What do you think of when you hear the words "global warming?" You might envision melting ice caps, drowning polar bears and shrinking coast lines. Or perhaps your mind turns to magazine covers, politicians and celebrity activists. Global warming has become a very divisive term, but is it real?
The short answer, according to environmental scientist David Keith, is yes.
"There is no disagreement among really anybody who is scientific in any way that the world is a lot warmer than it was 100 years ago," Keith says. "If there are interesting disagreements, the disagreements are about whether this is the warmest it's been since the ice ages 10,000 years ago."
A recipient of honors that include MIT's prize for excellence in experimental physics, Keith has spoken to governments, corporations and media outlets about climate change. As he points out, scientists use various methods to measure global warming; they produce varying answers.
"If all the scientists in the world believed there was only one answer, it would be right for all the rest of us to be skeptical," Keith said. "There's nothing in the world that one ever measures with perfect accuracy."
Those measurements include thermostatic records and satellite images that document temperature increases over the past century. Additionally, paleoclimate databases suggest the current rate of increase is substantially higher than normal.
While global warming is certainly an important aspect of climate change, the term's use in mass media may actually serve to distract people from the real issues. Keith uses the example of a human patient hooked up to a mercury drip to illustrate this point.
The hypothetical human will eventually die from mercury poisoning — it’s the scientific reality of the situation. The media focus on year-by-year warming or cooling, he argues, is akin to focusing on the patient's symptoms instead of the proven underlying condition and the cause behind it. In the case of climate change, elevated carbon dioxide (CO2) levels are the deadly mercury drip.
"The core theory says if you double or triple CO2 in the atmosphere, it's going to get warmer," Keith said. "This is something we've known from pretty basic physics and proved with a lot of good science for more than 100 years. That's the reason to worry, not the warming over the last few decades."
Scientists first raised concerns over the warming effects of CO2 in the atmosphere in the 1960s, when the climate was actually cooling. While there's nothing overtly problematic about natural climate change, it’s the rate of change that worries experts.