1998 Warmest In Last 1200 Years
By Mary K. Miller

Every morning at 8 a.m., Louise Hallberg walks through her butterfly garden to a weather station on the family farm just north of San Francisco. She checks the thermometer and the rain gauge, and carefully records the information.
The 81-year-old volunteer weather observer later calls it in to a National Weather Service office, as she has for 30 years. Well, 30 years minus the two days that she missed.
Her daily routine, and those of many like her, contributes to an enormous network of volunteer and professional thermometer-watchers around the world. They track temperatures that help researchers figure out whether the Earth is indeed heating up for the long haul and what exactly that means.
Mind-numbing numbers
Weather enthusiasts, forecasters and climate researchers track temperatures at airports, city parks, universities, corporations, military bases, mountain tops, desert basins, farms, and in the back yards of private citizens. Instruments on weather balloons, commercial jets, and satellites measure the temperature of the upper air, while ocean buoys and ships monitor the sea surface temperature. Torpedo-like devices dropped from ocean liners measure the cold and murky depths, and pulsing sound waves gauge changing temperatures across the world's ocean basins.
The mind-numbing mountain of data collected so far allowed climatologists to declare with confidence that 1998 was indeed a record-breaking year for the planet, the warmest in 1,200 years. From January to November, the Earth's average temperature was 58.4 degrees Fahrenheit, 1.2 degrees warmer than the average mean temperature from 1880-1997. What exactly this means and whether humans are the cause of this latest round of global warming in the planet's stormy climatic history is heavily debated.
Each day computers at the National Climate Data Center in North Carolina gobble up and feed new information into the world's largest archive of climate records. In addition to day-to-day information, the center also tracks down, verifies and archives as many historical records from farmers, sailors, scientists, and colonial settlers as it can find. In its own way, the Earth itself has been keeping historical climate records, and researchers mine them by chiseling information and trends from studies of glacier ice cores, ocean and lake sediments, tree rings, sea ice and sea levels.
"Gigabits of data come in daily," says Steve Delgreco, chief of quality control for data operations at NCDC. "We're looking at terabits in our archives."
Weather pioneers
Individual weather enthusiasts alone have taken over 300 million temperature readings since 1714 when Mr. Fahrenheit invented the mercury thermometer, estimates Tom Peterson, a research meteorologist for the center.
Thomas Jefferson kept meticulous rainfall and temperature records at his plantation and proposed that the country establish a grid of weather stations to keep track of the climate. The National Weather Service's Cooperative Observing Network, an array of 12,000 weather stations scattered in back yards, city streets, and institutions from Maine to California, does just that.
Louise was recruited as an official weather watcher in 1968. In a way, it was destiny: Louise's father started keeping track of weather on the Sebastopol farm in 1930, and she kept up the meticulous records after his death.
Unfortunately, there aren't enough Louises to go around and the National Weather Service is depending more and more on automated stations to collect weather data. San Francisco's official weather station, now in a city park, has been automated since 1983. Located in the same seven-block area since it was established in 1849, the station has sweeping views of the downtown skyline and bay -- a vista wasted on the thermometer and rain gauge that sit atop a two-story building in Duboce Park.
Keeping watch
What automated stations lack in human touch they make up for in the collection of voluminous data. The instruments are always on, continuously monitoring temperature and rainfall, and sending reports by modem or radio signal every minute of every day.
And Louise keeps her daily watch on her farm, charting rhythms of weather there and sending what she sees along to those creating larger global pictures.
"I never thought I'd be doing this for 30 years," she says, "but here I am."
Mary K. Miller, a freelance writer based in California, works as a senior science writer for The Exploratorium in San Francisco. She recently co-authored the book Watching Weather: A Low Pressure Book About High Pressure Systems and Other Weather Phenomena.