How has the increase in global CO2 been attributed to an anthropogenic cause?

So, We’re Responsible for the CO2 Spike, Huh? Here’s the Story.

Okay, let’s get straight to the point: the overwhelming scientific opinion is that we humans are the reason atmospheric carbon dioxide (CO2) is going through the roof. It’s not just one thing pointing the finger, but a whole stack of evidence that all adds up to the same conclusion.

Think about it this way: the speed at which CO2 levels are climbing is just bonkers. We’re talking about ice core data – ancient air bubbles trapped in ice that tell us what the atmosphere was like way back when. For the last 800,000 years, CO2 barely nudged past 300 parts per million (ppm). Even coming out of the last ice age, around 20,000 years ago, it was only around 280 ppm. Now? We’re knocking on the door of 420 ppm! That’s a jump of 140 ppm, mostly since we started burning stuff like crazy during the Industrial Revolution. To put it in perspective, this increase is happening up to 250 times faster than what nature cooked up coming out of those old ice ages. That kind of rapid change? Yeah, that’s us.

And where’s all this extra CO2 coming from? Well, the prime suspect is fossil fuels. Coal, oil, natural gas – they’re basically the leftovers of ancient plants that have been chilling underground for millions of years. When we burn them, we’re releasing that stored carbon, which then hooks up with oxygen to become CO2. The crazy part is, we’re digging up and burning so much of this stuff that it’s more than enough to explain the CO2 spike.

But it gets even more interesting! Scientists are like detectives, using “isotopic fingerprints” to track down the source of the CO2. Carbon comes in different flavors, called isotopes. Plants are picky and prefer the lighter carbon-12 (12C) when they’re doing their photosynthesis thing. Fossil fuels are made from old plants, so they’re low in carbon-13 (13C) and practically devoid of carbon-14 (14C), which decays over time.

So, guess what’s happening in the atmosphere? The amount of 13C compared to 12C is dropping, which tells us that the extra CO2 is coming from something low in 13C. Plus, carbon-14 is also on the decline. This “Suess effect” is like a neon sign pointing to fossil fuels. The carbon isotope changes match what we’d expect if we were burning a whole lot of ancient plant matter.

It’s not just about the chemical signatures, either. We can actually see the impact of all these greenhouse gasses on the planet’s energy balance. CO2 and other gasses trap heat, keeping it from escaping into space. Satellites and fancy instruments on the ground are measuring this “radiative forcing” directly. And guess what? They’re showing that the extra CO2 is trapping more heat and warming things up.

Then you have these “attribution studies” that use climate models and statistics to figure out what’s causing the climate to change. They consistently show that human-caused greenhouse gas emissions are responsible for more than 100% of the warming since 1850! How can it be more than 100%? Well, natural factors like volcanoes and changes in the sun’s energy have actually had a slight cooling effect, which we’ve more than offset.

Now, fossil fuels are the big kahuna, but we also need to talk about land use. When we chop down forests, we’re not only releasing CO2, but we’re also reducing the number of trees that can suck it up. Double whammy!

And if you want the official word, the Intergovernmental Panel on Climate Change (IPCC) – basically the UN’s climate dream team – has said, in no uncertain terms, that humans are warming the planet with greenhouse gas emissions. Their latest report is pretty blunt: it’s “unequivocal” that we’re the ones doing it.

So, there you have it. All the evidence points in the same direction. The rapid CO2 increase, the fossil fuel fingerprint, the trapped heat, the climate models – it’s all telling us that we’re the ones driving this change.