Geoscience Reference
In-Depth Information
The ice we skate is getting pretty thin The waters getting warm so you might as well swim
*
—Smashmouth, “All Star” (1999)
When I entered the field of climate research in the early 1990s, the science was just coming of age.
Major research centers around the world were using some of the fastest supercomputers available to
run ever-more sophisticated models of Earth's climate. Important new observations were coming in.
Thermometer measurements showed that the globe—both land and ocean—had by that time warmed
approximately 1 degree Fahrenheit over the past century. The accumulated loss of ice during the
previous four decades from melting glaciers around the world could fill Lake Huron. An increasing
number of climate measurements were painting a picture of a climate that was changing in much the
way models had been predicting it would if we continued to emit greenhouse gases. By the mid-
1990s, enough evidence had accumulated to convince the IPCC, as we've seen, that there was a
“discernible human influence on climate.” While the jury had been out when I began my studies in the
early 1990s, it had come in with a judgment by the time I was completing them in the mid-1990s.
What had led to that verdict can be described in five easy steps.
Climate Change in Five Easy Steps
By the mid-1990s, scientists were able to connect the dots when it came to establishing a human
impact on our climate.
(1) We knew for one thing that human activity—primarily the burning of fossil fuels—had
increased carbon dioxide (CO
2
) concentrations in the atmosphere. The legendary atmospheric
scientist Charles Keeling first began to make direct measurements of atmospheric CO
2
in 1958 at a
pristine location far from any pollution sources—nearly three miles above sea level at the top of
Mauna Loa in Hawaii. Thanks to Keeling's work, we had an instrumental record of CO
2
—the so-
called Keeling curve—going back nearly half a century. But we could go back even farther by
analyzing CO
2
content in samples of the ancient atmosphere recovered from the layers of ice in ice
cores stretching back hundreds of thousands of years.
