Credit: Pixabay.

Climate change denial comes in various stages and varieties. Some bury their heads in the sand and deny anything is happening, some take it a step further and call it a ‘Chinese hoax’, and some acknowledge that the climate is shifting but it’s all due to natural variability. We’re too small, too insignificant — a drop in the ocean — to alter the planet, the rhetoric goes. That’s an odd thing to say when humans have totally altered the planet’s environment, so much so that we’re officially in the Anthropocene. There are only a couple of virgin forests left in the world and some of our cities stretch for hundreds of square miles.

Pre-humans: 0.01°C rate of change / century. Human-age: 1.7°C rate of change / century

It’s true, however, that natural forces like the variability of the Earth’s climate system or that of the sun have an influence on shifting climates, but scientists agree that human activity is the main driver for the major shifts in the climate we see all over the world. Just how much influence wasn’t always clear, however, but we may now have an official figure. According to an international team of researchers who developed a new equation, human activity is driving climate change 170 times faster than natural forces.

In their paper, they write that for the past 4.5 billion years since our planet has been in existence,  astronomical and geophysical factors have been the dominating influences on the Earth system. In the past few decades alone, however,  humans “have driven exceptionally rapid rates of change in the Earth system,” the authors write in The Anthropocene Review.

“Over the past 7,000 years the primary forces driving change have been astronomical – changes in solar intensity and subtle changes in orbital parameters, along with a few volcanoes. They have driven a rate of change of 0.01 degrees Celsius per century,” said Professor Steffen, from the Fenner School of Environment and Society and the Climate Change Institute at the Australian National University (ANU).

“Human-caused greenhouse gas emissions over the past 45 years have increased the rate of temperature rise to 1.7 degrees Celsius per century, dwarfing the natural background rate.”

To determine the impact humans have on Earth’s system, Steffen and Owen Gaffney, from the Stockholm Resilience Centre, devised the “Anthropocene Equation.” Its final form is simple but it took into account rate of changes in the atmosphere, oceans, forests and wetlands, waterways and ice sheets, and biodiversity.

“The human magnitude of climate change looks more like a meteorite strike than a gradual change.”

The final equation, where E is the Earth System, A is astronomical forces, G is geophysical forces, I is internal dynamics. While A, G, and I have an influence of the Earth System, these tend to zero because the rate of change is an order of magnitude lower. As such, the rate of Earth System variability can be written as a function of industrialized societies (H). Credit: Owen Gaffney.

“This is a bold statement. But viewed this way, arguments about humans versus natural causes disappear. In 2016, Earth experienced a massive El Niño event affecting the global climate. But this is balanced by the cooler La Niña – taken together, the net rate of change of the Earth system resulting from these is zero over a decade or so,” Gaffney explained in a blog post for New Scientist.

“While the rate of change of the Earth system needs to drop to zero as soon as possible, the next few years may determine the trajectory for millennia. Yet the dominant neoliberal economic systems still assume Holocene-like boundary conditions – endless resources on an infinite planet. Instead, we need “biosphere positive” Anthropocene economics, where economic development stores carbon not releases it, enhances biodiversity not destroys it and purifies waters and soils not pollutes them,” he added.

This may not be the final word, but the order of magnitude seems right considering average CO2 levels crossed the 400ppm threshold — the highest it’s been in 66 million years; only 150 years ago it was 280ppm. It’s a useful thing to have, nevertheless, so people can have a sense of the kind of impact we’re having on the Earth climate system.

“It shows that while other forces operate over millions of years, we as humans are having an impact at the same strength as the many of these other forces, but in the timeframe of just a couple of centuries,” said Steffen.

The researchers note that human societies need to transition to a carbon-neutral future if we’re to avert a potential total collapse of human civilization. There is still time but it’s running out fast.