How fast can we stop Earth from warming?

The ocean retains heat for much longer than land does. Aliraza Khatri’s Photography via Getty Images

by Richard B. (Ricky) Rood, University of Michigan

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. 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 exaggerating the significance of the new research’s results. The authors applied the concept of peak warming to global surface air temperature. Global surface air temperature is, metaphorically, the temperature in the “room,” and is not the best measure of climate change. The concept of instantly cutting off human-caused heating is also idealized and entirely unrealistic – doing that would involve much more than just ending fossil fuel use, including widespread changes to agriculture – and it only helps illustrate how parts of the climate might behave.

Even if the air temperature were to peak and stabilize, “committed ice melting,” “committed sea level rise” and numerous other land and biological trends would continue to evolve from the accumulated heat. Some of these could, in fact, cause a release of carbon dioxide and methane, especially from the Arctic and other high-latitude reservoirs that are currently frozen.

For these reasons and others, it is important to consider the how far into the future studies like this one look.

Oceans in the future

Oceans will continue to store heat and exchange it with the atmosphere. Even if emissions stopped, the excess heat that has been accumulating in the ocean since preindustrial times would influence the climate for another 100 years or more.

Because the ocean is dynamic, it has currents, and it will not simply diffuse its excess heat back 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, because carbon dioxide is both absorbed and emitted by the oceans. Paleoclimate studies show large changes in carbon dioxide and temperature in the past, with the oceans playing an important role.

Chart showing ocean heating increasing fastest and going to greater depths over time.
The chart shows how excess heat – thermal energy – has built up in ocean, land, ice and atmosphere since 1960 and moved to greater ocean depths with time. TOA CERES refers to the top of the atmosphere. Karina von Schuckman, LiJing Cheng, Matthew D. Palmer, James Hansen, Caterina Tassone, et al., CC BY-SA

Countries aren’t close to ending fossil fuel use

The possibility that a policy intervention might have measurable impacts in 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 notional future benefits.

However, today, countries aren’t anywhere close to ending their fossil fuel use. Instead, all of the evidence points to humanity experiencing rapid global warming in the coming decades.

Our most robust finding is that the less carbon dioxide humans release, the better off humanity will be. Committed warming and human behavior point to a need to accelerate efforts both to reduce greenhouse gas emissions and to adapt to this warming planet now, rather than simply talking about how much needs to happen in the future.

Richard B. (Ricky) Rood, Professor of Climate and Space Sciences and Engineering, University of Michigan

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

Environmental protection: Net zero efforts add up

Read the full story in Chemical Processing.

The experiences of Solvay, BASF and Chemours illustrate how chemical companies are refining their strategies to reduce carbon dioxide (CO2) emissions and, ultimately, become carbon neutral, i.e., have net zero emissions. All aspects of production, from energy generation to global supply chains, are under the spotlight.

Purdue’s energy infrastructure contributes to climate change

Read the full story in the Purdue Exponent.

For Purdue to mitigate its contribution to climate change, some students say the university must find a carbon neutral way to power its campus.

A group of engineering students spent the last year developing a climate action plan for Purdue. The plan, which was released on Sunday, offers ideas for how Purdue can transition to be carbon neutral over the next decade while showing it is financially viable.

H&M announces winners of Global Change Award

Meet the winners of H&M’s Global Change Awards and find out how their innovations are reinventing the fashion industry.

A year in review of industry and government action on PFAS

Read the full story at Waste360.

The past year has been busy in the space of action around polyfluoroalkyl substances (PFAS)—from the proposal or adoption of federal and state policies, down to individual companies’ moves away from reliance on these toxic chemicals. Here’s a review of what’s been happening this 12 months or so around PFAS in both the private and public sectors.

What your T-shirt reveals about ‘carbon colonialism’ and the global economy’s vast hidden emissions


by Laurie Parsons, Royal Holloway University of London

Where does your T-shirt come from? It’s a question that apparently can be answered with an awkward neck twist and a glance at the label. But the real answer is way more complex.

Even producing a single T-shirt relies on coordinating an array of interconnected supply chains, usually spanning multiple nations. This globalised system is a marvel of human ingenuity and logistics.

But it also can obscure the true carbon emissions of the products we use, raising serious questions about their sustainability. And it enables wealthier countries to effectively outsource their emissions to less wealthy ones via “carbon colonialism”.

Let’s say your T-shirt’s label reads: “Cambodia”. It’s fair to assume that this clearly indicates its origin. But that’s not the whole story.

Cambodia exports 40,000 tonnes of garments to the UK annually (4% of British clothing), and most depart from the port of Sihanoukville. At 18,244km from the UK’s main shipping port, Felixstowe, that’s a huge distance for your T-shirt to travel. But as colleagues and I revealed in our recent research, this is only the final leg of an even longer journey.

The Chinese connection

Unlike other garment exporters, such as Bangladesh or Vietnam, Cambodia doesn’t grow cotton. Nor does it spin cotton, or manufacture artificial fibres. Instead, Cambodian factories import textiles from abroad, often only providing the finishing touches to partly completed garments. So, although your garment may say it’s from “Cambodia”, the textiles probably came from further afield – much further.

Map of Cambodia
Sihanoukville is Cambodia’s major shipping hub. Shutterstock

Between 2015 and 2019, 89,721 tonnes out of the total 161,455 tonnes of garments that the UK imported from Cambodia can be indirectly linked to cotton products, knitted fabrics and artificial fibres supplied to Cambodia by China. And most of China’s garment industry is located in the coastal provinces of Jiangsu, Zhejiang, Guangdong and Hubei – roughly 2,500km to 6,000km from Cambodia.

But the process stretches further still. 84% of China’s domestic cotton production occurs in the far western province of Xinjiang. This means the raw cotton processed in China’s coastal factories must first travel between 3,000km and 4,300km by rail from Xinjiang: roughly the distance between London and Lagos.

So even before your T-shirt labelled “Cambodia” arrives in Cambodia, the raw materials have travelled between 5,500 and 10,300km, by sea and rail. This adds a huge hidden carbon cost to the final garment.

And yet there is even more to the story. China is the largest cotton grower globally, producing over 25% of the world’s total crop. But it is also the world’s premier apparel manufacturer, and demand considerably outstrips supply. China produced 6.07 million tonnes of raw cotton in 2018-19, but consumed 8.95 million tonnes, leaving a massive shortfall.

China compensates for this shortfall with imports. Most – 88% of the total – come from Australia, US, Uzbekistan, India and Brazil. The distances travelled by these imports vary – from about 1,350km (between Tashkent, Uzbekistan and Xinjiang, China) to a maximum of 35,700km (between Los Angeles, US and Shanghai, China, if via Panama and Suez).

So the Cambodia label on that T-shirt marks just one stop along a vast global journey. Indeed, before you bought it in the UK, the T-shirt – and the raw materials behind it – probably travelled between 25,000km and a whopping 64,000km (over-one-and-a-half times the Earth’s circumference).

A long way round

A supply chain of this length is alarming. But the broader implications are starker still.

A typical T-shirt is expected to produce 6.75kg of carbon during its production and sale. A product’s carbon footprint is often estimated by adding up the carbon generated during the entire production process. This includes, for example, the growth of the cotton, its processing into textiles, its manufacture into clothing, transport, retail, usage, and disposal.

And when a country imports a product, all of these emissions are added to its imported, or embodied, carbon footprint. Since the processes involved are so complex and varied, however, we tend to use average figures for a given part of the production process, rather than empirically measuring the entire supply chain.

But this system fails to take into account the vast “hidden” distances our example T-shirt – and the raw materials behind it – travelled. At 25,000km, where the cotton comes exclusively from western China, the transportation of that single Cambodia branded T-shirt would likely emit 47g of C02. This is 7.1% of the carbon emitted during its entire production and 50% more than the estimates used by sustainability advocacy groups such as the Carbon Trust.

At 64,000km, where the cotton originates from the US or Brazil, the T-shirt will generate 103g of CO₂ on its journey around the world. That’s over 15% of the total emissions generated during its production and more than triple the average value on which carbon footprints are calculated.

Shipping containers at sea
On its way… Shutterstock

These errors may not seem like much on a single T-shirt. But they make a huge difference when scaled up to cover the entire UK-Cambodia apparel trade. Those 40,000 tonnes of clothing imported to the UK from Cambodia each year would be generally estimated to produce 8,304 tonnes of CO₂. Yet the true figure, taking into account the hidden distances travelled by the raw materials, is between 13,400 tonnes and 28,770 tonnes. That’s up to 20,466 tonnes unaccounted for: the equivalent of 4,422 cars being driven for a year.

Now imagine these numbers scaled up to truly reflect every product sold globally.

Invisible systems

Figures like these illuminate the otherwise invisible systems underlying our everyday lives, casting doubt on many of the assumptions we make about sustainability. Indeed, the lack of transparency surrounding global supply chains means that many sources of emissions are either hidden or significantly underestimated. And their extraordinary complexity impedes detailed analysis and undermines accountability, concealing many carbon emissions from public view.

This ability to “hide” emissions in complex global production processes has been called a “carbon loophole” or even “carbon colonialism” as it allows major importing economies to move carbon intensive production processes out of their headline domestic emissions statistics and onto those of other countries, often with less capacity to measure the full extent of these impacts.

And there is now growing recognition that these problems may lie at the root of our more general failure to cut carbon emissions. In total, imported emissions now account for a quarter of global CO₂ emissions – and addressing this should be seen as the next “frontier of climate policy”.

The single country origin label sewn into your T-shirt is an illusion, reflecting a problem that affects so many of the items we purchase and use daily. In fact, that country of origin is just one stop on a global journey of assembly that is anathema to truly sustainable production and a key obstacle in our fight against the climate crisis.

A better understanding of this hidden geography is the first step towards tackling the opaque and misunderstood carbon footprints of our global economy – and decolonising systems of environmental accounting that favour the world’s biggest polluters.

This article was updated to amend details of the distance travelled between Los Angeles and Shanghai.

Laurie Parsons, Lecturer in Human Geography, Royal Holloway University of London

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

Unnatural barriers: How the boom in fences is harming wildlife

Read the full story from e360.

From the U.S. West to Mongolia, fences are going up rapidly as border barriers and livestock farming increase. Now, a growing number of studies are showing the impact of these fences, from impeding wildlife migrations to increasing the genetic isolation of threatened species.

How the current siting regime stifles renewable energy

Read the full story from The Regulatory Review.

As the United States enters a “critical decade” in the fight against climate change, the need for rapid renewable energy deployment requires reassessing existing laws governing electricity generation and transmission projects, argues Uma Outka in a recent article. Siting laws and regulations govern where energy infrastructure can be located. Outka, a professor at the University of Kansas School of Law, contends that siting failures, such as the Maine transmission line, show the need for reforms that “anticipate the challenges” in siting renewable energy projects.

Coal mining emits more super-polluting methane than venting and flaring from gas and oil wells, a new study finds

Read the full story at Inside Climate News.

So much methane is released from coal mining, the Global Energy Monitor says, that it exceeds the carbon dioxide emissions from burning coal at over 1,100 coal-fired power plants in China.

How is Müller managing its food-grade packaging waste?

Read the full story at Sustainability Magazine.

In collaboration with its latest partner, Waitrose, Müller is making packaging changes to manage waste and create more sustainable food-grade packaging