A message from mother nature? There's no argument that the weather has been wild lately; the question is whether it's a sign of climate change.

• Author: Gillis, Justin
• Position: ENVIRONMENT

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Over the past few months, it feels like it's been one weather extreme after another. Torrential monsoon rains in Pakistan caused the worst flooding in decades, killing more than 1,500 people and uprooting millions.

In Russia, a record-breaking heat wave along with a record-breaking drought destroyed millions of acres of wheat and sparked wildfires that killed dozens.

In the United States, flooding battered New England, then Tennessee, Arkansas, and Oklahoma, while a record-breaking heat wave baked the entire eastern part of the country.

Scientists have long agreed that a single freak snowstorm or a particularly bad heat wave doesn't tell us much about climate change. But all these weather extremes in the past year--so many examples in so many different parts of the world--are making some climatologists wonder whether global warming is to blame. The collective answer of the scientific community can be boiled down to a single word: probably.

"The climate is changing," says Jay Lawrimore of the National Climatic Data Center in Asheville, N.C. "Extreme events are occurring with greater frequency, and in many cases with greater intensity."

Theory vs. Proof

Climatologists have theorized that a world warming up because of a buildup of greenhouse gases will feature heavier rainstorms in summer, bigger snowstorms in winter, more intense droughts in at least some places, and more record-breaking heat waves. Scientists and government reports say the statistical evidence shows that much of this is starting to happen.

Still, most scientists are reluctant to link specific weather events to climate change, noting that weather was characterized by remarkable variability long before humans began burning fossil fuels and releasing greenhouse gases into the atmosphere. "If you ask me as a person, do I think the Russian heat wave has to do with climate change, the answer is yes," says Gavin Schmidt, a climate researcher with NASA. "If you ask me as a scientist whether I have proved it, the answer is no--at least not yet."

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The Earth has warmed by about 1.4 degrees Fahrenheit since the Industrial Revolution, when humans began pumping enormous amounts of carbon dioxide, a heat-trapping greenhouse gas, into the atmosphere. For this January through July, average temperatures were the warmest on record, according to the National Oceanic and Atmospheric Administration.

Climatologists have long theorized that in a warming...