Armageddon Science (14 page)

That’s just how things are now. Killer heat waves like the one that struck Chicago in 1995 currently might be expected every twenty years or so, but are likely to be annual occurrences by the end of the century according to our best predictions. It is quite likely, according to today’s forecasts, that a summer with such temperatures would be average by 2040 and could be typical of the coldest summer of the decade by the 2060s. The one mitigating factor that might benefit some northern areas is the slowing down of the thermohaline circulation, the complex system of ocean currents that transport large amounts of heat from the tropics to northern latitudes. The section of this ocean conveyor system that runs in the surface layers of the Atlantic, stopping the northeastern coastline of the United States and northern Europe from being more like Siberia in temperatures, is the Gulf Stream.

There is some evidence that climate change could produce a reduction of strength in this ocean conveyor, because of the impact of freshwater from melting ice sheets. The collapse of the conveyor was the scenario dramatized in the movie
The Day After Tomorrow,
but this hugely overemphasized both the speed of the change and its impact. Early attempts to model the impact of climate change on the conveyor suggested that it might shut down entirely over this century, but current best estimates predict a decrease in strength of around 25 percent. This will help mitigate the heat impact of climate change in the areas warmed by the Gulf Stream, but will not totally counter it.

As the planet warms up, the delicate balance of coastal life will be devastated. Increasing temperatures inevitably result in sea-level rises. This is not just a case of irritating the coastal wildlife. Many of the world’s great cities from New York to London, and major sections of low-lying countries like Bangladesh, are at risk of destruction by relatively slight increases in sea level. In the storm surge of 1998, 65 percent of Bangladesh was inundated. It would not take much of a rise to make this a permanent state.

Climate change has a double impact on sea level. The headline-grabbing cause is the melting of vast tracts of ice, increasing the volume of water as they plunge into the sea, but there is a more direct effect too. As liquids get warmer they expand, and with the huge volume of water in the oceans this has a significant effect. Just a few degrees’ increase in temperature is enough to push the sea level up several feet from expansion alone. But the melting ice isn’t just featured more often in the news because it looks more dramatic on the TV screen. Though currently expansion is responsible for more rise than melting, the situation with the world’s frozen supplies of water is heading for potential catastrophe.

A very visual illustration of the impact of climate change is the way that ice is disappearing from the North Pole in the summer. Not only is this happening on a large scale, but also Arctic ice is melting much faster than was expected only a few years ago. NASA satellites have revealed that between the winters of 2004 and 2005, three quarters of a million square kilometers (280,000 square miles) of ice that was normally permanently frozen melted: this is without historical precedent. The summer low of 2005 had a polar ice cap with 20 percent less area than that of 1978. At least once in the last few years, the North Pole itself has disappeared. This can happen because the Arctic isn’t a landmass but a floating sheet of ice.

The good news here is that melting Arctic ice doesn’t contribute to an increase in sea levels. Floating ice is already displacing water just as a ship does—if the floating ice melts, the overall water level doesn’t rise. But that doesn’t mean the disappearing Arctic summer ice is a good thing. Not only is it a disaster for wildlife like the polar bear; it also has a direct impact on global warming. Melting ice drives another of the positive-feedback loops that are so common in the climate change world.

As we’ve seen, it’s the Sun’s energy that heats up the world. But not everywhere is equal when it comes to solar warming. The lighter in shade a surface is, the more energy is reflected back out to space (greenhouse gases permitting). The glittering whiteness of an ice sheet is ideal to flash back a good portion of the energy, while the dark waters of the ocean absorb significantly more. Water takes in more heat from sunlight than does ice. So the more the Arctic ice melts, the more energy is absorbed, melting even more ice—positive feedback. And even though the Arctic melting doesn’t contribute directly to sea-level rise, because of this positive feedback, it does contribute further to global warming.

Much more worrying than the Arctic from the point of view of ocean levels is Greenland. If we think of Greenland at all, it tends to be either as a cold little place between Europe and America, or as the first example of dubious advertising, when it was optimistically given a name that implied verdant pastures in an attempt to attract gullible Norse settlers. But in climate terms, the interesting (and potentially frightening) thing about Greenland is its ice sheet.

More accurately, this is no mere ice sheet, but an ice mountain range. The Greenland ice sheet covers over one and a quarter million square kilometers (half a million square miles)—think Texas, California, and Florida combined—and is mostly over 1.6 kilometers (a mile) high. At its thickest, the ice sheet is nearly two kilometers (ten thousand feet) high, half the height of the tallest mountain in the United States, Mount McKinley.

According to NASA, through the 1990s the ice sheet was shrinking by around fifty cubic kilometers (twelve cubic miles) a year. That’s a lot of ice—but it would still take between one thousand and ten thousand years for the Greenland ice sheet to melt completely. There’s no room for sighs of relief, though. As Jim Hansen, director of the Goddard Institute for Space Studies and George Bush’s top in-house climate modeler, graphically put it, “[Greenland’s ice is] on a slippery slope to hell.” By 2000, the rate the ice sheet was melting had accelerated so much that it was already losing vastly more than had been estimated just ten years before. The assumption had been that the ice would gradually melt from the surface downward, trickling its way to the sea as runoff water. But what is actually happening is startlingly different.

Lakes of water are forming on top of the ice sheets. These sheets aren’t always uniformly solid. If there’s a crack in the ice below a lake, the water can rush down, opening up the crevasse further as it flows until it has passed through the entire sheet to its interface with the rock below, where the water flow can eat away from beneath, enabling huge swaths of the ice sheet to float off the land. “[If] the water goes down the crack,” says Richard Alley of Pennsylvania State University, “it doesn’t take 10,000 years [to reach the base of the ice sheet], it takes 10 seconds.” If the entire Greenland ice sheet were to end up in the ocean, it would raise sea levels by seven meters (twenty-three feet). And this is without considering the impact of the melting of the Antarctic ice cap, which is on land, and so also contributes to the rise in sea level.

If the disappearing ice sheets weren’t enough, there is also plenty of evidence that the glaciers around the world are also disappearing with unprecedented speed. Not only do these contribute to sea-level rise (the glaciers of Tajikistan alone hold eight hundred cubic kilometers, or two hundred cubic miles of water), but water from glaciers is essential for the irrigation and drinking water of many countries. Around 10 percent of northwestern China’s water supply comes from glacier meltwater, for instance, and there are higher percentages elsewhere. Loss of glaciers will have a devastating effect on the economy and social well-being of a number of countries.

Sea-level rises are real and are happening. The Carteret Islands in the South Pacific are already being abandoned, their two thousand inhabitants displaced by the rising ocean. The current best guess suggests the islands will be totally submerged by 2020. Perhaps even more striking is the fate of Tuvalu, another collection of islands in the South Pacific, which forms a nation in its own right. The ten thousand people of Tuvalu are also having to give up their homeland. Before long that country will be a small modern-day equivalent of the mythical Atlantis, disappearing under the waters.

Many of the world’s great cities are on coastlines and would have to be abandoned if sea-level rises reach a fraction of the levels that now seem entirely feasible. The timescale for this is uncertain. Conservative estimates put the rise by 2100 at half a meter (1.6 feet) but this is without the impact of positive feedback and the unexpected behavior of the Greenland ice sheet. The change in the Arctic perennial ice in 2007 was eighteen times faster than was predicted just ten years ago. By February 2007, sea-level rises were happening twice as fast as was predicted in 2001. Without a transformation in approach to climate change, the five meter (sixteen feet) mark could easily be reached in our lifetime. It would take only an extra 2.7 degrees Celsius (5 degrees Fahrenheit) to take the world to the conditions of the mid Pliocene, when sea levels were 80 feet higher than today. Imagine the New Orleans flood, but massively deeper and never abating. Cities like New York and London would not stand a chance.

Global warming will change the shape of the inhabited world. Over 20 percent of the world’s population lives within thirty kilometers (twenty miles) of the coast, and the number of people living in these at-risk areas is growing at twice the average global rate. Rising seas would mean that most of the U.S. eastern seaboard would have to be abandoned, along with half of Florida, as would low-lying shore areas inhabited by hundreds of millions around the world. And this is not the limit. As we’ve seen, if the Greenland ice sheet melted, sea levels would rise seven meters (twenty-three feet.) The collapse of the fragile West Antarctic ice sheet would raise levels by up to another six meters (twenty feet), while the whole of the Antarctic ice cap melting would precipitate an extra sixty meter (two-hundred-foot) rise (though this is thought unlikely to happen with temperature rises of less than around 20 degrees Celsius (36 degrees Fahrenheit).

Any figures for sea-level rise also need to include the impact of storm surges. In some areas—around the New England coast, for example—when the storms are at their height there are expected to be sea-level rises of around three feet more than are otherwise predicted, well before the end of the century.

We might be dependent on energy coming in from the Sun, but in terms of matter, the Earth is largely a closed system. Extra droughts in some parts of the world mean more wetness elsewhere. As well as the impact of sea-level rise, some parts of the world can expect increased rainfall, and particularly more heavy storm rain. At the moment the increase is relatively slight—in 2001, the IPCC estimated increased precipitation of between 5 and 10 percent in the Northern Hemisphere over that of the previous hundred years—but there’s more to come.

A significant fear is that global warming will produce more hurricanes like Katrina, the storm that devastated New Orleans and the surrounding coast in 2005. There is no certain evidence that climate change was behind the significant rise in numbers of hurricanes in 2005. As the oceans heat up, it should be easier for hurricanes to form, but there are other factors that come into play, and scientists are reluctant to commit themselves to saying that hurricane formation is on the increase. (This is a reassuring counter to those who think climate change scientists have a hidden agenda and make predictions that show that man-made climate change is responsible for everything that goes wrong with the weather.)

However, even if the increase in numbers of hurricanes in 2005 was a blip, it does seem true that there is a rise in the power of the type of tropical storm that can cause so much damage. Two studies in 2005 both showed that the energy levels of hurricanes is on the rise, with twice as many storms at the highest category 4 and 5 levels as were recorded in the early 1970s. There shouldn’t be a similar effect with powerful tornadoes, though. The really big tornadoes are the product of a very special kind of thunderstorm that doesn’t seem to be influenced by global warming. The smaller, more common tornados may be on the rise, but equally it could be that we are just noticing and reporting them more.

As things get worse, there will be huge disruptions to normal services. Availability of electricity, gasoline, and natural gas will be increasingly restricted as the need to respond to climate change goes critical. At the same time, with stocks of nonrenewable fuels running short and sources of supply becoming more remote, there is a growing opportunity for disruption of supply by natural disasters and terrorists. We could see a regular or even permanent breakdown of these services that are essential for our everyday lives.

Climate change also contributes directly to power outages. Extreme summer temperatures are often responsible for failures of power systems, in part because of the heavy load from air-conditioning, and also when power lines expand and sag, coming into contact with nearby trees and causing blackouts. The dramatic weather systems generated by global warming, including tsunamis and hurricanes, can also wreak havoc with power distribution systems. In December 2006 around 1.5 million homes in the states of Washington and Oregon were blacked out, some for up to a week, as power lines were brought down by howling windstorms and heavy rains. In January 2007, storms in the United Kingdom left 300,000 households without power, many for several days. As the impact of climate change grows, these will become very familiar headlines.

It doesn’t help that the electricity grids of many countries are suffering from overload and age. As systems become more complex, their susceptibility to freak accidents and technical problems grows. In 2003 there were two large-scale electricity blackouts in Western countries. The Northeast blackout plunged a sizable part of Canada and the northeastern United States into darkness, leaving a total of 50 million people without power. The same year, an enormous power outage left the whole of Italy and parts of Switzerland without electricity, causing upheaval for a record 56 million people.