UN climate scientists are running out of ways to warn us

Internally displaced people wade through floodwaters after heavy monsoon rains in Pakistan’s Balochistan province on September 8, 2022.
Record flooding submerged one-third of Pakistan last year after heavy monsoon rains. Torrential rainfall events are poised to increase as average temperatures rise. | Fida Hussain/AFP via Getty Images

Coming soon: A world warmed by 1.5 degrees

There’s a simple reason to pay attention to a new report from the Intergovernmental Panel on Climate Change, the United Nations’ scientific body on climate change: it’s a reality check.

The report ties together the current round of comprehensive climate research assessments published in installments over the past two years, known as the Sixth Assessment Report, or AR6. What’s become clear is that climate change is no longer a distant, vague threat for future generations to contend with. It’s a near-term crisis. The impacts of the warming we’re already experiencing — 1.1 degrees Celsius of warming above preindustrial times — are unfolding faster than expected in every region of the world, and some of these changes are irreversible.

“Every increment of global warming will intensify multiple and concurrent hazards,” says the IPCC’s summary report published Monday.

If the world were serious about limiting more warming, global greenhouse gases would already be on the decline. The deadline for a different course is fast approaching; the official UN goal to limit warming this century to less than 1.5 degrees will be impossible to meet unless global emissions peak and decline in the next two years, according to the IPCC. Then, countries will need to still slash their emissions by 60 percent by 2035.

Based on our current trajectory, the world is on track for much more warming than that. In this likelier scenario, billions more people will face worsening heat waves, heavier rainfalls, food insecurity, and wiped-out ecosystems. Climate change is transforming the world more quickly than scientists had thought, and we’re already seeing the limits to how well parts of the globe can adapt.

Chart showing different greenhouse gas emissions trajectories.
The world will have to make aggressive cuts to greenhouse gas emissions to meet the goals of the Paris climate agreement.

But even in the most ideal scenario, the world is poised to overshoot the 1.5 degree Celsius target as early as the mid-2030s. “The real question is whether our will to reduce emissions quickly means we reach 1.5 degrees, maybe go a little bit over but then come back down, or whether we go blasting through … and even keep on going,” said Peter Thorne, an IPCC contributor and a climatologist at Maynooth University in Ireland.

In the UN body’s 30 years of issuing these reports, the latest is its most sober. Humanity is in a sprint against the clock to keep climate change in check. The upside to doing so is that both technological and economic trends make it easier than ever to switch away from planet-warming fossil fuels.

None of these conclusions are shocking revelations nor cutting-edge science, but rather a reflection of research that’s already been thoroughly vetted by hundreds of scientists and through thousands of papers. The new IPCC report, though, is the least technical of the reports released since 2021, and is aimed at policymakers and the wider public. It summarizes what the scientific community has learned since 2015, including the knowns and unknowns of climate science, our ability to adapt, and how the world can chart a more sustainable course. IPCC scientists often say that they are not trying to prescribe any specific policies with their work; they just want to give decision makers the imperative and the tools to act.

“The report offers hope, and it provides a warning,” said Hoesung Lee, chair of the IPCC, during a press conference on Monday. “It warns that the pace and scale of what has been done so far and current plans are insufficient to tackle climate change.”

Here are the key takeaways from the report:

Climate change really is our fault

If there was any hesitation among scientists about humanity’s role in warming the planet in the past, that was quashed with AR6. With the latest review of the science, IPCC authors said that it’s “unequivocal” that the burning of fossil fuels by humans is heating up the world. The report also highlighted advances in attribution science, where researchers can trace just how much human-induced warming has worsened the specific consequences of climate change, like more intense heat waves. From there, scientists have refined their forecasts of what’s in store for the world if humanity gets its act together to limit greenhouse gas emissions, and if it does not.

We’re on track for one of the darkest timelines

Today, carbon concentrations are at a 2 million-year high, and temperatures are already higher in the past 50 years than in the last 2,000.

Roughly half of the world’s population lives in areas highly vulnerable to climate change, and deaths from flooding, droughts, and storms in these regions were already 15 times higher than less vulnerable areas in the last decade, the report says.

Within 20 years, the planet will already be changed in some unfathomable ways: Large frozen areas will be erased, and 14 percent of all living species will be threatened by extinction. This unprecedented warming will also herald unprecedented economic disruption, and it will come sooner than we think.

A person or community’s vulnerability is shaped by all kinds of wealth, politics, identity, and gender dynamics. The hard sciences and traditional climate modeling typically fall short when it comes to incorporating these factors. Now, the latest IPCC synthesis includes far more economic and social research that subtly shifts the focus of much of the report. For the first time, the IPCC discusses colonization as a root cause of climate instability, and it is unequivocal in stating that inequality heightens climate risks.

While people will have to adapt to some degree to a warmer world, we are brushing up against the physical limits of what people can endure. Thus, mitigating climate change remains essential for our survival.

IPCC chair Hoesung Lee speaks from a lectern, with a blue screen behind him showing the IPCC logo.
Antoine Tardy/IPCC
IPCC Chair Hoesung Lee said the latest climate report provides a warning.

The world can’t burn all the fossil fuels it plans to if we want to limit warming

The IPCC warned last year that the world will miss its stated climate goals if it continues business as usual burning fossil fuels from all of its existing and planned infrastructure. Existing plans alone would blow through the world’s remaining carbon budget. Containing global warming means that the world will have to leave substantial fossil fuel resources unburned. An earlier IPCC report noted this translates into $1 trillion to $4 trillion in untapped infrastructure, and even more if the world were serious about limiting warming to 1.5 degrees.

Yet countries are planning to continue extracting fossil fuels for decades, even in some of the most pristine and fragile environments, like with the Willow oil drilling project in Alaska recently approved in the United States. There’s also the tricky question of fossil fuels in developing countries. These countries desperately need energy to escape poverty, but the promised financing from wealthy nations to deploy clean energy has fallen short. Merging economies now want to extract more of their own coal, oil, and natural gas.

Methane will decide our fate in the next 10 to 20 years

A major factor in how fast the world approaches these new thresholds will be determined not by carbon dioxide, but by a lesser-known greenhouse gas, methane. Over a 20-year timescale, methane is about 80 times more powerful than carbon dioxide when it comes to trapping heat in the atmosphere, so smaller amounts of methane emissions have an outsized impact on the planet’s temperature.

Much of the world’s methane emissions are due to human activities, like extracting natural gas, agriculture, damming rivers, and waste dumps. But that also means people can directly limit global methane emissions and alter the course of warming. More than 100 countries, representing nearly half of global methane pollution levels, signed a voluntary Global Methane Pledge to cut levels by at least 30 percent by 2030.

These methane cuts are necessary within the decade in addition to steep carbon dioxide reductions, according to the IPCC.

We have technologies to tackle climate change, but we’ll need more

Many of the tools we need to curb our impact on the planet’s temperature are already here and are getting cheaper. Per the IPCC, solar energy and lithium ion battery costs have fallen per unit by 85 percent, while wind energy costs have fallen by 55 percent from 2010 to 2019.

In much of the world, building new renewable energy sources is cheaper than running existing coal power plants. However, fossil fuels still fulfill about 80 percent of the world’s energy needs, so there’s a long way to go.

Looking ahead, the IPCC report finds that wind and solar energy still have the greatest potential to curb global emissions. But the world will also need advances in emerging technologies, like carbon dioxide removal directly from the atmosphere and the ocean.

We can still change course

While there are shifts to the climate that are now baked in, our actions now will change the course of warming in the coming decades, and the next few years are critical. The IPCC says worse change can only be “limited by deep, rapid and sustained global greenhouse gas emissions reduction.”

“The rest of this decade we’ll see whether we can apply the brakes and stop the warming at that level,” Thorne said.

Scientists have chalked out multiple scenarios for warming this century, and the question now is what we can do to get on the best pathway. It will require unprecedented investment in clean energy, funding for innovations, and adaptation to the changes we can’t avoid. But it also demands a political apparatus capable of making such massive decisions and ensuring that the jobs, clean air, and resilience stemming from the transition are spread around.

“Transformational changes are more likely to succeed where there is trust, where everyone works together to prioritize risk reduction, and where benefits and burdens are shared equitably,” IPCC’s Lee said. “We live in a diverse world in which everyone has different responsibilities and different opportunities to bring about change. Some can do a lot while others will need support to help them manage the change.”

The world has more than enough financing to handle this transition, says the IPCC, but there are barriers to redirecting to an all-hands-on-deck approach to the climate crisis. Ending fossil fuel subsidies and instituting carbon pricing are the types of policies that will help make a difference.

Some parts of the world are beginning to make these changes. The US, the world’s largest historical emitter of greenhouse gases, last year passed the Inflation Reduction Act, its largest and most comprehensive effort to fight climate change.

Solar panels are seen as part of a photovoltaic park, at Kokkinotrimithia, Cyprus, on March 15, 2023.
Kostas Pikoulas/NurPhoto via Getty Images
Cyprus is building a 72 MW photovoltaic park with a 41 MW battery system that would currently be the biggest in the country by far.

Climate change isn’t the only problem people have to worry about. With Russia’s invasion of Ukraine stretching into its second year, global energy markets remain unstable. Inflation and fears of a recession are hampering investments in wind and solar. But these shocks have accelerated the transition toward clean energy in Europe, helping countries produce more energy within their borders. Addressing climate change can therefore enhance economic and political stability, addressing multiple challenges at once.

UN Secretary-General António Guterres said the latest report should serve as a “clarion call to massively fast-track climate efforts by every country and every sector and on every timeframe.” He added, “The 1.5 degree target is feasible, but it will take a quantum leap in climate action.”

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