If you want to understand how our climate will change in the coming decades, you’ve got to understand feedback loops.
At its most basic, the science behind why our climate is changing is pretty straightforward. When we burn fossil fuels to produce electricity, heat, and more, they emit greenhouse gases (GHGs) like carbon dioxide (CO2) and methane. These gases trap the sun’s energy in Earth’s atmosphere as heat. As more and more GHGs are released, more heat gets trapped and the planet warms up, disrupting the long-standing, delicate climate systems that have made life on Earth possible.
The stronger storms and longer droughts we see becoming a dangerous new normal are a direct result. But how these impacts play off each other is far more nuanced. In many cases, the wildfires or disappearing glaciers we see in the headlines have unseen knock-on effects that lead to, well, more wildfires and disappearing glaciers.
Think of it like dominos lined up in an infinite spiral – once one domino falls, it creates a reaction that pushes over another and then another right on down the line.
Scientists call this process a “feedback loop” – and it’s got profound consequences for the planet.
What is a Feedback Loop?
Climate feedback loops are “processes that can either amplify or diminish the effects of climate forcings.” (“Forcings” here are the initial drivers of our climate – things like solar irradiance, GHG emissions, and airborne particles like dust, smoke, and soot that come from both human and natural sources and impact our climate.)
In plain English, feedback loops make the impacts of key climate factors stronger or weaker, starting a cyclical chain reaction that repeats again and again.
For our purposes, there are two major categories of climate feedback loops: positive and negative.
Negative feedback is a process that causes a decrease in function, often in an effort to stabilize the system.
A positive feedback loop, however, “accelerates a response.”
Using the water vapor cycle as an example, it goes a little something like this:
1. As more and more heat-trapping greenhouse gases are emitted, the atmosphere warms up.
2. This warmer air leads to more water evaporating from our oceans, rivers, lakes, and land, and entering the atmosphere.
3. Warmer air also holds more water vapor, and water vapor itself traps heat.
4. The extra water vapor in the already warmer air retains even more heat, amplifying the initial warming.
5. Even more warming leads to even more water evaporating, starting the cycle over again. And again. And again.
It’s a vicious cycle – climate change causing a cascade of effects that result in even more climate change. A problem we created taking on a life of its own… to potentially devastating effect.
Without the regulating action of the negative feedback loop, a positive loop can eventually spiral out of control, creating changes in the climate system we cannot ever undo. This is called a “tipping point.”
According to NOAA, “The accelerating effects of positive feedback loops can be at risk to irreversible tipping points, which are changes to the climate that are not steady and predictable. Basically, tipping points are small changes within the climate system that can change a fairly stable system to a very different state. Similar to a wine glass tipping over, wine is spilt from the glass as the tipping event occurs and standing up the glass will not put the wine back; the state of a full wine glass becomes a new state of an empty glass.”
All of which is to say, while we aren’t quite to a tipping point just yet, many facets of our climate system are already acting as part of dangerous positive feedback loops – creating compounding climate conditions and worsening impacts for people all over the world.
Feedback Loops and Climate
Two clear, powerful examples of a positive climate feedback loops are happening now in the Arctic. The first is happening on land, where permafrost that holds large amounts of both methane and carbon is thawing because of the climate crisis. The second on the ice and open ocean.
Methane is a very, very powerful greenhouse gas. In the atmosphere, compared to CO2, it’s fairly short-lived: only about 20 percent of the methane emitted today will still be in the atmosphere after 20 years. However, when it first enters the atmosphere, it’s around 120 times more powerful than CO2 at trapping heat and 86 times stronger over a 20-year period.
(CO2 hangs around for much longer: As much as 15 percent of today’s CO2 will still be in the atmosphere in 10,000 years.)
Arctic Methane and Carbon: The Time Bomb in the Soil
In the Arctic, methane and carbon can be found in permafrost, as well as in frozen peat bogs and under sediment on the sea floor. As these bogs and permafrost thaw thanks to climate change, the methane and carbon within are released into the atmosphere, adding yet more GHGs that can lead to further global warming. More warming results in more permafrost loss, adding yet more GHGs to the atmosphere to create even more warming and more melting permafrost, and on and on.
Given that frozen Arctic soil holds an estimated 1,460 to 1,600 billion tons of trapped carbon – almost twice the amount of GHGs currently in the atmosphere – scientists are deeply concerned about the unprecedented warming in the region and what it could mean for global efforts to halt rising temperatures.
Disappearing Ice, Warmer World
Another positive feedback loop in the Arctic with global implications: the reduction in sea ice coverage, particularly in the summertime.
Arctic Ocean ice cover is integral to regulating global land and sea temperatures. Sea ice creates a large white surface that reflects solar radiation away from Earth. This is known as “albedo,” and compared to other earth surfaces, sea ice is very good at it.
Unfortunately, sea-ice cover in the Arctic is shrinking. This past summer, Arctic sea ice extent was statistically tied with 2007 and 2016 for the second-lowest minimum on record. (2012 had the lowest ice extent ever recorded.)
“Since 1979, ice extent has shrunk by 40 percent,” NOAA reports, “and the loss is transforming Alaska’s climate, accelerating coastal erosion, reducing walrus and other marine mammal habitat, changing the timing and location of blooms of the food web’s microscopic plant life, and lowering survival rates for young walleye pollock—the nation’s largest commercial fishery.”
This lack of sea ice also contributes to further global warming and climate change, resulting in even more ice loss. (Remember the falling dominoes?)
This is because the absence of sea ice exposes the much, much darker ocean surface below. And open water absorbs the sun’s radiation rather than reflecting it back into space the way ice does.
Just how much solar radiation are we talking about here? The open ocean reflects just 6 percent of incoming solar radiation back to space, absorbing the rest and warming the water and the surrounding atmosphere. Sea ice, however, reflects 50-70 percent of incoming solar energy. Less absorbed heat energy means a cooler surface and a climate system working the way it’s meant to.
The disappearance of Arctic sea ice is quickly moving in the direction of an irreversible tipping point. Indeed, many researchers believe it’s a question less of if than when we will begin seeing sea ice-free summers in the Arctic.
“With current global emission rates of 35 to 40 billion metric tons of CO2 each year, we may get our first glimpses of ice-free Septembers in the next 20 to 25 years, when we will have added another 800 billion metric tons to the atmosphere,” Scientific American explains. “Yet it does not stop there. Other months of the year will become ice-free with additional atmospheric CO2. For example, with another 1,800 billion metric tons of CO2, the Arctic will likely have no ice from July through October.”
It’s worth noting that this assessment is taken from an article that begins by admitting that “observed ice loss is generally happening faster than climate models have forecasted.”
It’s Not Just the Arctic
Climate feedback loops reach around the planet. In the Amazon, we’ve already lost one-fifth of the rainforest to climate change and human-caused burning. Scientists warn that losing another fifth would trigger a phenomenon known as “dieback,” where the forest dries beyond human rescue, inviting more wildfires and releasing more carbon.
Elsewhere, hotter temperatures create the perfect conditions for wildfires that release GHGs and shrink the forests that absorb CO2 from the atmosphere, ultimately leading to even hotter temperatures and – you guessed it – even more wildfires.
The list goes on, but you get the picture. As one writer puts it, “the worse it gets – the worse it gets.”
Knowing what you now do about positive climate feedback loops, consider how much faster the climate crisis could accelerate if the Arctic Ocean become ice-free for some or all of the summer. Or as additional permafrost thaws, allowing more and more powerful methane to spill into our atmosphere.
Luckily, there’s still plenty we can do to limit the worst impacts of the climate crisis and support a safe, sustainable future.
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