Global warming does not stop suddenly. If people everywhere stopped burning fossil fuels tomorrow, the stored heat would continue to warm the atmosphere.
Imagine how a radiator heats a house. The water is heated by a boiler and the hot water circulates through the pipes and radiators of the house. Radiators warm and heat the air in the room. Even after the boiler is turned off, the already heated water still circulates through the system, heating the house. The radiators actually cool down, but their stored heat continues to warm the air in the room.
This is known as engaged warming. The Earth also has ways of storing and releasing heat.
Emerging research is refining scientists’ understanding of how the Earth’s committed warming will affect climate. While we once thought it would take 40 years or more for the planet’s surface air temperature to peak once humans stop heating the planet, research now suggests the temperature could peak in almost 10 years.
But that doesn’t mean the planet is returning to its pre-industrial climate or that we’re avoiding disruptive effects like rising sea levels.
I am a professor of climate science, and my research and teaching focus on the use of climate knowledge by practitioners such as urban planners, public health professionals and policy makers. With a new climate change mitigation report expected from the Intergovernmental Panel on Climate Change in early April, let’s take a look at the big picture.
How understanding of peak warming has changed
Today’s models can more explicitly represent the behavior of greenhouse gases, especially carbon dioxide. This allows scientists to better separate the heating due to carbon dioxide in the atmosphere from the role of heat stored in the ocean.
Thinking of our radiator analogy, increasing concentrations of greenhouse gases in the Earth’s atmosphere keep the boiler going – trapping energy near the surface and raising the temperature. Heat accumulates and is stored, mainly in the oceans, which act as radiators. Heat is distributed around the world by weather patterns and ocean currents.
the current understanding is that if all additional human-caused global warming were eliminated, a plausible outcome is that the Earth would reach a global peak in surface air temperature in less than 10 years than in 40. The previous estimate of 40 years or more has been widely used over the years, including by me.
It’s important to note that this is only the peak, when the temperature begins to stabilize – not the start of a rapid cooling or climate change reversal.
I believe there is enough uncertainty to warrant caution to exaggerate the importance of the results of the new research. The authors applied the concept of peak warming to the air temperature at the surface of the planet. Global surface air temperature is, metaphorically, the temperature in the “room”, and is not the best measure of climate change. The concept of cutting man-made heating instantly is also idealized and totally unrealistic – it would involve much more than just ending the use of fossil fuels, including widespread changes in agriculture – and it just does. help illustrate how certain parts of the climate might behave.
Even if the air temperature were to peak and stabilize, “ice melt committed“committed sea level rise” and many other terrestrial and biological trends would continue to evolve from the accumulated heat. Some of them could, in fact, cause a release of carbon dioxide and methaneespecially from the Arctic and other high latitude reservoirs that are currently frozen.
For these and other reasons, it is important to consider how far future studies like this go.
The oceans of the future
The oceans will continue to store heat and exchange it with the atmosphere. Even if emissions stopped, the excess heat that has been building up in the ocean since pre-industrial times would influence the climate for another 100 years or more.
Because the ocean is dynamic, it has currents, and it won’t just release its excess heat into the atmosphere. There will be ups and downs as the temperature adjusts.
The oceans also influence the amount of carbon dioxide in the atmosphere, as carbon dioxide is both absorbed and emitted by the oceans. Paleoclimatic studies show significant changes in carbon dioxide and temperature in the past, with the oceans playing an important role.
Countries are no closer to ending the use of fossil fuels
The potential for a policy intervention to have measurable effects on 10 years rather than several decades could motivate more aggressive efforts to remove carbon dioxide from the atmosphere. It would be very satisfying to see policy interventions having present rather than theoretical future benefits.[Over 150,000 readers rely on The Conversation’s newsletters to understand the world. Sign up today.]
However, today countries are not close to ending their use of fossil fuels. Instead, all evidence indicates that humanity is experiencing rapid global warming in the coming decades.
Our strongest finding is that the less carbon dioxide humans emit, the better off humanity will be. Committed warming and human behavior point to the need to accelerate efforts both to reduce greenhouse gas emissions and to adapt to this now warming planet, rather than just talking about whatever must happen in the future.