Few individuals today deny that humans are causing climate change on the planet. The real question is how rapidly we can stop, if not reverse, the harm.
The idea of 'committed warming,' often known as 'pipeline warming,' provides part of the solution to this question.
It refers to future global temperature rises induced by already-emitted greenhouse gases. To put it another way, how much warming would still occur if the clean energy transition occurred over night?
Earth's energy budget is out of balance
Human activities generate greenhouse gases, which trap heat in the lower atmosphere and prevent it from escaping into space, causing global warming.
Earth's energy budget was fairly balanced before mankind began burning fossil fuels to power industries and automobiles and rearing methane-emitting livestock in practically every arable zone. The Sun was bringing in almost the same amount of energy that it was releasing.
Carbon dioxide concentrations in the atmosphere are now more than 50 percent greater than they were at the start of the industrial age, trapping even more energy.
These carbon dioxide emissions, when combined with other greenhouse gases like methane and mitigated by some components of aerosol air pollution, trap enough energy to detonate five Hiroshima-style atomic bombs per second.
Earth's thermal energy grows when more energy enters than leaves, boosting the temperature of land, oceans, and air and melting glaciers.
Warming in the pipeline
The consequences of altering Earth's energy balance take time to manifest. Consider what happens when you turn the hot water faucet all the way up on a chilly winter day: the pipes are full of cold water, so it takes a long time for the warm water to reach you - hence the name "pipeline warming."
There are three primary reasons why the Earth's climate is predicted to continue to warm even if emissions are reduced.
First, the main contributors to global warming, carbon dioxide and methane, stay in the atmosphere for a long time: methane stays in the atmosphere for about 10 years on average, and carbon dioxide stays in the atmosphere for 400 years on average, with some molecules staying in the atmosphere for millennia. As a result, turning off emissions does not immediately result in a decrease in the amount of heat-trapping gases in the atmosphere.
Second, man-made emissions of another type of pollution, sulfate aerosols, microscopic particles released by fossil fuel combustion that reflect sunlight out to space, have partially countered this warming.
This global dimming has been disguising the warming effect of greenhouse gasses for the past century. However, these and other man-made aerosols are hazardous to human health and the environment.
Removing those and other short-lived greenhouse gases will result in a few tenths of a degree of more heat over the next decade until a new equilibrium is reached.
Finally, any shift in energy balance requires time for the Earth's climate to respond. Water makes up around two-thirds of the Earth's surface, including some extremely deep water, which takes a long time to absorb extra carbon and heat.
Over 91 percent of the heat produced by human activities has gone into the oceans, as has approximately a quarter of the surplus carbon.
While land residents may appreciate the buffer, the increased heat adds to sea level rise through thermal expansion and marine heat waves, and the excess carbon makes the water more corrosive to many shelled species, potentially disrupting the ocean food chain.
Earth's surface temperature is still playing catch-up with its main control knob: carbon dioxide concentration, which is driven by an imbalance of radiant energy at the top of the atmosphere and controlled by the massive thermal inertia of its oceans.
How much warming?
So, how much global warming can we expect? There isn't a straightforward solution.
In comparison to pre-industrial levels, the earth has already warmed by more than 1.1 degrees Celsius. To limit the harm, nations agreed in 2015 to strive to keep the global average temperature from increasing over 1.5°C, but the globe has been reluctant to respond.
It's difficult to predict how much warming will occur in the future. Climate models have been used in several recent research to forecast future warming. When emissions were shut off, some models continued to warm for decades to hundreds of years, while others began to cool fast, according to a study of 18 Earth system models.
According to a research published in June 2022, there is a 42% possibility that the world has already committed to 1.5 degrees.
The quantity of warming matters because the dangers of global warming don't merely grow in proportion to world temperature; they usually increase exponentially, especially for food production, which is threatened by heat, drought, and storms.
Furthermore, there are tipping points on Earth that might cause permanent changes to sensitive components of the Earth system, such as glaciers and ecosystems. We won't always be able to tell when the earth has reached a tipping point since changes take time to manifest. The precautionary concept of keeping warming below 2°C, and preferably 1.5°C, is based on this and other climate-sensitive systems.
The essence of the climate dilemma, which is buried in this notion of committed warming, is that changes in human behavior take a long time to reflect in the climate.
While the exact amount of committed warming is still up for debate, data demonstrates that the safest path ahead is to quickly transition to a carbon-free, more egalitarian economy that emits substantially less greenhouse gases.
