- and that we have already a greater than 50% likelihood of a shutdown if we do not enact strict climate policies.
The amount of heat transported North by the Gulf Stream, which keeps Western Europe 5 to 10 degrees Celsius warmer than it would normally be at its latitude, equals one million billion watts -- sufficient to satisfy the energy needs of 100 Earths. Even a partial failure of the Gulf Stream would have huge consequences.
The Gulf Stream picks up heat from the equatorial sun. Driven by warmth, the stream flows northeast towards Europe and the Greenland ice sheets, where the water cools and sinks. The cooler and saltier the water, the stronger the sinking motion. Dense cool and salty water from the Gulf Stream then flows back to the tropics at a deeper ocean level.
As the Polar Regions and the oceans are warming, melt-water from ice sheets and glaciers is changing the salinity of the ocean. A combination of the rising ocean surface temperature, and the decreasing salinity, already visibly changes the movement of sea currents that depend on differences in warmth and coolness, and the weight that higher salinity adds to the water as the driving force.
Large-scale salinity changes in the Arctic and sub-Arctic Seas were reported in June 2005, in the journal Science. Ruth Curry from the Woods Hole Oceanographic Institution on Cape Cod, in Massachusetts, analyzed temperature, salinity, and density data, collected in the North Atlantic Ocean over the last 55 years. Curry warned that excessive amounts of freshwater dumped into the North Atlantic could affect the flow of the Gulf Stream.
We know, from ice-core data, when the Gulf Stream has stopped flowing before. The most recent collapse, 15,000 years ago during the Younger Dryas, was caused by the sweetening of the North Atlantic Ocean, when glaciers covering North America melted and began flowing through the St. Lawrence waterway into the Atlantic, instead of into the Gulf of Mexico via the Mississippi. Today’s accelerated melting of the Arctic and Antarctic ice sheets may recreate these conditions, not just for the Gulf Stream but also for other parts of the global ocean circulation.
In May of this year, the London Times reported that first signs of a slow down of the Gulf Stream had been detected by a Cambridge University researcher, who hitches rides on a Royal Navy submarine to one of the three areas where the Gulf Stream reverses its course. Peter Wadhams said that “until recently we could find giant ‘chimneys’ in the sea where columns of cold, dense water were sinking from the surface to the seabed 3,000 meters below, but now they have almost disappeared.”
Off the coast of Greenland, the Odden Ice Shelf once grew out into the Greenland Sea every winter, and receded in the summer. The Odden triggered the annual formation of sinking water columns in that area. However, since 1997, the shelf has ceased to form. Where Wadhams had once observed 12 giant columns of sinking water under the ice, he now found only two -- and they were so weak that they were unable to reach the seabed.
Wadhams also predicts complete summer melting of the Arctic ice cap by as early as 2020. On his submarine journeys, using sonar to survey the ice cap from underneath, he has observed a 46% thinning over the past 20 years.
The Greenland Ice Sheet is Melting
The biggest danger to the Gulf Stream comes from melt-water off the Greenland ice sheet, the second largest store of fresh water on this planet. If all of it were to melt, sea levels around the world would rise by 7 meters -- over 20 feet. However even a partial meltdown would affect the Gulf Stream, by diluting the salt water right at the crucial point where the Gulf Stream sinks and returns to the tropics.
Prof. Michael Schlesinger from the University of Illinois, Urbana-Champaign, whose climate model already predicts a 50% chance of Gulf Stream shutdown if we do not enact climate policies, and a 25% shutdown even if we limit greenhouse gases, based his estimate only on increased rainfall, due to global warming. He now says he will have to include additional melt-water from the Greenland ice sheet into his next set of data, because it appears that the melt has begun.
Observations on the Greenland ice sheet are done by G.P.S. (global positioning systems) and radar and laser via satellites and airplanes. G.P.S. data of the past 5 years show accelerated melting, and even the beginning of a possible feedback effect: the more the ice sheet melts the faster it starts to move. The reason for this acceleration, it is believed, is that melt-water from the surface of the ice sheet makes its way down to the bedrock below, where it acts as a lubricant, further speeding up the slippage and disintegration.
The question now is, when does this feedback process reach the point of no return? James Hansen, head of the Goddard Institute for Space Studies, says that if greenhouse-gas emissions are not controlled now, the total disintegration of the Greenland ice sheet could be set in motion in a matter of decades. Although it could take hundreds, perhaps thousands, of years to fully play out, once begun the process would become self-reinforcing and cannot be halted.
The Gulf Stream is just one part of a complex global system of ocean currents that affect temperatures, winds, and rain across the whole planet. We now have charts of these powerful currents driven by heat and coolness, traversing all oceans, - Atlantic, Pacific, and Indian. And they are all interconnected via the huge circumpolar current flowing around the Antarctic. Changes at the South Pole therefore would have an even larger effect than those in the Arctic.
Ice Shelf Collapses and the Melting of Antarctica
Antarctic is the 5th largest continent. It holds 90% of the
world’s fresh water. A comparison in scale to the Greenland ice sheet
shows that if all Antarctic ice were to melt, sea levels would rise by
over 169 feet. The Antarctic has had a permanent ice sheet for the last 30