May 16, 2018, by Faye Flam
As scientific terms go, “climate change” is failing. Good terms are specific, descriptive and help people to understand complex concepts. Climate change is ambiguous, referring perhaps to the most pressing human-generated environmental problem of the century, or to other kinds of changes that happen through natural forces and have been going on since long before humans arose.
Last week I chatted with Columbia University paleontologist Dennis Kent about some new work he and his colleagues published in the Proceedings of the National Academy of Sciences about the surprisingly big influence of Venus and Jupiter on the climate of Earth. The gravitational tug of the second and fifth planets from the sun act to stretch Earth’s annual orbit like a rubber band, pulling it into a more oblong ellipse and then back to something very close to a perfect circle over a cycle of 405,000 years. And that leads to big changes in our climate – or the climate of whatever creatures lived here.
The ambiguity of “climate change” plays into the problems that a Wall Street Journal op-ed identified last week in a piece headlined “Climate Activists Are Lousy Salesmen.” This is science, not advertising, and the terms that scientists come up with aren’t decided by public-relations experts using focus groups. Most of the burden of explaining climate changes, past and present, has fallen not to “activists” but to scientists, whether or not they have an interest in or aptitude for persuasion.
According to historians, the same people who were fascinated by dramatic natural climate changes were the ones to discover that burning up lots of fossil fuel was likely to cause a short-term spike in the global temperature. The start of that spike is already measurable. Research on human-generated and natural climate changes are related, and many of the same people still study both kinds in order to get a better handle on where things are headed in the coming decades, centuries and millennia.
Back in the 19th century, scientists started to investigate signs in the geologic record that dramatic ice ages had been occurring every 40,000 years or so, during which glaciers crept over much of the Northern Hemisphere. Eventually, they realized that these are driven by what Kent calls an ice age pacemaker – the interplay between the tilt of the planet’s axis and our planet’s distance from the sun. Those factors change the way sunlight is distributed, concentrating more or less over the Northern Hemisphere, where there’s more land and the potential to build up glaciers. Glaciers reflect sunlight, absorbing less of its heat energy than dark surfaces would, which makes the cold periods colder worldwide. Similarly, warmth releases carbon dioxide, which acts as a greenhouse gas traps solar heat and amplifies warm periods.
Adding to all this complexity is the subject of the new paper – a 405,000-year-long cycle caused by our fellow planets. Kent said that basic Newtonian physics shows that Venus and Jupiter actually change Earths’ orbit significantly. At its most oblong, the long axis of the orbit is five percent longer than the shorter one. During that more oblong part of the cycle, the Earth strays farther than normal from the sun and also flirts closer to the sun than usual. So other natural changes reach greater extremes – the ice ages colder and the periods in between warmer.
What Kent and his colleagues did was expand the record of those cycles by digging out cores of Earth hundreds of feet long from Arizona and Northern New Jersey. They used the natural clocks provided by radioactive materials and signs of reversal of the Earth’s magnetic field to figure out when and how the climate changed. The cycles, he said, go back more than 200 million years, to the time when dinosaurs first appeared.
We are currently in the rounder, more even phase of our orbital cycle, Kent said, meaning the ice ages should be relatively mild. We’re also in between ice ages and could go into a new one in a few thousand years, though some think that human-generated global warming will be enough to offset it.
And herein lies the confusion. People hear “climate change” and think, what’s the big deal? The climate has been changing for millions of years. Or they note that scientists used to think we were headed into another ice age. But the time scales matter. Fossil fuel burning and other human-generated changes are likely to warm the overall planet’s temperature by more than 4 degrees Fahrenheit over the coming decades. The next ice age isn’t expected for a few millennia. That’s a long time to wait for a potential cooldown.
One could distinguish the current, more rapid climate change by calling it “anthropogenic climate change,” but that term makes people trip over their own tongues, so it’s understandable that people shorten it. There’s also the term “global warming,” which is a little more descriptive, but scientists say it fails to capture changes in rainfall patterns, wind and currents that go along with the general trend of warming.
The Wall Street Journal piece was right about a sales problem. It’s too bad there isn’t a catchy term or acronym — such as WMD or GMO — to describe the buildup of greenhouse gases in the atmosphere from fossil fuel burning, deforestation, domestic cattle and other human activities.
The complexity of climate science may always be at odds with the simplicity that’s key to inspiring action.
Remember the hole in the ozone layer? It was more of a thin spot, but in the 1980s, that dramatic term may have helped spur a global movement to reduce certain pollutants staved off disaster.
It’s too late to prevent anthropogenic climate change, or unnatural climate change, or global warming — call it what you will. But it isn’t too late to slow the warming, and perhaps even reverse it. If only someone could sell the idea.