Why the new UN IPCC climate change report is so critically important

Climate 101 is a Mashable series that answers provoking and salient questions about Earth’s warming climate.

Nearly 110 years ago, a New Zealand newspaper warned that carbon emissions from burning fossil fuels in the great “furnaces of the world” would raise Earth’s temperature. “The effect may be considerable in a few centuries,” the paper wrote.

It was a decent prediction. Yet it turns out a momentous climate effect has occurred faster, in just around one century, and earth scientists expect impacts — severe droughts, pummeling rains, rapidly-spreading wildfires, destabilized Antarctic ice sheets, and beyond — to grow worse as the planet warms.

On Monday, the UN’s Intergovernmental Panel on Climate Change, or IPCC, published its clearest picture yet on the updated science of planetary heating. The nearly 4,000-page report, authored by 234 scientists from 66 nations (and over 500 more contributing scientists), emphasizes that climate change is widespread and intensifying — but also shows that humanity has agency to avoid the worst impacts of a warming globe.

Linda Mearns, a senior scientist at the National Center for Atmospheric Research who worked as a lead author of the new publication, has worked on IPCC reports for over 25 years. Following the best available science, she used to say that “Climate change is serious, certain, and soon.”

“But that’s no longer accurate,” Mearns told Mashable. “It’s very serious, it’s very certain, and it’s now.”

“It’s very serious, it’s very certain, and it’s now.”

“Hopefully this report will make a difference in terms of showing this urgency,” Mearns said.

Here are some major points of the climate report:

Extreme weather events are growing more extreme

“Both the frequency and intensity of many climate extremes increase as the planet warms,” Greg Flato, a senior research scientist for the Canadian government who helped organize the IPCC report, told Mashable.

For example, as the climate warms the atmosphere can hold more water, resulting in increasingly heavy downpours. The heaviest precipitation has “increased since the 1950s over most land area for which observational data are sufficient,” the report concludes. These areas include much of North America and Europe.

But extremes don’t always act alone.

“One of the most important messages coming out of the report is the emphasis on extreme, but particularly compound extreme, events,” explained Mearns. A compound extreme event is when more than one extreme happens at once.

The current fires in the Western U.S. are a salient example. Modern fires out West are creating unnatural infernos, due to a potent combination of warming temperatures and mismanaged forests, among other factors. Yet drought — made worse by warmer temperatures and heat waves — further parches the land and evaporates moisture from forests and vegetation, creating more fuel ready to burn. The result? Amplified fire conditions on top of extremes in drought and heat.

“Those are a lot of heavy-duty extremes,” said Mearns.

For decades, the science has been right

Earth and climate scientists have known for decades that humans are causing the rapid warming of the planet, with many predictable consequences like rising sea levels, more extreme heat, and devastating flooding.

“This report really confirms information that was already previously available,” emphasized Flato, noting the inclusion of updated climate observations and analysis in the new IPCC publication. “Human influence has caused the climate to change,” is the bottom line of all the research, he added.

There simply aren’t any other recent factors that would push the climate to rapidly warm, like prodigiously erupting volcanoes or enhanced activity from the sun. In fact, during the last four decades the sun’s output has slightly decreased, while Earth warmed.

“It is unequivocal that human influence has warmed the atmosphere, ocean and land,” the IPCC concluded.

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The data, on Earth’s accelerated warming alone, is overwhelming and clear.

Since the late 1800s, the planet has already warmed by 2 degrees Fahrenheit (or 1.1 Celsius), though regionally many areas on land have warmed significantly more. NASA uses over 26,000 weather stations and thousands of ocean sensors to monitor warming temperatures. “Since the first IPCC report in 1990, large numbers of new instruments have been deployed to collect data in the air, on land, at sea and from outer space,” the IPCC wrote.

The oceans are changing in intense, unsettling ways

Land-dwelling humans may sometimes forget, but Earth is an ocean planet, dominated by marine critters. The latest UN report dedicates a chapter to how the oceans are changing. These changes, because they’re happening rapidly compared to the gradual, natural climate changes of the past, adversely impact civilization (especially along the coasts) and life in the seas. Adaptation isn’t like flipping a switch.

One glaring and well-predicted consequence of a warming climate is rising sea levels. Thick masses of ice, frozen on Antarctica, Greenland, and mountains, are melting into the ocean. Already, sea levels globally have risen by some eight to nine inches since the late 1800s. In the coming thousands of years, these changes cannot be undone.

“It’s one of the aspects of climate change that is effectively irreversible,” said Flato.

Sea levels rose faster in the 20th century than in any prior century over the last three thousand years, the IPCC found, based on research of fossilized coastal creatures. By this century’s end, under intermediate (not extremely high or low) carbon emission scenarios, the IPCC predicts sea levels will rise by another 1.5 to 2.5 feet, and then continue rising.

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The oceans are expected to change in other momentous ways, too, though the changes will be less extreme if carbon emissions are slashed this century:

• By the end of many Arctic summers, the Arctic Ocean will “likely become practically sea ice–free” before 2050, the IPCC said. This has giant implications for weather, climate, and Arctic life.

• The oceans, which absorb over 90 percent of heat trapped on Earth by human activities, will continue to warm for centuries, until at least 2300, even if carbon emissions are vastly reduced this century. A warming ocean means more rapid melting of ice sheets, profound habitat challenges for marine life, and added fuel for hurricanes.

• Marine heat waves — unusual and prolonged warm ocean temperatures — became more frequent over the 20th century and will become even more frequent this century.

• The ocean is losing oxygen as the climate warms, which is problematic for sea life that relies heavily on oxygen to function.

• The ocean is growing more acidic as it absorbs more CO2, which will harm marine life, particularly species that can’t adapt to a notable surge in acidity.

We have control over the future

The amount of heat-trapping carbon humanity emits into the atmosphere this century will largely dictate Earth’s future in the coming centuries. The more carbon, the worse the impacts, particularly extremes in weather.

“Every bit of warming that we allow to happen increases these impactful extreme events,” emphasized Flato.

The crucial point is that we can still limit warming to vastly less adverse levels

Already, Earth (whose atmosphere is loaded with the highest levels of heat-trapping carbon dioxide in some 3 million years) will continue warming through at least mid-century, even if society radically cuts carbon emissions, the IPCC said. The agency finds Earth’s temperature may creep 2.7 F (1.5 C) above 19th century levels — the extremely ambitious goal agreed to by global nations at the historic Paris agreement — sometime in the early 2030s.

“Global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades,” the IPCC said.

The crucial point is that we can still limit warming to vastly less adverse levels: For example, stabilizing global temperatures around 3.6 F (2 C) above 19th-century levels would be considerably less severe than hitting 5.4 degrees Fahrenheit (3 C).

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Avoiding the worst impacts of climate change requires systemic, societal changes. People can make better climate and energy decisions if they have the ability to do so — like a nationwide plan to vastly expand electric vehicle charging stations to spur EV adoption.

Right now, in a fossil fuel-dominated society, that’s challenging. “Even a homeless person living in a fossil fuel-powered society has an unsustainably high carbon footprint,” Benjamin Franta, who researches law and history of science as a J.D.-Ph.D. student at Stanford Law School, told Mashable last year. Our food, transportation, and beyond largely relies on burning ancient, carbon-rich fuels.

The picture is clear.

“We have a narrow window of time to avoid very costly, deadly, and irreversible future climate impacts,” National Oceanic and Atmospheric Administration administrator Richard Spinrad said in a statement. “It is the consensus of the world’s scientists that we need strong, and sustained reduction in greenhouse gases.”