01/05/2021

(New Yorker) Renewable Energy Is Suddenly Startlingly Cheap

The New Yorker

Now the biggest barrier to change is the will of our politicians to take serious climate action.

Because its costs continue to slide with every quarter, solar energy will be cheaper than fossil fuels almost everywhere on the planet by the decade’s end. Photograph by Irfan Khan / Los Angeles Times / Getty

Author
Bill McKibben is a founder of the grassroots climate campaign 350.org and a contributing writer to The New Yorker. He writes The Climate Crisis, The New Yorker’s newsletter on the environment.
Earth Week has come and gone, leaving behind an ankle-deep and green-tinted drift of reports, press releases, and earnest promises from C.E.O.s and premiers alike that they are planning to become part of the solution.

There were contingent signs of real possibility—if some of the heads of state whom John Kerry called on to make Zoom speeches appeared a little strained, at least they appeared. (Scott Morrison, the Prime Minister of Australia, the most carbon-emitting developed nation per capita, struggled to make his technology work.)

But, if you want real hope, the best place to look may be a little noted report from the London-based think tank Carbon Tracker Initiative. Titled “The Sky’s the Limit,” it begins by declaring that “solar and wind potential is far higher than that of fossil fuels and can meet global energy demand many times over.” Taken by itself, that’s not a very bold claim: scientists have long noted that the sun directs more energy to the Earth in an hour than humans use in a year. But, until very recently, it was too expensive to capture that power. That’s what has shifted—and so quickly and so dramatically that most of the world’s politicians are now living on a different planet than the one we actually inhabit.

On the actual Earth, circa 2021, the report reads, “with current technology and in a subset of available locations we can capture at least 6,700 PWh p.a. [petawatt-hours per year] from solar and wind, which is more than 100 times global energy demand.” And this will not require covering the globe with solar arrays: “The land required for solar panels alone to provide all global energy is 450,000 km2, 0.3% of the global land area of 149 million km2. That is less than the land required for fossil fuels today, which in the US alone is 126,000 km2, 1.3% of the country.” These are the kinds of numbers that reshape your understanding of the future.

We haven’t yet fully grasped this potential because it’s happened so fast. In 2015, zero per cent of solar’s technical potential was economically viable—the small number of solar panels that existed at that time had to be heavily subsidized. But prices for solar energy have collapsed so fast over the past three years that sixty per cent of that potential is already economically viable. And, because costs continue to slide with every quarter, solar energy will be cheaper than fossil fuels almost everywhere on the planet by the decade’s end. (It’s a delicious historical irony that this evolution took place, entirely by coincidence, during the Administration of Donald Trump, even as he ranted about how solar wasn’t “strong enough” and was “very, very expensive.”)

 The Carbon Tracker report, co-written by Kingsmill Bond, is full of fascinating points, including how renewable energy is the biggest gift of all for some of the poorest nations, including in Africa, where solar potential outweighs current energy use by a factor of more than a thousand. Only a few countries—Singapore, Japan, Korea, Taiwan, and a handful of European countries—are “stretched” in their ability to rely on renewables, because they both use a lot of energy and have little unoccupied land. In these terms, Germany is in the third-worst position, and the fact that it is nonetheless one of the world’s leaders in renewable energy should be a powerful signal: “If the Germans can find solutions, then so can everyone else.”

Clearly, those few nations are going to be importing some renewable energy—a more farsighted Australian Prime Minister would be figuring out how to send ships full of solar-generated hydrogen to Japan, not how to continue shipping coal to China. (And, in fact, the world’s largest solar farm is set to end up in the Australian outback, connected by at least two thick undersea cables to Singapore.)

The numbers in the report are overwhelming—even if the analysts are too optimistic by half, we’ll still be swimming in cheap solar energy. “We have established that technical and economic barriers have been crossed by falling costs. It follows that the main remaining barrier to change is the ability of incumbents to manipulate political forces to stop change,” the report reads. Indeed. And the problem is that we need that change to happen right now, because the curves of damage from the climate crisis are as steep as the curves of falling solar prices.

Given three or four decades, economics will clearly take care of the problem—the low price of solar power will keep pushing us to replace liquid fuels with electricity generated from the sun, and, eventually, no one will have a gas boiler in the basement or an internal-combustion engine in the car. But, if the transition takes three or four decades, no one will have an ice cap in the Arctic, either, and everyone who lives near a coast will be figuring out where on earth to go.

That conundrum was illuminated on Friday, when word came that Governor Gavin Newsom, of California, who has been under pressure from an unrelenting activist campaign, agreed to ban new fracking permits in his state and end fossil-fuel production there altogether. This is a stunning achievement—for the planet and also for the California communities (and you can guess what kinds of communities they are) that currently have oil wells in their schoolyards and next to their hospitals.

The environmentalists who banded together in the Last Chance Alliance should be incredibly proud; Newsom (who is now facing a recall election) deserves credit, as well, because this is precisely the step that his famously green predecessor, Jerry Brown, did not take. The fracking ban, though, only affects a small percentage of California’s oil production, and won’t take effect until 2024. The ban on oil production would not happen until 2045, which in climate terms is the very distant future—a decade past the date when California will ban the sale of new gas-powered cars, which are the main use of oil in the state.

It’s clear why Newsom is slow-walking the changes. An executive secretary of a building-trades council immediately responded, “We will work to oppose this effort for our membership, their families, our schools, and our future. I have one question for Gavin Newsom: Are our jobs too dirty for you?”

Change is hard. The job of politicians is to make it easier for those affected, so that what must happen can happen—and within the time we’ve been allotted by physics. But that hard job is infinitely easier now that renewable energy is suddenly so cheap. The falling price puts the wind at our backs, as it were. It’s the greatest gift we could have been given as a civilization, and we dare not waste it.

Passing the Mic

Audrea Lim is a Brooklyn-based journalist who has written for this magazine, and also for Harper’s, the Times, and The Nation. She is the editor of the book “The World We Need: Stories and Lessons from America’s Unsung Environmental Movement,” which the New Press will publish next week. For the book, she surveyed America, finding the people who are powering the environmental movement now. (Our conversation has been edited for length.)

Bill McKibben: People may have an image in their mind of what an environmentalist looks like—but what does an environmentalist actually look like in 2021?

Audrea Lim: They don’t look any one way! Far from the “white college-educated hippie” stereotype, environmentalists are Black and brown youth transforming an abandoned jail into a community farm; a former coal miner turned blogger and environmental advocate; Asian, Latinx, and indigenous people creating healthier and more equitable neighborhoods for their kids.

“Environmentalist” just describes any people defending the quality of their surroundings. This work can be local (protecting air or water from toxic emissions or lead paint in the walls) or global (protecting the glaciers and oceans that regulate local climates, from Brooklyn’s streets to the Alaskan coast). The health, safety, and well-being of their communities hang in the balance, but many activists understand that these goals also require bigger changes, from better access to parks, recreation, and community spaces to more localized food systems and good, clean jobs.

I think that’s why many environmentalists don’t even call themselves “environmentalists.” They are culture-makers, or community, housing, labor, and immigration activists who understand that environmental issues are ingrained in every part of society, and have simply made them a core element of their work.

Bill McKibben: What are the most important insights that came as, say, the climate movement morphed into the climate-justice movement?

Audrea Lim: That climate change will touch every community, demographic, and region, but is also on track to devastate poor and BIPOC communities the most. Many of these communities already struggle to meet basic needs—food, housing, education, physical and mental health—making them more vulnerable to sudden shocks, as we’ve seen through the pandemic.

Many of these communities also live near polluting developments (factories, refineries, waste incinerators) or on eroded and contaminated lands (mines, Superfund sites), or lack proper water and sewage infrastructure. These are added risks when the fires and floods arrive.

This uneven burden is part of America’s legacy of environmental racism: a history of hazardous, polluting fossil-fuel developments being concentrated in communities of color—sometimes by design and often through neglect. It’s the conjoined twin of residential segregation. But, in addressing this reality head on, the climate-justice movement also has another important insight to offer: everyone benefits when we empower these communities to build more equitable, resilient local economies, and transition away from the dirty industries long looming over them.

Bill McKibben: If you could pick one story that would really stick in people’s minds and hearts, what would it be?

Audrea Lim: Eric Enos grew up on the Waianae Coast of Oahu, with little knowledge of his Native Hawaiian culture, including the central importance of taro, a root vegetable. (Native culture was suppressed under U.S. colonialism.) After graduating from college, in the seventies, he began teaching art to Native youth-gang members, taking them to dive in the ocean, protest the conversion of local fishing grounds into a resort, and hike in the back of the desiccated Waianae Valley. Here they found abandoned walls and terraces in the ground. These were clearly cultural sites, but what were they?

Archeologists at the Bishop Museum found that the entire area was once under taro cultivation, as well as other traditional Hawaiian plants. The water had long ago been diverted toward colonial sugar plantations, but, with guidance from a state senator and local agencies, Enos, the youth, and community members built a new irrigation system. A group of multi-ethnic taro farmers, whom they had earlier helped defend against eviction from their lands, helped prepare the terraces for cultivation. And, with seeds donated from the Lyon Arboretum, they began growing native plants, learning about the land, their own culture, and taro in the process.

These were the beginnings of Ka‘ala Farm, a cultural learning center that connects troubled youth to the land. The story underscores how different institutions and people from different communities can collaborate toward a more equitable and resilient future.

Climate School

Two former Prime Ministers of Australia wrote an insightful op-ed about why their country, bathed in sun, continues to insist on building more coal mines and gas wells. They note that “the main thing holding back Australia’s climate ambition is politics: a toxic coalition of the Murdoch press, the right wing of the Liberal and National parties, and vested interests in the fossil fuel sector.” Last week, the center-left Australian Labor Party, too, said that it will not stand against building more coal mines, and believes that the nation will be exporting the black rocks past 2050.

A wonderful leftover from Earth Day: Tia Nelson, the daughter of the late senator Gaylord Nelson, who launched the April day of action, in 1970, wrote about how her father helped welcome Joe Biden to the Senate, in 1973, comforting him after his wife and infant daughter had been killed in a car crash. Nelson said, of her father, “It would delight him to see that something he started so long ago, to shake the Washington establishment out of its lethargy, still playing such an important role these many years later. And he would be moved to see that the heartbroken young man he helped recover from despair is carrying his legacy forward.” It’s remarkable how long Biden has been around—one good effect is that he’s known some superb people.

A new study has found that climate change will cause lakes in the Northern Hemisphere to stratify earlier in the year and over longer periods, and that “many of the ecosystem services that lakes provide, ranging from the delivery of drinking water and food to recreation, may be endangered by the projected change in stratification phenology during the twenty-first century, particularly in urbanized and agricultural regions where lakes are already eutrophic.”

A sign of what’s to come: a new renewable-energy project in Oregon marries solar power, wind turbines, and large-capacity battery storage. A spokesman for the local utility, Portland General Electric, said, “We feel pretty certain that this is what the future of renewable power looks like. It’s more diverse, and it’s more flexible.” A little further south and looking a little further into the future, the invaluable Sammy Roth, in his weekly “Boiling Point” newsletter, discusses the possibility of covering California’s irrigation canals with solar panels, to both generate clean energy and cut evaporation.

The Movement for Black Lives is launching a Red Black and Green New Deal, with a virtual summit on May 11th. Its Web site states, “We are organizing to introduce a National Black Climate Agenda that includes federal legislation to address the climate crisis by investing in Black communities and repairing past harms.”

A Yale team has developed a podcast devoted to climate policy and carbon pricing—the most recent episode is about why conservatives might be comfortable with the tactic. As Naomi Shimberg, a junior, explains, “Many conservatives echo the classic economic argument: pricing harm across the economy, rather than controlling it with direct forms of government regulation, is the most efficient way to cut pollution.”

Scoreboard

A new report from the World Meteorological Organization documented just how dismal 2020 was in climatic terms: it was one of the three warmest years on record, with more than eighty per cent of the world’s oceans subject to at least one “marine heat wave;” extensive flooding in the Greater Horn of Africa helped trigger a plague of locusts; and severe drought in South America caused three billion dollars in crop losses in Brazil alone.

A Baylor College of Medicine pediatrician and a University of California, Davis, environmental economist published an assessment, in Scientific American, of the actual health impact of climate change. They argue that the Biden Administration should set the “social cost” of carbon at a higher level, to reflect the damage that it’s doing to “every organ system in the human body.”

Water levels in Lake Powell and Lake Mead are expected to drop to record lows in the coming months, and reduced snowpacks and increased evaporation along the Colorado watershed may trigger the first-ever official water-shortage declaration in the area—and, hence, cuts in the water supply to Arizona and Nevada.

The student-body presidents of all the Ivy League schools signed a joint call for full fossil-fuel divestment last week. Meanwhile, divestment campaigners at Harvard produced a series of comic sketches as part of their ongoing efforts, and Christiana Figueres, the former head of the United Nations convention on climate change who spearheaded the push for the Paris accord, criticized the university for its investments in fossil-fuel companies, warning that Harvard management is on the verge of “breaching its true fiduciary responsibility.”

The Times obtained a detailed summary of an upcoming United Nations scientific report, which makes clear that, in addition to cutting carbon emissions, controlling methane emissions is crucial in solving the climate crisis. Along with issuing calls for plugging leaks, the report makes the critical point, according to the Times, that “expanding the use of natural gas is incompatible with keeping global warming to 1.5 degrees Celsius, a goal of the international Paris Agreement.”

Warming Up

Bonnie Raitt and the Indigo Girls are among the artists who cut “No More Pipeline Blues (On this Land Where We Belong),” to raise money and awareness for the fight against Minnesota’s Line 3 pipeline. Listen for the voice of the first enrolled member of a Native American tribe to be named U.S. Poet Laureate, Joy Harjo.

Links

German Climate Change Law Violates Rights, Court Rules

BBC

Reuters

Germany's climate change laws are insufficient and violate fundamental freedoms by putting the burden of curbing CO2 emissions on the young, its highest court has ruled.

It says the law fails to give enough detail on cutting CO2 emissions after current targets end in 2030.

"The provisions irreversibly offload major emission reduction burdens on to periods after 2030," it found.

The government will now have to revise the law by the end of the next year.

The decision comes a week after the EU unveiled ambitious new climate change targets.

Under the law, which was agreed between member states and the European Parliament, the bloc will cut carbon emissions by at least 55% by 2030, compared with 1990 levels.

What does the law say?

Like the EU legislation, Germany's domestic climate change law provides for a 55% reduction in greenhouse gases by 2030.

The 2019 law was agreed as part of Germany's response to the 2016 Paris climate deal, which aims to keep the global temperature rise well under 2C - and preferably to 1.5C - to prevent the worst effects of climate change.

What is climate change?

But the German Constitutional Court said on Thursday that current measures "violate the freedoms of the complainants, some of whom are still very young" because they delay too much of the action needed to reach the Paris targets until after 2030.

"In order to achieve this, the reductions still required after 2030 will have to be achieved more urgently and at short notice," it said.

Should Germany use up most of its permitted CO2 emissions by this time, future generations could face a "serious loss of freedom".

"Virtually any freedom is potentially affected by these future emission reduction obligations, because almost all areas of human life are still associated with the emission of greenhouse gases and are therefore threatened by drastic restrictions after 2030," the court said.

How did Germans react?

Thursday's ruling partially upheld complaints brought by climate change activists - most of them young - and environmental groups between 2018 and 2020.

Luisa Neubauer (L) with Swedish climate activist Greta Thunberg and German activist Jakob Blasel at a protest in Berlin in 2019. AFP

German climate activist Luisa Neubauer from the Fridays for Future movement and one of the plaintiffs in the case, described the decision as a "huge win for the climate movement".

"Today's inaction mustn't harm our freedom & rights in the future," she said.

One of the lawyers involved in the case, Felix Ekardt, hailed the "ground-breaking victory".

Following the announcement, German organisation Deutsche Umwelthilfe (DUH) tweeted a letter written by an 11-year-old girl (in German) in 2019, which had led to its own involvement in the case.

"I would like to take the government to court because the politicians aren't taking the impending climate catastrophe seriously enough, and I want people in 100 to 150 years to still know what snow is," the pupil wrote.

German Environment Minister Svenja Schulze also welcomed the decision, which she described as "a clear strengthening of climate protection".

"I would have liked to have included a further interim goal for the 2030s in the [2019] law but at the time there was no majority for that," she said.

What are other countries doing?

Other countries have also focused on climate change in recent days, with Poland reaching a draft agreement with trade unions to close all of its coal mines by 2049 and organise severance payments for the tens of thousands of workers affected.

Last week, the US hosted a virtual climate summit of 40 global leaders, with President Joe Biden pledging to cut US carbon emissions by 50-52% below 2005 levels by the year 2030.

Meanwhile, the UK announced radical plans to cut carbon emissions by 78% by 2035, although environmentalists warn that the government has consistently failed to achieve previous targets set by its independent Climate Change Committee.

Links

(NYTimes) The Science Of Climate Change Explained: Facts, Evidence And Proof

New York Times - Julia Rosen

Definitive answers to the big questions

Photo Illustration by Andrea D'Aquino

Author
Julia Rosen is a journalist with a Ph.D. in geology. Her research involved studying ice cores from Greenland and Antarctica to understand past climate changes.
The science of climate change is more solid and widely agreed upon than you might think.

But the scope of the topic, as well as rampant disinformation, can make it hard to separate fact from fiction.

Here, we’ve done our best to present you with not only the most accurate scientific information, but also an explanation of how we know it. 

How do we know climate change is really happening?

Climate change is often cast as a prediction made by complicated computer models. But the scientific basis for climate change is much broader, and models are actually only one part of it (and, for what it’s worth, they’re surprisingly accurate).

For more than a century, scientists have understood the basic physics behind why greenhouse gases like carbon dioxide cause warming. These gases make up just a small fraction of the atmosphere but exert outsized control on Earth’s climate by trapping some of the planet’s heat before it escapes into space. This greenhouse effect is important: It’s why a planet so far from the sun has liquid water and life!

However, during the Industrial Revolution, people started burning coal and other fossil fuels to power factories, smelters and steam engines, which added more greenhouse gases to the atmosphere. Ever since, human activities have been heating the planet.

We know this is true thanks to an overwhelming body of evidence that begins with temperature measurements taken at weather stations and on ships starting in the mid-1800s. Later, scientists began tracking surface temperatures with satellites and looking for clues about climate change in geologic records. Together, these data all tell the same story: Earth is getting hotter.

Average global temperatures have increased by 2.2 degrees Fahrenheit, or 1.2 degrees Celsius, since 1880, with the greatest changes happening in the late 20th century. Land areas have warmed more than the sea surface and the Arctic has warmed the most — by more than 4 degrees Fahrenheit just since the 1960s. Temperature extremes have also shifted. In the United States, daily record highs now outnumber record lows two-to-one.

Source: NASA Goddard Institute for Space Studies. By Veronica Penney

This warming is unprecedented in recent geologic history. A famous illustration, first published in 1998 and often called the hockey-stick graph, shows how temperatures remained fairly flat for centuries (the shaft of the stick) before turning sharply upward (the blade). It’s based on data from tree rings, ice cores and other natural indicators. And the basic picture, which has withstood decades of scrutiny from climate scientists and contrarians alike, shows that Earth is hotter today than it’s been in at least 1,000 years, and probably much longer.

In fact, surface temperatures actually mask the true scale of climate change, because the ocean has absorbed 90 percent of the heat trapped by greenhouse gases. Measurements collected over the last six decades by oceanographic expeditions and networks of floating instruments show that every layer of the ocean is warming up. According to one study, the ocean has absorbed as much heat between 1997 and 2015 as it did in the previous 130 years.

We also know that climate change is happening because we see the effects everywhere. Ice sheets and glaciers are shrinking while sea levels are rising. Arctic sea ice is disappearing. In the spring, snow melts sooner and plants flower earlier. Animals are moving to higher elevations and latitudes to find cooler conditions. And droughts, floods and wildfires have all gotten more extreme. Models predicted many of these changes, but observations show they are now coming to pass.


How much agreement is there among scientists about climate change?

There’s no denying that scientists love a good, old-fashioned argument. But when it comes to climate change, there is virtually no debate: Numerous studies have found that more than 90 percent of scientists who study Earth’s climate agree that the planet is warming and that humans are the primary cause. Most major scientific bodies, from NASA to the World Meteorological Organization, endorse this view. That’s an astounding level of consensus given the contrarian, competitive nature of the scientific enterprise, where questions like what killed the dinosaurs remain bitterly contested.

Scientific agreement about climate change started to emerge in the late 1980s, when the influence of human-caused warming began to rise above natural climate variability. By 1991, two-thirds of earth and atmospheric scientists surveyed for an early consensus study said that they accepted the idea of anthropogenic global warming. And by 1995, the Intergovernmental Panel on Climate Change, a famously conservative body that periodically takes stock of the state of scientific knowledge, concluded that “the balance of evidence suggests that there is a discernible human influence on global climate.” Currently, more than 97 percent of publishing climate scientists agree on the existence and cause of climate change (as does nearly 60 percent of the general population of the United States).

So where did we get the idea that there’s still debate about climate change? A lot of it came from coordinated messaging campaigns by companies and politicians that opposed climate action. Many pushed the narrative that scientists still hadn’t made up their minds about climate change, even though that was misleading. Frank Luntz, a Republican consultant, explained the rationale in an infamous 2002 memo to conservative lawmakers: “Should the public come to believe that the scientific issues are settled, their views about global warming will change accordingly,” he wrote. Questioning consensus remains a common talking point today, and the 97 percent figure has become something of a lightning rod.

To bolster the falsehood of lingering scientific doubt, some people have pointed to things like the Global Warming Petition Project, which urged the United States government to reject the Kyoto Protocol of 1997, an early international climate agreement. The petition proclaimed that climate change wasn’t happening, and even if it were, it wouldn’t be bad for humanity. Since 1998, more than 30,000 people with science degrees have signed it. However, nearly 90 percent of them studied something other than Earth, atmospheric or environmental science, and the signatories included just 39 climatologists. Most were engineers, doctors, and others whose training had little to do with the physics of the climate system.

A few well-known researchers remain opposed to the scientific consensus. Some, like Willie Soon, a researcher affiliated with the Harvard-Smithsonian Center for Astrophysics, have ties to the fossil fuel industry. Others do not, but their assertions have not held up under the weight of evidence. At least one prominent skeptic, the physicist Richard Muller, changed his mind after reassessing historical temperature data as part of the Berkeley Earth project. His team’s findings essentially confirmed the results he had set out to investigate, and he came away firmly convinced that human activities were warming the planet. “Call me a converted skeptic,” he wrote in an Op-Ed for the Times in 2012.

Mr. Luntz, the Republican pollster, has also reversed his position on climate change and now advises politicians on how to motivate climate action.

A final note on uncertainty: Denialists often use it as evidence that climate science isn’t settled. However, in science, uncertainty doesn’t imply a lack of knowledge. Rather, it’s a measure of how well something is known. In the case of climate change, scientists have found a range of possible future changes in temperature, precipitation and other important variables — which will depend largely on how quickly we reduce emissions. But uncertainty does not undermine their confidence that climate change is real and that people are causing it.

Do we really only have 150 years of climate data?
How is that enough to tell us about centuries of change?
Earth’s climate is inherently variable. Some years are hot and others are cold, some decades bring more hurricanes than others, some ancient droughts spanned the better part of centuries. Glacial cycles operate over many millenniums. So how can scientists look at data collected over a relatively short period of time and conclude that humans are warming the planet? The answer is that the instrumental temperature data that we have tells us a lot, but it’s not all we have to go on.

Historical records stretch back to the 1880s (and often before), when people began to regularly measure temperatures at weather stations and on ships as they traversed the world’s oceans. These data show a clear warming trend during the 20th century.

Source: NASA Goddard Institute for Space Studies. By Veronica Penney

Some have questioned whether these records could be skewed, for instance, by the fact that a disproportionate number of weather stations are near cities, which tend to be hotter than surrounding areas as a result of the so-called urban heat island effect. However, researchers regularly correct for these potential biases when reconstructing global temperatures. In addition, warming is corroborated by independent data like satellite observations, which cover the whole planet, and other ways of measuring temperature changes.

Much has also been made of the small dips and pauses that punctuate the rising temperature trend of the last 150 years. But these are just the result of natural climate variability or other human activities that temporarily counteract greenhouse warming. For instance, in the mid-1900s, internal climate dynamics and light-blocking pollution from coal-fired power plants halted global warming for a few decades. (Eventually, rising greenhouse gases and pollution-control laws caused the planet to start heating up again.) Likewise, the so-called warming hiatus of the 2000s was partly a result of natural climate variability that allowed more heat to enter the ocean rather than warm the atmosphere. The years since have been the hottest on record.

Still, could the entire 20th century just be one big natural climate wiggle? To address that question, we can look at other kinds of data that give a longer perspective. Researchers have used geologic records like tree rings, ice cores, corals and sediments that preserve information about prehistoric climates to extend the climate record. The resulting picture of global temperature change is basically flat for centuries, then turns sharply upward over the last 150 years. It has been a target of climate denialists for decades. However, study after study has confirmed the results, which show that the planet hasn’t been this hot in at least 1,000 years, and probably longer.



How do we know climate change is caused by humans?

Scientists have studied past climate changes to understand the factors that can cause the planet to warm or cool. The big ones are changes in solar energy, ocean circulation, volcanic activity and the amount of greenhouse gases in the atmosphere. And they have each played a role at times.

For example, 300 years ago, a combination of reduced solar output and increased volcanic activity cooled parts of the planet enough that Londoners regularly ice skated on the Thames. About 12,000 years ago, major changes in Atlantic circulation plunged the Northern Hemisphere into a frigid state. And 56 million years ago, a giant burst of greenhouse gases, from volcanic activity or vast deposits of methane (or both), abruptly warmed the planet by at least 9 degrees Fahrenheit, scrambling the climate, choking the oceans and triggering mass extinctions.

In trying to determine the cause of current climate changes, scientists have looked at all of these factors. The first three have varied a bit over the last few centuries and they have quite likely had modest effects on climate, particularly before 1950. But they cannot account for the planet’s rapidly rising temperature, especially in the second half of the 20th century, when solar output actually declined and volcanic eruptions exerted a cooling effect.

That warming is best explained by rising greenhouse gas concentrations. Greenhouse gases have a powerful effect on climate (see the next question for why). And since the Industrial Revolution, humans have been adding more of them to the atmosphere, primarily by extracting and burning fossil fuels like coal, oil and gas, which releases carbon dioxide.

Bubbles of ancient air trapped in ice show that, before about 1750, the concentration of carbon dioxide in the atmosphere was roughly 280 parts per million. It began to rise slowly and crossed the 300 p.p.m. threshold around 1900. CO2 levels then accelerated as cars and electricity became big parts of modern life, recently topping 420 p.p.m. The concentration of methane, the second most important greenhouse gas, has more than doubled. We’re now emitting carbon much faster than it was released 56 million years ago.

Note: Total carbon dioxide emissions are from fossil fuels and cement production and do not include land use and forestry-related emissions. Russia data includes the Soviet Union through 1991, but only the Russian Federation afterward. Source: Research Institute for Environment, Energy and Economics at Appalachian State University. By Veronica Penney

These rapid increases in greenhouse gases have caused the climate to warm abruptly. In fact, climate models suggest that greenhouse warming can explain virtually all of the temperature change since 1950. According to the most recent report by the Intergovernmental Panel on Climate Change, which assesses published scientific literature, natural drivers and internal climate variability can only explain a small fraction of late-20th century warming.

Another study put it this way: The odds of current warming occurring without anthropogenic greenhouse gas emissions are less than 1 in 100,000.

But greenhouse gases aren’t the only climate-altering compounds people put into the air. Burning fossil fuels also produces particulate pollution that reflects sunlight and cools the planet. Scientists estimate that this pollution has masked up to half of the greenhouse warming we would have otherwise experienced.

Since greenhouse gases occur naturally,
how do we know they’re causing Earth’s temperature to rise?

Greenhouse gases like water vapor and carbon dioxide serve an important role in the climate. Without them, Earth would be far too cold to maintain liquid water and humans would not exist!

Here’s how it works: the planet’s temperature is basically a function of the energy the Earth absorbs from the sun (which heats it up) and the energy Earth emits to space as infrared radiation (which cools it down). Because of their molecular structure, greenhouse gases temporarily absorb some of that outgoing infrared radiation and then re-emit it in all directions, sending some of that energy back toward the surface and heating the planet. Scientists have understood this process since the 1850s.

Greenhouse gas concentrations have varied naturally in the past. Over millions of years, atmospheric CO2 levels have changed depending on how much of the gas volcanoes belched into the air and how much got removed through geologic processes. On time scales of hundreds to thousands of years, concentrations have changed as carbon has cycled between the ocean, soil and air.

Today, however, we are the ones causing CO2 levels to increase at an unprecedented pace by taking ancient carbon from geologic deposits of fossil fuels and putting it into the atmosphere when we burn them. Since 1750, carbon dioxide concentrations have increased by almost 50 percent. Methane and nitrous oxide, other important anthropogenic greenhouse gases that are released mainly by agricultural activities, have also spiked over the last 250 years.

We know based on the physics described above that this should cause the climate to warm. We also see certain telltale “fingerprints” of greenhouse warming. For example, nights are warming even faster than days because greenhouse gases don’t go away when the sun sets. And upper layers of the atmosphere have actually cooled, because more energy is being trapped by greenhouse gases in the lower atmosphere.

We also know that we are the cause of rising greenhouse gas concentrations — and not just because we can measure the CO2 coming out of tailpipes and smokestacks. We can see it in the chemical signature of the carbon in CO2.

Carbon comes in three different masses: 12, 13 and 14. Things made of organic matter (including fossil fuels) tend to have relatively less carbon-13. Volcanoes tend to produce CO2 with relatively more carbon-13. And over the last century, the carbon in atmospheric CO2 has gotten lighter, pointing to an organic source.

We can tell it’s old organic matter by looking for carbon-14, which is radioactive and decays over time. Fossil fuels are too ancient to have any carbon-14 left in them, so if they were behind rising CO2 levels, you would expect the amount of carbon-14 in the atmosphere to drop, which is exactly what the data show.

It’s important to note that water vapor is the most abundant greenhouse gas in the atmosphere. However, it does not cause warming; instead it responds to it. That’s because warmer air holds more moisture, which creates a snowball effect in which human-caused warming allows the atmosphere to hold more water vapor and further amplifies climate change. This so-called feedback cycle has doubled the warming caused by anthropogenic greenhouse gas emissions.

Why should we be worried that the
planet has warmed 2°F since the 1800s?

A common source of confusion when it comes to climate change is the difference between weather and climate. Weather is the constantly changing set of meteorological conditions that we experience when we step outside, whereas climate is the long-term average of those conditions, usually calculated over a 30-year period. Or, as some say: Weather is your mood and climate is your personality.

So while 2 degrees Fahrenheit doesn’t represent a big change in the weather, it’s a huge change in climate. As we’ve already seen, it’s enough to melt ice and raise sea levels, to shift rainfall patterns around the world and to reorganize ecosystems, sending animals scurrying toward cooler habitats and killing trees by the millions.

It’s also important to remember that two degrees represents the global average, and many parts of the world have already warmed by more than that. For example, land areas have warmed about twice as much as the sea surface. And the Arctic has warmed by about 5 degrees. That’s because the loss of snow and ice at high latitudes allows the ground to absorb more energy, causing additional heating on top of greenhouse warming.

Relatively small long-term changes in climate averages also shift extremes in significant ways. For instance, heat waves have always happened, but they have shattered records in recent years. In June of 2020, a town in Siberia registered temperatures of 100 degrees. And in Australia, meteorologists have added a new color to their weather maps to show areas where temperatures exceed 125 degrees. Rising sea levels have also increased the risk of flooding because of storm surges and high tides. These are the foreshocks of climate change.

And we are in for more changes in the future — up to 9 degrees Fahrenheit of average global warming by the end of the century, in the worst-case scenario. For reference, the difference in global average temperatures between now and the peak of the last ice age, when ice sheets covered large parts of North America and Europe, is about 11 degrees Fahrenheit.

Under the Paris Climate Agreement, which President Biden recently rejoined, countries have agreed to try to limit total warming to between 1.5 and 2 degrees Celsius, or 2.7 and 3.6 degrees Fahrenheit, since preindustrial times. And even this narrow range has huge implications. According to scientific studies, the difference between 2.7 and 3.6 degrees Fahrenheit will very likely mean the difference between coral reefs hanging on or going extinct, and between summer sea ice persisting in the Arctic or disappearing completely. It will also determine how many millions of people suffer from water scarcity and crop failures, and how many are driven from their homes by rising seas. In other words, one degree Fahrenheit makes a world of difference.

Is climate change a part of the planet’s
natural warming and cooling cycles?
Earth’s climate has always changed. Hundreds of millions of years ago, the entire planet froze. Fifty million years ago, alligators lived in what we now call the Arctic. And for the last 2.6 million years, the planet has cycled between ice ages when the planet was up to 11 degrees cooler and ice sheets covered much of North America and Europe, and milder interglacial periods like the one we’re in now.

Climate denialists often point to these natural climate changes as a way to cast doubt on the idea that humans are causing climate to change today. However, that argument rests on a logical fallacy. It’s like “seeing a murdered body and concluding that people have died of natural causes in the past, so the murder victim must also have died of natural causes,” a team of social scientists wrote in The Debunking Handbook, which explains the misinformation strategies behind many climate myths.

Indeed, we know that different mechanisms caused the climate to change in the past. Glacial cycles, for example, were triggered by periodic variations in Earth’s orbit, which take place over tens of thousands of years and change how solar energy gets distributed around the globe and across the seasons.

These orbital variations don’t affect the planet’s temperature much on their own. But they set off a cascade of other changes in the climate system; for instance, growing or melting vast Northern Hemisphere ice sheets and altering ocean circulation. These changes, in turn, affect climate by altering the amount of snow and ice, which reflect sunlight, and by changing greenhouse gas concentrations. This is actually part of how we know that greenhouse gases have the ability to significantly affect Earth’s temperature.

For at least the last 800,000 years, atmospheric CO2 concentrations oscillated between about 180 parts per million during ice ages and about 280 p.p.m. during warmer periods, as carbon moved between oceans, forests, soils and the atmosphere. These changes occurred in lock step with global temperatures, and are a major reason the entire planet warmed and cooled during glacial cycles, not just the frozen poles.

Today, however, CO2 levels have soared to 420 p.p.m. — the highest they’ve been in at least three million years. The concentration of CO2 is also increasing about 100 times faster than it did at the end of the last ice age. This suggests something else is going on, and we know what it is: Since the Industrial Revolution, humans have been burning fossil fuels and releasing greenhouse gases that are heating the planet now (see Question 5 for more details on how we know this, and Questions 4 and 8 for how we know that other natural forces aren’t to blame).

Over the next century or two, societies and ecosystems will experience the consequences of this climate change. But our emissions will have even more lasting geologic impacts: According to some studies, greenhouse gas levels may have already warmed the planet enough to delay the onset of the next glacial cycle for at least an additional 50,000 years.

How do we know global warming
is not because of the sun or volcanoes?
The sun is the ultimate source of energy in Earth’s climate system, so it’s a natural candidate for causing climate change. And solar activity has certainly changed over time. We know from satellite measurements and other astronomical observations that the sun’s output changes on 11-year cycles. Geologic records and sunspot numbers, which astronomers have tracked for centuries, also show long-term variations in the sun’s activity, including some exceptionally quiet periods in the late 1600s and early 1800s.

We know that, from 1900 until the 1950s, solar irradiance increased. And studies suggest that this had a modest effect on early 20th century climate, explaining up to 10 percent of the warming that’s occurred since the late 1800s. However, in the second half of the century, when the most warming occurred, solar activity actually declined. This disparity is one of the main reasons we know that the sun is not the driving force behind climate change.

Another reason we know that solar activity hasn’t caused recent warming is that, if it had, all the layers of the atmosphere should be heating up. Instead, data show that the upper atmosphere has actually cooled in recent decades — a hallmark of greenhouse warming.

So how about volcanoes? Eruptions cool the planet by injecting ash and aerosol particles into the atmosphere that reflect sunlight. We’ve observed this effect in the years following large eruptions. There are also some notable historical examples, like when Iceland’s Laki volcano erupted in 1783, causing widespread crop failures in Europe and beyond, and the “year without a summer,” which followed the 1815 eruption of Mount Tambora in Indonesia.

Since volcanoes mainly act as climate coolers, they can’t really explain recent warming. However, scientists say that they may also have contributed slightly to rising temperatures in the early 20th century. That’s because there were several large eruptions in the late 1800s that cooled the planet, followed by a few decades with no major volcanic events when warming caught up. During the second half of the 20th century, though, several big eruptions occurred as the planet was heating up fast. If anything, they temporarily masked some amount of human-caused warming.

The second way volcanoes can impact climate is by emitting carbon dioxide. This is important on time scales of millions of years — it’s what keeps the planet habitable (see Question 5 for more on the greenhouse effect). But by comparison to modern anthropogenic emissions, even big eruptions like Krakatoa and Mount St. Helens are just a drop in the bucket. After all, they last only a few hours or days, while we burn fossil fuels 24-7. Studies suggest that, today, volcanoes account for 1 to 2 percent of total CO2 emissions.


How can winters and certain places
be getting colder if the planet is warming?

When a big snowstorm hits the United States, climate denialists can try to cite it as proof that climate change isn’t happening. In 2015, Senator James Inhofe, an Oklahoma Republican, famously lobbed a snowball in the Senate as he denounced climate science. But these events don’t actually disprove climate change.

While there have been some memorable storms in recent years, winters are actually warming across the world. In the United States, average temperatures in December, January and February have increased by about 2.5 degrees this century.

On the flip side, record cold days are becoming less common than record warm days. In the United States, record highs now outnumber record lows two-to-one. And ever-smaller areas of the country experience extremely cold winter temperatures. (The same trends are happening globally.)

So what’s with the blizzards? Weather always varies, so it’s no surprise that we still have severe winter storms even as average temperatures rise. However, some studies suggest that climate change may be to blame. One possibility is that rapid Arctic warming has affected atmospheric circulation, including the fast-flowing, high-altitude air that usually swirls over the North Pole (a.k.a. the Polar Vortex). Some studies suggest that these changes are bringing more frigid temperatures to lower latitudes and causing weather systems to stall, allowing storms to produce more snowfall. This may explain what we’ve experienced in the U.S. over the past few decades, as well as a wintertime cooling trend in Siberia, although exactly how the Arctic affects global weather remains a topic of ongoing scientific debate.

Climate change may also explain the apparent paradox behind some of the other places on Earth that haven’t warmed much. For instance, a splotch of water in the North Atlantic has cooled in recent years, and scientists say they suspect that may be because ocean circulation is slowing as a result of freshwater streaming off a melting Greenland. If this circulation grinds almost to a halt, as it’s done in the geologic past, it would alter weather patterns around the world.

Not all cold weather stems from some counterintuitive consequence of climate change. But it’s a good reminder that Earth’s climate system is complex and chaotic, so the effects of human-caused changes will play out differently in different places. That’s why “global warming” is a bit of an oversimplification. Instead, some scientists have suggested that the phenomenon of human-caused climate change would more aptly be called “global weirding.”

Wildfires and bad weather have always happened.
How do we know there’s a connection to climate change?
Extreme weather and natural disasters are part of life on Earth — just ask the dinosaurs. But there is good evidence that climate change has increased the frequency and severity of certain phenomena like heat waves, droughts and floods. Recent research has also allowed scientists to identify the influence of climate change on specific events.

Let’s start with heat waves. Studies show that stretches of abnormally high temperatures now happen about five times more often than they would without climate change, and they last longer, too. Climate models project that, by the 2040s, heat waves will be about 12 times more frequent. And that’s concerning since extreme heat often causes increased hospitalizations and deaths, particularly among older people and those with underlying health conditions. In the summer of 2003, for example, a heat wave caused an estimated 70,000 excess deaths across Europe. (Human-caused warming amplified the death toll.)


Climate change has also exacerbated droughts, primarily by increasing evaporation. Droughts occur naturally because of random climate variability and factors like whether El Niño or La Niña conditions prevail in the tropical Pacific. But some researchers have found evidence that greenhouse warming has been affecting droughts since even before the Dust Bowl. And it continues to do so today. According to one analysis, the drought that afflicted the American Southwest from 2000 to 2018 was almost 50 percent more severe because of climate change. It was the worst drought the region had experienced in more than 1,000 years.

Rising temperatures have also increased the intensity of heavy precipitation events and the flooding that often follows. For example, studies have found that, because warmer air holds more moisture, Hurricane Harvey, which struck Houston in 2017, dropped between 15 and 40 percent more rainfall than it would have without climate change.

It’s still unclear whether climate change is changing the overall frequency of hurricanes, but it is making them stronger. And warming appears to favor certain kinds of weather patterns, like the “Midwest Water Hose” events that caused devastating flooding across the Midwest in 2019.

It’s important to remember that in most natural disasters, there are multiple factors at play. For instance, the 2019 Midwest floods occurred after a recent cold snap had frozen the ground solid, preventing the soil from absorbing rainwater and increasing runoff into the Missouri and Mississippi Rivers. These waterways have also been reshaped by levees and other forms of river engineering, some of which failed in the floods.

Wildfires are another phenomenon with multiple causes. In many places, fire risk has increased because humans have aggressively fought natural fires and prevented Indigenous peoples from carrying out traditional burning practices. This has allowed fuel to accumulate that makes current fires worse.

However, climate change still plays a major role by heating and drying forests, turning them into tinderboxes. Studies show that warming is the driving factor behind the recent increases in wildfires; one analysis found that climate change is responsible for doubling the area burned across the American West between 1984 and 2015. And researchers say that warming will only make fires bigger and more dangerous in the future.

How bad are the effects of climate change going to be?
It depends on how aggressively we act to address climate change. If we continue with business as usual, by the end of the century, it will be too hot to go outside during heat waves in the Middle East and South Asia. Droughts will grip Central America, the Mediterranean and southern Africa. And many island nations and low-lying areas, from Texas to Bangladesh, will be overtaken by rising seas. Conversely, climate change could bring welcome warming and extended growing seasons to the upper Midwest, Canada, the Nordic countries and Russia. Farther north, however, the loss of snow, ice and permafrost will upend the traditions of Indigenous peoples and threaten infrastructure.

It’s complicated, but the underlying message is simple: unchecked climate change will likely exacerbate existing inequalities. At a national level, poorer countries will be hit hardest, even though they have historically emitted only a fraction of the greenhouse gases that cause warming. That’s because many less developed countries tend to be in tropical regions where additional warming will make the climate increasingly intolerable for humans and crops. These nations also often have greater vulnerabilities, like large coastal populations and people living in improvised housing that is easily damaged in storms. And they have fewer resources to adapt, which will require expensive measures like redesigning cities, engineering coastlines and changing how people grow food.

Already, between 1961 and 2000, climate change appears to have harmed the economies of the poorest countries while boosting the fortunes of the wealthiest nations that have done the most to cause the problem, making the global wealth gap 25 percent bigger than it would otherwise have been. Similarly, the Global Climate Risk Index found that lower income countries — like Myanmar, Haiti and Nepal — rank high on the list of nations most affected by extreme weather between 1999 and 2018. Climate change has also contributed to increased human migration, which is expected to increase significantly.

Even within wealthy countries, the poor and marginalized will suffer the most. People with more resources have greater buffers, like air-conditioners to keep their houses cool during dangerous heat waves, and the means to pay the resulting energy bills. They also have an easier time evacuating their homes before disasters, and recovering afterward. Lower income people have fewer of these advantages, and they are also more likely to live in hotter neighborhoods and work outdoors, where they face the brunt of climate change.

These inequalities will play out on an individual, community, and regional level. A 2017 analysis of the U.S. found that, under business as usual, the poorest one-third of counties, which are concentrated in the South, will experience damages totaling as much as 20 percent of gross domestic product, while others, mostly in the northern part of the country, will see modest economic gains. Solomon Hsiang, an economist at University of California, Berkeley, and the lead author of the study, has said that climate change “may result in the largest transfer of wealth from the poor to the rich in the country’s history.”

Even the climate “winners” will not be immune from all climate impacts, though. Desirable locations will face an influx of migrants. And as the coronavirus pandemic has demonstrated, disasters in one place quickly ripple across our globalized economy. For instance, scientists expect climate change to increase the odds of multiple crop failures occurring at the same time in different places, throwing the world into a food crisis.

On top of that, warmer weather is aiding the spread of infectious diseases and the vectors that transmit them, like ticks and mosquitoes. Research has also identified troubling correlations between rising temperatures and increased interpersonal violence, and climate change is widely recognized as a “threat multiplier” that increases the odds of larger conflicts within and between countries. In other words, climate change will bring many changes that no amount of money can stop. What could help is taking action to limit warming.

What will it cost to do something about climate change,
versus doing nothing?
One of the most common arguments against taking aggressive action to combat climate change is that doing so will kill jobs and cripple the economy. But this implies that there’s an alternative in which we pay nothing for climate change. And unfortunately, there isn’t. In reality, not tackling climate change will cost a lot, and cause enormous human suffering and ecological damage, while transitioning to a greener economy would benefit many people and ecosystems around the world.

Let’s start with how much it will cost to address climate change. To keep warming well below 2 degrees Celsius, the goal of the Paris Climate Agreement, society will have to reach net zero greenhouse gas emissions by the middle of this century. That will require significant investments in things like renewable energy, electric cars and charging infrastructure, not to mention efforts to adapt to hotter temperatures, rising sea-levels and other unavoidable effects of current climate changes. And we’ll have to make changes fast.

Estimates of the cost vary widely. One recent study found that keeping warming to 2 degrees Celsius would require a total investment of between $4 trillion and $60 trillion, with a median estimate of $16 trillion, while keeping warming to 1.5 degrees Celsius could cost between $10 trillion and $100 trillion, with a median estimate of $30 trillion. (For reference, the entire world economy was about $88 trillion in 2019.) Other studies have found that reaching net zero will require annual investments ranging from less than 1.5 percent of global gross domestic product to as much as 4 percent. That’s a lot, but within the range of historical energy investments in countries like the U.S.

Now, let’s consider the costs of unchecked climate change, which will fall hardest on the most vulnerable. These include damage to property and infrastructure from sea-level rise and extreme weather, death and sickness linked to natural disasters, pollution and infectious disease, reduced agricultural yields and lost labor productivity because of rising temperatures, decreased water availability and increased energy costs, and species extinction and habitat destruction. Dr. Hsiang, the U.C. Berkeley economist, describes it as “death by a thousand cuts.”

As a result, climate damages are hard to quantify. Moody’s Analytics estimates that even 2 degrees Celsius of warming will cost the world $69 trillion by 2100, and economists expect the toll to keep rising with the temperature. In a recent survey, economists estimated the cost would equal 5 percent of global G.D.P. at 3 degrees Celsius of warming (our trajectory under current policies) and 10 percent for 5 degrees Celsius. Other research indicates that, if current warming trends continue, global G.D.P. per capita will decrease between 7 percent and 23 percent by the end of the century — an economic blow equivalent to multiple coronavirus pandemics every year. And some fear these are vast underestimates.

Already, studies suggest that climate change has slashed incomes in the poorest countries by as much as 30 percent and reduced global agricultural productivity by 21 percent since 1961. Extreme weather events have also racked up a large bill. In 2020, in the United States alone, climate-related disasters like hurricanes, droughts, and wildfires caused nearly $100 billion in damages to businesses, property and infrastructure, compared to an average of $18 billion per year in the 1980s.

Given the steep price of inaction, many economists say that addressing climate change is a better deal. It’s like that old saying: an ounce of prevention is worth a pound of cure. In this case, limiting warming will greatly reduce future damage and inequality caused by climate change. It will also produce so-called co-benefits, like saving one million lives every year by reducing air pollution, and millions more from eating healthier, climate-friendly diets. Some studies even find that meeting the Paris Agreement goals could create jobs and increase global G.D.P. And, of course, reining in climate change will spare many species and ecosystems upon which humans depend — and which many people believe to have their own innate value.

The challenge is that we need to reduce emissions now to avoid damages later, which requires big investments over the next few decades. And the longer we delay, the more we will pay to meet the Paris goals. One recent analysis found that reaching net-zero by 2050 would cost the U.S. almost twice as much if we waited until 2030 instead of acting now. But even if we miss the Paris target, the economics still make a strong case for climate action, because every additional degree of warming will cost us more — in dollars, and in lives.

Links