26/12/2020

IEA: A Rebound In Global Coal Demand In 2021 Is Set To Be Short-Lived, But No Immediate Decline In Sight

International Energy Agency

After a major drop in recent years, global coal demand is forecast to rise by 2.6% in 2021 before flattening out to 2025

Summary
 A global economic recovery in 2021 is expected to drive a short-lived rebound in coal demand following the major drop this year triggered by the Covid-19 crisis, according to a new report from the International Energy Agency.

However, there is little sign that the world’s coal consumption is set to decline substantially in the coming years, with rising demand in some Asian economies offsetting declines elsewhere.

As coal is by far the single largest source of global energy-related carbon emissions, the trends outlined in the report pose a major challenge to efforts to put those emissions on a path compatible with reaching climate and sustainable energy goals.

The past two years have seen historic falls in global coal demand, led by unprecedented drops in the United States and Europe, says Coal 2020, the latest edition of the IEA’s annual market report on the sector.

A 1.8% decline in coal demand in 2019 resulted mainly from weak growth in electricity demand and low natural gas prices. Latest estimates from the IEA suggest coal demand will have plunged by a further 5% in 2020 on the economic fallout from Covid-19.

“The Covid-19 crisis has completely reshaped global coal markets. Before the pandemic, we expected a small rebound in coal demand in 2020, but we have since witnessed the largest drop in coal consumption since the Second World War,” said Keisuke Sadamori, the IEA’s Director of Energy Markets and Security.

“The decline would have been even steeper without the strong economic rebound in China – the world’s largest coal consumer – in the second half of the year.”

Based on the assumption of a recovery in the world economy, the IEA report forecasts a 2.6% rise in global coal demand in 2021, driven by higher electricity demand and industrial output.

China, India and Southeast Asian economies account for most of the growth, although the United States and Europe may also both see their first increases in coal consumption in nearly a decade.

However, global coal demand in 2021 is still forecast to remain below 2019 levels and could be even lower if the report’s assumptions for the economic recovery, electricity demand or natural gas prices are not met.

The rebound in coal demand in 2021 is set to be short-lived, with coal use forecast to flatten out by 2025 at around 7.4 billion tonnes. This would make 2013, when global coal demand reached 8 billion tonnes, coal’s all-time peak.

But while coal’s share in both the electricity mix and the overall energy mix are in steady decline, coal use in absolute terms is not set for a rapid decline in the immediate future.

“Renewables are on track to surpass coal as the largest source of electricity in the world by 2025. And by that time, natural gas will likely have taken over coal as the second largest source of primary energy after oil,” said Mr Sadamori.

“But with coal demand still expected to remain steady or to grow in key Asian economies, there is no sign that coal is going to fade away quickly.”

The future of coal will largely be decided in Asia. Today, China and India account for 65% of global coal demand. With Japan, Korea, Taiwan and Southeast Asia included, that share rises to 75%.

China, which currently accounts for half of the world’s coal consumption, will be especially influential.

By 2025, the European Union and United States will account for less than 10% of global coal demand, down from 37% in 2000.

This will make the impacts of any further changes in demand in these markets very limited.
An electricity-driven decline in coal demand in 2019

 In 2019, global coal demand decreased 1.8% after two years of growth. Power generation from coal declined 3%, and coal use in industry increased only slightly.

Two trends affected coal-fired power generation in 2019: weak electricity demand growth and low natural gas prices.

Global electricity generation grew 1% in 2019, the lowest rate since 2009 and almost one-third of the average annual increase since then.

Electricity generated from renewables increased in 2019, squeezing coal and gas generation.

Expanding LNG supply put pressure on natural gas prices, which fell by two‑thirds in Europe from January to September 2019. 

In the United States, where natual gas is generally cheap, prices in 2019 were 30% lower on average than the previous year. This spurred significant coal-to-gas switching in the power sector. 

In the European Union, coal-fired power generation saw its largest drop ever, both in relative and absolute terms. 

In the United States, it experienced its largest drop in percentage terms and second-largest in absolute terms. 

In India, 2019 marked the first year in four decades in which coal-fired power generation declined, reflecting the country’s economic slowdown, above average hydropower output, and expanding wind and solar PV capacity. 

Only China and Southeast Asia saw significant growth in coal-fired power generation in 2019, but not enough to offset declines elsewhere. 

In China, growth in coal-fired power generation, increased steel production and shrinking coal use in small industrial and residential boilers resulted in an overall increase in coal consumption of 1%. 

Across members of the Association of Southeast Asian Nations (ASEAN), coal use rose 14% in 2019, mainly reflecting demand growth in Viet Nam and, to a lesser extent, in Indonesia.

A pandemic-driven drop in coal demand in 2020

In 2020, global coal demand will experience its largest drop since the Second World War, falling 5% from 2019 levels. Coal’s decline is only slightly sharper in power generation than in industrial applications. 

 Except for China, industrial output has been severely subdued by the Covid-19 crisis. In China, switching away from small coal boilers for air quality reasons continues. Both of these factors weighed on non-power coal demand in 2020.

Measures to slow the transmission of Covid-19, notably in the first half of 2020, resulted in an unusual drop in electricity demand. This in turn significantly affected the use of coal for power generation – a trend that was compounded by low natural gas prices.

The overall decline in global coal demand in 2020 has turned out to be lower than was estimated in the early months of the year as the pandemic spread and intensified around the world. 

This can be attributed to a smaller decrease in global electricity demand than was predicted earlier in the year and to the robust economic recovery in China, where more than half of global coal is consumed. 

Coal’s partial recovery is set to fade after 2021

Global coal consumption is estimated to have fallen by 7%, or over 500 million tonnes, between 2018 in 2020. A decline of this size over a two-year period is unprecedented in IEA records, which go back as far as 1971. 

Based on the assumption of a global economic recovery in 2021, we expect both electricity demand and industrial output to increase. As a result, we forecast a rebound in global coal demand of 2.6%, led by China, India and Southeast Asia. 

Higher natural gas prices and electricity demand are set to slow the structural decline of coal use in the European Union and the United States, which both might see their coal consumption grow for the first time in nearly a decade.

By 2025, global coal demand is forecast to flatten out at around 7.4 billion tonnes. Trends are expected to vary by region over the next five years. 

In Europe and North America, coal continues its decline after a temporary uptick in 2021. Given that the combined coal consumption of the European Union and the United States now represents around 10% of global coal use, further declines in those markets will have a limited effect at a global level. 

In China, coal demand is reaching a plateau, although our 2025 forecast will need to be reviewed following the release of the Chinese government’s 14th Five-Year Plan. 

China’s pledge of reaching carbon neutrality before 2060 requires a long-term roadmap to enable the smooth transition of an economy which consumes 4 billion tonnes of coal each year. India and some other countries in South and Southeast Asia are forecast to increase coal use through 2025 as industrial production expands and new coal-fired capacity is built. 

In India, however, the demand outlook to 2025 is considerably lower than it was a year ago as a result of the pandemic. By 2025, ASEAN will become the third-largest coal-consuming region, surpassing the United States and the European Union. 

In 2020, some countries made pledges that involve reducing coal use in the coming years (Korea, Japan), downsizing planned coal expansion (Viet Nam, Bangladesh, Philippines), and cancelling plans for coal development (Egypt). 

Strategies vary for managing future coal supply

China and India – the two most coal-reliant major countries – are taking steps to ensure adequate coal supply to fuel their economies and rein in imports. In China, the government is continuing efforts to increase the competitiveness and profitability of the coal sector. In 2020, the Coal Trading Centre opened in Beijing and two big new corporations were formed, Jinneng Holding Group (in Shanxi) and Shandong Energy Group. 

These companies, together with China Energy Investment Corporation, will produce more than 1 billion tonnes of coal each year. In India, the government intends to transform its coal sector by increasing efficiency and competitiveness, and, notably, by introducing commercial mining. 

In November 2020, 50 million tonnes of annual coal mining capacity was allocated via an auction process.This initial offering is still small in volume relative to the production level of Coal India (600 million tonnes a year) and India’s total domestic production (about 800 million tonnes a year).

In the United States, despite the easing in competitive pressures as a result of higher natural gas prices and the expected pickup in coal demand in 2021, coal’s prospects do not improve in the medium term. 

Some of the big US mining companies are now increasingly shifting away from thermal coal, which is mostly used for power generation, and focusing on metallurgical coal, which is mainly used in iron and steel production. 

The few coal‑producing countries that remain in Europe are largely preparing for orderly closures to minimise the social impacts on communities that rely heavily on the industry.

Lower import volumes affect some major exporters more than others

The international coal trade was seriously disrupted in 2020 by the Covid-19 crisis. Exports contracted by around 11%, with more than two-thirds of the decline coming from thermal coal. New import quotas in China compounded the uncertainty in the coal trade. Imports in India and Europe experienced the largest drops, but they also declined in Japan, Korea and elsewhere. Very few big markets increased their imports in 2020.

A combined reduction of over 25 million tonnes of thermal coal exports from the United States and Colombia balanced the Atlantic Basin market. It took more time to balance the Asia Pacific market, which came at the expense of Indonesian and Australian producers.

After the adjustments on the supply side, which have also included some cuts in coal exports from the Russian Federation and South Africa, thermal coal prices at the end of 2020 are just about where they were a year ago.

In the near-term outlook, another factor driving uncertainty is lower imports of Australian coal by China. 

While we expect a recovery in the international coal trade in 2021, supported by increased global demand, the medium-term outlook is highly uncertain. 

This is particularly the case with regard to the evolution of Chinese import policies and developments in India’s indigenous thermal coal production. 

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Sea-Level Rise From Climate Change Could Exceed The High-End Projections, Scientists Warn

CBS News - Jeff Berardelli

Of the many threats from climate change, sea-level rise will most certainly be among the most impactful, making hundreds of thousands of square miles of coastline uninhabitable and potentially displacing over 100 million people worldwide by the end of the century.

This threat is a top concern for national security experts because forced migration poses significant risks to international security and stability. 

The magnitude of this threat depends heavily on how much the oceans rise in the coming decades. But because of the complex dynamics of massive ice sheets in Greenland and Antarctica, exact estimates remain elusive, ranging from just over a foot to several feet above current levels.

That disparity is the difference between tens of millions of people forced from their homes or a much more unmanageable hundreds of millions displaced.

Now, a new paper published in the past week warns that if global warming continues at the current pace — reaching high-end warming projections for 2100 — then sea-level rise will probably surpass those projections.

Since the late 1800s, sea level has risen an average of about 10 inches globally, but the amount varies from region to region. Last century the largest contributor to the rise of the oceans was thermal expansion; simply put, warmer water expands. But now the melting of ice sheets, mainly from Greenland and Antarctica, constitutes a greater proportion, and that fraction will only grow. 

In fact, there is enough ice locked up in Greenland and Antarctica such that if all the ice melted it would cause a sea-level rise of 210 feet, a little taller than the Leaning Tower of Pisa. No scientist is expecting anything even close to that this century, but after the Earth surpasses a certain level of warming, ice sheets become less stable and less predictable, with potential tipping points coming into play. 

In the most recent report from the U.N.'s Intergovernmental Panel on Climate Change (IPCC AR5), the median sea-level rise projections by the end of the century range from 16 inches for a low-end warming scenario to 2 feet for a high-end scenario (compared to the average sea level from 1986-2005). The estimates also come with a large degree of uncertainty, which pushes the top bound of likely sea-level rise above 2 and a half feet.

The new paper, titled "Twenty-first century sea-level rise could exceed IPCC projections for strong-warming futures," takes issue with that upper estimate, saying it is likely too low. The paper was published by a who's who of the most well known glaciologists and sea-level rise experts, including Martin Siegert, Richard Alley, Eric Rignot, John Englander and Robert Corell.

Greenland’s melting ice sheet is contributing to a rise in sea levels that could threaten millions in low-lying areas.

John Englander is a co-author of the paper and author of the books "High Tide on Main Street" and the soon-to-be-released "Moving to Higher Ground: Rising Sea Level and the Path Forward." He says this paper is a reaction to a "chorus of concern in the scientific community that the projections for rising sea level were understated." 

He said the research team hopes their work can inform the next major IPCC report, since that's the most widely cited document on climate change. "With the next report now being prepared for release in 2021-22, our intent was to make the case to the IPCC leadership to explain the reality of Antarctic potential melting better, as it might significantly add to sea level rise this century."

In a Zoom conversation with CBS News, Englander illustrated that sea-level rise contribution from Antarctica, by far Earth's largest ice sheet, does not increase from a low-end warming scenario to a high-end warming scenario in the IPCC's latest report — but in the real world it should. While the possibility of significantly higher sea-level rise due to Antarctica is mentioned in a footnote, it is by no means front and center.  

The reason for this, Englander explains, is because IPCC is very cautious with the data it uses in the report and only includes "numbers that meet their criteria for scientific accuracy with an acceptable degree of confidence." The level of uncertainty in the scientific community stems from the fact that glaciers can be unstable and the computer models used to project melting are still not sophisticated enough. 

In the paper, they write: "Existing ice-sheet models are more likely to provide reliable projections if global warming is kept below 2º Celsius [3.6º Fahrenheit], but a world in which warming exceeds 4º Celsius [7.2º Fahrenheit] presents a much more challenging situation. It is quite possible that this extreme situation will lead to reactions and feedbacks in the atmosphere-ocean-ice systems that cannot be adequately modeled at present…"  

In the graphic below, put together by Englander and based on the IPCC report, the various contributors to sea-level rise (in inches) are projected out to the end of the century. Antarctica's contribution is shown in turquoise blue. 

Projections of sea-level rise in four warming scenarios using IPCC data broken down by contribution from various sources. John Englander

Englander explains that in a high-end warming scenario, obviously Antarctica's ice melt should contribute more to sea-level rise than in a low-end warming scenario, but that is not reflected in the report. "The slight contribution shown of 2 inches in three scenarios, and then one inch in the highest scenario, is clearly paradoxical," says Englander. 

This paradox is something the paper's authors aim to push the IPCC to clarify in the upcoming report.

Another paper published in Nature this week makes a similar case, focused on the evidence from Greenland. Employing the latest models used to inform the next IPCC report, the authors found that in a high-warming scenario Greenland may contribute an extra 3 inches to sea-level rise by the end of the century, when compared to the former version of models used by the IPCC. This extra sea-level rise is due to an additional 2 degrees Fahrenheit of warming projected by the new climate models in the Arctic.   

A big concern of Englander's for our future is the non-linear behavior of sea-level rise. In recent years the pace of sea-level rise has been accelerating. In the 1990s the oceans rose at about 2 millimeters per year. From 2000 to 2015 the average was 3.2 millimeters per year. But over the past few years the pace has quickened to 4.8 millimeters per year. 

The pace of sea-level rise is accelerating. John Englander

At the current pace, we can expect at least 15 more inches of sea-level rise by the year 2100. But, as has been the case for the past few decades, the pace of sea-level rise is expected to continue to increase for the foreseeable future. So,15 inches is not only a lower bound, it is also extremely unlikely.

Adding confidence to the paper's warning that IPCC projections for a strong warming scenario may be too low, is the evidence that sea-level rise has been running on the high end of IPCC projections for decades. In the below visual, projections from 1990 and 2002 are shown in blue and green, compared to actual observations in gold and red. It is clear that actual measurements are above the top end of past expectations.

Actual sea-level rise is tracking on the top-end of previous projections from IPCC. John Englander

Because of this evidence and the possibility of "tipping-point behavior," the paper argues, "outcomes above this [IPCC] range are far more probable than below it."

For most of us, it is human nature to assume that the height of the oceans we've observed in our lives is a constant, but Englander says this perception is misleading. "Rising sea level is easy to miss because it's a slow effect, like a drip filling a bucket, as the ice sheets on Greenland and Antarctica melt," he said.

For the past 8,000 years — much of humanity's modern existence — that expectation of a constant ocean height has remained true. However, the height of the oceans has always changed, sometimes dramatically.

Since the last Ice Age, which reached its maximum extent about 20,000 years ago, global temperatures have warmed about 18 degrees Fahrenheit and sea levels have risen 425 feet; that's greater than the length of the football field. 

Historically speaking, simple math reveals that for every degree Fahrenheit the Earth warms, sea-level eventually rises by an astonishing 24 feet. There is, however, a sizable lag time between warming, melting and consequent sea-level rise. 

Considering that Earth has already warmed 2 degrees Fahrenheit since the late 1800s, we know that substantial sea-level rise is already baked in, regardless of whether we stop global warming. Scientists just don't know exactly how long it will take to see the rise or how fast it will occur. But using proxy records, glaciologists can see that as we emerged from the last Ice Age, sea level rose at remarkable rates — as fast as 15 feet per century at times.

Since the end of the last Ice Age 20,000 years ago, sea levels have risen dramatically, sometimes at a very fast pace. John Englander

That said, the fact that there is a lot less ice on Earth today than there was 20,000 years ago means the amount of sea-level rise per degree would likely be less now, and the maximum pace may be tempered as well. But even a pace that's half the historical maximum would still be catastrophic to an Earth with billions of people who depend on stability. 

We must also remember that warming today, due to human-caused climate change, is happening faster than it has in at least 2,000 years and possibly over 100,000 years. So scientists just don't have a directly comparable situation to measure against — once again highlighting our uncertain future. 

While scientists and scientific periodicals tend to be conservative in their public projections of sea-level rise, scientists will often remark that they are concerned it may be much worse. When CBS News asked Englander what he thinks is a "realistic range" of sea-level rise by 2100, he said, "With the current global temperature level and rate of temperature increase I believe that we could get 5 to 10 feet before the end of this century."

While this is just one expert's opinion, if sea-level rise even comes close to those levels, the impacts would be truly dangerous and destabilizing, dramatically reshaping nations' coastlines and forcing hundreds of millions of people to abandon their homes. Englander says to reduce the potential impacts, it is better to be prepared for a worst-case scenario. 

"We need to begin planning and designing for that while there is time to adapt."

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Humanity’s Immense Impact On Earth’s Climate And Carbon Cycle

The Economist

Much needs to be done for the damage to be reversed


IT IS ALL, in the end, a matter of chemistry. Carbon dioxide is a form of what chemists call inorganic carbon—a simple molecule that is pretty inert. Fossil fuels are made of carbon in its organic form—often complex molecules that are far from inert. Combustion turns these organic complexities into inorganic simplicities: carbon dioxide, water vapour and heat.

Of the energy that people pay for (as opposed to the energy that comes from burning firewood) 34% comes from burning oil, 27% from coal and 24% from gas. Nuclear power, hydroelectric power and all other renewables combined provide just 15%. The result of all this fossil fuel use is a modern industrial economy and an annual flow of 9.5bn tonnes of carbon out of the ground and into the atmosphere.

Through its effects on the plants, animals and microbes which make up the biosphere, on the climate and on the oceans, this industrial flow of carbon links the Earth’s distant geological past to its future over millennia to come. It is the single clearest piece of evidence for the idea that humans now have a power over the Earth as great as the forces of nature, and that their use of this power has opened up a new geological epoch that some scientists call the Anthropocene.

To appreciate the importance of this industrial carbon flow, you have to understand the carbon cycle in which it sits. At first, this context seems reassuring. Almost all microbes, and all animals, get the energy that they need for life from breaking up food made of organic molecules. The flame-free, internalised form of combustion by which they do so, which biologists call respiration, produces much more carbon dioxide than industry does.

But respiration has a counterpart: photosynthesis, through which plants, algae and some bacteria use sunlight to turn inorganic carbon back into organic molecules. These new molecules are the raw material from which almost all living things on Earth are made; the sunlight stored within them is the source of all the energy that is released through respiration when those living things are eaten.

The other great flow of carbon dioxide into the atmosphere is similarly balanced. Carbon dioxide dissolved in seawater naturally diffuses into the air above. Carbon dioxide in the atmosphere dissolves into seawater. Left to themselves, the two flows balance (see diagram).

These flows create a system in what is called dynamic equilibrium; if you push it away from current conditions, it pulls itself back. If atmospheric carbon-dioxide levels go up, the rate at which carbon dioxide dissolves into the “sinks” provided by the oceans and plants will also, all things being equal, go up. This reduces the surplus, restoring the status quo. Until the 19th century this dynamic equilibrium had kept atmospheric carbon-dioxide levels pretty stable for most of the 10,000 years since the end of the most recent ice age.

The plants-and-food branch of the carbon cycle, though, is not quite perfect. Like the little bit left in the corner of the sardine can that you can’t get out, not all the organic matter made through photosynthesis gets used by creatures that respire. Some ends up buried in sediments instead.

The amount of carbon which leaks out of the biosphere this way is tiny compared with the flow returned to the atmosphere. But the leak has gone unstopped for a very long time, and that has allowed the Earth’s crust to build up a significant store of organic matter. Now human industry’s use of the most concentrated and readily available deposits of these fossil fuels has returned to the carbon cycle in a couple of centuries a fair fraction of what was stashed away over hundreds of millions of years. It is the addition of this new source with no new sink that has knocked the cycle out of whack.

The world’s seas and plants have tried their best to keep things in equilibrium, responding to rising levels of carbon dioxide by stashing more away in the biosphere and oceans. They suck up roughly half of all the extra carbon dioxide that industry puts into the atmosphere. But that is as much as they can do. And so the amount in the atmosphere grows.

This intensification of the carbon cycle has side-effects. Plants fed with extra carbon dioxide tend to grow more, if circumstances allow. Current estimates suggest the global rate of photosynthesis is 3-7% higher than it was 30 years ago; satellite images show the Earth is getting greener. Such “carbon-dioxide fertilisation” has improved the yields of some crops, and the growth of some forests and other ecosystems. This is not enough to compensate for the damage climate change does to agriculture by higher temperatures and altered rainfall. But, on balance, it is hard to see it as much of a problem.

The same cannot be said of the increased flow into the ocean sink. More dissolved carbon dioxide makes seawater more acidic. How bad this acidification will prove is open to debate. But the process will probably be very damaging to some ecosystems, including reefs already stressed by rising temperatures. Even if fossil-fuel use were not warming the climate, this acidification would in itself count as a frightening global change.

The growth of the two carbon sinks is also, left to itself, unsustainable. Warm water absorbs less carbon dioxide than cold water. So as the oceans warm their ability to offset emissions weakens. As to the land sink, higher temperatures speed up microbial respiration, especially in soils, more reliably than higher carbon-dioxide levels speed up photosynthesis.


Until a few hundred years ago there was a perfect balance of carbon dioxide in the Earth's atmosphere. Human activity has disrupted that balance. What can be done to restore it?

The Paris agreement of 2015 calls for increases to the atmosphere’s carbon-dioxide level caused by fossil fuels to end by the second half of this century. Even if that deadline is not met, some mixture of policy, catastrophe and/or resource depletion will eventually bring the rise to an end. The flows of carbon between the atmosphere, oceans and biosphere will then come back into balance.

But the equilibrium thus restored will not be the pre-industrial one. The carbon-dioxide level will settle down not far short of whatever the 21st century’s peak level turns out to be. Which means that temperatures will stay high, too—with all that entails for crops, ice caps and the like.

This plateau will eventually subside. The erosion of the Earth’s crust exposes silicate minerals that react with carbon dioxide, eventually producing solid carbonate minerals from which the carbon cannot readily escape. But this “chemical weathering” works on a much longer timescale than the sinks. Geochemists think it would take 1,000 years for a post-fossil-fuel carbon-dioxide level of around 550 parts per million to be brought back below today’s 415ppm towards a mid-20th century level of 315ppm.

Going backwards

What, though, if the Anthropocene transitioned from a past dominated by anthropogenic carbon sources to a future characterised by anthropogenic sinks? There are two reasons why this might be appealing. One is that some fossil-fuel emissions may be very hard to eliminate from the economy. If they could be counterbalanced by “negative emissions” that take carbon dioxide out of the atmosphere at a similar rate, the Paris goal of stopping any further increase to the carbon-dioxide level would be far easier to meet.

The second attraction of the idea stems from the other Paris goal, that of keeping the global temperature increase, compared to pre-industrial times, well below 2°C. Doing this simply by reducing emissions would require much steeper cuts than any seen to date, and they would have to continue for decades. If the world developed negative-emission technologies, more gentle emissions cuts in the near future could be made up for by negative emissions later on, which would bring the carbon-dioxide level back down from its excessive peak.

Some forms of negative emission look fairly benign: farming in ways that make the soil richer in organic carbon; restoring degraded forests and planting new ones. More ambitious is the idea of harnessing photosynthesis to industry; growing plantation crops, burning them to generate electricity and sequestering the carbon dioxide given off underground, rather than letting it out into the atmosphere, an approach called bioenergy with carbon capture and storage, or BECCS.

Then there is the idea of stripping carbon dioxide out of the atmosphere with renewably powered open-air chemical engineering: “direct air capture”, or DAC. And there is also the possibility of helping along the chemical weathering process by grinding up silicate rocks into fine dusts, thus speeding up the reactions that store carbon dioxide away in stable minerals.

There are two big problems with these ideas. One is the scale at which they need to operate to make a difference. Imagine that in 2060 the world had, through a vast effort, renounced 90% of its fossil-fuel use. To offset the remaining recalcitrant 10% would still require a sink capable of soaking up about 1bn tonnes of carbon a year. The industrial systems for taking carbon dioxide from the air currently on the drawing board operate at barely a thousandth of that scale. Creating such a flow through photosynthesis would require a plantation about the size of Mexico.

This leads to the second problem. Imaginary backstops are dangerous. If countries build negative emissions into their thinking, they will cut emissions more slowly on the basis that any overshoot can be mopped up later. But they will not necessarily undertake the huge efforts required to make those negative emissions a reality. The Anthropocene fact that humans are now integral to the processes of the planet does not mean that they can change those processes without great effort—let alone just through wishful thinking.

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