I recently chatted with a man who denies that human activity has anything to do with changes in Earth's climate. "It's natural cycles," he insisted. "The temperature fluctuates in natural cycles over thousands of years."
When I asked very gentle questions, he raised his voice and turned red in the face. "Global warming is a lie!" he spluttered. "The earth gets warmer and colder and has for millions of years. They've proven it."
That kind of response -- getting angry, supporting an argument by repeating it, and making vague references to proof -- is usually a sign someone has adopted an idea without much study. So I asked my new friend to share the facts he had based his conclusions on. Surely, as someone so passionate about the issue, he had done some research?
"Watch Fox News," he said, waving my questions away. "They're the only people telling the truth about it."
On the bright side: at least my friend's assertion that the Earth gets warmer in cycles is an admission that the Earth is, in fact, getting warmer. Some people still deny that, often citing articles like this one that are known to be hoaxes.
But what about the idea that planetary warming is "just a cycle" and that "it's been this warm before?" Is that true?
The facts: the planet *does* go through cycles of warming and cooling. Here's a chart from the Marian Koshland Science Museum Academy of Sciences that does a good job of showing how polar temperatures have varied by 20 degrees Fahrenheit over the last 350,000 years:
See? Cycles! Cooler, warmer. Cooler, warmer. Cooler, warmer. It's been going on forever. At first glance, my friend seems right.
That said: note that the chart above tracks more than temperature: it also tracks the amount of carbon dioxide gas in the atmosphere. See how closely the two track together?
Now, to be honest, I've tricked you a bit, because I cut off the right-hand edge of the chart. Here's how it looks if you include temperature and atmospheric data through 2007:
Hmmm. For some reason, over the last 150 years, CO2 levels, which have always tracked hand in hand with temperature fluctuations, suddenly don't. They skyrocket in the modern era, about the time that humans began burning massive amounts of fossil fuel -- coal, oil, and gas.
So: while the Earth's temperature does cycle … this is the first cycle *ever* in which humans have, in a very short period of time, been producing 21.3 billion tones of carbon dioxide per year. That's an important number -- because natural processes can only absorb about half that amount. And because carbon dioxide is a greenhouse gas, it might make sense to ask, "Will adding extreme amounts of carbon dioxide to the air make the planet extremely warmer?"
Here's what we know:
- Last year was the hottest year ever recorded in the United States, hotter than the previous year by a full degree Fahrenheit. Normally, year-to-year average temperature fluctuations are measured by fractions of a degree.
- Last year, we set more than 34,008 daily record highs versus only 6,664 record lows. As recently as the 1970's, record highs and lows were very much in balance. Since the 1980's, that balance has been shifting at an increasingly rapid pace.
- "The ten warmest years on record all fell within the past fifteen years."
- When you look at temperature data over the past several decades, you'll often see decade-long stretches of time when not much is changing. But if you look at a series of decades strung together, you'll see a steady stair-step upward: what climatologists call The Escalator:
So: Earth is getting warmer, at the rate of about five degrees Fahrenheit per decade, for the past three decades. And my little summary just scratches the surface: there's a huge amount of data showing the terrible impact this rapid warming is having on systems all over the planet.
In the end: the argument that dramatic, unprecedented warming trends are part of a natural cycle is unsupported by science … and is a position that is rejected by 97% of climate experts.
To my new friend: I'm sorry that the facts conflict with your belief. But perhaps it's time to stop believing in something attractive just because some talking head says it's true … to stop mistaking passion for accuracy … and start doing your homework before drawing conclusions.