For many years now, researchers have been studying tree rings, ice cores, and other natural archives to determine whether Earth is in the midst of a sustained warming trend. What they've found while gazing at these climatological tea leaves is proof not just that the planet is warming, but that it is doing so at a disturbingly fast and damaging rate.
In a number of new studies, evidence suggests that the atmosphere and oceans are warming, that the glaciers are melting, that growing seasons are lengthening, that El Ninos are intensifying, that the world's coral reefs are under assault, and that all of these changes are having profound effects on the planet and its inhabitants.
For example, according to the authors of a recent global warming study, the past decade was the warmest in 1,000 years, the 1990s are the warmest decade ever, and 1998 set the benchmark for the warmest year yet. Furthermore, the warming curve seems to be on a dramatic upswing, with 1998 showing a major leap forward.
Conducted by Michael Mann and Raymond Bradley of the University of Massachusetts at Amherst and Malcolm Hughes, director of the Laboratory of Tree Ring Research at the University of Arizona, the study adds new weight to the growing body of evidence suggesting Earth is in the midst of a serious and prolonged warming trend that could spell trouble for a planet still reeling from the previous year's meteorological mayhem.
"Temperatures in the latter half of the 20th century were unprecedented," said Bradley who, along with his team members, studied tree ring records from North America, Scandinavia, northern Russia, Tasmania, Argentina, Morocco and France, and ice cores from Greenland and the Andes Mountains.
Using sophisticated computer analysis on these "proxy indicators," the research team was able to roughly reconstruct the planet's climate dating back to 1,000 A.D.
The results painted a startling picture of a 900-year cooling trend suddenly interrupted by an abrupt and increasingly severe warming trend this century. Such a finding adds additional currency to the notion that human activities are at least playing a role in the planet's changing climate.
Mann said that although centuries-old evidence can be sketchy, "our results do reveal that significant changes have occurred, and temperatures in the latter 20th century have been exceptionally warm compared to the preceding 900 years."
Mann added that although "substantial uncertainties exist in the estimates, these are nonetheless startling revelations."
The new study's findings are ominous because they support computer models which not only predicted the warming trend, but also prophecy a world of increasingly turbulent and severe weather extremes that could claim tens of thousands of lives, cost billions in damages, and produce enormous hardships for a growing number of the world's denizens.
Another recent study bolsters recent claims that the world's glaciers and polar ice sheets are melting. According to the new National Aeronautics and Space Administration (NASA) study, glaciers along the southeastern coast of Greenland are shrinking by more than three feet per year -- much faster than expected.
"Why [the glaciers] are behaving like this is a mystery," said Bill Krabill, a researcher with NASA's Goddard Space Flight Center. "But it may indicate that the coastal margins of ice sheets are capable of responding quite rapidly to external changes, such as a warming climate."
For years scientists have expressed growing alarm at the rate at which mountain glaciers have been melting. Now, with evidence that the polar ice sheets and glaciers also are shrinking, there is real concern that sea levels could be affected. Additionally, a massive influx of fresh water could alter the ocean's salt content and eventually impact the great ocean circulatory systems that regulate the planet's climate.
"If temperatures change slowly, society and the environment have time to adjust," noted Mann. "The slow, moderate, long-term cooling trend that we found makes the abrupt warming of the late 20th century even more dramatic. The cooling trend of over 900 years was dramatically reversed in less than a century. The abruptness of the recent warming is key, and it is a potential cause for concern."
The temperature rise has been especially profound in the Arctic, where temperatures have risen almost 59 degrees (Fahrenheit) in the past 50 years. In Antarctica, the temperature has increased about 20 degrees in the past two decades. "What we see in Antarctica looks very, very similar to what we see in Greenland," said University of Colorado climatologist James White. White, who has studied Antarctic ice cores for clues to the past, said the "challenge is to determine if a climate change will be a nice and gradual thing that we can adapt to, or will it be a mode shift that happens suddenly."
Ironically, a rapid warming of polar climes would release enormous reserves of greenhouse gases trapped in the ice and frozen tundra, accelerating the warming trend that many blame on an accummulation of such gases in the atmosphere.
Kevin Trenberth, director of the Climate Analysis Section of the National Center for Atmospheric Research (NCAR) agrees. "The warming air and sea surface temperatures certainly are indications of increased risk of storms and droughts. We're always careful with the language we use discussing these topics, but I think [the recent findings] are ominous."
Although scientists for years have speculated that the planet is warming, proving it has been exceptionally difficult. The climate is an incredibly complex system about which mankind still knows relatively little. Whether current trends represent natural perturbations in this system or are indicative of a more serious problem is difficult to determine.
In recent years, however, significant and sustained increases in global air and sea surface temperatures have been recorded across the planet to the extent that nine of the 10 warmest years in recorded history are now judged to have occurred in the past decade. As a result, the majority of scientists today are convinced Earth is warming.
In independent studies and reports, scientists with the National Oceanic and Atmospheric Administration, the World Meteorological Organization, and NASA all have concurred that not only is the planet warming, but the warming trend appears to be growing more dramatic. For example, the global average temperature shot up 0.34 degrees Fahrenheit in 1998, a significant jump over previous years.
"It is really quite extraordinary," said NOAA Director James Baker, when the news was released. "We've got a record and it's one of the largest increases that we've ever seen in one year."
Perhaps just as important, human activities, including the burning of fossil fuels and ecologically destructive practices such as deforestation, are believed to be contributing to the warming trend, although to what degree remains to be determined. Trees, for example, are one of Earth's natural temperature control mechanisms (they also help regulate greenhouse gases, limit flooding, and fend off droughts). With the majority of the world's native forests gone and the remainder under assault, concerns are mounting that mankind is pushing the planet to its ecological limits. Numerous studies are under way to determine precisely how mankind may be impacting the climate, and what, if anything, can be done to remedy the situation.
Some of the blame for the warming also has been laid at the feet of El Nino, that now-infamous Pacific warm water phenomenon that has been on the lips of the world's meteorologists since 1997. Unfortunately, most scientists see El Nino as a convenient though not altogether sensical villain in the global warming story.
After all, the warming trend has preceded and outlasted recent El Nino episodes, meaning that while the planet has exhibited signs of a significant and sustained warming trend for more than 30 years, only a handful of El Ninos have occurred during that same time span. Additionally, it would follow that if El Nino is responsible for the warming trend, then its cold water cousin, La Nina, would be responsible for any cooling trends. But those haven't occurred.
To the contrary, there is a growing body of evidence suggesting that this chicken-and-egg discussion has the equation exactly backward. Rather than contributing to global warming, El Ninos actually are being intensified by the warming trend. This argument takes on added legitimacy when one considers that the two most powerful El Ninos ever recorded occurred during the past 20 years (1982-1983 and 1997-1998).
NCAR's Trenberth, a chief proponent of this theory, has noted that since the mid-1970s global temperatures have risen dramatically at the same time powerful El Nino events have laid siege to the earth. In Trenberth's mind, the connection is obvious.
"It is no coincidence that the exceptional warmth in the first seven months of 1998 occurred as the Pacific Ocean lost heat following the peak of the 1997-98 El Nino in December 1997," he said. Trenberth believes that the growing volume of greenhouse gases in the atmosphere - which leads to the so-called Greenhouse Effect - is trapping enormous amounts of heat which is transferred to the oceans. This thermal energy subsequently is released through El Nino events in a process akin to throwing fuel on a fire.
And not only are modern-era El Ninos more severe, they're also becoming more commonplace. Tree ring studies carried out across the globe indicate that until 1880, El Ninos occurred about once every 7.5 years. During the past century, however, the phenomenon has been observed about once every 4.9 years.
All of which begs the question, So what? According to Trenberth and other atmospheric researchers, the warming trend poses potentially dire consequences for the planet. The additional heat pulls more moisture into the atmosphere, leading to heavier, more sustained rains; increasingly violent storms; and severe droughts.
"When it rains, it pours, much more now than in the past," said Trenberth. Indeed, recent studies indicate the moisture content of the atmosphere is 10 percent higher today that it was 20 years ago, leading to the recent toppling of numerous flood records around the world.
Similarly, as more moisture is drawn from the earth, some areas are starved of water, leading to harsh droughts, crop failures and famine.
Such droughts have become so severe that tropical regions, which historically have been immune to large-scale wildfires, in recent years have been plagued by massive conflagrations that destroy millions of acres of rainforest and paint the skies black. In the past two years, for example, massive fires have swept through low-latitude forests in Brazil's Amazonia region, Mexico's Chiapas state, Indonesia, and Florida.
In a recent report, Jonathan Overpeck, director of NOAA's Paleoclimatology Program, suggested that the "mega-droughts" that periodically occur across the planet could be exacerbated by global warming and lead "to a natural disaster of a dimension unprecedented in the 20th century."
In short, if it's true that El Ninos are strengthening as a result of the warming trend, then the aforementioned problems could be orders of magnitude worse in future years.
One of the world's great sentinel species is its coral reefs. In a report soon to be released to the Coral Reef Task Force, the State Dept. indicates that 1998 witnessed the single largest die-off of coral reefs in recorded history. In some regions of the world, more than 70 percent of the reefs were killed or badly damaged.
Their immune systems weakened by the warm water, huge numbers of the world's coral reefs, which predate the dinosaurs, are plagued by pathogenic attacks that have led some scientists to publicly worry whether coral reefs are in danger of extinction. "In 1998, coral reefs around the world appear to have suffered the most extensive and severe bleaching and subsequent mortality in the modern record," said the report. Furthermore, the authors maintain that these die-offs "cannot be accounted for by localized stressors or natural variability alone."
Which is to say that El Nino, which periodically lays siege to the natural world, is not the sole culprit in the species' decline. The report is more blunt: "At this time, it appears that only ... global warming could have induced such extensive bleaching simultaneously throughout the disparate reef regions of the world."
And warm ocean waters are prime breeding pools for the hurricanes that captured so many headlines last year, including Hurricane Mitch, one of the most powerful storms ever to ply the waters of the Caribbean. William Gray, a professor of atmospheric sciences at Colorado State University and the man to whom many look for hurricane prognostications, predicts coming years are going to produce bumper crops of hurricanes, many of them similar to the monsters that filled the Atlantic Basin in 1998.
However, Gray isn't committed to the notion that the global warming trend necessarily spawns more hurricanes. He notes, for example, that the United States experienced a substantial decrease in hurricane activity between 1970-1994, the same time significant warming was taking place. In the minds of Gray and others, the planet's climate is an incredibly complex system not given to simplistic meteorological prescriptions.
Trenberth concurs, noting that a warming planet could produce numerous storms rather than large hurricanes. "It depends, to a large extent, on how the atmosphere behaves," he said.
Trenberth and others believe the real story may lie in the monsoons and "conventional" storms that in recent years have taken on an increasingly malignant behavior. For example, across the globe last year, 100- and even 500-year flood records fell as unusually heavy rains besieged some areas for weeks or even months at a time. China, Korea, Mongolia, Australia, Indonesia, Europe, Brazil, Peru, Mexico, the United States, and many other nations and regions of the globe faced epic onslaughts of rain.
Even this winter's record-setting snowstorms in the European Alps and the U.S. Sierra Nevada ranges are indicative of this trend. Meteorologists in both regions claim they have seen some of the largest snowfalls ever this winter.
Conversely, serious and long-lasting droughts also laid waste to vast regions of the globe. "When you have these big, heavy rainstorms, the water has to come from somewhere," noted Trenberth. "That's what you get with global warming. The warmer temperatures pull tremendous amounts of moisture into the atmosphere, leaving some areas dry while delivering a lot of rain to other regions. These droughts, in turn, lead to massive crop failures and famine. As one example, Texas and Oklahoma suffered through the second worst drought of their history last summer, resulting in billions in aid to farmers and ranchers.
While meteorologists have been quick to place the blame for this year's woes on La Nina just as they blamed last summer's storms on El Nino, others see a larger theme being played out. Rather than El Nino or La Nina dictating the weather's events, they are part of a much larger problem. Put another way, we shouldn't be focusing on "the boy child" or "the girl child" but instead on Mother Nature herself.
"I don't know whether we'll see more hurricanes or not," said Trenberth. "I think what is more robust is these heavy thunderstorms that deliver a lot of rain over an extended period of time.
Hurricane Mitch was an example where even though its winds were really strong, the real impact came from the tremendous amount of rain it delivered."
Indeed, in the wake of Mitch, meteorologists and disaster preparedness officials acknowledged that they need to pay more attention to the potential of storms to deliver heavier-than-usual rains rather than focus primarily on wind damage.
"The issue you have with these warmer sea surface temperatures is that they lead to the evaporation of immense quantities of water into the atmosphere," said Trenberth. And what goes up must come down.
There is some good news from all this. In a study released earlier this month, two researchers at the University of Munich in Germany noted that the global warming trend is leading to a substantial increase in growing seasons. The proof comes by way of a 35-year study of 77 International Phenological Gardens spread across Europe. From Scandinavia to Spain and from Ireland to Poland, the gardens contained genetically identical plant and tree species that have been monitored since 1959.
After analyzing more than three decades' worth of results, Annette Menzel, a forest specialist, and Peter Fabian, a climatologist, announced that the verdict was in: spring is arriving six days earlier and fall is being delayed five additional days.
The study, which is contained in the Feb. 25 issue of Nature, offers a clear indication of what the world can expect if the current warming trend continues. Menzel noted that plant life responds most favorably to increases in the average daily temperature. Other studies also have indicated that animals are birthing earlier, that plants are budding earlier in other parts of the globe as well, and that crops are growing for longer periods of time.
The question remains to be seen, however, whether the good will outweigh the bad.