Global Warming: Not the End of the World as We Know It

Spiegel Online
Wednesday May 09, 2007 

How bad is climate change really? Are catastrophic floods and terrible droughts headed our way? Despite widespread fears of a greenhouse hell, the latest computer simulations are delivering far less dramatic predictions about tomorrow's climate.

Svante Arrhenius, the father of the greenhouse effect, would be called a heretic today. Far from issuing the sort of dire predictions about climate change which are common nowadays, the Swedish physicist dared to predict a paradise on earth for humans when he announced, in April 1896, that temperatures were rising -- and that it would be a blessing for all.

Arrhenius, who later won the Nobel Prize in Chemistry, calculated that the release of carbon dioxide -- or carbonic acid as it was then known -- through burning coal, oil and natural gas would lead to a significant rise in temperatures worldwide. But, he argued, "by the influence of the increasing percentage of carbonic acid in the atmosphere, we may hope to enjoy ages with more equable and better climates," potentially making poor harvests and famine a thing of the past.

Arrhenius was merely expressing a view that was firmly entrenched in the collective consciousness of the day: warm times are good times; cold times are bad.

During the so-called Medieval Warm Period between about 900 and 1300 A.D., for example, the Vikings raised livestock on Greenland and sailed to North America. New cities were built all across Europe, and the continent's population grew from 30 million to 80 million.

The consequences of the colder temperatures that plunged civilization into the so-called Little Ice Age for several centuries after 1300 were devastating. Summers were rainy, winters cold, and in many places temperatures were too low for grain crops to mature. Famines and epidemics raged, and average life expectancy dropped by 10 years. In Germany, thousands of villages were abandoned and entire stretches of land depopulated.

The shock produced by the cold was as deep-seated it was long-lasting. When temperatures plunged unexpectedly once again in the 1960s, many meteorologists were quick to warn people about the coming of a new ice age -- supposedly triggered by man-made air pollution. Hardly anyone at the time believed a warming trend could pose a threat.

It was not until the rise of the environmental movement in the 1980s that everything suddenly changed. From then on it was almost a foregone conclusion that global warming could only be perceived as a disaster for the earth's climate. Environmentalists, adopting a strategy typical of the Catholic Church, have been warning us about the horrors of greenhouse gas hell ever since -- painting it as a punishment for the sin of meddling with creation. What was conveniently ignored, however, is that humanity has been reshaping the planet for a very long time, first by clearing forests and plowing fields, and later by building roads, cities and factories.

In the age of climate change, it has become a popular social pastime to scour the weather forecast for omens of doom. Has it ever been as hot in April as it is this year? Is this lack of rain normal? Could all this mean that the end is nigh?

Nowadays hardly anyone dares to question the increasingly shrill warnings about our climate, as more and more people jump on the hand-wringing bandwagon. United Nations Secretary General Ban Ki-moon, for example, recently said that climate change poses at least as big a danger to the world as war. German Chancellor Angela Merkel agrees, calling developments "more than alarming," and asking: "Are we willing to accept the fact that we now have completely unprecedented weather phenomena, such as tropical nights in the Harz (Mountains) region?" The fact that tropical nights, as every meteorologist knows, are nothing new in Germany -- every summer has always had a few -- seems to have escaped her attention.

The apocalyptic mood seems to grow each time the United Nation's Intergovernmental Panel on Climate Change (IPCC) releases a new section of its climate change report. Climate hysteria appears to be more contagious than a flu epidemic. "We only have 13 years left to save the earth," screamed a recent front-page headline in the German tabloid Bild. "If mankind is unable to stop the greenhouse effect by the year 2020, it will bring about its own demise -- and a horribly tortured one at that."

Young girls sit on a pier at the beach of Lake Constance during sunset in late April in Langenargen, Germany. April was unusually warm in Germany, prompting speculation the hot weather was due to climate change.

But how bad is climate change really? Will global warming trigger plagues of Biblical proportions? Can we look forward to endless droughts and catastrophic floods?

Or will Arrhenius end up being right after all? Could rising temperatures lead to higher crop yields and more tourism in many places? In other words, is humanity actually creating new paradises?

The truth is probably somewhere between these two extremes. Climate change will undoubtedly have losers -- but it will also have winners. There will be a reshuffling of climate zones on earth. And there is something else that we can already say with certainty: The end of the world isn't coming any time soon.

Largely unnoticed by the public, climate researchers are currently embroiled in their own struggle over who owns the truth. While some have always seen themselves as environmental activists aiming to shake humanity out of its complacency, others argue for a calmer and more rational approach to the unavoidable.

One member of the levelheaded camp is Hans von Storch, 57, a prominent climate researcher who is director of the Institute for Coastal Research at the GKSS Research Center in Geesthacht in northern Germany. "We have to take away people's fear of climate change," Storch told DER SPIEGEL in a recent interview. "Unfortunately many scientists see themselves too much as priests whose job it is to preach moralistic sermons to people."

Keeping a cool head is a good idea because, for one thing, we can no longer completely prevent climate change. No matter how much governments try to reduce carbon dioxide emissions, it will only be possible to limit the rise in global temperatures to about 2 degrees Celsius (3.6 degrees Fahrenheit) by the end of the century. But even this moderate warming would likely have far fewer apocalyptic consequences than many a prophet of doom would have us believe.

For one thing, the more paleontologists and geologists study the history of the earth's climate, the more clearly do they recognize just how much temperatures have fluctuated in both directions in the past. Even major fluctuations appear to be completely natural phenomena.

Additionally, some environmentalists doubt that the large-scale extinction of animals and plants some have predicted will in fact come about. "A warmer climate helps promote species diversity," says Munich zoologist Josef Reichholf.

Also, more detailed simulations have allowed climate researchers to paint a considerably less dire picture than in the past -- gone is the talk of giant storms, the melting of the Antarctic ice shield and flooding of major cities.

Improved regionalized models also show that climate change can bring not only drawbacks, but also significant benefits, especially in northern regions of the world where it has been too cold and uncomfortable for human activity to flourish in the past. However it is still a taboo to express this idea in public.

For example, countries like Canada and Russia can look forward to better harvests and a blossoming tourism industry, and the only distress the Scandinavians will face is the guilty conscience that could come with benefiting from global warming.

There is no doubt that there will be droughts in other parts of the world, especially in subtropical regions. But the widespread assumption that it is developing countries -- that is, the world's poor -- who will, as always, be the ones to suffer is incorrect. According to current predictions, precipitation in large parts of Africa will hardly decrease at all, except in the southern part of the continent. In fact, these same forecasts show the Sahel, traditionally a region beset by drought and famine, actually becoming wetter.

By contrast, some wealthy industrialized nations -- in fact, those principally responsible for climate change -- will likely face growing problems related to drought. The world's new drought zones lie in the southern United States and Australia, but also in Mediterranean countries like Spain, Italy and Greece.

All of this will lead to a major shift within Europe, potentially leading to tough times for southern Spain's mega-resorts and boom times for hotels along the North Sea and Baltic Sea coasts. While the bulk of summer vacationers will eventually lose interest in roasting on Spain's Costa del Sol, Mediterranean conditions could prevail between the German North Sea island of Sylt and Bavaria's Lake Starnberg. The last few weeks of spring in Germany offered a taste of what's to come, as sun-loving crowds packed Berlin's urban beach bars and Munich's beer gardens.

The predicted temperature increase of 3 degrees Celsius would mean that summers in Hamburg, not far from the North Sea coast, would be as warm as they are today in the southwestern city of Freiburg, while conditions in Freiburg would be more like those in Marseille today. Germany will undoubtedly be one of the beneficiaries of climate change. Perhaps palm trees will be growing on the island of Helgoland in the North Sea soon, and German citizens will be saving billions in heating costs -- which in turn would lead to a reduction in CO2 emissions.

But climate change will also have its drawbacks. While German summers will be less rainy, fall and winter rainfall in the country's north will increase by up to 30 percent -- and snow will be a thing of the past. Heavy downpours will also become more common. To avoid flooding, steps will have to be taken to provide better drainage for fields and farmlands, as well as to restore natural flood plains.

Meanwhile, the Kiel Institute for World Economics warns that higher temperatures could mean thousands of heat-related deaths every year. But the extrapolations that lead to this dire prediction are based on the mortality rate in the unusually hot summer of 2003, for which Germans were wholly unprepared. But if hot summer days do become the norm, people will simply adjust by taking siestas and installing air-conditioning.

The medical benefits of higher average temperatures have also been ignored. According to Richard Tol, an environmental economist, "warming temperatures will mean that in 2050 there will be about 40,000 fewer deaths in Germany attributable to cold-related illnesses like the flu."

Another widespread fear about global warming -- that it will cause super-storms that could devastate towns and villages with unprecedented fury -- also appears to be unfounded. Current long-term simulations, at any rate, do not suggest that such a trend will in fact materialize.

"According to our computer model, neither the number nor intensity of storms is increasing," says Jochem Marotzke, director of the Hamburg-based Max Planck Institute for Meteorology, one of the world's leading climate research centers. "Only the boundaries of low-pressure zones are changing slightly, meaning that weather is becoming more severe in Scandinavia and less so in the Mediterranean."

According to another persistent greenhouse legend, massive flooding will strike major coastal cities, raising horrific scenarios of New York, London and Shanghai sinking into the tide. However this horror story is a relic of the late 1980s, when climate simulations were far less precise than they are today. At the time, some experts believed that the Antarctic ice shield could melt, which would in fact lead to a dramatic 60-meter (197-foot) rise in sea levels. The nuclear industry quickly seized upon and publicized the scenario, which it recognized as an argument in favor of its emissions-free power plants.

But it quickly became apparent that the horrific tale of a melting South Pole was nothing but fiction. The average temperature in the Antarctic is -30 degrees Celsius. Humanity cannot possibly burn enough oil and coal to melt this giant block of ice. On the contrary, current climate models suggest that the Antarctic will even increase in mass: Global warming will cause more water to evaporate, and part of that moisture will fall as snow over Antarctica, causing the ice shield to grow. As a result, the total rise in sea levels would in fact be reduced by about 5 cm (2 inches).

It's a different story in the warmer regions surrounding the North Pole. According to an American study published last week, the Arctic could be melting even faster than previously assumed. But because the Arctic sea ice already floats in the water, its melting will have virtually no effect on sea levels.

Nevertheless, sea levels will rise worldwide as higher temperatures cause the water in the oceans to expand. In addition, more water will flow into the ocean with the gradual thawing of the Greenland ice sheet. All things considered, however, in the current IPCC report climatologists are predicting a rise in sea levels of only about 40 centimeters (16 inches) -- compared with the previous estimate of about one meter (more than three feet). A 40-centimeter rise in sea levels will hardly result in more catastrophic flooding. "We have more computer models and better ones today, and the prognoses have become more precise as a result," explains Peter Lemke of the Alfred Wegener Institute for Polar and Marine Research in the northern German port city of Bremerhaven.

Some researchers do, however, estimate that regional effects could produce an 80-centimeter (31-inch) rise in the sea level along Germany's North Sea coast. This will lead to higher storm surges -- a problem the local population, already accustomed to severe weather, could easily address by building taller dikes.

Another comforting factor -- especially for poorer countries like Bangladesh -- is that none of these changes will happen overnight, but gradually over several decades. "We still have enough time to react," says Storch.

In short, the longer researchers allow their supercomputers to crunch the numbers, the more does the expected deluge dissipate. A rise in sea levels of several meters could only occur if Greenland were largely ice-free, but this is something scientists don't expect to happen for at least a few more centuries or even millennia. This lengthy timeframe raises the question of whether the current prognoses are even reliable.

A healthy dose of skepticism is a good idea, especially when scientists become all too confident and make themselves out to be oracles. But there can be a wide gap between their predictions and the end result -- a fundamental weakness of all computer simulations that present only incomplete pictures of reality.

In the early years, for example, computer modelers underestimated the influence of aerosols, especially the sulfur particles that are released into the atmosphere during the combustion of oil and coal or during volcanic eruptions. These pollution particles block sunlight and thus cause significant cooling. The failure to adequately take aerosols into account explains why earlier models predicted a more drastic rise in temperatures than those in use today. One major unknown in the predictions depends on how quickly countries like China will filter out the pollutants from their power plant emissions -- if the air becomes cleaner it will also heat up more rapidly.

Other factors that can either weaken or strengthen the greenhouse effect are still not fully understood today. For example, will the carbon dioxide trapped in the world's oceans be released as the water heats up, thereby accelerating global warming? And how much faster do land plants and sea algae grow in a milder climate? Plant proliferation could bind more carbon dioxide -- and serve to slow down the greenhouse effect.

But the main problem lies in correctly calculating the effects of clouds. The tops of clouds act as mirrors in the sky, reflecting sunlight back into space -- thus cooling the planet. But the bottom sides keep the heat radiated by the earth from escaping into the atmosphere -- causing temperatures to rise.

Which of the two effects predominates depends primarily on the altitude at which clouds form. Simply put, low clouds tend to promote cooling while high clouds increase warming. So far scientists agree on only one thing, namely that more clouds will form in a greenhouse climate. They just don't know at which altitude.

Even the most powerful computer models are still too imprecise to simulate the details. However, the clouds alone will determine whether temperatures will increase by one degree more or less than the average predicted by the models. This is a significant element of uncertainty. "Clouds are still our biggest headache," concedes Erich Roeckner of the Max Planck Institute for Meteorology.

Roeckner is a conscientious man and a veteran of climate research, so he, of all people, should know the limits of simulation programs. Roeckner, who constantly expects surprises, neatly sums up the problem when he says: "No model will ever be as complex as nature."

Translated from the German by Christopher Sultan



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