Global warming doesn’t stop on a dime. If people everywhere stopped burning fossil fuels tomorrow, stored heat would still continue to warm the atmosphere.
Picture how a radiator heats a home. Water is heated by a boiler, and the hot water circulates through pipes and radiators in the house. The radiators warm up and heat the air in the room. Even after the boiler is turned off, the already heated water is still circulating through the system, heating the house. The radiators are, in fact, cooling down, but their stored heat is still warming the air in the room.
This is known as committed warming. Earth similarly has ways of storing and releasing heat.
Emerging research is refining scientists’ understanding of how Earth’s committed warming will affect the climate. Where we once thought it would take 40 years or longer for global surface air temperature to peak once humans stopped heating up the planet, research now suggests temperature could peak in closer to 10 years.
But that doesn’t mean the planet returns to its preindustrial climate or that we avoid disruptive effects such as sea level rise.
I am a professor of climate science, and my research and teaching focus on the usability of climate knowledge by practitioners such as urban planners, public health professionals and policymakers. With a new report on mitigating climate change expected from the Intergovernmental Panel on Climate Change in early April, let’s take a look at the bigger picture.
How understanding of peak warming has changed
Historically, the first climate models represented only the atmosphere and were greatly simplified. Over the years, scientists added oceans, land, ice sheets, chemistry and biology.
Today’s models can more explicitly represent the behavior of greenhouse gases, especially carbon dioxide. That allows scientists to better separate heating due to carbon dioxide in the atmosphere from the role of heat stored in the ocean.
Why global warming is ocean warming.
Thinking about our radiator analogy, increasing concentrations of greenhouse gases in Earth’s atmosphere keep the boiler on – holding energy near the surface and raising the temperature. Heat accumulates and is stored, mostly in the oceans, which take on the role of the radiators. The heat is distributed around the world through weather and oceanic currents.
The current understanding is that if all of the additional heating to the planet caused by humans was eliminated, a plausible outcome is that Earth would reach a global surface air temperature peak in closer to 10 years than 40. The previous estimate of 40 or more years has been widely used over the years, including by me.
It is important to note that this is only the peak, when the temperature starts to stabilize – not the onset of rapid cooling or a reversal of climate change.
I believe there is enough uncertainty to justify caution about…