IPCC Climate Change Reports: Why They Matter to Everyone on the Planet
Ice melt in East Greenland
You’d be forgiven for losing track of all the reports on climate change. There are a lot—each seemingly more dire than the last. But perhaps none are more important than those released by the United Nations’ Intergovernmental Panel on Climate Change (IPCC), a group made up of thousands of unpaid, volunteer scientists from around the world. In recent years, the IPCC’s reports have sounded the alarm with increasing clarity: We must cut emissions sharply and immediately to avoid the most catastrophic effects of a warming planet. Here’s a look at how the IPCC came to be the leading authority on climate, the panel’s latest findings—and why it’s so critical that our leaders pay attention.
What Is the IPCC?
The IPCC stands for the Intergovernmental Panel on Climate Change, and it’s the leading scientific authority on all things related to global warming. Established in 1988 as part of the United Nations Environment Programme (UNEP) and World Meteorological Organization (WMO), the panel aims to inform policymakers around the world on the risks of fossil fuel–driven climate change so they can take appropriate action. Currently, 195 countries participate as members, determining the overall direction of the IPCC’s work.
At the time of the IPCC’s founding, many policymakers were just starting to grapple with a phenomenon known as the “greenhouse effect” (though the concept itself has been known to scientists for more than a century). Today, 30 years later, most school-age children are familiar with the basic ideas behind our climate crisis: Global warming occurs when greenhouse gases, most notably carbon dioxide (CO2), collect in the atmosphere. These pollutants, which can stick around and pile up for decades, prevent the sunlight and solar radiation that bounce off the earth’s surface from escaping back into space, instead trapping the heat and warming the planet.
Lamma Island Power Station, Hong Kong
Today the earth has already warmed more than 1 degree Celsius (1.8 degrees Fahrenheit) above preindustrial levels. The climate crisis, once talked about in the future tense, has already arrived. If we continue business as usual (by continuing to burn fossil fuels, for one thing), the best science says the world will warm as much as a catastrophic 4.4 degrees Celsius (8 degrees Fahrenheit) by the turn of the century. The IPCC is central to our efforts to avoid this outcome, providing accurate analysis that global policymakers can use to take swift, effective action to fend off the worst impacts.
What Does the IPCC Do?
The IPCC has a small staff to support its work, but the bulk of its authority comes from the thousands of highly credentialed volunteer scientists from around the world who participate as authors or reviewers. The panel does not conduct its own science. Instead, it reviews and synthesizes the latest climate change research (thousands of published, peer-reviewed studies) into its own predictions and digestible reports, which come out roughly every six years, in addition to special reports that are published more frequently. While the reports steer clear of being overly policy-prescriptive, they are intentionally “policy-relevant,” meaning their conclusions can easily be translated into real-world policy outcomes.
The IPCC’s work is funded by voluntary contributions from U.N. member countries (with the United States traditionally paying the largest share), as well as from intergovernmental organizations like the UNEP, the WMO, and the U.N. Framework Convention on Climate Change (UNFCCC), which are also funded through voluntary contributions.
Storms approach the North Rim of Grand Canyon National Park, Arizona.
IPCC Report History
The IPCC has been sounding the alarm on climate change for decades, putting out regular, comprehensive assessments that summarize the most current research on our warming planet. Periodically, it also issues special reports on topics like land use, the ocean and cryosphere (frozen portions of the earth), and the consequences of 1.5 degrees Celsius (2.7 degrees Fahrenheit) of warming.
The IPCC’s warnings began in 1990 with its First Assessment Report, which successfully predicted the pace of global warming, even without the highly complex computer models of today. The Second Assessment, published in 1995, expressed greater certainty that climate change was largely caused by human activities. In 2001, the Third Assessment warned that the temperature increases would become worse than previously feared if we didn’t reduce our carbon emissions. Meanwhile, the world ramped up fossil fuel production and consumption.
By the time of its Fourth Assessment, in 2007, the IPCC was using words like unequivocal to describe the consensus that humans were the main cause of warming. In 2014, the Fifth Assessment dealt the world a hard truth: Greenhouse gas emissions were higher than ever, causing an unprecedented acceleration of climate change’s impacts.
And in the Sixth Assessment—which was released in three parts, beginning in 2021——the panel warned that nations are reducing climate pollution far too slowly, risking severe damages, costs, and upheaval. It also concluded that decades’ more warming should be expected—even if we sharply reduced emissions today—making adaptation essential, particularly for the world’s most vulnerable populations. (The full Sixth Assessment report synthesis will be available in September 2022.)
These report releases often coincide with—and help shape—critical moments of international climate collaboration. The First Assessment Report supported the creation of the UNFCCC, which has become a foundation for coordinated political action. The Second Assessment provided key input to the 1997 Kyoto Protocol, a historic agreement that put binding emissions targets on developed countries for the first time. The Fifth Assessment informed 2015’s Paris Agreement, the landmark global accord that has since been adopted by every nation to address climate change. Most recently, the first part of the Sixth Assessment informed the COP26 meeting in Glasgow, where world leaders and climate experts came together to commit to more ambitious emissions reduction targets.
Yet despite three decades of warnings by the IPCC—and sporadic displays of global coordination—world leaders have done far too little, far too slowly to stop further warming. The concentration of carbon dioxide in the atmosphere is now the highest ever recorded, when looking back two million years. As the IPCC’s latest report shows, the need for immediate action is clearer than ever. Every ton of emissions reduction matters. Every investment in adaptation matters.
The Latest IPCC Report on Climate Change
When was the last IPCC report?
In August 2021, the IPCC began to release its three-part Sixth Assessment Report—each written by a corresponding working group. The first part synthesized the current, best-available physical science on climate change. The second, released in February 2022, covered impacts, adaptation, and vulnerability to climate change, for both ecosystems and people. And the third part covered mitigation and was released in March 2022. A Sixth Assessment synthesis report will be available in September 2022.
How many scientists contributed to the latest IPCC report?
Across all three working groups who contributed to the Sixth Assessment Report, 782 scientists (and hundreds more contributing authors) analyzed more than 66,000 peer-reviewed studies.
What are the important findings of the current IPCC report?
Widespread, rapid, and intensifying: Those are the words used by the IPCC to describe climate change in the Sixth Assessment Report—the most comprehensive look at present and future climate impacts to date. Its conclusions, based on the latest generation of climate models, are clear: “Observed changes in the atmosphere, oceans, cryosphere, and biosphere provide unequivocal evidence of a world that has warmed,” the report says—and human activity is “indisputably” the cause.
Sharks and anthias swim near the Jarvis Island National Wildlife Refuge.
The report lays out five possible scenarios—–from better to worse to apocalyptic—–that correspond to different timelines of climate action and their predicted degrees of warming. Under even the most optimistic scenario, one in which the world bands together to slash emissions immediately, the world can avoid the most catastrophic version of the climate crisis but will continue to warm until at least mid-century, due to the impact of past emissions. “Some of the changes already set in motion—such as continued sea level rise—are irreversible over hundreds to thousands of years,” the report says. That means we can expect climate impacts, from storms to sweltering temperatures, to get worse before they get better, though these interactions are complex and can vary by region.
In the latest report, the panel also makes clear that the world is not doing enough to adapt to current and worsening climate impacts, particularly in vulnerable communities where the climate crisis can exacerbate existing social and economic inequities. Adaptation efforts have so far been “fragmented” and “incremental,” the panel says, when instead, governments should be urgently making “transformational” changes to secure food supplies, build more resilient electricity grids, and protect people’s health.
Why Is the 1.5 degrees Celsius Target Important?
The stated aim of the 2015 Paris Agreement is to keep global temperature rise “well below” 2 degrees Celsius and to “pursue efforts” to limit it to 1.5 degrees Celsius (2.7 degrees Fahrenheit). But during the tense negotiations that led to the agreement, many countries, particularly island nations and others most vulnerable to rising seas, argued that anything above 1.5 degrees Celsius of warming—not 2 degrees—would be too dangerous. While some scientific findings already supported this idea, there wasn’t enough information at that point to accurately predict the ramifications of that seemingly small half degree. Therefore, the IPCC was tasked with finding out: Should we aim for 1.5 degrees Celsius instead? Would it even be possible? And if so, what would it take?
Forest fires from around the United States
The conclusions of the IPCC’s Global Warming of 1.5° C special report were startling: A half degree more of warming would mean substantially more poverty, extreme heat, sea level rise, habitat and coral reef loss, and drought. And we cannot prevent this unless we act immediately to cut emissions deeply. The 2018 report confirmed what those vulnerable nations feared to be true: Every tenth of a degree of warming has grave consequences.
Limiting global warming to 1.5 degrees Celsius, rather than 2 degrees, “could reduce the number of people exposed to climate-related risks and susceptible to poverty by up to several hundred million by 2050,” the report states. At 1.5 degrees Celsius, the number of people across the globe at risk of inadequate water supplies could be 50 percent lower than at 2 degrees.
Storms over New York City
Other species are also worse off with a two-degree increase. At that level of warming, coral reefs could nearly all be dead. Just half a degree cooler and the survival rate for reefs could be as high as 30 percent. Twice as many plant species—and three times as many insects, which are critical to our food supply—could lose at least half of their habitat under a 2 degree Celsius versus a 1.5 degree rise. And the melting of Arctic ice—particularly concerning the positive feedback loop it would create by no longer reflecting the sun’s rays—would be far more drastic at 2 degrees. Summers warm enough to melt all of the Arctic’s ice would occur only once every 100 years at 1.5 degrees Celsius of warming. At 2 degrees Celsius, the ice would vanish every 10 summers.
In fact, if we continue with business as usual, the IPCC predicts the world could warm 2.4 degrees Celsius by mid-century—surpassing critical tolerance thresholds for agriculture and health—and an incomprehensibly devastating 4.4 degrees Celsius (8 degrees Fahrenheit) by 2100. And as we’re already seeing today, the impacts will be felt hardest by those who have historically contributed the least to climate change, including women and low-income communities, as well as Indigenous and people of color around the world.
Women shoring up the embankment on Shakbaria River in Bangladesh
The IPCC’s Recommendations
The IPCC reports spell out how the world must take ambitious climate action within this decade in order to keep warming to within 1.5 degrees Celsius above preindustrial temperatures. That requires decreasing carbon pollution by 45 percent from 2010 levels by 2030 and reaching net-zero carbon emissions by 2050. (Net-zero refers to balancing the amount of emissions put into the atmosphere with the amount taken out.) Even then, we will likely overshoot the 1.5-degree target initially—hitting 1.6 degrees Celsius between 2041 and 2060, and then dropping back below 1.5 degrees by 2100. (In addition to slashing carbon, we’ll need to dramatically cut other greenhouse gas emissions, including methane, nitrous oxide, and fluorinated gases.)
It can be helpful to think of this ticking climate clock in terms of our remaining carbon budget. According to the Sixth Assessment Report, the world can emit just 460 gigatonnes more of carbon dioxide, measured from the start of 2020, if we want at least a 50 percent chance of staying below 1.5 degrees. In recent years, the world has emitted about 36.4 gigatonnes annually. If we continue at that pace, we will blow our entire carbon budget in about a decade.
To limit warming to 1.5 degrees Celsius by century’s end, we’ll need system-wide changes on a scale never before seen. It means shifting the way we produce and consume energy, from carbon-intensive fossil fuels to clean, renewable energy. It means changing how we manage our land, consume goods and services, store our waste, travel, and even how we eat.
True solutions will also be borne out of “inclusive development choices that prioritize risk reduction, equity, and justice,” the panel states, and forming partnerships with historically marginalized groups, who often experience climate impacts first and more acutely.
Technicians working on a massive wind turbine in Normandy, France
Any net-zero pledges, of which there are now hundreds from governments and corporations alike, must have real substance. That means enacting measures that curb pollution in the short term, rather than allowing emissions reductions to exist as a math trick on paper. Indeed, many of the scenarios considered by the IPCC rely on “negative-emissions technologies,” which remove carbon pollution from the atmosphere and store it in order to spare our planet from further warming. Some of these methods are relatively straightforward—such as capturing more carbon in forests and soil—but others aren’t quite as simple. One controversial negative-emissions technology is bioenergy coupled with carbon capture and storage (BECCS), which the IPCC includes in several possible scenarios in its Global Warming of 1.5° C special report. BECCS involves growing plants to naturally absorb carbon dioxide, burning them to generate power, and then capturing the resulting emissions and storing them deep underground. Unfortunately, studies indicate that massive use of BECCS could be untenable and exact too high an ecological cost. Thankfully, there are many other ways to reduce emissions, most notably by decreasing the extraction and use of fossil fuels and ramping up renewables.
Where Do We Go from Here?
The best time to reduce greenhouse gases was in the mid-19th century, when scientists first began realizing the effect that burning fossil fuels could have on our climate. The second-best time is right now. Indeed, the most alarming part of the latest IPCC reports is the sheer speed at which the world needs to overhaul foundational elements of modern life, such as our energy, transportation, land use, and food systems.
We haven’t been going nearly fast enough: Even when considering updated 2030 emissions reduction targets and tangible net-zero–by–mid-century pledges from COP26, the world is still on track to see 2.1 degrees of warming. And those pledges will still require significant political will to fully enact. Even optimists would agree that we have a dizzyingly large task ahead. In the United States, political polarization in Congress—and the continued support of fossil fuels by members on both sides of the aisle—has derailed the ambitious climate legislation we desperately need.
But rather than being universally accepted as a harbinger of doom, the IPCC’s reports serve as a wake-up call to take action. Many of the necessary next steps are already happening—just not at the speed or scale that’s needed. The bigger challenge is whether there is the political will to change, particularly in the United States, which is the second-biggest carbon polluter after China and still far and away the biggest polluter in history. (A commitment at COP26 for these two top emitters to work together provides a strong foundation for further progress.)
Hikers cross Specimen Ridge in Yellowstone National Park, Wyoming.
Of course, successful climate action doesn’t look like just one thing—it looks like many things, happening all at once. It means ending our addiction to fossil fuels. But it also means deploying electric cars and offshore wind farms and reducing our food waste. It means rewriting building codes to be more energy efficient, developing higher-capacity energy storage, and making this technology accessible for all. It means protecting forests and using less land to raise methane-producing livestock. And it’s not just mitigation—trying to reduce greenhouse gases—it’s about building resilience and adapting to the impacts of a changing climate.
For individuals, taking action may look like buying less plastic, installing LEDs, or using more public transportation. It also means making our voices heard to convince our leaders that urgent climate action is not only necessary but possible. Most importantly, it’s about knowing that every action we take to fight climate change matters.
This story was originally published on November 21, 2018, and has been updated with new information and links.
This NRDC.org story is available for online republication by news media outlets or nonprofits under these conditions: The writer(s) must be credited with a byline; you must note prominently that the story was originally published by NRDC.org and link to the original; the story cannot be edited (beyond simple things such as time and place elements, style, and grammar); you can’t resell the story in any form or grant republishing rights to other outlets; you can’t republish our material wholesale or automatically—you need to select stories individually; you can't republish the photos or graphics on our site without specific permission; you should drop us a note to let us know when you’ve used one of our stories.
How do we define and measure biodiversity—and just why is it so important?
The U.N. panel’s latest report paints a picture of the grim effects of global warming—and underscores the need for urgent, transformative adaptation.
A climate job isn’t what it used to be. Neither is the path to getting one.
The ubiquitous climate target comes with big loopholes, but that doesn’t mean we shouldn’t hit it.
IPCC Report: We’ve Already Warmed the Planet to Catastrophic Effect, but the Level of That Catastrophe Is Still Up to Us
There’s no going back, but there is a way forward: Act now and go big.
Food insecurity, biodiversity collapse, and skyrocketing global temps loom. But a new U.N. report says we have the tools to fix it.
By increasing the concentration of greenhouse gases in the atmosphere, we’re amplifying the planet’s natural greenhouse effect and turning up the dial on global warming.
Scientists say we must fight the biodiversity crisis and climate change at the same time.
How much longer can politicians pretend that it’s a divisive issue?
A new novel imagines what life in Bangkok would be like if nearly half the city were underwater—which some experts say is a real possibility.
The systems that allow life on earth to exist are breaking down. We’re responsible. But we also have the power to turn things around.
The appointment of William Happer shows that as public opinion and government reports increasingly back climate science, deniers (including the president) are getting desperate.
To ignore this fact—as the Trump administration insists on doing—is to hamper U.S. foreign policy.
Looking for a silver lining in the harrowing United Nations climate change report? Here it is: We can determine the impact of climate change by the political, economic, and social choices we make today.
The Trump administration thought that releasing a blockbuster climate assessment on Black Friday would keep people from talking about it. That’s not what happened.
The administration cites the likelihood of catastrophic global temperature rise to justify gutting fuel-efficiency standards. Yes, you read that correctly.
So we’d better get it together and do something NOW.
The administration released climate doomsday predictions while you were at the mall, and Scott Pruitt is the gift that keeps on giving.
The president doesn’t know what the U.N.’s climate report is, Ryan Zinke’s “pay-to-protest” plan, and Andrew Wheeler’s racist index finger.
The lowdown on the earth’s central environmental threat.
NRDC is working to help make the Global Climate Action Summit a success by inspiring more ambitious commitments to the historic 2015 agreement and enhanced pollution-slashing initiatives.
Leaders from around the world are gathering in San Francisco right now for the largest climate event ever held in the United States. Here are all the pledges made so far.
The American people believe in climate change—and are committed to doing something about it.
We know that you know that Trump’s assessment of the Paris Agreement is way off base. Here’s how to convince those who don’t.
Gun-control activists want to use financial levers to curtail firearm sales. Can we do the same for carbon emissions?
Everything you wanted to know about our changing climate but were too afraid to ask.
Today’s young people are finally realizing just how much power their voices actually wield. These millennial climate activists have every intention of using it.
In quantifying carbon pollution's damage to society, Trump sees America as an island unto itself—and we all know what climate change does to islands.