Global Warming After Emissions End

Climate scientist Julien Emile-Geay discusses the implications of “committed warming.”

Greenhouse gases emitted today will warm the planet for years. (David McNew/Getty Images)

By Julien Emile-Geay 
USC Dornsife College of Letters, Arts and Sciences

By now, few people question the reality that humans are altering Earth’s climate. The real question is: How quickly can we halt, even reverse, the damage?

Part of the answer to this question lies in the concept of “committed warming,” also known as “pipeline warming.”

It refers to future increases in global temperatures that will be caused by greenhouse gases that have already been emitted. In other words, if the clean energy transition happened overnight, how much warming would still ensue?

Earth’s Energy Budget Out of Balance

Humans cause global warming when their activities emit greenhouse gases, which trap heat in the lower atmosphere, preventing it from escaping out to space.

Before people began burning fossil fuels to power factories and vehicles and raising methane-emitting cattle in nearly every arable region, Earth’s energy budget was roughly in balance. About the same amount of energy was coming in from the Sun as was leaving.

Today, rising carbon dioxide concentrations in the atmosphere are more than 50 percent higher than they were at the dawn of the industrial age, and they’re trapping more of that energy.

Earth’s delicate energy balance. (California Academy of Sciences)

Those carbon dioxide emissions, together with other greenhouse gases such as methane, and offset by some aspects of aerosol air pollution, are trapping energy equivalent to the detonation of five Hiroshima-style atomic bombs per second.

With more energy coming in than leaving, Earth’s thermal energy increases, raising the temperature of land, oceans and air and melting ice.

Warming in the Pipeline

The effects of tampering with Earth’s energy balance take time to show up. Think of what happens when you turn the hot water faucet all the way up on a cold winter day: The pipes are full of cold water, so it takes time for the warm water to get to you – hence the term “pipeline warming.” The warming hasn’t been felt yet, but it is in the pipeline.

There are three major reasons Earth’s climate is expected to continue warming after emissions stop.

First, the leading contributors to global warming – carbon dioxide and methane – linger in the atmosphere for a long time: about 10 years on average for methane, and a whopping 400 years for carbon dioxide, with some molecules sticking around for up to millennia. So, turning off emissions doesn’t translate into instant reductions in the amount of these heat-trapping gases in the atmosphere.

Second, part of this warming has been offset by man-made emissions of another form of pollution: sulfate aerosols, tiny particles emitted by fossil fuel burning, that reflect sunlight out to space. Over the past century, this global dimming has been masking the warming effect of greenhouse emissions. But these and other man-made aerosols also harm human health and the biosphere. Removing those and short-lived greenhouse gases translates to a few tenths of a degree of additional warming over about a decade, before reaching a new equilibrium.

Finally, Earth’s climate takes time to adjust to any change in energy balance. About two-thirds of Earth’s surface is made of water, sometimes very deep water, which is slow to take up the excess carbon and heat. So far, over 91% of the heat added by human activities, and about a quarter of the excess carbon, have gone into the oceans. While land-dwellers may be grateful for this buffer, the extra heat contributes to sea level rise through thermal expansion and also marine heat waves, while the extra carbon makes the ocean more corrosive to many shelled organisms, which can disrupt the ocean food chain.

Earth’s surface temperature, driven by the imbalance of radiant energy at the top of the atmosphere, and modulated by the enormous thermal inertia of its oceans, is still playing catch up with its biggest control knob: carbon dioxide concentration.

How Much Warming?

So, how much committed warming are we in for? There isn’t a clear answer.

The world has already warmed more than 1.1 degrees Celsius (2 F) compared to pre-industrial levels. Nations worldwide agreed in 2015 to try to prevent the global average from rising more than 1.5°C (2.7 F) to limit the damage, but the world has been slow to react.

Determining the amount of warming ahead is complicated. Several recent studies use climate models to estimate future warming. A study of 18 Earth system models found that when emissions were cut off, some continued warming for decades to hundreds of years, while others began cooling quickly. Another study, published in June 2022, found a 42 percent chance that the world is already committed to 1.5 degrees.

The amount of warming matters because the dangerous consequences of global warming don’t simply rise in proportion to global temperature; they typically increase exponentially, particularly for food production at risk from heat, drought and storms.

Further, Earth has tipping points that could trigger irreversible changes to fragile parts of the Earth system, like glaciers or ecosystems. We won’t necessarily know right away when the planet has passed a tipping point, because those changes are often slow to show up. This and other climate-sensitive systems are the basis for the precautionary principle of limiting warming under 2°C (3.6 F), and preferably, 1.5°C.

The heart of the climate problem, embedded in this idea of committed warming, is that there are long delays between changes in human behavior and changes in the climate. While the precise amount of committed warming is still a matter of some contention, evidence shows the safest route forward is to urgently transition to a carbon-free, more equitable economy that generates far less greenhouse gas emissions.The Conversation

Julien Emile-Geay is associate professor of Earth sciences, USC Dornsife College of Letters, Arts and Sciences.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The views expressed are solely those of the author and may or may not reflect those of Consortium News.

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8 comments for “Global Warming After Emissions End

  1. mgr
    June 11, 2022 at 10:04

    More clarity on why the ONLY plan to mitigate global warming and the ensuing climate catastrophe is to keep fossil fuels in the ground, as much and as quickly as possible. Anything less is a deflection or bait&switch. Check out a movie like Soylent Green from the 1970s. Even then they were speaking about global warming, although, usually mocking it. Now, we are here. This is the all-hands-on-deck moment and yet the fossil fuel companies, in collusion with governments, in particular, the US government, have been working feverishly as a fifth column movement since the ’70s to keep the oil flowing until the last drop. And now the Biden admin has arrived to put the last nails in our coffin. A death wish perhaps? I guess their goal in life is to die rich, while taking everyone else with them. Treat them as criminals along with the governments that support them. Or, watch the future and the future of our children slip away, with a mere whimper and a sigh.

  2. Vesa
    June 11, 2022 at 03:00

    The empire managers dont worry. They can always launch sanctions and launch missiles. It works always.

  3. Jethro Clampett
    June 11, 2022 at 01:28

    “Emissions” are the acceleration of the equations.

    Emissions are essentially the rate of change of the concentration of Greenhouse gasses in the atmosphere. Then it is that concentration that traps heat and creates warming. And that’s the simple version ignoring timings and time lags, which exist in any real world system.

    Cutting emissions down to what the world does lose in a year, is like if you are driving a car and you are taking your foot off of the accelerator and no longer accelerating. It does not immediately stop the vehicle. All you did is to stop accelerating.

    However, if you are doing this so late that you are already close to going over to cliff, about all you do is change by a small amount your eventual impact speed when you arrive at the bottom.

  4. bobLich
    June 10, 2022 at 19:45

    Whenever the term “Global Warming” is used instead of “Climate Change”, I have more faith in what an author says. Saying “Climate Change” seems to create a user-friendly facade that that hides reality . Thank you Julien Emile-Geay.

  5. irina
    June 10, 2022 at 13:58

    Al Gore discussed this easily understood concept (he called it ‘climate change lag time’) in his 1991 book
    “Earth in the Balance”. Then, inexplicably, it fell off the radar of climate reporting for public consumption.

    In his book, Gore estimated a 30 year lag time between when greenhouse gases went into the atmosphere,
    and when their effects would begin to manifest. As warming accelerates, that lag time shrinks. But what it
    means is that today we are seeing the effects of GHG’s that were entering the atmosphere around the turn
    of the 21st century. Everything since then is still in the ‘pipeline’. An unsettling thought !

  6. Rudy Haugeneder
    June 10, 2022 at 10:45

    No matter what actions our human species decides to take, it is a simple matter of much too little, much too late. It is a good time to be a senior in a prosperous Western-type nation. Unfortunately, for the rest of you, it is too late.

    • June 10, 2022 at 17:12

      I notice there are no other comments. Perhaps yours, Rudy, made them speechless. You know, of the many who have predicted the end of the world, somebody sooner or later might be right. The doomsayers were often religious,n ow they are environmentalists.

    • June 11, 2022 at 18:44

      The doomsayers are wrong, even if their predictions are correct. What is needed instead is a good faith effort to lower pollution but also mitigate against the effects of warming. Needed are more construction decisions that help reduce damage. Florida, I think, did that sometime ago to require hurricane resistant construction. Manage of our forests with more effective management, sea walls and levees where they are needed and any other measure to mitigate weather damage.

      Al Gore is an environment guru, but have you checked his predictions or the predictions of even earlier predictors as to when New York becomes Venice. Doesn’t mean he is wrong nor does it prove he is right.

      Emmet is probably correct. Most scientists agree that there is warming, and now we are told the damage has already begun. There is a crying need to clean up the environment, Fatalism, we don’t need.

      Gurus should always be suspect, no matter how many there are. Remember the oil gurus armed with charts predicting the imminent end of oil resources, Carter wearing a sweater in the White House? WMDs. Tonkin incident. On and on.

      There are doubters out there but their voices are seldom heard. Wokism has always been with us on global warming. Like anywhere else, there is no place for it.

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