Two hands holding a mini globe to show conservation on the plant. iStockPhoto

A sad, new record was set last month: the amount of carbon dioxide we're putting into the atmosphere is now officially more than double the rate of what it was just a generation ago, according to meticulous monthly records kept at NOAA and at the Mauna Loa Observatory in Hawaii. And it shows no sign of stopping. For those who understand compound interest, this doesn't bode well for the planet.



In fact, CO2 levels last year jumped nearly 3 parts per million over the previous year (to 393.39 PPM). That's one of the largest yearly jumps in a century of careful monitoring. But the number by itself isn't what matters – it's the fact that atmospheric CO2 is now accelerating from decade to decade. Climate models all assume the world's leaders will slow atmospheric CO2. The opposite is happening, which means that we're now conducting a very large science experiment with our planet's atmosphere.



For the past ten years, the average, annual rate of increase in atmospheric CO2 was 2.07 ppm, according to CO2Now.org. That's more than double the increase in the 1960s, when it was less than 1 ppm a year. Here are the hard numbers: CO2 increases averaged 2.07 ppm from 2003 to 2012; 1.67 ppm from 1993 to 2002; 1.52 ppm from 1983 to 1992; 1.37 ppm from 1973 to 1982; and 0.90 ppm from 1963 to 1972.



This accelerating rate of increase in the amounts of CO2 we're putting into the atmosphere year by year, decade by decade, is a definitive science fact with untold consequences for the planet and us.



The late scientist Charles Keeling discovered the Earth breathes - an important fact about our planet -in the past half century. He began to very meticulously measure carbon dioxide levels near the top of a volcano in Hawaii. He discovered that carbon dioxide levels rise and fall throughout the year as the plants on Earth take in CO2, and then shed that CO2 as the leaves fall and decay.



But, while measuring that rise and fall, Keeling also discovered a disturbing trend. CO2 levels, averaged annually, rose just a little more each year. They were at 310 parts per million when he began to measure them in the 1950s. A half century later, they'd risen to nearly 380 parts per million.



The rise in carbon dioxide in Earth's atmosphere now is relentless, indisputable, unmistakable, and incontrovertible. You can argue about anything you'd like when it comes to global warming, but one thing you can't argue about is Charles Keeling's curve.



And his curve—even to a casual, cynical, or skeptical observer—shows that we're likely to reach 450 parts million in the next 15 to 20 years unless something changes the planet's energy balance equation.



But even as Keeling, a registered Republican, meticulously chronicled CO2 levels, others took up the search for what it meant. Keeling's widow told Justin Gillis of The New York Times last year that her husband didn't believe global warming was all that political. It was just an inexorable fact, one that he'd studied his entire career up until he died in 2005. His son Ralph has continued the research since.



Scientists began to study past levels of carbon dioxide in air bubbles trapped in the ice in Antarctica. They found that CO2 levels have naturally risen and fallen and ranged between 200 and 300 parts per million in the past 400,000 years. They also studied past temperatures from hydrogen isotopes in the same ice in Antarctica, going back 400,000 years. And they discovered a pattern.



As carbon dioxide levels rose, so did the planet's temperature. And as CO2 fell, the temperature did, too. But what the Earth has never experienced before is the trend that Keeling found. As we continue to burn fossil fuels at an unprecedented pace in human history, accelerating the greenhouse gas effect, we are approaching a point of no return.



So what happens when we get to 450 parts per million, with greenhouse gases like CO2 trapping heat on the planet at an ever-increasing rate - when greenhouse gases in a planet's atmosphere move beyond a critical threshold? The truth is: we don't really know.



In the very extreme, you can take a look at the surface of Venus to see what happens when a runaway greenhouse effect takes over. Venus is about the same size as Earth, though closer to the sun. It has an atmosphere. But it's vastly different than Earth. About 97 percent of Venus' atmosphere is made up of carbon dioxide, compared to less than 1 percent CO2 on Earth.



Once upon a time, there was probably water on Venus and its surface temperature was about twice that of Earth (120 degrees Fahrenheit or so). But as CO2 took over Venus' atmosphere, temperatures began to rise. The water disappeared. Today, temperatures on Venus can reach 900 degrees Fahrenheit. That's the greenhouse effect, in extreme.



On Venus, it increased the temperature to a point where the atmosphere would crush a human being and melt lead. (We learned an awful lot about Venus when NASA's Messenger mission flew by the planet in 2006 and 2007 on its way to the first-ever orbit of Mercury.)



But that's the extreme. Here on Earth — if we exceed 450 parts per million — we could move past a point at which everything accelerates beyond our control. Earth's system is a complex web. We've never pushed it to this point before, and hazarding a guess about what might happen when CO2 levels are 50 percent higher than they've been in the recent history of the planet is just that — a guess.



If Earth's climate changes sooner than we expect, it could bring about substantial sea level increases, considerable ocean acidification, rapid warming of ice at both poles, an unprecedented change in freshwater patterns in the oceans, and eventual shifts in circulation patterns in both the atmosphere and the oceans. In other words, our basic Earth geosystem could change in very dramatic ways.



Beyond 450 parts per million, coral reefs could start dissolving. Average temperatures could rise dramatically. Half the species on our planet could disappear. Dust bowls could become commonplace. Drought and monsoons could become the norm in parts of the world. And, unfortunately, it would take the human species a thousand years — or longer — to reverse the damage.



We know what happens when greenhouse gases in the atmosphere increase. We can measure it, study it, and map it. We know what a greenhouse effect is. The question is whether we can keep that from happening on Earth — before we've gone beyond 450 parts per million and a possible point of no return.



Regardless of your beliefs or skepticism, carbon dioxide levels are rising and accelerating. Temperatures will rise along with them, at some rate. Lowering fossil fuel consumption and reducing greenhouse gas levels can't do harm to the planet. But allowing CO2 and other greenhouse gases to reach critical levels in our atmosphere quite possibly could mean the end of life as we know it on our planet at some point.