Greenhouse gases emitted present day linger in the air for decades or even hundreds of years. David McNew/Getty Images Julien Emile-Geay, USC Dornsife College of Letters, Arts and Sciences
Today, very few think that we are altering Earth’s climate. The real question is: How quickly can we slow down, or even reverse the destruction?
One of the answers to this question lies in the notion of ” committed warming,” often referred to as “pipeline warming.”
It’s about future growth in global temperatures that will originate from greenhouse gases which have already been released. If, for instance, the transition towards clean energy happened within a few days, how much warming will still occur?
Earth’s energy budget is out of equilibrium
Humans contribute to global warming because their activities emit greenhouse gases that hold heat within the atmospheric layer, which prevents it from reaching space.
Before the people started using fossil fuels for powering manufacturing and transport and to rear methane-emitting cattle in nearly every region of arable, the energy system of Earth was in balance. Around the same amount of energy came from the Sun that was being released.
Earth’s delicate energy balance. California Academy of Sciences.
Carbon dioxide emissions, as well as other greenhouse gases such as methane and neutralized by certain aspects of aerosol air pollution, capture energy equal to detonation five Hiroshima-style nuclear bombs per second.
As more energy is coming into than it is leaving, Earth’s thermo energy increases, raising temperatures of the land, oceans and air and melting ice.
Heating in the pipeline
The effects of changing Earth’s balance of energy are gradual to be noticed. Consider the consequences of turning the hot water tap fully on a cold winter day: The pipes are full of cold water. So it takes time for the warm water to get to your body – thus the phrase “pipeline warming.” The warming isn’t yet felt however, it’s already within the pipeline.
There are three major reasons why Earth’s temperature is likely to keep warming even once emissions are stopped.
One of the principal contributors for global warming are carbon dioxide and methane – are present in the atmosphere for a long time: roughly 10 years for methane and a whopping 400 years for carbon dioxide. Some molecules sticking around for as long as millennia. Also, turning off the emissions won’t result in instant cuts in the volume of these heat-trapping gases on the planet.
Second, part of this warming was offset by man-made emissions of another form of pollutant: sulfate aerosols, small particles released through fossil fuel burning that reflect light out into space. Since the beginning of the century, this worldwide dimming is masking the warming effect of greenhouse emissions. But these and other man-made aerosols have also harmed human health as well as life on the planet. Removal of greenhouse gases will result in a few tenths of the degree of further warming in roughly a decade, prior to getting to an equilibrium.
Finally, Earth’s climate takes time to adjust to changes to the energy balance. Around two-thirds of the Earth’s surface is composed up of water. Sometime, this is very deep, and is slow to absorb excess carbon and heat. To date, over 91% of the energy generated by humans as well as nearly a quarter the carbon that has accumulated, have gone into the oceans. Although land dwellers might be thankful for this buffer, extra heat contributes to the rise in sea level through heat expansion and also ocean heat waves as well as carbon makes the ocean more corrosive to many shelled organisms that can cause disruption to the chain of food that the oceans rely on.
The surface temperature of Earth, caused by the imbalance of radiation energy that is at the highest of the atmosphere, as well as modulated by the enormous thermal inertia in the oceans it is playing catch-up in relation to its most important controlling knob the concentration of carbon dioxide.
How much of warming?
So, how much committed warming will we be committing to? The answer isn’t clear.
The planet has already warmed more than 1.1 degree Celsius (2 F) compared to preindustrial temperatures. Nations worldwide agreed in 2015 to stop the global average from rising over 1.5degC (2.7 F) to limit the damage, but the world has been in a slow reaction.
Estimating how much warming is ahead is complicated. A number of recent research studies employ climate models to predict future warming. A study of 18 Earth model systems showed that, when emissions were cut off, there was a steady warming over the course of centuries or more while others started cooling fast. Another study published in June of 2022, revealed a 42% chance that the planet is determined to 1.5 degrees.
The degree of warming is important as the negative effects of global warming don’t simply grow in relation to the temperature of the world; they usually expand exponentially, especially in the case of food production susceptible to damage from severe droughts, extreme heat and even storms.
Further, Earth has tipping points that could trigger irreversible changes to fragile parts of the Earth ecosystem, including glaciers or ecosystems. There is no way to know whether the Earth is at a point of tipping due to the fact that these changes tend to take a long time to show in the first place. This and other climate-sensitive systems provide the principle of precaution that limits warming to 2 degrees Celsius (3.6 F), and more preferably, 1.5degC.
The heart of the climate problem, embedded in this concept of committed heating, is that there is a long intervals between the changes in human behavior and changes in the climate. The exact quantity of committed warming remains an issue of debate however, the most secure option is to quickly move to a carbon free, more equitable economy that releases lower greenhouse gas emissions.