The latest IPCC report argues that stabilizing the climate requires swift action

THE WINDOW to prevent global temperatures from rising more than 1.5°C above the pre-industrial average is fast approaching completion. Decisions made this year could determine whether that goal is met, or whether the world surpasses it by mid-century and must contend with severe climate extremes before attempting to turn the thermostat back on in the second half of the century to turn down.

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These are the warnings of the Intergovernmental Panel on Climate Change (IPCC) in the third volume of their latest assessment report, published on April 4th. It follows previous tomes published in recent months, which first presented the current state of knowledge on the physics of climate change and then examined the effects of warming on the human and natural world.

The third report offers a comprehensive menu of ways humans could stabilize the climate and avoid catastrophic global warming while meeting the commitments of the 2015 Paris Agreement. The goal of this pact was to keep average global warming to 1.5°C to 2°C above pre-industrial levels.

That IPCCThe menu of includes options for power generation and energy efficiency, transport, buildings, urbanization, agriculture and food security, forestry, consumer choices and much more. Its 278 authors have gone to great lengths to offer a smorgasbord of emission reduction and climate stabilization options, and to point out that not all are outrageously expensive.

There’s only one catch. To meet the Paris goals, humanity must order almost everything on the menu, and fast.

“We have to get on with it now, don’t we [the goal of] 1.5°C will be out of reach,” said the report’s co-chair, Jim Skea of ​​Imperial College London, upon publication. “If there’s no progress on the kind of commitments countries are making before we get to that COP27 in Egypt,” he added, referring to the next U.N. climate summit scheduled for November, “we may have to conclude that we are actually below 1.5°C.”

Climate scientists are generally unwilling to concede defeat when it comes to this goal, in part because the research has been merged into another IPCC A 2018 report showed that the consequences of 2°C global warming were significantly worse than 1.5°C, particularly for the poorest parts of the world and low-lying regions prone to rising seas and destructive storm surges. But the measures they are proving necessary to reach the target are so stringent that exceeding 1.5°C of warming now seems all but certain.

Now or never

However, the physics of the global climate system leaves little room for excuses, and Dr. Skea’s stark warning comes directly as a result of the figures in the latest report. The “carbon budget” represents the total amount of carbon dioxide that can still be pumped into the atmosphere before some warming is likely. For example the IPCC says that for a 50% chance of limiting warming to 1.5°C by 2100, no more than 500 billion tons of CO will be produced2 can be emitted beyond 2020, which at current rates equates to just over a decade of emissions.

The report states that to avoid warming in excess of 1.5°C, global emissions must peak before 2025 and then fall by 43% by 2030 compared to 2019 levels. Yet human societies emit more greenhouse gases with each decade, and the last saw the largest increase in emissions in human history. While the report’s socio-economic simulations for the coming decades show that it is theoretically possible to cut emissions by the required amounts, the political realities and inherent inertia of economies largely fossil-fuelled make the transition one Challenge, especially required at current speed.

Reaching the Paris target of 1.5°C means that global coal consumption must fall by 95% by 2050 compared to 2019. Oil consumption must fall by 60% and gas consumption by 45% over this period. The cuts required to keep warming below 2°C are not much less. In all scenarios, there is no room for new, unmitigated fossil fuel projects (like power plants) and most existing ones will need to be wound down more quickly than would otherwise have been the case. “Estimated emissions from electricity [fossil-fuel] Infrastructure over the projected lifetime is about what we can emit for a 2°C scenario,” said Michael Grubb of University College London, one of the researchers IPCC Authors of the report.

Limiting warming to less than 2°C would therefore mean shortening the lifespan of existing fossil fuel power plants and refineries. These could be retrofitted with facilities that capture warming gases before they escape into the atmosphere for storage underground or under the oceans. However, as the report’s authors note, for decades governments and companies have promised to develop such an industry (dubbed “carbon capture and storage”), but have not done so.

Beneath the darker warnings are some rays of light. The cost of solar energy has fallen by 85% and wind energy by 55% in the 2010s. During the same period, the electric vehicle market grew 100-fold. That IPCC The report finds that at least 24 countries have consistently reduced emissions for at least a decade. Despite worrying trends, the Brazilian Amazon today has more forest and less deforestation than in 2010. In 2020, more than 20% of global emissions were covered by carbon taxes or trading schemes. And even in 2020, more than 50 countries, which account for more than half of the world’s emissions, had enacted climate laws to reduce emissions.

The energy intensity of the world economy (a measure of the amount of energy expended to produce a unit of GDP) decreased by 2% per year between 2010 and 2019. At the same time, the amount of carbon dioxide emitted per unit of energy generated (known as “carbon intensity”) has fallen – an indication that energy is becoming greener around the world.

But those gains are nowhere near what the models say are needed to stabilize the climate before it’s too late. Carbon intensity, for example, fell by 0.3% per year in the 2010s, a fraction of the 3.5% per year that models show is needed to have a good chance of limiting warming to 2°C. For a 1.5°C target, the annual improvement would need to be 7.7%.

A common thread runs through the Paris-compliant scenarios presented IPCC is the inclusion of options to remove greenhouse gases from the atmosphere. That’s because all scenarios assume that even under the most optimistic assumptions, there will be residual emissions from some sectors of the economy by mid-century. Viable options for eliminating fossil fuels from aviation and heavy industry are currently lacking, and few envisage sufficient change in the coming decades.

There are two types of options for removing these residual emissions: ecological (reforestation, ecosystem restoration, programs to increase the amount of carbon sequestered in agricultural soils) and chemical (using minerals or reagents that selectively bind to atmospheric CO).2 and allow it to be stored underground, under water, or in solid form).

The former appears simple and cheap, but is potentially unreliable. Forests burn, releasing greenhouse gases; in a warmer, drier world they will burn more. Long-term carbon storage requires trees to be managed and protected, which humans generally don’t always do well. Ecological solutions can also compete with agriculture for land, especially at the scales demanded by climate models.

suck it up

On the other hand, technological solutions to remove carbon dioxide from the atmosphere are still in their infancy and extremely expensive. The two commercial companies are offering to remove a ton of carbon dioxide for between $300 and $1,000. For comparison, a single economy seat on a return flight from London to San Francisco is responsible for almost a tonne of emissions.

These carbon removal technologies can see rapid cost reductions. Proponents point to the recent successes of solar and wind energy projects — all three technologies involve small modular components, making them relatively easy to scale, and fans of the “direct air capture” industry have used the similarities to suggest their technology is going fast, too take off. Still, it’s worth noting that even solar power, a modern day darling of the green energy world, took several decades to get to where it is today.

For some, calls to end the fossil fuel age or face the consequences of letting the world burn may seem detached from immediate reality, especially as European countries desperately seek gas to replace Russian supplies and to avert fuel shortages and crippling prices in the coming winter.

But there are some synergies between the two crises. In the long list of ways to reduce emissions, improving energy efficiency in transport, buildings and industry, and behavioral changes such as switching from private cars to public transport are low-hanging fruits. Encouraging consumers to reduce energy demand in this way would also increase energy security. And every fraction of a degree saved in future warming reduces climate risks, even if the 1.5 degree target is missed.

The Covid-19 pandemic presented an opportunity to use the resulting economic turmoil to boost green growth. Government response has been patchy at best. Today, as the West grapples with a deepening energy crisis, it faces a similar challenge, but with added urgency given the US’ recent climate warnings IPCC‘s scientist.

Correction (04/08/2022):A previous version of this article says global emissions need to fall by 43% by 2030 to avoid warming of more than 2°C. In fact, this is the reduction that would be required to prevent 1.5°C of warming. (The estimated required reduction by 2030 for a 2nd°C target is 27%.)

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This article appeared in the Science & Technology section of the print edition under the headline “Tick, tick, tick”

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